We propose a different type of asymmetric photonic crystal waveguide to achieve slow light with improved normalized delay-bandwidth product and low group velocity dispersion. The lateral symmetry of the proposed waveguide is broken by periodically shifting the two rows of air holes adjacent to the line defect. Under two simple different procedures of shifting air holes, the group indices of 41, 50, 68, and 114 with bandwidths over 14.9, 11, 7.8, and 4.7 nm, and the group indices of 43, 54, 73, and 124 with bandwidths over 13.9, 10.4, 7.1, and 4.3 nm around 1550 nm are obtained, respectively. Low-dispersion slow light propagation is confirmed by studying the relative temporal pulse-width spreading with the two-dimensional finite-difference time-domain method.
Ultrafast-photonic logic circuits are crucial elements to perform ultrafast-optical signal processing functions in the next-generation ultrahigh-speed networks. A 160 Gbit/s all-optical data distributor based on cross-phase modulation in a single highly nonlinear fiber is investigated and demonstrated. The numerical calculation is conducted, and the result shows that the data distributor can be realized in 160 Gbit/s for the data signals of return-to-zero format with logical correctness and high quality. To evaluate the performance of the scheme, the Q-factor of the output signal on signal wavelength, the peak power of signals, the initial delay, and the filter position are calculated and discussed, respectively. The proposed data distributor is suitable for ultrafast applications for the emerging all-optical networks.
KEYWORDS: Raman spectroscopy, Quantitative analysis, Chemical analysis, Molecules, Spectroscopy, Sodium, Potassium, Industrial chemicals, Raw materials, Process control
Raman spectroscopy combines the fingerprinting advantage of mid-JR spectroscopy with the ease of use and remote,
non-invasive capability of near-JR spectroscopy. Now, Raman spectroscopy is fast becoming a perfect technique of
analysis in raw material identification, verification, process control in biological, chemical and industrial fields, because
Raman spectra are a fingerprint for the molecular species present in a specimen and can be used for both qualitative
identification and quantitative determination. This paper introduces that low-resolution Raman spectroscopy (LRRS)
satisfies the need for a highly useful, low-cost spectroscopic approach to both qualitative and quantitative analyses. First
the principles and methods of analyses were introduced, especially quantitative analyses based on ratio method, and then
several applications were described, which were representatives of qualitative and quantitative analyses. Secondly, these
experimental results were discussed and analyzed in detail. The results show that the Raman spectroscopy technology is
flexible, affordable and easily adapted to on-site and in situ analysis.
By means of Artificial Neural Network and Back-Propagation algorithm, the multi-component of azo-dyes can be
qualitatively and quantitatively analyzed simultaneously, though their Raman spectra are overlapped. This article
designed a Back-Propagation algorithm network to analyze the multi-component of azo-dyes (Sudan I and Sudan III). In
conclusion, by using the Artificial Neural Network and Raman spectrum can be a good choice for resolving
multi-component.
The characterization of species in aqueous solutions has presented a challenge to analytical and physical chemist,
because the JR absorption of the aqueous solvent is so intense that it becomes difficult to observe the solute in the water
by JR absorption. In contrast, Raman spectrum of the solute is unaffected by the water, so the weak scattering of water
makes the technique well suited to aqueous samples, and the Raman spectrum exhibits well-defined bands corresponding
to fundamental modes of vibration. In addition, Raman spectroscopy has some inherent advantages in aqueous solution
analysis, because the spectral features of signals from different species are much more distinct, and it provides
characteristic signatures for samples, such as blood, protein and cholesterol. All the advantages make Raman
spectroscopy be a potential alternative for the study of aqueous solutions. Now, Raman spectroscopy has been applied to
studying samples in aqueous solutions, blood serum, intracellular protein levels. Now, industrial wasted water contains
many organic contaminants, and it is necessary to determine and monitor these contaminants. The paper first introduces
Raman spectroscopy, and then describes its applications to determining the components in aqueous solutions, analyzes
and assignes the Raman spectra of o-dichlorobenzene, o-xylene, m-xyiene and p-xylene in detail. The experimental
results demonstrate that Raman spectroscopy is a particularly powerful technique for aqueous solutions analyses.
Being an industrial dye, the Sudan I may have a toxic effect after oral intake on the body, and has recently been shown to cause cancer in rats, mice and rabbits. Because China and some other countries have detected the Sudan I in samples of the hot chilli powder and the chilli products, it is necessary to study the characteristics of this dye. As one kind of molecule scattering spectroscopy, Raman spectroscopy is characterized by the frequency excursion caused by interactions of molecules and photons. The frequency excursion reflects the margin between certain two vibrational or rotational energy states, and shows the information of the molecule. Because Raman spectroscopy can provides quick, easy, reproducible, and non-destructive analysis, both qualitative and quantitative, with no sample preparation required, Raman spectroscopy has been a particularly promising technique for analyzing the characteristics and structures of molecules, especially organic ones. Now, it has a broad application in biological, chemical, environmental and industrial applications. This paper firstly introduces Sudan I dye and the Raman spectroscopy technology, and then describes its application to the Sudan I. Secondly, the fingerprint spectra of the Sudan I are respectively assigned and analyzed in detail. Finally, the conclusion that the Raman spectroscopy technology is a powerful tool to determine the Sudan I is drawn.
Laser-induced ultrasonic technology has been extensively studied and widely applied recently, for its advantages such as noncontract operation, nondestructive testing, broad bandwidth, high time, and space resolution, no shape limits on samples, etc. Firstly, the principles of laser ultrasonic generation and detection were introduced. Secondly, the application of the ultrasonic ratio method in measuring the surface defects was presented in detail. The experimental results were analyzed. Because the ratio method avoids measuring the velocity of the surface wave and reduces the experimental error, it is much more practical, reliable and effective in surface defect measurements.
Raman Spectroscopy is a molecular vibrational spectroscopic technique based on the Raman effect, which is characterized by the frequency shift that caused by interactions of molecule and photon and shows the information in molecules. There are many advantages to study the sample with Raman spectroscopy, such as simple system structure with relative lower cost, wide variety of detectable masses, nondestructive detect for multicomponent sample, good sensitivity, feasibility of real-time analysis and online examination assisted with optical fiber and computers, etc. As a powerful tool for quantitative or qualitative analysis, Raman spectroscopy has been employed to solve certain unique problems in chemical and environmental analysis and in industrial process monitoring and control. Now, there are many kinds of organic contaminants, particularly aromatic molecules, in industrial waste water, so it is essential to determine and monitor these contaminants. This paper analyzed the Raman spectra of benzene and benzene derivatives (toluene, ethylbenzene, chlorobenzene, and nitrobenzene) in detail, and assigned their Raman identified spectra. The results show that Raman spectroscopy is useful to analyze benzene derivatives in waste water.
As a new branch of ultrasonics, laser-induced ultrasonics is developed quickly, and has wide applications in many areas recently, for its advantages such as non-contract operation, non-destructive testing, broad bandwidth, high time resolution, high space resolution, no shape limits on samples, etc. Firstly, the principles of the laser-induced ultrasonic generation, e.g., the thermoelastic excitation theory and the ablation excitation theory, were introduced. This paper also described the laser-induced ultrasonic detection by means of the confocal Fabry-Perot interferometer (CFPI). And then its applications in non-destructive testing in solids were introduced in detail. Based on the principles of the laser-induced ultrasonic generation and detection, the structure of the laser ultrasonic detection system was presented. From the velocities of compress wave and surface wave measured by the detection system, elastic constants of aluminium were worked out. The experimental results were in good accordance with the theoretical predictions, which demonstrated that laser ultrasonic technique is practical, reliable and effective. Future prospects for such technology were pointed out finally.
Grating-type substrates with nanometer dimensions offer the possibility of enhancing the electromagnetic field close to surface. Binary silver grating has been used to investigate the Surface-enhanced Raman Scattering (SERS). This paper describes the electromagnetic theory of SERS effect on the surface of a binary silver grating with nanometer dimension and discusses the TM-polarized incident light because surface plasmons excitation require this polarization . Laplacian's equation is given for this model in the grating region. We use the rigorous coupled wave analysis (RCWA) to solve the Maxwell differential equations in the grating region . The consideration of optimum incident angles for different gratings is also shown by analyzing the surface plasmon (SP) excitation . SERS enhancement factor is considered for binary grating with respect to the influence of angle incidence, grating depth and ratio of grating ridge width to grating period on both surface plasmon and SERS enhancement factor. Compared with the other SERS surface models, such as the isolated spheres model and other irregular models, this one-dimension regular model allows more quantitative estimates of the surface structures for the SERS effect.
With rapid development of electronic imaging and multimedia technology, the telemedicine is applied to modern medical servings in the hospital. Digital medical image is characterized by high resolution, high precision and vast data. The optimized compression algorithm can alleviate restriction in the transmission speed and data storage. This paper describes the characteristics of human vision system based on the physiology structure, and analyses the characteristics of medical image in the telemedicine, then it brings forward an optimized compression algorithm based on wavelet zerotree. After the image is smoothed, it is decomposed with the haar filters. Then the wavelet coefficients are quantified adaptively. Therefore, we can maximize efficiency of compression and achieve better subjective visual image. This algorithm can be applied to image transmission in the telemedicine. In the end, we examined the feasibility of this algorithm with an image transmission experiment in the network.
KEYWORDS: Image segmentation, Medical imaging, Image processing algorithms and systems, Wavelet transforms, Image processing, Magnetic resonance imaging, Tissues, Information fusion, 3D image processing, Brain
A novel method providing a supervised processing of medical image for segmentation is presented. This method was based on a pyramid-structured wavelet-transform and improved watershed transform algorithm. The method contains three consecutive stages: image segmentation based on multi-resolution watershed transform, region projection and mergence with extracted multi-future information, edge refinement based on fuzzy information fusion. In the processing, both texture and gray variation information are used inside the tissue regions, and only gradation information is used near the edges of regions. Experimental results for the proposed algorithm indicate feasibility and reliability for certain medical images segmentation.
KEYWORDS: Charge-coupled devices, Calculus, Spectroscopy, Signal processing, Video, Signal to noise ratio, Image processing, CCD cameras, Image quality, Data acquisition
A design of spectrometer is presented, which uses a holographic grating and a two-dimensional color CCD camera connected with PC via video format port. And in the image post-procession, a real-time frame calculus technique and a non-linear filter were applied to provider higher image quality and better resistant to background noise. With improved designed zoom mechanics, the device has a wide resolution dynamic range and high frequency, since it can gather more spectrum information than linear black-white CCD. The spectrum analysis experiments for water quality detection indicate that the device can meet variant requirements of analysis at low cost.
In this paper, we simulate the quantum channel with a binary symmetric channel and a binary erasure channel, a series channel and a Markovian chain channel in classical information theory, then calculate respectively the mutual information between the signal's deliverer, the legal receiver and the eavesdropper, the bit error rate during propagating the signals with the theory about the quantum measurement channel and the quantum information theory. For B92 protocol, a simple quantum cryptography distribution scheme, we study the bound and the property of mutual information obtained by the legal receiver and the eavesdropper, seek the relationship between the bit error rates and the eavesdropper's way, in two cases of the opaque eavesdropping and the translucent eavesdropping. A new criteria for checking the eavesdropper and ensuring the legal correspondent is estimated. Furthermore, the comparison in bit error rates caused respectively in two different measuring ways indicates that POVM is better than the standard measurement by the way of orthogonal projecting for reducing the bit error rate and increasing effective communication.
In this paper, a novel double encryption technology is presented. It can encrypt data with not only double phase codes, but also the wavelength. The phase keys and the wavelength keys must be known simultaneously to retrieve the encrypting data, otherwise, the reconstructed data will be white noise like. The basic configuration and principle of optical holographic storage system are first introduced. Holographic data storage can be encrypted by coding the phase of reference beams through orthogonal phase coding. Double phase-encoded holographic storage can be done by placing two phase masks on the input plane and FP plane respectively. When one wants to retrieve the data, he must have the same mask placed on the FP plane, otherwise the data can not be reconstructed. Finally, the encrypted holographic storage system combining optical wavelength and double phase codes is presented theoretically, and proved to be valid by the computer simulation.
On the basis of the arrayed waveguide grating (AWG) and the optical fiber grating, a novel kind of dispersion compensation used for fiber communication is presented in this paper. First, a dispersion equation of a uniform fiber grating in the vicinity of its reflection band gap is deduced using the mode-coupled theory. Then, a dispersion compensation of a wavelength division multiplexing (WDM) system is analyzed using the AWG and the uniform fiber grating. Finally, the results of dispersion compensation for an 8-channel WDM system are calculated and discussed. It results in that this method can compensate the dispersion of every channel of the WDM system respectively, and make the compensation efficiency maximum theoretically.
KEYWORDS: Head, Binary data, Optical storage, Optical design, Data storage, 3D optical data storage, Absorption, Near field optics, Optics manufacturing, Diffraction
The two-photon storage technology is discussed for the ultra-high-density three-dimensional optical data storage in this paper. We present the miniatured design of the optical head for the two-photon storage. Binary optical technology is used to obtain the desired reading and writing beams in an integrated optical head. Arrayed optical head system is designed to increase the data transmission speed. This design can reduce the weight and simplify the structure of the optical head system, and is helpful to make the two- photon storage technology commercialized.
The object distance is the important parameter for image recognition and robot 3D view. This paper presents a novel method of pixel dither passive ranging. We derived the mathematical model of ranging, obtains the ranging mirror equation using lens equation, and analyzed the effect of light spectrum wide and the limit for demodulation. It shows that this method has the performances of high precision, high sensitivity and good anti-interference. In the process of ranging, it is not necessary to require the detector plane on the imaging plane exactly.
FTTH/FTTC systems will be soon used in both a broadcast service and a wavelength-addressed point-to-point communication service. Optical wavelength routers will be the key devices in these systems. In this paper, we propose a new method for high-density optical routing using arrayed- waveguide gratings (AWGs), present the transmission properties of the wavelength router, and analyze the channel crosstalks and the insertion losses of the 16-channel wavelength router. The results show that the channel crosstalks are less than -18 dB, and the insertion losses are less than -6 dB. Its advantages include small volume with miniatured structure, low insertion loss, low coupling loss to fiber, and compatible with the microelectronics technology. It can be used to construct photonic integrated circuits with the waveguide laser diodes and photodetectors.
KEYWORDS: Near field, Particles, Optical tweezers, Near field optics, Near field scanning optical microscopy, Dielectrics, Cladding, Numerical analysis, Electromagnetism, Optical microscopy
A new scheme for optical trapping is presented in this paper. The method is based on a tapered filter probe with a tip diameter less than a light wavelength. A three-dimension gradient optical field is formed within the optical near field of the filter probe, and a particle approaching the fiber probe tip will be trapped. The evanescent eletromagnetic field in the vicinity of the fiber tip is calculated by the multiple multipole method (MMP). The intensity distributions and the trapping potentioal of the near fields of the tip versus the longitudinal and transverse distances from the tip are analyzed respectively. The trapping force is obtained for a dielectric particle. The numerical calculating results show the availability of this method.
Based on Fresnel diffractive theory, a binary optical laser cavity is designed for a circle, flat topped fundamental mode. Instead of the traditional spherical mirrors for a laser cavity, the diffractive mode-selecting mirrors are used to optimize the amplitude and phase of the laser mode by simulated annealing algorithm. The computer simulation results show that the mode loss rate between TEM00 and TEM01 is 1:430 for a round trip in the cavity, and only the required fundamental mode is established in the laser cavity.
A new device used for tilted wavefront correction in adaptive optical cavity of CO2 laser was presented. The devices are composed of a pair of microlens arrays in the Galilean telescopic geometry, which is designed using binary optical technology. The microlens arrays pair is used for correction one order aberration of the laser resonator. The analyses show that the device has the advantages.
A binary optical resonator (BOR) can effectively improve the quality of the output beam. However, the process quality of the binary optical element (BOE) affects the laser beam closely. In this paper, a BOR, whose eigenmode is square- cross-section 10th order super-Gaussian fundamental beam, with a 16 levels BOE having square aperture, as an example, the fabrication errors such as step width error, etching depth error and mask offset error were discussed. The affect of root mean square (rms) of the output wave relative to desired wave was analyzed. The relationship of rms of output wave relative to step width error, etching depth error and mask offset error were presented respectively. Research shows that the etching depth error has a large affect for the mode distribution in resonator.
It is important for a laser beam with divergence angle as small as possible and large mode volume. For the fundamental mode of the common laser resonator, in which the reflective mirrors are spherical, the beam waist is very small, so the output power is very poor. The separation of adjacent transverse modes is often small. Maximizing the discrimination to gain a single mode output with larger power is necessary. It is very difficult to meet these requirements for the common laser resonators. So it is necessary for the laser resonator to perform the mode selecting.
Many experiments and industrial applications require a laser beam irradiance that is nominally constant over a specified area. Such applications include surface treatment, drilling and welding, as well as the processing and recording of optical information. So in many case it is desirable that the beam-shaping operation conserves energy. For a beam with Gaussian profile, it is possible to map the beam into a uniform intensity profile with steep skirt.
A laser beam with uniform intensity and plain phase is advantageous for many applications. Based on diffractive theory, a binary optical resonator was developed according to phase-conjugate principle in this paper. Replacing the sphere mirror of a semiconfocal resonator with a 16 levels binary optical mirror, having square aperture, a square- cross-section 10th order super-Gaussian bema is designed as the eigenmode of the new resonator. A few different original beam distributions mirror can select the desired beam profile or not. THe resulting square-cross-section 10th order super-Gaussian fundamental mode reproduced itself after some roundtrips in the laser resonator successfully and the other modes were attenuated.
A novel method for mode regulation of a laser resonator is presented this paper. The traditional spherical mirrors of the laser resonator are substituted by the micro-optic mirrors, which are produced by the binary optical technology. The phase distributions of the micro-optic mirrors may be designed carefully so that the output mode of the laser resonator is regulated as an arbitrary desired field distribution. Several mode fields, such as a fundamental-mode Gaussian distribution and a circular or rectangular uniform intensity distribution, are analyzed in our discussion.
KEYWORDS: Near field scanning optical microscopy, Optical microscopes, Wavelength division multiplexing, Near field, Laser sources, Near field optics, Laser beam diagnostics, Signal detection, Fiber characterization, Physics
A superfluorescent source used for scanning near-field optical microscope (SNOM) has been developed in this paper. The superfluorescent source originates from an amplified spontaneous emission (ASE) produced by an Er-doped fiber, with a relatively wide spectrum from 1531 nm to 1537 nm. This kind of superfluorescent fiber probe has relatively high photon flux over an ordinary probe. Different image qualities are obtained by the SNOM system with the superfluorescent source and the laser source respectively. Experimental result shows that the coherent noise of the SNOM image is dramatically reduced with the superfluorescent source.
By using composite self-focus rod, LD-pumped frequency doubling Nd:YVO4 laser and 3D fine regulation stand, a new Fizeau-type interferometer is developed. It can apply to measuring the micro-vibration and deformation of micro- surface at the same time. The theoretical analysis and the experimental results for the interferometer of self-focus sensor are given.
KEYWORDS: Near field scanning optical microscopy, Fiber lasers, Near field, Signal detection, Laser beam diagnostics, Cladding, Optical microscopes, Optical imaging, Near field optics, Waveguides
Passive and active fiber probes, used for the scanning near- field optical microscope, show different image properties. For the passive fiber probe, a better optical image contrast has been obtained with a parabolic taper than with a linear taper. The reflected fields in different fiber tapers have been discussed. For the active fiber probe, an ASE probe made of Er3+-doped fiber has shown a higher efficiency of several times and a lower image noise than the usual passive probe.
A novel method for mode optimization of a high-power laser is presented in this paper. A binary optical resonator is formed through introducing binary optical technology into a laser resonator. The traditional spherical mirrors are substituted by binary optical mirrors. Diffraction analyses show that this kind of resonator can construct any modes as desired with a strong ability of mode selecting and optimization. For a high-power CO2 laser, an optimum design of the binary optical resonator is implemented to obtain a fundamental-mode laser output with a uniform intensity distribution.
This paper derives the light amplitude distribution expression of a laser resonator. Using a numerical analysis, the result shows that the laser output power is maximum when no dynamic aberrations are in the laser cavity. The power and mode distribution of the laser are obtained. The paper presents an adaptive correction theory of laser resonator phase aberrations by using a 3D model deformable mirror. The result of the computer simulation in the close loop system shows that the system can compensate the dynamic phase aberrations up to 90% for the phase disturbance within 0 - 10 Hz frequency range.
The object distance is an important parameter for image recognition and robot 3D view. This paper presents a novel method of image pixel multidither passive ranging. Based on Fourier transform theory of lens imaging, we derive the mathematical model of ranging, obtain the ranging error equation using lens equation, and analyze the effect of spectrum width and the limit for demodulation. It shows that the performance of this method has high sensitivity and precise measurement.
By means of return wave algorithm, acquisition performance equations for multiple glints are derived. It is found that phase conjugation adaptive optical system can lock to the glint of the highest reflectivity. Computer simulation of the acquisition process of multiple glints in the view field has been implemented. The acquisition behavior in the temporal and spatial domain is achieved.
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