Wave propagation in thin-film optical waveguides using gyrotropic or anisotropic material as substrate is studied. At the film-substrate boundary, the relation between the incident and reflected fields can be expressed in terms of a scattering matrix with matrix elements representing the TE-to-TE and TM-to-TM reflection coefficients and the TE-to-TM and TM-to-TE conversion factors. The property of the scattering matrix is examined, and the condition for continuous and complete mode conversion is derived. Various schemes to achieve complete mode conversion are proposed and the performance characteristics, including the physical dimension and the tolerances in the incident angle and film thickness, for several mode-converting structures are computed and compared. Once the practicability of complete mode conversion is established, it is possible to study the feasibility of practical devices. Various schemes for the realization of such devices as the gyrator, the isolator, the optical switch, and the nondestructive read out are proposed.
Optical waveguides produced in LiNbO3 by immersing the x-cut plates into molten AgNO3 are reported. An increase in the extraordinary refractive index of LiNbO3 at the surface of the plate due to silver exchange is estimated to be 0.12. In such a waveguide, optical losses of 6 dB/cm were measured for the highest-order mode; losses were higher for the lower-order modes.
A fast acoustic diffraction-type thin-film optical waveguide modulator is described. Modulation was observed for the drive signal over the 150–550-MHz frequency range. A depth of modulation of 10% per electrical watt was estimated from the diffracted spots. The scheme presented here widens the selection of materials for acousto-optic modulations in an optical waveguide and may find some useful applications in the infrared region where suitable electro-optic materials are few.
The e x p e r i m e n t a l r e s u l t s on i n t e r f e r om e t r i c B r a g g C e l l Spectrum Analyzer a r e indeed encouraging. An experiment w a s p e r f o r m e d using a 5 mW HeNe l a s e r in Mach-Zehnder i n t e r f e r o m e t r i c Configuration. A l i n e a r c h i r p w a s u s e d to g e n e r a t e the r e f e r e n c e b e a m . W e w e r e a b l e to obserw58 dB Dynamic Range f o r CW and 54 d B DR f o r 5ps pulsed signals with 100% Probability of I n t e r c e p t and less than 1 p s T i m e of A r r i v a l a c c u r a c y . Pseudo Noise Sequence w a s a l s o t r i e d i n a n o t h e r e x p e r i m e n t with good r e s u l t s at reduced s y s t e m bandwidth.
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