[16a-2F-1~12] 3.14 Optical control devices and optical fibers

△ [16a-2F-10] TE-TM Mode Converter for GaInAsP/InP Waveguide Optical Isolator

〇kei masuyama¹, Shoji Yuya², Mizumoto Tetsuya¹ (1.Dept. of EEE, Tokyo Tech, 2.QNERC, Tokyo Tech)

Keywords:mode converter,GaInAsP/InP,single trench

An optical isolator plays an essential role for protecting optical active devices such as laser diodes and semiconductor optical amplifiers by preventing backward reflections from degrading the device performances. Waveguide optical isolators operate only for the TM mode. On the other hand, optical active devices typically operate for the TE mode. In this paper, we investigate a single-trench TE-TM mode converter composed of a GaInAsP/InP waveguide for the monolithic integration of these components on an InP platform. This device has the advantages of low insertion loss and being fabricated by a single masking and etching process. However, the core height of the GaInAsP waveguide isolator that minimizes the device length is not compatible with the mode converter providing a high conversion efficiency with large tolerances for dimensional errors. In this work, an additional InP cladding layer is prepared on the GaInAsP core layer to enlarge an effective core height. The designed waveguide structure was successfully fabricated utilizing the “RIE lag” effect. In the measurement of the fabricated device, the conversion efficiency shows a square of sinusoidal dependence as a function of the mode conversion length. A maximum TE-TM mode conversion efficiency of 91.6 % was obtained for a conversion length of 200 μm.