E. Garmire

Channel optical waveguide directional couplers

We report the first demonstration of channel optical waveguide directional couplers. The closely spaced channel waveguides were fabricated in GaAs by proton implantation. Optical coupling was observed at 1.15 μ with complete light transfer out of the initial channel into adjacent channels in lengths of typically 2 mm.

Optical waveguiding in proton-implanted GaAs

We have produced optical waveguides in n‐type GaAs by implantation with 300‐keV protons. The guiding is shown to be due to the elimination of charge carriers from the implanted region. Annealing of the waveguide leads to very large reductions in the 1.15‐μ guided‐wave absorption.

SECOND HARMONIC GENERATION FROM SHORT PULSES

The second harmonic pulse shape generated from ultrashort pulses is calculated. In long dispersive crystals the pulse width may be much broader than the incident pulse and the power conversion ratio may saturate at a low value. These effects should be prominent in LiNbO3 with 4 × 10−13 sec pulses.

Ion beam micromachining of integrated optics components.

Thin film integrated optics components such as light guides, modulators, directional couplers, and polarizers demand high quality edge smoothness and high resolution pattern formation in dimensions down to submicrometer size. Fabrication techniques combining holographic and scanning electron beam lithography with ion beam micromachining have produced planar phase gratings with intervals as small as 2800 A, guiding channel couplers in GaAs, and also wire- grid polarizers for 10.6-,microm radiation.

Propagation losses in metal-film-substrate optical waveguides

The propagation losses in metal-film-substrate two-dimensional optical waveguides are calculated. Losses for confined modes may become large and are at least an order of magnitude larger for TM than for TE modes. Higher order modes suffer more loss than the fundamental mode. Such mode-dependent loss can make efficient mode analyzers, useful for integrated optics modulation schemes.

Laser oscillation in epitaxial GaAs waveguides with corrugation feedback

Laser action was observed in GaAs epitaxial films using corrugation feedback. The output wavelength was found to depend on the corrugation period. The loss, threshold gain, and feedback parameters were determined and compared with theoretical predictions.

OBSERVATION OF PROPAGATION CUTOFF AND ITS CONTROL IN THIN OPTICAL WAVEGUIDES

The first observation of optical cutoff in thin‐film waveguides is reported. The waveguides consist of thin (∼10μ) epitaxial layers of high‐resistivity GaAs deposited on lower‐resistivity GaAs substrates. The optical cutoff is controlled through the electro‐optic effect by applying an electric field across the epitaxial layer.

Channel Optical Waveguides and Directional Couplers in GaAs–Imbedded and Ridged

Two-channel imbedded directional couplers were fabricated with proton implantation, yielding complete light transfer in 2 mm. Ridged channel guides were fabricated by ion-micromachining epitaxial layers, and a method of directional coupling was demonstrated.

Laser mode-locking with saturable absorbers

In this paper we describe a mode-locked laser in terms of traveling pulses of light. We show that the energy absorbed by a saturable absorber is a minimum if the pulselength is a minimum, and that two pulses are essentially as favorable as one if they meet at the position of the dye cell. Under steady-state pulsing conditions, however, we show that the pulses will have a width which depends on their energy. We find that for parameters appropriate to present Nd: glass experiments, the expected length is about 10-11seconds, in agreement with observations. Finally, we demonstrate the rather surprising result that a linearly dispersive medium does not broaden the mode-locked laser pulses to first order.

Optical Guiding and electro-optic modulation in GaAs epitaxial layers

Abstract Single mode TE or TM propagation is demonstrated in an optical waveguide consisting of a high resistivity semiconductor (GaAs) layer (≈ 10 μ) which is sandwiched between a metal film and a lower resistivity semiconductor. A reverse bias applied to the metal-seminconductor Schottky barrier causes an electro-optic retardation (or, in general, phase variation) which can be used for modulation purposes. Amplitude modulation with a “half-voltage” V 1 2 = 84 volts is demonstrated at λ o = 1.15μ with a sample 2.4 mm long.