Impact of Optical Pulsewidth on the Frequency Response of P-i-N Photodiodes

An analytical model to study the influence of the finite optical pulsewidth on the frequency response of P-i-N photodiode is presented. The derivation takes into account the nonuniform carrier generation, the resistance-capacitance (RC) parasitic effects and the Gaussian temporal profile of the generating function. For an InGaAs photodiode with 0.5-??m intrinsic length and 10-?? m radii excited by 5-ps full-width at half-maximum (FWHM) pulses at 1.3 ??m , previously published theory overestimates the bandwidth by over 30% as compared to the present model. The results suggest that for the faithful measurement of the bandwidth, the FWHM of the Gaussian pulses used should be at least an order of magnitude smaller than the transit time of the slower moving carriers.