Abstract: A process is described for making semiconductor lasers with cleaved facets for end mirrors. The process involves electrochemically photoetching slots with deep, narrow cross-sections in a wafer and applying stress to cleave the wafer in the desired place. Extremely short and reproducible semiconductor lasers can be made by this procedure (less than 50 or even 25 .mu.m) which yields extremely useful semiconductor lasers particularly for communication applications. Also, the procedure requires a minimum of skill to produce excellent quality cleaved semiconductor lasers (including short-length lasers) with high yields.

Abstract: Single longitudinal mode operation is achieved and maintained under CW and high speed (Gbps) current modulation conditions by a short coupled cavity laser including a short cavity semiconductor laser having two parallel mirror facets and a reflective surface spaced apart from and in predetermined relationship with one of the mirror facets. A short external cavity resonator is formed between the one mirror facet and the reflective surface. In general, the laser cavity length is related to the external cavity resonator length by the equation, nL=md, where nL is the effective optical length of the injection laser, d is the length of the external cavity resonator, and m is a positive number preferably between 2 and 10.

Abstract: A method for manufacturing silica-based optical fiber, and for manufacturing optical fiber preforms, the method comprising deuterium/hydrogen exchange in the silica-based material carried out subsequent to formation of the silica.

Abstract: A three terminal, totally integrated demultiplexing photodiode is disclosed wherein information present simultaneously at two wavelengths can be developed into two separate currents available at the three terminals. Two quaternary layers (203 and 205) of indium, gallium, arsenide phosphide having unequal bandgaps and each having a pn junction are separated by a buffer layer (204) of n type indium phosphide. Operation at longer wavelengths is achieved by causing the bottom quaternary layer to have the higher bandgap energy thereby permitting it to detect the shorter wavelengths in the radiation and causing the topmost quaternary layer (205) to have the lower bandgap energy thereby permitting it to detect the longer wavelengths. The bottom contact (213) on the substrate has an opening thereby providing a window (230) through which incoming radiation (250) can be coupled through the substrate to the two quaternary layers.