Based on restricted interferences mechanism in a 1x2 MMI beam splitter, we theoretically investigate and experimentally demonstrate an ultra-compact MMI-based demultiplexer for the NIR/MIR wavelengths of 1.55 μm and 2 μm. The device is fabricated on 340 nm SOI platform, with a footprint of 293x6 μm 2 . It exhibits extremely low insertion losses of 0.14 dB and 1.2 dB at the wavelengths of 1.55 μm and 2 μm, respectively, with contrasts of approximately 20 dB for both wavelengths, and a cross-talk of 18.83 dB.

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We report charge-compensated modified uni-traveling-carrier photodiodes (MUTC-PDs) with high photocurrent and fast response, grown using liquid group-V precursor, in an AIXTRON MOCVD system. The liquid group-V precursors involve less toxicity with better decomposition characteristics. Device fabrication is completed with standard processing techniques with BCB passivation. DC and RF measurements are carried out using a single mode fiber at 1.55 μm. For a 24-μm-diameter device (with diode ideality factor of 1.34), the dark current is 32.5 nA and the 3-dB bandwidth is ≫20 GHz at a reverse bias of 5 V, which are comparable to the theoretical values. High photocurrent of over 150.0 mA from larger diameter (>60 μm) devices is obtained. The maximum DC responsivity at 1.55 μm wavelength is 0.51 A/W, without antireflection coating. These photodiodes play a key role in the progress of the future THz communication systems.

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