Integrated optical components produced in GaAs and InP epitaxial layers using the photo-elastic effect.

Studies have been made of optical waveguides produced
in GaAs and InP epitaxial layers. Of the possible waveguiding
mechanisms present in these devices the contribution from the
photo-elastic effect (strain-induced refractive index changes)
dominates. Stresses in evaporated metal films and their
control have been investigated.
Strain-induced waveguides have been used to produce a
novel directional-coupler structure with a short coupling
length (~2mm). In GaAs bias has been applied to control the
amount of light at the output of each of the two waveguides
forming these couplers and it has been possible to isolate
the light in either the excited or the coupled waveguide.
A new theoretical model, based on finite difference
techniques, has been developed and used to analyse strain-induced,
slab and rib waveguide structures. Results obtained
have been compared with those from other methods. Theoretical
predictions of guiding properties in GaAs strain-induced waveguides
give good agreement with experimental results in all
cases. Optical waveguiding in InP layers using the same photoelastic
mechanisms, assessed experimentally, indicates that
the refractive index changes are similar to those in GaAs but
slightly larger. One of the first measurements of the nonzero
electro-optic coefficient, r41, of InP is described.
Guiding properties vary little with time in both InP and GaAs.
The reflection of light guided in a single-mode photoelastic
waveguide into a second perpendicular guide using a
vertical etched facet running at 450
to the direction of
propagation is proposed for providing bending with negligible
loss and some experimental results are reported.