Resonant leaky modes can be induced on dielectric, semiconductor, and metallic periodic layers patterned in one or two
dimensions. Potential applications include bandpass and bandstop filters, laser mirrors, ultrasensitive biosensors,
absorption enhancement in solar cells, security devices, tunable filters, nanoelectromechanical display pixels,
dispersion/slow-light elements, and others. As there is now a growing realization worldwide of the utility of these
devices, it is of interest to summarize their physical basis and present their applicability in photonic devices and systems.
In particular, we have invented and implemented highly accurate, label-free, guided-mode resonance (GMR) biosensors
that are being commercialized. The sensor is based on the high parametric sensitivity inherent in the fundamental
resonance effect. As an attaching biomolecular layer changes the parameters of the resonance element, the resonance
frequency (wavelength) changes. A target analyte interacting with a bio-selective layer on the sensor can thus be
identified without additional processing or use of foreign tags. Another promising pursuit in this field is development of
optical components including wideband mirrors, filters, and polarizers. We have experimentally realized such devices
that exhibit a minimal layer count relative to their classical multilayer thin-film counterparts. Theoretical modeling has
shown that wideband tuning of these filters is achievable by perturbing the structural symmetry using
nano/microelectromechanical (MEMS) methods. MEMS-tuned resonance elements may be useful as pixels in spatial
light modulators, tunable lasers, and multispectral imaging applications. Finally, mixed metallic/dielectric resonance
elements exhibit simultaneous plasmonic and leaky-mode resonance effects. Their design and chief characteristics is
We investigated analytically and numerically the occurrence of modulation instability in fibers with periodic changes both in dispersion and gain. Previously, it has been known that the modulation instability is suppressed in dispersion managed solitons where dispersion is managed in such a way that the local dispersion alternates between the normal and the anomalous regimes. In this work, we enhanced the advantage of the dispersion management scheme by additionally introducing proper gain/loss profiles in fibers. The gain/loss profile is given by Γ(z)=0.5/D(z)*(dD/dz), where D(z) represents the dispersion profile. The fundamental gain spectrum of the modulation instability in the dispersion and gain managed fibers have been derived analytically and confirmed by numerical calculation. Our investigation reveals that in the dispersion and gain fibers the modulation instabilities are always much more suppressed compared to the case that only dispersion managed. In practical dispersion management schemes, dispersion profiles show discontinuity, and thus, the corresponding gain/loss profiles tend to finite. In these cases, the gain/loss profiles were approximated by lumped gains/losses of finite values. Our numerical calculations confirm that this approximation also works well.
Photonic band gap (PBG) structures or photonic crystals have attracted a lot of interest since one of their promising applications is to build compact photonic integrated circuits (PIC). One of key components in PICs is a 1 x 2 optical power splitter or a 2 x 1 combiner. Design of 1 x 2 optical power splitters based on photonic crystal has been investigated by several research groups, but no attention has been paid to the design of 2 x 1 optical combiners. In conventional dielectric waveguide based circuits, optical combiners are obtained just by operating the splitters in the opposite direction and the isolation between two input ports in the combiners is naturally achieved. In photonic crystal based circuits, however, we have found that reciprocal operation of the splitters as combiners will not provide proper isolation between the input ports of the combiners. In this work, microwave-circuit concept has been adopted to obtain isolation between two input ports of the combiner and compact optical power splitters/combiners of good performance have been designed using 2-D photonic crystal. Numerical analysis of the designed splitters/combiners has been performed with the finite-difference time-domain method. The designed splitters/combiners show good isolation between input ports in combiner operation with small return losses.