Charles M. Bowden

Blue and green light emission: new directions and perspectives of applications of one-dimensional photonic band gap structures

Nonlinear quadratic interactions near the band edge of a finite length photonic band gap structure are studied. A strong enhancement of the nonlinear response is found due to the essential role played by the electromagnetic density of modes and phase matching conditions. This open the door to a new generation of very compact nonlinear devices. The blue and green light emission conditions are discussed.

Transparent, conducting films based on metal/dielectric photonic band gaps

A transparent conductor has been developed based on 1D metal/dielectric photonic band gap structures. Laminated metal/dielectric filters containing 100 nm of silver have been fabricated with > 50% transmittance. Applications for transparent, conducting films include antennas embedded in windshields, electrodes on flat panel displays, electromagnetic shielding, and solar window panes.

Highly efficient parametric interactions in one-dimensional photonic band gap structures

Band edge effects such as increased density of modes, large field enhancement, and low group velocity will provide highly efficient parametric amplification if the proper phase matching conditions can be established. We derive the phase matching conditions for 1D-photonic band gap structures. Direct integration of Maxwells equations in the time domain confirms these conclusions, and show that parametric amplification in 1D-photonic band gap structures provide much larger conversion efficiencies compared with quasi-phase-matching.

Birefringence in one-dimensional finite photonic bandgap structures

The spectral and dispersive behavior of anisotropic layered structures forming a one dimensional polarization dependent photonic band gap are discussed. The finite dimension of the structure has been taken into account. Interesting field localization properties are found when the optical axis of layesr are not aligned each with the other one, i.e. principal axis of layers are rotated one with respect to the other. The field localization behavior has been also discussed through a suitable definition of density of modes for the anisotorpic layered structure.

Highly efficient simultaneous second and third harmonic generation via /spl chi//sup (2)/ interactions in 1D-photonic band gap crystals

Summary form only given. Simultaneous second and third harmonic generation via a /spl chi//sup (2)/ interactions was first investigated theoretically by Akhmanov in 1964. He found that it was impossible to achieve simultaneous phase matching conditions for both the second harmonic process and the sum frequency generation in ordinary materials, and the process remains inefficient. Interest in nonlinear frequency conversion has increased thanks to a technique referred to as quasi-phase matching (QPM). QPM yields good conversion efficiencies for simultaneous multi-wavelength generation, thus reopening the challenge for the realization of compact, multicolor laser sources for laser scanners, printers, and color display devices. In this paper, we show that a photonic band gap (PBG) crystal can be used to achieve efficient, simultaneous, collinear second and third harmonic generation without the need for uniaxial crystals or periodic domain inversion, as required by QPM.

Photonic bandgap structures in planar nonlinear waveguides: application to second harmonic generation

Second harmonic generation (SHG) in planar nonlinear waveguides is investigated under conditions for which the use of a linear grating fabricate don top of the waveguide reproduces a photonic band-gap structure. The fundamental mode of the guide, at the fundamental frequency, is tuned at the photonic band edge resonance thus experiencing a great confinement and enhancement of the electromagnetic field inside the structure. The linear grating alone is however not able to produce both field confinement and phase- matching of the SHG process. Phase-matching is obtained by an additional modulation of the non linear susceptibility (chi) (2), as in the conventional quasi-phase-matching scheme. The conversion efficiency achieved using both linear and nonlinear gratings is orders of magnitude greater than that of a quasi-phase-matched device of the same length.

Phase matching conditions for parametric interactions in one-dimensional photonic band gap structures

Phase-matching conditions for parametric interaction in 1D photonic band gap (PBG) structures are studied. Band edge effects, such as field localization, increased density of modes, and `effective phase matching between pump and signal fields are responsible for the high predicted enhancement of nonlinear processes in PBGs.

Influence of local-field effects on the dynamics of superradiance by a dense medium

The theory of superradiance by an ensemble of two-level atoms embedded in a dielectric host is developed. It is shown that the near dipole-dipole interaction of a dense collection of two-level atoms is enhanced by the presence of the host material, decreasing the pulse temporal width and increasing the peak pulse intensity of superradiative emission. The influence of the inversion-dependent detuning effect on the parameters of the emitted pulses is investigated.

Local field effects in multicomponent media

At densities that are typical of condensed matter, a propagating electromagnetic field mediates interactions between polarizable constituents of a material in what is known as the local-field effect. Previous investigations of the local-field effect have been limited to a single polarizable component of a nonlinear material. For multicomponent media, we have found that the interaction of laser radiation with an optically nonlinear component of condensed matter is fundamentally altered by the presence of another polarizable component as a result of the local-field effect. Novel effects include local-field enhancement effects, local cooperative decays, and coherence transfer and coherence exchange processes.

Characterization of optical instabilities and chaos using fast multilayer perceptron training algorithms

A new and novel training algorithm, based upon the matrix pseudoinverse least-squares method, is introduced for training hidden layer, forward-feed neural networks with high accuracy and speed for nonlinear and chaotic time series prediction. Model-generated chaotic time series, including that of the Lorenz system, are used to measure performance and robustness. Our new training algorithm has rendered application of forward-feed, hidden-layer neural networks for adaptive chaotic time series analysis, as well as other signal processing, practical and near real time using standard desktop computation facilities. We have applied our method, in conjunction with other standard methods, to the analysis of stimulated Brillouin scattering under cw pump conditions involving a single Stokes and pump signal in a single- mode optical fiber as the nonlinear medium. We use Stokes signal data generated from a standard model and correlate the training performance of our algorithm with statistical and dynamical characteristics of the system determined by other means.