Abstract: As the fundamentals of the fabrication of monolithically integrated optical receiver, a photodiode has been fabricated using laser assisted microprocessing. Laser induced local zinc diffusion has been used to form the p-n junction of the photodiode. The diffusion process was implemented by using the focused laser spot to heat the diffusion window. A spin-on film doped by Zn was used as the diffusion source. Lithography, passivation, electrodes fabrication and packaging are conventional, as the wafers don't endure high temperature in these steps. The responsivity of the fabricated Planar InGaAs/InP PIN photodiodes arrived 0.21 A/W. It was found that some factors in the laser induced diffusion process caused the low performance of the photodiodes. Then improvements including the automatic co