Thin Film Optical Switch.
Quarterly rept. no. 3, 22 Jul-21 Oct 76,
HUGHES RESEARCH LABS MALIBU CALIF
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During the third quarter of this program, the measurement of single mode coupling efficiency for linear tapers of four different taper lengths was continued. For TM wave propagation, the coupling efficiency was much lower than for TE wave propagation. The difference in coupling efficiency was due to the presence of Li2O out-diffusion waveguide modes, which occurred only when the TE mode was excited in Ti-diffused channel guide. The coupling efficiency of a given taper structure depends strongly on the expansion ratio of the channel width final width to initial channel width. So it is important to know the amount of lateral diffusion which proceeds simultaneously with the downward diffusion. We have studied the Ti concentration profile near the edge of a stripe of 70 microns initial width using electron microprobe technique. The lateral spread of this 70 microns wide channel guide was about 6 micrometers on each side. We concluded that enhanced lateral diffusion was not observed in this study.