C. T. Seaton

Third order nonlinear integrated optics

The authors review progress in the application of nonlinear optical phenomena to integrated optics. Essentially all integrated optics devices such as directional couplers, Mach-Zehnder interferometers, prism couplers, etc., can be used for all-optical signal processing when at least one of the waveguiding media exhibits an intensity-dependent refractive index. Experimental and theoretical results on the operating characteristics and figures of merit of such devices, as well as a new class of phenomena based on large nonlinear changes in waveguide properties will be summarized. Also discussed are measurement techniques for evaluating waveguide nonlinearities. Progress in the implementation of other nonlinear third order interactions, such as degenerate four-wave mixing and nonlinear spectroscopy, will also be reviewed. >

Nonlinear integrated optics

We review the work done to date in the field of nonlinear integrated optics. Emphasis is placed on (intrinsic) second‐ and third‐order phenomena occurring in planar geometry structures and several applications are discussed. All of the nonlinear interactions are discussed in a single notation.

Calculations of nonlinear TE waves guided by thin dielectric films bounded by nonlinear media

The dispersion relations for TE polarized waves guided by thin dielectric (planar integrated optics) films, surrounded on one or both sides by media with intensity-dependent refractive indexes, are solved numerically and interpreted. Comparisons are made between these nonlinear guided waves and the usual integrated optics modes associated with linear media. For media characterized by self-defocusing nonlinearities, increasing guided wave power leads to a decrease in the guided wave effective index and to mode cutoffs characterized either by finite or diverging total guided wave powers. For self-focusing media, the effective index increases with increasing power. New wave solutions are obtained with power thresholds and anomalous power-dependent field distributions. These characteristics are illustrated by numerical calculations for a specific material system and possible applications to optical devices are discussed.

Ultrafast carrier and grating lifetimes in semiconductor‐doped glasses

The time dependence of both the photoluminescence due to carrier recombination and the gratings created by degenerate four‐wave mixing were measured in semiconductor‐doped color‐filter glasses. Values ranging from 80 to less than 16 ps (laser pulse width limited) are measured in several different samples at various excitation levels. A slower mechanism, believed to be thermal in nature, is also observed with a lifetime in excess of 9 ns.

Experimental observation of polarization instability in a birefringent optical fiber

We present the first experimental demonstration of spatial instability in the nonlinear evolution of the state of polarization of an intense light beam in a birefringent Kerr‐like medium. As the peak power crosses the threshold for the instability, we observed strong intensity‐dependent power transfer between the two counter‐rotating circularly polarized waves propagating along a birefringent optical fiber. The experimental results agree well with the theory.

Nonlinear Guided Wave Applications

Potential device applications of third-order nonlinear phenomena in guided wave structures are discussed. One of the waveguiding media is assumed to exhibit an intensity-dependent refractive index that results in both an intensity-dependent propagation wavevector and field distribution for the guided waves. These two characteristics lead to many interesting all-optical devices whose operating principles and power levels are outlined here. For example, the intensity-dependent field patterns can be used for thresholding and switching operations in a waveguide context. The intensity-dependent wavevector, used in conjuction with a distributed input or output coupler, can lead to devices such as optical limiters and light-controlled spatial scanners. When gratings are used as distributed feedback elements within a nonlinear waveguide, a whole class of novel devices such as bistable switches and optically tunable optical filters should be feasible.

Observation of intensity-dependent guided waves

We have observed an intensity-dependent hysteresis in the transmission of guided waves through a thin-film waveguide with a cladding characterized by an intensity-dependent refractive index. Good agreement with theory was obtained.

Nonlinear waves guided by thin films

The dispersion relations for waves guided by thin dielectric films surrounded on one or both sides by media with intensity‐dependent refractive indices are solved numerically. A number of new modes as well new features in the usual low power modes are predicted.

Nonlinear electromagnetic waves guided by a single interface

Electromagnetic waves guided by the interface between two nonlinear media, and a nonlinear and a linear medium are investigated theoretically and numerically. Both s‐ and p‐polarized waves are analyzed and the guided wave power versus guided wave vector is evaluated for a variety of material conditions. The consequences of two different versions of the uniaxial approximation for the p‐polarized case are compared. The power‐dependent attenuation is approximately evaluated.

Exact dispersion relations for transverse magnetic polarized guided waves at a nonlinear interface

We derive exact dispersion relations for transverse magnetic polarized guided waves at an interface between either a linear dielectric or a metal and a nonlinear dielectric. The nonlinearity is taken to be a Kerr-type nonlinearity. Numerical results are presented for the dielectric-metal case.