Linearity improvement in photo-detectors by using index-matching layer extensions

Abstract: Uniform photocurrent densities can be achieved in waveguide photodetectors by tailoring the extension length of an index-matching layer in eont of the diode. We demonstrate up to 9dB improvement in RF linearity at 2OGHz. Introduction: Spur hx Dynamic Range (SFDR), RF insertion loss and signal to noise ratio of analog fiber optic links improve with increasing maximum linear photocurrent [I]. The maximum linear photocurrent of photodetectors is limited either by thermal failure or by charge screening and can be increased by either tailoring absorption in the diode [2,3] or by tailoring carrier transport [4]. Standard waveguide photodetectors have an exponential distribution of photocurrent along the wave propagatio