Abstract: The photonic band gap (PBG) dual-spectrum sensor utilizes the frequency-selective properties of a photonic band gap device constructed in accordance with this invention to separate incident electromagnetic wave into two frequency bands. The parameters of the PBG device are chosen so that one frequency band is transmitted through the device with low attenuation while the second band is reflected with low attenuation from the front face of the device. This separation of the two frequency bands allows separate detection processes to be performed to recover the information content of the two signals before the information is fused in subsequent signal processing operation. Such a PBG device would be useful in missile seekers that seek to distinguish a target object from its background.

Abstract: A photonic signal is applied to a photonic bandgap structure having a photonic band edge transmission resonance at the frequency of the photonic signal and having a photonic band edge transmission resonance bandwidth which is at least as wide as the bandwidth of the photonic signal. When a photonic band edge transmission resonance is matched to the photonic signal which is being transmitted, a controllable delay is imparted to the photonic signal without significantly altering the photonic signal itself.

Abstract: An optical switch in a one-dimensional multilayer dielectric stack having a photonic band gap, composed of at least two groups of layers of dielectric material whose operating wavelength is near the edge of said photonic band gap. At least one layer of each of the groups is composed of a nonlinear c.sub.3 dielectric material, which creates an intensity-dependent shift in the location of the band gap and produces a dynamical change in the transmissive and reflective properties of the multilayer dielectric stack in response to changes in the intensity of light or the transmittance of electromagnetic radiation passing through the multilayer dielectric stack. The width of the photonic band gap is determined by the differences between the refractive indices of the nonlinear dielectric material and that of the other layers of dielectric material in the multilayer dielectric stack.

Abstract: A new optical diode is disclosed that permits unidirectional transmission of light, the direction of transmission depending on the direction of incidence. The diode comprises a stack of alternating layers of a low-index material and a high-index material. The layers are arranged within the stack such that there is spatial anisotropy of optical pathlengths in the stack and at least the low-index layers or the high-index layers have an optical nonlinearity, either inherently or by doping. At sufficiently high incident intensifies and appropriate wavelengths, such a diode exhibits partial transmission of input light incident from one direction while reflecting almost totally input light incident from the opposite direction.

Abstract: Described here is an all-optical switch having two states, one that absorbs ncident coherent optical radiation and another that amplifies incident coherent optical radiation. The state of switch is changed in response to the passage of an ultra-short coherent optical pulse when the peak field strength of the pulse is in a wide region about the effective dipole moment per unit volume, a characteristic material parameter proportional to the density and the dipole transition moment of the selected active two-level systems which are uniformly distributed with sufficient density so that there is more than one two-level system per cubic transition wavelength causing dipole-dipole interactions to be non-negligible.

Abstract: A block of composite material includes a dielectric material with a dielectric constant of .epsilon..sub.d =4.66 and which is at least 4 .mu.m thick and has electrically conductive microparticles randomly distributed throughout. The composite material exhibits an optical bistability without cavity feedback. The microparticles must be nearly uniform in size and of spherical diameter much smaller than the wavelength of light in the particle. The composite, when illuminated by laser light in the range of 500 nm and of varying intensity, becomes opaque at a critical input intensity and stays opaque until the input intensity reaches a certain level both below and above the intensity at which it initially became opaque. Thus the material behaves as an optical switch and a limiter.

Abstract: An optically bistable, nonlinear optical device that produces an output that follows two hysteresis loops for an optical intensity variation input at a given frequency. One hysteresis loop follows a clockwise path of development, the other follows a counterclockwise path when the input field or optical intensity is ramped to a large value and returned again to a small value. These features of the device are effectively engineered by controlling the temperature of the input and output faces of the device, allowing optical logic gating and multiplex operation.