Optical-waveguide hybrid coupler

High-contrast channel waveguide switch with two sections of a nematic liquid crystal covering

Theoretical and experimental results for waveguide modes with a distinctive channel waveguide switching geometry are presented from the viewpoint of improving the switching contrast for hybrid-mode propagation. The channel waveguide structure consists of two types of active material covering regions of a nematic liquid crystal; one has a pair of strip electrodes, and the other is without electrodes. An experimental switch is demonstrated to have the contrast ratio of 1430 for the hybrid modes with E(1n)(y) primary components.

Experimental demonstration of optical field evolution in waveguide junctions by using a video camera observing system

We have experimentally proved the optical field evolution in waveguide junctions formed by potassium ion exchange in a glass substrate using a microcomputer assisted video camera observing system. The optical field profiles in various waveguide junctions such as Y- and X-junctions have been clearly observed. Most of the results support the predicted operation of the junctions.

Adiabatic invariance in GRIN channel waveguides and its use in 3-dB cross couplers

We have extended the local normal mode approach of Burns and Milton to derive the condition for adiabatic invariance in graded-index channel waveguides. The results show that in spite of the index-grading and 2-D confinement, the inequality describing the adiabatic condition is basically the same as that for step-index slab waveguides. To verify the predictions of the theory, we have fabricated, using ion exchange in glass, a cross coupler with two asymmetric input channel waveguides and two symmetric output guides. The experimental results show equal output power (3.0 +/- 0.1 dB) from the two symmetric guides when either of the two unequal guides is excited, demonstrating excellent agreement with the theory.