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Evanescently-coupled photodiodes were realised for high-power operation at a wavelength of 1.55 µm and wide-band operation beyond 30 GHz. Evanescent coupling allows for uniform carrier generation, which avoids electrical breakdown at the beginning of the active waveguide. The evanescently-coupled photodiodes, with an active length of 70 µm, reach a bandwidth of 40 GHz. Their average photocurrent at the -1 dB saturation point is 14 mA at 40 GHz. The evanescently-coupled photodiodes, with an active length of 120 µm, reach a bandwidth of 30 GHz. Their average photocurrent at the -1 dB saturation point is 22 mA at 40 GHz. The dual-depletion active region allows for reduced capacitance, and therefore higher bandwidth. The measured polarisation dependent loss is, on average, 1.2 dB on the 30 GHz devices. More work is needed to understand this high value, compared with the low theoretical value of 0.01 dB. [ABSTRACT FROM AUTHOR]

Describes a monolithic polarization-selective side-illuminated pin detector using the coupling properties of symmetric and asymmetric slab optical waveguides. Modal analysis of the proposed basic structure; Replacement of the symmetric waveguide with a multiple diluted waveguide optimized by a genetic algorithm coupled to a beam propagation method; Improvement in the performance of the device and the computer polarization ratio.