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Fabrication of a planar silica-based cascaded symmetric Y-branch 1 8 optical power splitter is described in this study. Post-fabrication, thorough analysis of device-performance is presented in terms of insertion loss, nonuniformity and polarization-dependent loss. The fabricated device is designed based on cascaded Y-branching waveguide, comprising of a linear taper and symmetric S-bend arc branching waveguides. The simulated values of the average insertion loss, non-uniformity and polarization-dependent loss at the wavelength of 1550 nm are found to be 9.37 dB, 0.35 dB and 0.04 dB respectively. However, the above parameters have been measured to be around 17.5 dB, 1.5 dB and 1.8 dB respectively, for the fabricated device at that wavelength. Measured parameters are compared with the simulated results over a wavelength region of C & L band range. Some preventive points to minimize the deviation of the measured values of the parameters from those of the simulated results are also discussed.

A 775 nm femto-second laser annealed approach for the inter-pixel isolation, without mesa etching, to reduce dark currents of type-II InAs/GaSb superlattice photodiodes is presented. A greater than two fold improvement of the pixel isolation and a corresponding reduction in the dark current are observed for laser annealed superlattice photodiodes with a 5.5 µm cutoff wavelength, operating at 10K. A higher band gap barrier material from the superlattice structure in the inter-pixel region is expected to form after femto-second laser annealing, which has been explained on the basis of a superlattice inter-diffusion model. The increase in inter-pixel barrier height at 10K is estimated to be ∼ 4 meV in the laser annealed superlattice photodiodes.

An inductively coupled CH 4 /H 2 plasma etching process for delineation of InAs/GaSb type-II superlattice pixels is presented. An optimised CH 4 /H 2 etch recipe without alternate O 2 plasma cleaning step showed an etch rate as high as 0.11 μm/min that results in smooth vertical sidewalls for the type-II superlattice pixel arrays with 10 μm pitch size and 2.4 μm deep trenches. At 70 K, the dark current density for the mesa etched + SU-8 polymer passivated type-II superlattice photodiodes was found to be 0.11 A/cm 2 at an applied reverse bias voltage of 0.2 V. The activation energy of 13 meV obtained from the Arrhenius plot and a variable area diode array technique showed that the measured dark current is mainly attributed to bulk tunnelling current. This technique of mesa delineation for the type-II superlattice pixel arrays with small pitch size is a viable option in realising next-generation infrared focal plane arrays.