Development of a vertical optical coupler using a slanted etching of InP/InGaAsP waveguide

We demonstrate a simple and efficient optical coupler for vertical coupling between optical fibers and InP-based waveguides using a slant-etched mirror. The angle of the etched mirror can be controlled by using an aluminum jig with a beveled surface inserted under the substrate during RIE (reactive ion etching) of InP/InGaAsP. The offchip coupler is fabricated simultaneously with a high-mesa waveguide with only one etching process. Coupling loss of 7.3 dB between the tapered single-mode fibers is obtained within the wavelength of 1530– 1570 nm.