InP/InGaAsP-Based Integrated 3-dB Trench Couplers for Ultra-Compact Coherent Receivers

• Published in: IEEE photonics technology letters Vol. 23; no. 5; pp. 311 - 313
• Main Authors: Krishnamachari, U, Ristic, S, Chin-Hui Chen, Johansson, L, Ramaswamy, A, Klamkin, J, Norberg, E, Bowers, J E, Coldren, L A
• Format: Journal Article
• Language: English
• Published: IEEE 01-03-2011
• Subjects: 3-dB coupler; Beam splitter; coherent mixing; Couplers; etched slot; frustrated total internal reflection (FTIR); Modulation; Optical polarization; Optical receivers; Optical reflection; Optical waveguides; trench
• ISSN: 1041-1135; 1941-0174
• DOI: 10.1109/LPT.2010.2100376

We present the design, fabrication, and test results for ultra-compact 3-dB frustrated total internal reflection-based trench couplers in an InP/InGaAsP monolithic integration platform. The trench coupler is integrated with phase modulators and a balanced photodiode (BPD) pair to enable a 180° hybrid ultra-compact coherent receiver. Several trench splitter designs exhibit near 3-dB splitting with a loss of 3 dB. The BPD pair is used to characterize coherent mixing of two input optical signals into the trench splitter, and coherence efficiency of 75% is achieved.