R. V. Schmidt

Metal‐diffused optical waveguides in LiNbO3

Deposited films of transition metals (Ti, V, and Ni) have been diffused into LiNbO3 crystals to form low‐loss TE and TM mode optical waveguides. Using Ti, single‐mode low‐loss waveguides which confine the guided light to within ∼1 μm of the surface have been constructed. The choice of diffusion parameters allows independent control of important waveguide parameters.

Grating filters for thin‐film optical waveguides

The fabrication and evaluation of corrugation grating filters with reflectivities better than 75% and bandwidths less that 2 A is reported. Grating filters were fabricated on glass waveguides using standard interferometric and ion‐beam machining techniques and evaluated with a tunable dye laser. Measured and calculated filter responses are found to be in excellent agreement. Tolerances for realizing ideal filter performances are given.

Electro‐optically switched coupler with stepped Δβ reversal using Ti‐diffused LiNbO3 waveguides

An experimental electro‐optical switched directional coupler is reported which is formed in LiNbO3 by diffused Ti strip waveguides and uses stepped reversed phase mismatching to provide electrical adjustment of both switch states. A measured 400:1 conversion of light from one guide to the other was obtained.

Characteristics of Ti-diffused lithium niobate optical directional couplers

The dependence of the coupling strength of titanium-diffused lithium niobate directional couplers upon fabrication parameters and guided wavelength has been investigated. Measurements of the coupling strength as a function of interguide separation have been made at He-Ne, GaAs, and Nd:YAG wavelengths. To good approximation, the coupling strength depends exponentially upon guide separation. Rather strong dependence upon the metal thickness diffused and the guided wavelength were observed. Good comparison was obtained with theoretical results calculated using an effective index method. Transfer lengths as short as 200 microm have been obtained. Fabrication parameters for which the coupling strength for the TE and TM modes are equal were determined.

Lithium niobate ridge waveguide modulator

A narrow ridge was ion‐beam etched on an outdiffused LiNbO3 crystal to form a single‐mode waveguide confining the beam in both transverse dimensions. Electrodes were evaporated along the ridge to produce a very efficient electro‐optic phase modulator requiring a power of 20 μ W/MHz of bandwidth and a voltage of 1.2 V to produce a modulation index of 1 rad.

Optical technique for producing 0.1‐μ periodic surface structures

Surface corrugations with a period of 1108 A and a depth of [inverted lazy s] 500 A have been fabricated in glass. These corrugations were first produced in a photoresist film on glass by the optical interference of two 3250‐A laser beams. The corrugation was transferred to the glass by ion beam etching.

Optically controlled two channel integrated-optical switch

An integrated optical bistable device based on a waveguide directional coupler switch is demonstrated. The device has four optical ports, and the power incident on the two input ports exists from two distinct output ports so that all-optical data processing or remote optical switching can be performed. On/off ratios as high as 12 dB have been observed. A switching time of \sim300 \mu s and switching energy of ∼3 pJ have been achieved.

Narrow‐band grating filters for thin‐film optical waveguides

Criteria and tolerances are discussed for realizing grating filters with bandwidths as narrow as 0.1 A. Techniques are presented for minimizing the adverse effect of film thickness variations which broaden filter response and raise out of band ripple. Using these techniques a grating filter fabricated on a glass thin‐film waveguide is demonstrated which has 73% reflectivity and a 3‐dB bandwidth of 0.15 A.

Double‐heterostructure GaAs distributed‐feedback laser

The fabrication and operation of a GaAs–GaAlAs heterostructure distributed‐feedback laser are described in which fine optical corrugations (≈ 1150 A) are etched and regrown into the interface between two layers of the heterostructure. Laser operation has been observed before and after the growth of the final layer with optical pumping.

Acousto‐optic diffraction of guided optical waves in LiNbO3

We report acousto‐optic diffraction modulation of a guided optical wave in LiNbO3 by an acoustic surface wave. 250 mW of acoustic power produces 100% modulation of the zero‐order beam.