Never intensely religious and now indifferent to religion for over three decades, I have been relentlessly pursued by religion all my life. Every atom of India, where I was born and raised, is steeped in religious lore. At temples that are liberally sprinkled all over, devotees let the bells rest only at the peak of the night. Most days in every neighborhood, a Brahmin recounts a scriptural saga on a loudspeaker. Several times during the day, the muezzin issues his call to the faithful, also on a loudspeaker. In this atmosphere, which is quite often marred by clashes between the adherents of different religions, I went to college for five years in Varanasi, perhaps the holiest city for Hindus.

One of my graduate students decided to use a popular commercial software in order to investigate scattering by three-dimensional (3-D) objects. Within a few weeks, he came up with very nice plots of scattering patterns as well as colorful spatial profiles of scattered fields. As the 3-D objects were of complicated shapes and my brain is still wired to analytical treatments of scattering, I asked him to repeat his calculations for a sphere made of an isotropic material. After looking at the diagrams he supplied, I decided that something had gone wrong.

An ultrasmall plasmonic coaxial laser made of metal–semiconductor–metal on a silicon substrate through an interlayer bonding was designed. From the effective refractive indices and the transparent material gain, the nanoscale structural dimensions with both the radius and the width at 80 nm for the coaxial plasmonic waveguide were decided. The influence of the interlayer bonding material on the optimization of resonant wavelength and Q-factor was evaluated. A three-dimensional body-of-revolution finite-difference time-domain method was used to show that a coaxial cavity with a SiO₂ interlayer can laze at around 1480-nm wavelength with a net optical threshold power density of about 800  W/cm₂ and a subwavelength mode volume of 0.014(λ/2n)³. This nanolaser on silicon platform will benefit those working on nanophotonic integrated circuits.

Paper-supported solvent-responsive elastomeric opal films based on hard-soft core-interlayer-shell spheres featuring remarkably distinct iridescent reflection colors were investigated. By using extrusion and compression molding, elastomeric opal films could be obtained, which were incorporated into a porous paper sheet to build robust composites. Swelling of the opal paper composites caused by various solvents was accompanied with a tremendous photonic band gap shift of the reflection colors. The combination of the extraordinary optical properties of the elastomeric opal films used with the remarkable features of highly porous paper can be the basis for a whole family of polymer-based soft sensors featuring a fascinating optical, fast and reversible response.

Raman scattering is a nondestructive technique that is able to supply information on the crystal and electronic structures, strain, temperature, phonon–phonon, and electron–phonon interaction. In the particular case of semiconductor nanowires, Raman scattering provides additional information related to surfaces. Although correct, a theoretical approach to analyze the surface optical modes loses critical information when retardation is neglected. A comparison of the retarded and unretarded approaches clarifies the role of the electric and magnetic polarization in the Raman selection rules. Since most III–V compounds growing in the zincblende phase change their crystal structure to wurtzite when growing as nanowires, the polariton description will be particularized for these two important crystal phases. Confined phonons exist in cylindrical nanowires and couple with longitudinal and transverse modes due to the presence of the nanowire’s surface. This coupling vanishes in the case of rotational symmetry. The boundary conditions of the electromagnetic fields on small-size nanowires (antenna effect) have a dramatic effect on the polarization properties of a Raman spectrum.

The internalization of bioactive molecules is one of the most critical problems to overcome in theranostics. In order to improve pharmacokinetic and pharmacodynamic properties, synthetic transporters are widely investigated. A new nanotechnological transporter, gH625, is based on a viral peptide sequence derived from the herpes simplex virus type 1 glycoprotein H (gH) that has proved to be a useful delivery vehicle, due to its intrinsic properties of inducing membrane perturbation. The peptide functionalization with several kinds of nanoparticles like quantum dots, dendrimers, and liposomes could be of particular interest in biomedical applications to improve drug release within cells, to increase site-specific action, and eventually to reduce related cytotoxicity.

Nanostructures of lead sulfide (E_g ∼0.67 to 1.7 eV) corresponding to different quantum confinement regimes (weak, moderate, and strong with radii 14, 11, and 7 nm, respectively) have been synthesized through facile aqueous colloidal method and have been capped using poly vinyl alcohol. There is a marked difference in electron-lattice coupling properties as revealed through Fourier transform infrared data with strong quantum confined PbS quantum dots (QDs) exhibiting pronounced electron-lattice coupling characteristics. Opto-impedance characteristics of these samples suggest the enhanced mobility of charges, in particular under the supra gap excitation for strong quantum confined QDs.

The main drawback of the rapidly evolving field of silicon photonics lies in the absence of efficient monolithically integrated radiation sources as a consequence of the indirect bandgap of Si and Ge. Relevant alternatives based on the hybrid combination of Si with optically active materials have to be technologically simple, temporally stable, and provide efficient coupling to the Si waveguides. Lead-sulfide nanocrystals (NCs) were blended into a polymer resist suitable for deep-UV- and electron-beam lithography and integrated into Si-based vertically slotted waveguides and ring resonators. The polymer both stabilizes the NC’s photoluminescence emission against degradation under ambient conditions and allows lithographic patterning of this compound material. After integration into the optoelectronic structures and upon optical pumping, intense photoluminescence emission from ring resonators was recorded at the output of bus-waveguides. The resonator quality factors were investigated for polymer-NC compounds with NC concentrations in the range between 0.1 and 8 vol%. The spontaneous emission rate enhancement for vertically slotted resonators was estimated to be a factor of two higher as compared to unslotted ones. The stable integration of colloidal NCs as well as the improved light coupling to silicon circuits is an important step in the development of silicon-based hybrid photonics.

An integrated plasmonic resonator was proposed and analyzed. The detection performance of our device has been numerically verified by finite-difference time-domain simulations. The spectral sensitivity obtained was found to be 700  nm/RIU , where RIU is the refractive index unit. Our proposed sensor was found to have a detection limit in the order of 10 ⁻⁶   RIU . The plasmonic sensor could be fabricated using focus ion beam milling. Our design leads to an ultra-compact sensor suitable for on-chip sensing applications associated with a high sensitivity. For biosensing, the proposed sensor could have the ability for a specific capture of biomolecules at the sensor surface that enables for quantification of the biomolecules.

Optoacoustic spectroscopy can overcome the drawbacks of all-optical techniques for biomedical spectroscopy, as the acoustic waves generated from the optical absorption and thermoelastic expansion of the targeted medium are attenuated very little. The spectral information can be resolved using a high energy, short-pulsed tunable laser, operating over a spectral range from 410 nm to 1000 nm. The amplitude of the induced pressure waves is directly proportional to the absorbed optical energy at each wavelength.

As the effect of group-velocity dispersion (GVD) on the stability of midinfrared quantum-cascade lasers (QCLs) has not been explored so far, both amplitude and phase instabilities of QCLs were analyzed in the presence of a background saturable absorber in the lasing medium. The investigation was carried out through the linearization of the Maxwell–Bloch formalism for the lasing medium by including second-order dispersion of group velocity and intensity-dependent loss accounting for the saturable absorber. The effect of the GVD on laser instability was found to be strongly related to the strength of the saturable absorber and pumping. The effect of the GVD is more significant at lower pumping levels and with weaker saturable absorbers.

The visibility of Moiré fringes is a major feature for their application in optical metrology. With the help of surface plasmon polariton (SPP) waves excited for a metal layer whose permittivity match with that of its dielectric partner, the visibility of Moiré fringes is improved. For a dielectric-metal-dielectric sandwich structure between two subwavelength gratings with the optimum thicknesses of the layers but not appropriately matched permittivity, we found that it is easy to achieve a remarkable enhancement (visibility up to 0.88) of the Moiré fringes facilitated by the excitation of SPP waves.

The spin and the orbital parts of the angular momentum of multiple surface-plasmon-polariton (SPP) waves guided by the planar interface of a metal and a periodically nonhomogeneous sculptured nematic thin film (SNTF) were theoretically investigated. Both the Minkowski and Abraham formulations of angular momentum were considered. Multiple SPP waves guided by the metal/SNTF interface propagating along a direction that does not lie wholly in the morphologically significant plane of the SNTF were found to have different magnitudes and directions of the spin and the orbital parts of the angular momentum. The spin angular momentum is oriented in a variety of directions, but the orbital angular momentum is perpendicular to the direction of propagation and lies in the interface plane. Not only does the periodic nonhomogeneity of the partnering dielectric material engender a multiplicity of SPP waves, but also it can enhance the magnitudes of the spin and orbital parts of their angular momentums.

A silicon light-emitting device is designed and realized in standard 3-μm complementary metal oxide semiconductor (CMOS) integrated circuitry. Accordingly, it can be integrated with its signal processing CMOS and BiCMOS circuits on the same chip, thus enabling the fabrication of much needed all-silicon monolithic optoelectronic systems operated by a single supply. The device emitted light in a broad, bell-shaped spectrum from 500 to 850 nm with characteristic peaks at 650 and 750 nm. Initial investigations indicate that the quantum efficiency is of the order of 10 ⁻⁸ and the electric-to-optical power conversion efficiency is of the order of 10 ⁻⁹ . This silicon light-emitting device has obvious applications in the electro-optical interconnect.

The performance of short-wavelength infrared (SWIR) cameras in the visible and ultraviolet (UV) regions is limited by the absorption of high-energy photons in inactive regions of the imaging array. Dual-band UV-SWIR imaging can be achieved by using PbS colloidal quantum dots (CQD) to downshift incident UV light to the SWIR band. The CQD downshifting layer has minimal impact on the SWIR imaging performance and greatly increases the UV sensitivity of an InGaAs camera. A dual-lens design in which the QDs are incorporated on a removable substrate is demonstrated, which provides UV sensitivity without modification of the InGaAs camera focal plane array. A single-lens design in which the QDs are deposited directly on the focal plane array is demonstrated using both a standard InGaAs focal plane and a substrate-thinned focal plane. Higher UV resolution for the substrate-thinned focal plane is observed.

A multitaper (MT) coupler is fabricated on a silicon chip for light coupling with high efficiency and resistance to fabrication errors. Other coupling techniques such as a single taper are less efficient and prone to fabrication errors. The dimensions of the MT can be optimized for a specific coupling geometry and can span sizes from several nanometers up to several microns.

A terahertz range nanoantenna of a new type was conceptualized. The physical mechanism underlying the concept is population waveguiding, the Rabi wave, in tunneling-coupled one-dimensional and two-dimensional arrays of quantum dots (QDs) excited by the light wave traveling along the antenna. The terahertz component of the emission is stimulated by the tunneling current induced on the Rabi frequency by the motion of quantum transitions along the QD array. We calculated the antenna characteristics for the Rabi-wave loop nanoantenna and found its emission characteristics to be electrically tunable via varying the intensity and phase velocity of the light wave. The conceptualized antennas are promising for many practical applications due to their ability of electrical scanning of the antenna radiation pattern.

Gradient refractive index metamaterials are of interest for various applications of transformation optics. Wave propagation through gradient index metamaterials using an exact analytical approach is investigated. Composite materials containing constituents with negative real and positive real indexes of refraction are considered. An exact analytical solution for the field distribution is obtained for the sinusoidal spatial variation of complex effective permittivity and permeability along a fixed direction, under the assumption that the wave impedance remains spatially uniform across the structure. Loss factors in the constituent materials can be different from each other corresponding to the realistic situations. Temporal dispersion can be arbitrary subject to the physical limitations imposed by the Kramers-Kronig relations. A numerical model based on the Z -transform is developed to verify the analytical results. The approach can be applied to arbitrary periodic refractive index profiles using the Fourier series method.

The effective refractive index of the active region of 1.3 μm edge-emitting tilted wave lasers based on InAs/InGaAs self-assembled quantum dots by the analysis of the far-field pattern is investigated. The obtained values of 3.485 and 3.487 in the operating lasers and in the cold waveguides, respectively, are well comparable with the refractive index of bulk InAs at corresponding wavelength.

Triangular nanowires that present a high birefringence and a very strong confinement were fabricated by tapering suspended-core fibers (SCFs) down to core diameters below 1000 nm. Each nanowire presented a high birefringence with an order of magnitude of 10 ⁻³ . As the spectra of the SCF tapers inserted in fiber loop mirrors can be used to generate a sinusoidal interference pattern from the two main modes (fast and slow axis), a nanowire was employed as a sensing element in a Sagnac interferometer for measuring temperature. Temperature sensitivity was determined to be -56.2  pm/K using a triangular nanowire of 810 nm in-circle diameter when compared with that of a conventional untapered SCF whose temperature sensitivity is −2.1  pm/K .

We investigated a multilayer graphene–dielectric composite material, comprising graphene sheets separated by subwavelength-thick dielectric spacer, and found it to exhibit hyperbolic isofrequency wavevector dispersion at far- and mid-infrared frequencies, allowing propagation of waves that would be otherwise evanescent in an isotropic dielectric. Electrostatic biasing was considered for tunable and controllable transition from hyperbolic to elliptic dispersion. We explored the validity and limitation of the effective medium approximation (EMA) for modeling wave propagation and cutoff of the propagating spatial spectrum due to the Brillouin zone edge. We reported that EMA is capable of predicting the transition of the isofrequency dispersion diagram under certain conditions. The graphene-based composite material allows propagation of backward waves under the hyperbolic dispersion regime and of forward waves under the elliptic regime. Transition from hyperbolic to elliptic dispersion regimes is governed by the transverse epsilon-near-zero (TENZ) condition, which implies a flatter and wider propagating spectrum with higher attenuation, when compared to the hyperbolic regime. We also investigated the wide-angle tunable transparency of the multilayer at that condition in contrast to other materials exhibiting ENZ phenomena.

A monolithic quasi-solid-state dye-sensitized solar cell (DSSC) based on graphene-modified mesoscopic carbon-counter electrode is developed. A TiO ₂ -working electrode layer, ZrO ₂ spacer layer, and carbon counter electrode layer were constructed on a single conducting glass substrate by screen printing. The quasi-solid-state polymer gel electrolyte employed a polymer composite as the gelator, and effectively infiltrated the porous layers. Fabricated with normal carbon-counter electrode (NC-CE) containing graphite and carbon black, the DSSC had a power conversion efficiency (PCE) of 5.09% with the fill factor of 0.63 at 100  mW cm ⁻² AM1.5 illumination. When the NC-CE was modified with graphene sheets, the PCE and fill factor were enhanced to 6.27% and 0.71, respectively. This improvement indicates excellent conductivity and high electrocatalytic activity of the graphene sheets, which have been considered as a promising platinum-free electrode material for DSSCs.

Symmetric metallo-dielectric multilayered stacks (MDMS) are investigated to improve the spatial resolution of subwavelength imaging operated in canalization regime. Simulation results revealed that subwavelength imaging capability is very sensitive to the thickness and material of the MDMS terminal layers. Furthermore, the coupling and decoupling of the Bloch modes in MDMS, between the object and image space, strongly depend on the terminal layer parameters which can be tuned to achieve the optimal imaging improvement. In contrast to metal-dielectric periodic MDMS, using MDMS with the developed symmetric surface termination, subwavelength imaging with optimal intensity throughput and improved field spatial resolution (∼20.4% ) can be obtained. Moreover, optical singularity, in the form of Poynting vector saddle point, has been found in the free space after lens exit for the two kinds of symmetric MDMS that exhibit improved superresolution imaging performance with 100% energy flux visibility. The improved subwavelength imaging capabilities, offered by this proposed termination design method, may find potential applications in the areas of biological imaging, sensing, and deep subwavelength lithography, and many others.

Surface-enhanced Raman spectroscopy (SERS) biotags (SBTs) that carry peptides as cell recognition moieties were made from polymer-encapsulated silver nanoparticle dimers, infused with unique Raman reporter molecules. We previously demonstrated their potential use for identification of malignant cells, a central goal in cancer research, through a multiplexed, ratiometric method that can confidently distinguish between cancerous and noncancerous epithelial prostate cells in vitro based on receptor overexpression. Progress has been made toward the application of this quantitative methodology for the identification of cancer cells in a microfluidic flow-focusing device. Beads are used as cell mimics to evaluate the devices. Cells (and beads) are simultaneously incubated with two sets of SBTs while in suspension, then injected into the device for laser interrogation under flow. Each cell event is characterized by a composite Raman spectrum, deconvoluted into its single components to ultimately determine their relative contribution. We have found that using SBTs ratiometrically can provide cell identification in flow, insensitive to normal causes of uncertainty in optical measurements such as variations in focal plane, cell concentration, autofluorescence, and turbidity.

The electric currents induced by infrared radiation incident on optical antennas and resonant structures increase their temperature through Joule heating as well as change their electric resistance through the bolometric effect. As the thermo-electric mechanism exists throughout a distributed bolometer, a multiphysics approach was adopted to analyze thermal, electrical, and electromagnetic effects in a dipole antenna functioning as a resonant distributed bolometer. The finite element method was used for electromagnetic and thermal considerations. The results showed that bolometric performance depends on the choice of materials, the geometry of the resonant structure, the thickness of an insulating layer, and the characteristics of a bias circuit. Materials with large skin depth and small thermal conductivity are desirable. The thickness of the SiO ₂ insulating layer should not exceed 1.2 μm, and a current source for the bias circuit enhances performance. An optimized device designed with the previously stated design rules provides a response increase of two orders of magnitude compared to previously reported devices using the same dipole geometry.

Brillouin light scattering (BLS) and picosecond laser ultrasonics (PLU) are two noncontact optical techniques that have garnered significant interest for thin film elastic constant measurements. PLU and BLS measurements were utilized to determine the elastic constants of 100 to 500 nm thick nanoporous low-k dielectric materials of significant interest for reducing capacitive delays in nanoelectronic interconnect circuits. PLU measurements with and without a metal acousto-optic transducer are described in detail and compared to previously reported BLS measurements. The values of Young’s modulus determined by both BLS and PLU were found to be in excellent agreement and consistent with nanoindentation measurements on thicker 2 micrometer films. While successful BLS measurements were achieved for films as thin as 100 nm, PLU measurements were limited to <∼200  nm thick films due to experimental constraints on observing acoustic pulses in thinner films. However, these results clearly demonstrate the capability of both BLS and PLU to determine the elastic constants of low-k dielectric materials at the desired thickness targets for future nanoelectronic interconnect technologies.

Tight confinement of light in photonic cavities helps realize high optical intensity with strong field gradients. We designed a nanoscale resonator device based on a one-dimensional photonic crystal slot cavity. Our design allows for highly localized optical modes with theoretically predicted quality factors (Q factors) in excess of 10⁶ . The design was implemented experimentally both in a high-contrast refractive index system (silicon), as well as in medium refractive-index-contrast devices made from aluminum nitride. We achieved an extinction ratio of 21 dB in critically coupled resonators using an on-chip readout platform with loaded Q as high as 33,000. Our approach holds promise for ultrasmall optomechanical resonators for high-frequency operation and sensing applications.

An all optical Viterbi decoder, realized on a silicon chip was designed. The device relies on mode coupling inside a ring resonator, and is composed of an optical memory cell and two interfering input arms that use QPSK modulation to encode the incoming bits. The device has a dimension of a few micrometers, and is capable of processing bits with a length of just a few picoseconds. The approach chosen in this research demonstrates the capability to design all-optical processing units which are not composed of single building blocks.

We devise a method to design quarter-wave dielectric multilayers, which exhibit reflection properties approximating a given reflection spectrum. The method can be used as a design procedure for N-band antireflection coatings. Dual- and three-band antireflection coatings are designed using this method.

Electric conduction in structures containing fullerenes was simulated. The electric current was calculated as a function of the bias voltage using the Landauer approach, thereby connecting charge transport with the transmission of electrons. To obtain the transmission matrix components, the supplementary problem of the electron scattering by the model potential was solved. Three types of structures were considered: a single fullerene molecule, a dimer of fullerenes, and a cluster of eight fullerenes. The current-voltage characteristics of these structures may have negative-conductance regions which make it possible to use them as active components of nanoelectronic devices.

The dependence of photon absorption by a low-dimensional cadmium-sulfide/cadmium-telluride (CdS/CdTe) heterostructured absorber on the thickness and number of CdTe active layers is investigated. The equation for the photon absorption coefficient (α) used is based on the partial momentum k-selection approach. Theoretical results show that absorption greater than 4×10⁴  cm⁻¹ is obtained when the thickness of the active layer reaches 50 Å. Similarly, with each additional CdTe active layer in the heterostructured absorber, a relative increase of 0.5×10⁴  cm⁻¹ in photon absorption is achieved. The relation between photoelectric quantum efficiency and photon absorption is determined by the number and thickness of the CdTe active layers in the heterostructured absorber. A quantum efficiency greater than 0.9 is obtained using 15 active layers with a thickness of 50 Å.

Nanotechnology has progressed by leaps and bounds since it became the focus of intense applied research activity in the late 20th century. In particular, thin films with engineered structures at nanometer length scales have figured prominently in this nanotechnological revolution. Their unique and sometimes exotic and counterintuitive properties present engineers and scientists with tantalizing opportunities and often demanding challenges. The list of potential applications for nanostructured thin films grows longer each year. This growth is matched, and often fueled, by the ever more complex nanostructures that can be achieved in practice due to advances in manufacturing techniques. The annual Nanostructured Thin Films conference, which is a constituent of the SPIE Optics + Photonics annual meeting, provides a forum for the exchange of the most recent developments in this rapidly developing field.

Sculptured thin films (STFs) are nano-engineered materials that have controllable porosity, structural chirality, and periodicity in one, two, or three dimensions. They have been exploited in developing optical elements such as thin-film filters, polarizers, sensors, and waveguides for integrated optics. A grating theory-based modeling approach for STFs as fully three-dimensional (3-D) periodic structures is developed. Input for this model consists of a structural parameter set that is easily accessible experimentally. This parameter set is common to evaluating STFs from a fabrication as well as modeling perspective and thus furnishes a basis for developing appropriate process monitoring and control methods necessary for successful commercial production. Using the proposed model, a quantitative understanding of the limits of applicability of traditional modeling methods for STFs and guidelines for robust design of STF-based devices are developed. This knowledge gained is applied to explore STFs in two illustrative examples: (1) as a notch filter and (2) as a 3-D photonic crystal.

Random metallic films have very specific optical properties due to disorder. Strong localization of electromagnetic fields can be observed due to plasmons. This localization strongly depends on excitation conditions, and different optical regimes can exist. To characterize these regimes, we investigated the spatial intensity correlation functions using near-field scanning optical microscopy for different excitation wavelengths and different incident polarization states. The transition between a weak scattering regime where no plasmon resonances are excited and a regime where strong plasmon resonances occur has clearly been observed. In the strong plasmonic regime, by varying the incident polarization direction, the shape of the correlation function has been correlated to the intensity enhancement which raises the possibility to control the intensity localization using the incident polarization state.

Collagen thin films consisting of randomly oriented and oriented collagen fibrils/fibers are fabricated by hydrodynamic flow and spin coating, and then they are characterized by atomic force microscopy (AFM). Fibroblasts are cultured on these films in order to correlate their morphology and alignment, which are assessed with fluorescence and AFM imaging with different film characteristics. The results showed that the formed films could be used as substrates for culturing cells. Furthermore, cells reacted to film nanocharacteristics and especially to the orientation of fibrils/fibers. The investigation of the influence that the substrate nanotopography has on cells will help to elucidate the mechanisms of cell–biomaterial interactions, and will enable the design of intelligent coatings for implants and tissue engineering purposes.

A structurally right-handed chiral sculptured thin film (STF) with a central 90 deg-twist defect was made by thermal evaporation of chalcogenide glass and the use of a serial bi-deposition process to exhibit a narrowband hole in the spectrum of the right-circularly polarized light reflected when right-circularly polarized light is normally incident on the chiral STF. In an attempt to build a tunable filter, the chiral STF was then infiltrated with a highly birefringent nematic liquid crystal (LC), which caused a linear reflectance peak to redshift by ∼350  nm . But the circular Bragg phenomenon exhibited by the uninfiltrated chiral STF was greatly diminished owing to the similarity in the constitutive properties of the LC and the chalcogenide glass. No temperature dependence of the shifted peak was observed, which provided clear evidence that the LC molecules are not ordered inside the chiral STF but are randomly aligned instead.

The dependence of magnitude of the electric near-field on the separation between metal nanoparticles for surface-enhanced Raman spectroscopy (SERS) substrates was experimentally verified. Diameters of gold-coated nanopores in a ceramic alumina substrate were varied to study the charge buildup near interparticle junctions and its effect on the enhancement factor due to SERS. The substrates were characterized by sensing a Rhodamine dye and calculating the associated Raman enhancement factors. Decreasing Au interparticle distance increases the electric near-field and shifts the plasmon resonance peak accordingly.

Many attempts have been made to fully explore flexibility, resistance to corrosion, and processing advantage of epoxy resin filled with carbon nanotubes (CNTs) as conductive filler, although sometimes with a certain degradation of polymers’ intrinsic properties. It is important to move the percolation threshold into the region of smaller CNTs’ concentration. The results of a broadband dielectric investigation of multiwalled CNT (MWCNT)/epoxy resin composites in wide temperature range from room temperature to 450 K were analyzed for percolation. Far below the percolation threshold (0.25 wt. % MWCNT) the dielectric properties of the composite are mostly determined by alpha relaxation in pure polymer matrix and the freezing temperature decreases due to the extra free volume at the polymer–filler interface. Close to the percolation threshold, the composite shows the negative temperature coefficient effect in the temperature region, where the pure polymer matrix becomes conductive. The activation energy of DC conductivity increases with the MWCNT concentration far below the percolation threshold and decreases close to it (1.5 wt. % MWCNT). The dielectric analysis of the MWCNT/epoxy resin reveals a significant influence of the polymer matrix on the temperature dependence of composite dielectric properties.

Three different antireflecting structures (ARS), namely, single-diameter nanorods, dual-diameter nanorods, and biomimetic nanotips (resembling moth-eye’s submicrostructures) were compared to each other analytically for their reflectivities, using finite difference time domain calculations. Simulation results establish the biomimetic nanotips as better ARS than the others, in the visible and near-infrared wavelength zone and over a wider angle of incidence. The reflectance values in the nanotips are significantly lower compared to both types of nanorods and also the planar silicon below the Brewster angle (∼75  deg ). The low antireflection translated to enhanced optical absorption in these subwavelength structures. A general antireflection design rule emerged from the simulation results.

We experimentally investigated the electrical and electromagnetic (EM) properties of pyrolytic carbon (PyC) ultrathin films synthesized on a quartz substrate by chemical vapor deposition at 1100°C using low pressure CH4∶H2 gas mixture as carbon source. PyC films consist of randomly oriented and intertwined graphene ribbons, which have a typical size of a few nanometers. We discovered that the manufactured PyC films of 35-nm thickness provided remarkably high attenuation caused by absorption of 37% to 24% of incident microwave power. The temperature dependence of PyC’s direct-current (DC) conductivity represents typical behavior for disordered systems. Being semitransparent in visible and infrared spectral range and highly conductive at room temperature, PyC films emerge as a promising material for manufacturing ultrathin microwave (e.g., Ka band) coatings to be used in aerospace applications.

A self-assembled polytetrafluoroethylene (PTFE) nanostructure is deposited on microcrystalline diamond (MCD) films, by use of physical and chemical vapor deposition in a two-step process, to produce (fully) superhydrophobic surfaces: high water contact angle (static, 165±2  deg ), very low hysteresis (dynamic, ∼4  deg ), and associated sliding angle (1 deg 5 ′ ±15 ′ ), thus combining the diamond infrared transparency and self-cleaning properties. These are interpreted in light of Wenzel and Cassie-Baxter wetting models, associated with structural microscopy of nano-micro rough PTFE/MCD surfaces, and present a promising perspective for self-cleaning infrared optics applications.

Although the physics of structural color has been investigated, it remains a challenge to create artificial replicas of the natural photonic crystal structure. The concave multilayer replica of Papilio blumei butterflies is successfully fabricated by the following three main steps: self assembly of polystyrene spheres, deposition using an electron-beam gun, and inductively coupled plasma etching. The green iridescence of the wings of P. blumei is successfully reproduced.

Even prior to the recent advent of advanced top-down processes, shadowing growth by oblique angle deposition (OAD) has long been providing self-assembled nanostructures over much larger areas for much lower costs. In the past two decades, significant progress has been made in the development of well-controlled three-dimensional nanomorphologies such as zigzags and helixes. Much effort has been put into theoretical and numerical understanding of the growth mechanism to improve morphology. Many researchers in academia have been investigating useful properties of nanocolumnar thin films in their laboratories. However, most companies seem hesitant to introduce OAD techniques into the factory, owing to the prejudice that the OAD thin films are neither durable nor reproducible. The progress in OAD technology for practical applications is reviewed and discussed.

Chiral sculptured thin films (STFs) produced by substrate rotation during physical vapor deposition exhibit the circular Bragg phenomenon, whereby normally incident left- and right-circularly polarized plane waves are discriminated in a spectral regime called the circular Bragg regime. Theory had predicted that substrate rocking, in synchrony with substrate rotation, during deposition could suppress the propensity to exhibit the circular Bragg phenomenon. Therefore chiral STFs of a dielectric material were fabricated with/without substrate rocking, and their transmittance spectrums for incident linearly and circularly polarized plane waves were measured. With sufficient rocking amplitude, the discrimination between incident left- and right-circularly polarized light nearly vanished, whereas a Bragg phenomenon for all normally incident plane waves was observed. Thus, chiral STF technology can be used to produce both ordinary and circular-polarization Bragg filters.

Nanobiotechnology is the convergent field of nanotechnology and biotechnology, and it has received a lot of attention in the 21st century. Typical technical fields of nanobiotechnology are the design and synthesis of biological molecules with new functionality, nanobiosensors, nanoimaging technology of cell and biosystems, and nanomaterials for drug delivery and therapy. Nanotechnology based on the structure and principle of biomaterials is the emerging field to develop new nanodevices and systems that were not possible with existing macroscale technology. It is evaluated as a core technology that can lead to new industries in the 21st century.

The evanescent field–based polymeric planar waveguide refractive index sensors having a high Q Fabry–Pérot (FP) cavity between identical dual Bragg gratings corrugated on the surface of the planar waveguide were developed. The FP Bragg gratings cavity was fabricated with a cavity size of 5 and 7 mm, respectively. The spectra of light reflected from fabricated Bragg gratings, which were butt joined, were measured and compared with different indices of surrounding media. It was obtained that the FP Bragg gratings cavity is more sensitive than the single Bragg grating. The sensor developed shows much promise in the application of biomedical diagnostics such as a biosensor and/or environmental monitoring systems.

The precise detection of chemicals and biomolecules is of great interest in the areas of biotechnology and medical diagnostics. Thus, there is a need for highly sensitive, small area, and low-cost sensors. We fabricated and optically characterized hydrogenated amorphous silicon photonic resonators for label-free lab-on-chip biosensors. The sensing was performed with small-footprint microdisk and microring resonators that detect a refractive-index change via the evanescent electric field. Homogeneous sensing with NaCl and surface-sensing experiments with immobilized bovine serum albumin (BSA) were carried out. A sensitivity as high as 460  nm/RIU was measured for NaCl dissolved in deionized water for the disk, whereas about 50  nm/RIU was determined for the ring resonator. The intrinsic limits of detection were calculated to be 3.3×10 ⁻⁴ and 3.2×10 ⁻³ at 1550-nm wavelength. We measured the binding of BSA to functionalized ring resonators and found that molecular masses can be detected down to the clinically relevant femtogram regime. The detection and quantification of related analytes with hydrogenated amorphous silicon photonic sensors can be used in medical healthcare diagnostics like point-of-care-testing and biotechnological screening.

Recently, mouse neuroblastoma cells have been considered as an attractive model for the study of human neurological and prion diseases, and they have been intensively used as a model system in different areas. For example, the differentiation of neuro2a (N2A) cells, receptor-mediated ion current, and glutamate-induced physiological responses have been actively investigated with these cells. These mouse neuroblastoma N2A cells are of interest because they grow faster than other cells of neural origin and have a number of other advantages. The calcium oscillations and neural spikes of mouse neuroblastoma N2A cells in epileptic conditions are evaluated. Based on our observations of neural spikes in these cells with our proposed imaging modality, we reported that they can be an important model in epileptic activity studies. We concluded that mouse neuroblastoma N2A cells produce epileptic spikes in vitro in the same way as those produced by neurons or astrocytes. This evidence suggests that increased levels of neurotransmitter release due to the enhancement of free calcium from 4-aminopyridine causes the mouse neuroblastoma N2A cells to produce epileptic spikes and calcium oscillations.

The carrier concentration injected from a silicon substrate to a copper phthalocyanine thin film was found to depend on the incidence polarization of the photoexciting beam. The modulation efficiency of terahertz transmission due to transverse-magnetic (TM)-polarized excitation is distinctly higher than that due to transverse-electric (TE)-polarized excitation. Underlying this difference is the enhancement of carrier injection when the TM-polarized light is more transmitted through the surface of organic thin films than the TE-polarization light.

An optical near field should promote phonon-assisted multiple excitation in nanoscale structures. With the phonon-assisted process, greater catalytic activity is expected without heating. To confirm this effect, photo-induced current generation using platinum black electrodes in ferricyanide solution (an absorption band-edge wavelength of 470 nm) under visible light irradiation continuous wave [(CW), λ=532  nm ] was observed. Higher order dependence of the generated current density on the incident light power was observed, indicating two-step activation of electron transfer, which originated from the phonon-assisted near-field effect on the nanostructured surface of the electrode.

In order to observe the morphology of nanostructures at the submicroscale, we use a confocal laser scanning (CLS) microscope built in our laboratory. The theoretical resolution of the hand-made CLS microscope is 150 nm and the performance of the microscope is evaluated by observing a USAF target. Vanadium pentoxide nanorods grown by electron beam irradiation and thermal oxidation methods are used as nanostructures and the morphologies of the nanorods observed by confocal laser scanning microscopy (CLSM) are compared with those obtained by scanning electron microscopy. The magnification and resolution of the CLSM were estimated to be approximately 1500 and 800 nm, respectively. From the results, we confirm that the CLSM can be used to measure nanostructures at the sub-micro-scale without a preconditioning process.

Well-ordered Ag nanodot array on indium-tin-oxide (ITO) glass is adopted as a sensor platform based on surface-enhanced Raman scattering (SERS). SERS has attracted extensive attention in the development of sensitive chemical or biological sensors due to its property of the amplification of electromagnetic fields on a metal nanostructure. The key issue for the applications of SERS is to secure the fabrication technique of a noble metal nanostructured surface. For an SERS-active surface with stability and reproducibility, a Ag nanodot array is fabricated on the ITO glass using a nanoporous alumina mask with uniform through holes. The signal intensity of SERS from methylene blue (MB) adsorbed on the Ag nanodot array showed much stronger scattering than the one from the Ag film of 50-nm thick. The SERS intensity on the Ag nanodot array is consistently enhanced by increased concentration of MB. These results confirm that the Ag nanodot array on ITO glass can be utilized as a stable platform for the sensitive detection of chemical materials based on SERS.

An optical method of measuring the number of layers in a graphene sample is formulated and compared with the conventional surface plasmon resonance (SPR) detection scheme, the latter being appropriate only for a very few graphene layers. Numerical results based on transfer-matrix method support that an alternative method, wherein the SPR substrate includes a dielectric overlayer, is feasible over a wide range of graphene layer numbers. While the multilayer graphene may lead to a broad and shallow SPR curve owing to the nonzero imaginary part in its relative permittivity, the dielectric overlayer makes the resonant surface plasmons less affected by graphene, resulting in a strong and deep absorption band at resonance. Linear regression analysis shows that the measurable graphene layer number can be as high as 50.

One-dimensional compound semiconductor nanolasers, especially nanowire (NW)-based nanolasers utilizing III-nitride (AlGaInN) materials system, are an emerging and promising area of research. Significant achievements have been made in developing III-nitride NW lasers with emission wavelengths from the deep ultraviolet (UV) to the near-infrared spectral range. The types of lasers under investigation include Fabry-Pérot, photonic crystal, plasmonic, ring resonator, microstadium, random, polariton, and two-dimensional distributed feedback lasers. The lasing thresholds vary by several orders of magnitude, which are a direct consequence of differing NW dimensions, quality of the NWs, characteristics of NW cavities, and coupling with the substrate. For electrically injected, such as ultralow-threshold and continuous-wave III-nitride NW lasers that can operate at room temperature, the following obstacles remain: carrier loss mechanisms including defect-related nonradiative surface recombination, electron overflow, and poor hole transport; low radiative recombination efficiency and high surface recombination; poor thermal management; and highly resistive ohmic contacts on the p-layer. These obstacles must be overcome to fully realize the potential of these lasers.

Miniaturized optical instruments have become very important in industry as smart phones and tablet PCs increase in popularity. A chronology of spectrometer development shows that a simple numerical point of view affords important insights. A tiny spectrometer, which is smaller than a few millimeters size, cannot easily rely on the conventional Fraunhofer diffraction due to its optical criterion limit. As an alternate solution to build smaller spectrometers, a Fresnel spectrometer chip with a gradient line grating is attractive. The fabricated Fresnel spectrometers have optical path volumes of about 1 mm3 and spectral resolutions of 10 to 23 nm.

Nonlinear effects can be enhanced and tailored on a subwavelength scale by taking advantage of high field confinement by selective coupling among resonant plasmonic nanostructures, called plasmonic nanoresonators and nanoantennas. In particular, we focus our attention on the process of second-harmonic (SH) generation. Excitation of localized surface plasmon polaritons at the fundamental frequency in these structures can remarkably modify the response of the system by enhancing surface and/or bulk nonlinear contributions to the overall SH field. Moreover, the radiation pattern of the generated field can be controlled and directed. Indeed, the overall structure behaves as a nonlinear nanoantenna for the SH harmonic field, whose emission pattern can be tailored.

Advances in computational power over the last few decades have dramatically opened up the modeling capability of the typical researcher. Although laborious analysis and approximations of physical systems were quite the norm some decades ago, today complex problems can be simulated extensively before being built or committed to design. Today, the pursuit of computational experimentation has displaced, to a large extent, either laboratory experimentation or extensive theoretical analysis, especially in systems in which the governing equations are well developed. Indeed, in the field of electromagnetics (EM), where only select canonical problems are amenable to analytical solutions, computer simulations have allowed for great flexibility in searching for new applications to Maxwell’s equations. In light of this flexibility, however, one should not abandon completely either the approaches or models researchers have developed over the years.

A thin light beam, such as that emitted by a laser, may possess a hidden rotational structure, invisible to the naked eye. This structure is rooted in the electromagnetic wave nature of light and it takes two distinct forms, which may be dubbed spin and twist. Spin is associated with the rotation of the electric and magnetic fields oscillating within the optical wave—i.e., the circular polarization of light. Twist instead occurs in light waves having a helical-shaped (or twisted) wavefront and an optical vortex located at the beam axis. When a free material particle absorbs light having spin or twist, it is itself made to spin—in other words, the light exerts a rotational form of radiation pressure, showing that this kind of light carries angular momentum. More specifically, the angular momentum of light having circular polarization is named as spin angular momentum (SAM), while that associated with a spiral wavefront is called orbital angular momentum (OAM). The OAM of light has recently been attracting much attention for its possible technological applications in the areas of particle manipulation, optical sensing, and classical and quantum optical communication.

During the last two decades, the deployment of solar cells for the direct generation of electricity has been quite notable, and photovoltaic (PV) systems can at present be considered as a mature technology that is often incorporated in utilities portfolios. Of all sources of renewable energy, PV solar cells probably constitute the best example illustrating the technology-learning mechanism. The last decade has seen a real fall of prices of PV solar cells after the silicon shortages of the 2003 to 2006 period. Figure 1 shows in a log-log space the cost (in constant 2012 dollars) evolution of PV modules in relation to the cumulative1 installed capacity, which at present is about 100 GW in the whole world.^1,2

Microlenses have diameters about 1 mm and smaller. Highly focused, the authors waste no space in this monograph to get from Robert Hooke’s experiments to 21st-century science in just three sentences right on p. 1. Clearly, the reader will get a concise description of the state of art in microlenses from this volume.

Stefano Cabrini and Satoshi Kawata, Eds., 546 pages, 463 illustrations, ISBN: 978-1-4200-9052-9 (hardback) and 978-1-4200-9053-6 (eBook), CRC Press, Boca Raton (2012), £82.00 (hardback). Reviewed by Raúl J. Martín-Palma, Departamento de Física Aplicada, Universidad Autónoma de Madrid, 28049 Cantoblanco, Madrid, Spain, rauljose.martin@uam.es

Hwi Kim, Junghyun Park, and Byoungho Lee, 2012, ISBN-10: 1420088386, ISBN-13: 9781420088380, xii+313 pages, CRC Press, Boca Raton, $179.95 hardcover, $125 e-book. LCCN: 2011046920, OCLC:768728882Reviewed by Chandraprakash Chindam, Pennsylvania State University, Department of Engineering Science and Mechanics, University Park, Pennsylvania 16802, USA

The pharmaceutical and biotech industries face difficult problems. Namely, enormous amounts of capital are spent on research and development, but a very small number of tested compounds become truly marketable. Moreover, many of the compounds currently on the market are, in essence, evolutionary designed. Thus, although it is equipped with the most advanced technology and backed up with a comprehensive theoretical framework, the current biotech industry lags in productivity when compared to the old-style, animal-model-based research. Some researchers have expressed their belief in a need for a paradigm shift. But what might that paradigm shift be? It may be a new way to screen and test molecules, but it could also be an introduction of a completely new set of molecular building blocks. The new book by G. A. Mansoori et al. on diamondoid molecules may be one of the first steps toward that shift. Diamondoid Molecules is a thorough presentation of current and future applications of diamondoids. It is composed of seven chapters and a comprehensive glossary. Every chapter is excellently illustrated with plenty of clearly designed figures and graphs and well-organized tables.