The enhancement of evanescent waves in multilayer planar waveguides with a uniaxially anisotropic metamaterials layer
is investigated. Without loss of generality, we assume that the anisotropic metamaterials have an arbitrary angle between
the optical axis and the interface, and then we derive the characteristic equations and the analytical expression of energy
flux of this waveguides. It is found that the enhancement factor increases rapidly at first with increasing of the thickness
of the metamaterials in the case when the optical axis is parallel to or normal to the interface, namely the angle is equal
to 0 or π/2. The enhancement factor eventually reaches its maximum when complete surface polaritons are established at
the boundary between the metamaterials and the cladding [D.-K. Qing, G. Chen, Appl. Phy. Lett. 84(5), 669-671 (2004).].
Numerical results confirm our theoretical analysis.
The lowest oscillating waveguide mode can exist in guiding layer of a double-negative material that is symmetrically encapsulated in a double-positive material, even when the guiding layer's thickness is many times smaller than the operating free-space wavelength.
In this paper, we apply the coordinate transformation technique to the design of perfect lenses, which are able
to perfectly reproduce an image on another surface. In particular, anisotropic metamaterials that magnify
two-dimensional planar images beyond the diffraction limit are designed by the use of spheroidal coordinates.
We show that the technique can be used to design transformation media that magnify images beyond the
diffraction limit.
A dual-order Raman fiber laser (RFL) is numerically presented with suppressed low-frequency relative-intensity-noise
transfer from pump sources to both the first- and second-order Stokes output. It is accomplished by generating the
amplified spontaneous emission near second-order Stokes shift from the launched pump. Their powers can be tuned in a
large dynamic range. Besides these, the low-power second-order Stokes output is also stabilized in the RFL setup. These
special behaviors fit the proposed RFL for use as dual-order pump sources in Raman fiber amplifiers.
In this paper, we investigate the possibility of superlensing with two dielectric planar waveguides in detail by studying
the transmission of evanescent waves through one double-waveguide structure. We derive the total transmission and
reflection coefficients for the double-waveguide structure. It is found that when one field component of an evanescent
wave coincides with one of the single-waveguide bound-state eigenvalues, the total transmission increases exponentially
with respect to the distance between two dielectric planar waveguides, and zero reflection can be found. An important
interplay between propagating waves and evanescent waves on image formation is revealed, which makes the
appearance of the image of a superlens substantially different from that of a real image behind a free space. We derive
the resolution of the double-waveguide structure and infer that resolution arbitrarily smaller than the wavelength should
be possible in principle, provided that sufficiently high dielectric contrast of two waveguides can be obtained. The
numerical results confirm the qualitative discussions in this paper.
We discuss the diffraction of waves due to the periodically corrugated boundary of vacuum and a linear, homogeneous
negative refraction index metamaterials (NIM). We show by numerical simulation that the grating surfaces can give rise
to a well-defined diffracted beam in addition to the negatively refracted beam. The direction of the diffracted beam is
consistent with elementary diffraction theory; however, the coupling to this higher order beam is much larger than would
be the case for a positive index material (PIM). To explore the properties of diffracted beams in a negative-index sample,
we simulate a wave incident on the interface between a NIM grating and free space. The numerical study provides an
indication of the relative coupling of the incident wave to the zeroth and first order beams.
In this paper, we focus on the properties of the complex modes in negative-refractive-index fibers. The characteristic
equations for TE and TM modes in negative-refractive-index fibers are given. These solutions, termed complex surface
waves, form another set of proper modes. We show that dispersion diagram for both TE and TM modes in
negative-refractive-index fibers, including evanescent, ordinary, and complex surface modes. It is found that the complex
surface modes have high cutoff frequencies which means they exist only when the frequency is lower than their
respective cutoff frequencies. After a careful examination, we found that the total power flow turns out to be simply zero.
A systematic study of the omnidirectional reflection range (ODR) of one-dimensional (1-D) staggered photonic crystals
(PC) containing negative refraction medium (i.e., negative index medium (NIM)) is presented, based on numerical
simulations performed with the well-known transfer-matrix method without any simplifying assumptions. It is found that
total omnidirectional reflected frequency band is enlarged considerably by using onedimensional photonic crystal
structure composed of alternate layers of positive index material (PIM) and NIM. We discover that the ODR in staggered
1-D PCs range can be significantly broadened in a staggered structural design.
We first propose the genetic algorithms (GA) to deal with strictly non-blocking grooming problems in optical tree
networks. We describe strictly non-blocking grooming problems in Wavelength Division Multiplexing (WDM) optical
trees with traffics and find the lower and upper bounds. Here we use the (μ + λ)-strategy to produce offspring for the
genetic algorithm, and apply the technology of wavelengths-reuse in the decoding of the individual in the genetic
algorithms. The performance of the proposed strictly non-blocking grooming algorithm was tested in tree networks with
different granularity and different number of traffic patterns. Computer simulation results show that our algorithm can
achieve very good results in saving both ADM's and wavelength in tree networks.
Traffic grooming in WDM optical networks is one of the most important and hot problem in the area of optical networks. We first systematically investigated the grooming problems in WDM optical tree networks with traffic requirements in this thesis. We first propose the genetic algorithms (GA) to deal with a variety of grooming problems in tree networks, and propose the connection model of optical tree networks, and apply the technology of wavelengths-reuse in the decoding of the individual in the genetic algorithms, and get good grooming results.
A novel wavelength detection and demodulation technique of fiber Bragg gratings sensors is put forward. The principle, experimental setup and results of the sensor are analyzed. The new technique converts detections of shift of center reflecting wavelength into detection of light intensity extremum. Furthermore, a spatial division multiplexing system of Bragg gratings sensors based on the novel technique is developed. The multiplexing numbers are not confined by bandwidth of light source and tunable scope of single fiber Bragg grating.
A N X N integrated planar optical waveguide acousto-optical switch design is presented based on waveguide geodesic lenses and acousto-optical deflector. This kind of switches gets over the difficulties occurred in integrated switches based on strip waveguide. It can be integrated in a chip, and the channel numbers N can be up to 218. As an example, a 2 X 2 integrated planar optical waveguide acousto-optical switch has been fabricated and tested. Experiment result shows only one mode is transmitted in the Ti:LiNbO3 waveguide; the chip insertion loss is 0.8 dB; the central acoustic frequency is 150 MHz; the 3 dB bandwidth of IDT is 56 MHz; the chip acoustic frequency resolution is 6 MHz and the chip extinction ratio is larger than 20 dB.
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