Low-cost, polarisation independent, tapered photodiodes with bandwidth over 50 GHz

High-speed, waveguide photodiodes

“…It also exhibits low TE/TM polarization dependence. In one approach, the transition region consists of laterally [5][6][7] or vertically [8,9] tapered layers that adiabatically transfer the light from an underlying dilute waveguide to a photodiode on top of the transition region. In recent years, this structure has been refined and optimized to achieve high coupling efficiency between an optical fiber input and the photodiode and to extend bandwidths to 100 GHz and beyond [10][11][12].…”

High-speed integrated photodetectors for 40-Gbit/s applications

“…In surface illuminated conventional p-i-n photodiodes or metal-semiconductor-metal photodetectors a high bandwidth entails a limited responsivity [1]. In contrast, structures with illumination perpendicular to the electric field, such as waveguide detectors [2][3][4] or waveguide integrated photodiodes [5][6][7][8] provide high responsivities at ultrahigh frequencies. Furthermore, conventional top or back illuminated photodetectors suffer from a limited power handling behavior since the carriers are generated within a small volume.…”

“…Due to the slightly different field distribution of TE an TM polarized light in the waveguides, a remaining polarization dependence of 0.4 dB was observed. Other authors [7] have combined two lateral tapers and achieved 0.5A/W responsivity of a 50 GHz photodiode. Just recently a short multimode diluted waveguide was applied at the fiber end of the photodetector as depicted in Fig.…”

Space charge balance in high-speed high-saturation-current photodetectors

“…To increase the output photocurrent several types of surface-normal 3-8 and waveguide [9][10][11][12][13] photodiodes have been investigated. Three techniques have been utilized to characterize the saturation current: small-signal compression 3,4,14 , large-signal compression [9][10][11]15 , and pulse compression [5][6][7]13 .…”

“…Three techniques have been utilized to characterize the saturation current: small-signal compression 3,4,14 , large-signal compression [9][10][11]15 , and pulse compression [5][6][7]13 . The compression current is defined as the average DC photocurrent at which the RF responsivity decreases by 1 dB.…”