We present a novel all-optical quaternary shift keying (4-ASK) modulation technique based on the cross-gain modulation in a semiconductor optical amplifier (SOA) of a modulated probe with moderate extinction ratio. Experimental demonstrations are presented for 20-Gb/s non return to zero (NRZ) and return to zero (RZ) 4-ASK signals with different level distributions and extinction ratios. The dispersion tolerance limitations are investigated. RZ 4-ASK signals show better dispersion robustness (with accumulated dispersion range from −240 to 350 ps/nm) than NRZ 4-ASK signals due to their reduced frequency chirp.
Quantum efficiency of long-base n+p junction silicon solar cells with SiO2 layer deposited on the top cell, and with one-dimensional gratings etched in the cell's top is considered. It is assumed that the region where the useful absorption occurs is outside the grating region. The efficiency is independently optimized by adjusting the layer depth, and the grating dimensions, respectively. It is shown that optimum efficiency of the cells with grating is higher than that of the cell with SiO2 layer.
S-matrix propagation algorithm for electromagnetic analysis of multilayer gratings with Rayleigh-Fourier implementation and TM-polarization issue renewal is overviewed. Examples of polarized-antireflection grating design are considered.
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