Low-power photonic demodulator

A time-of-flight imaging system for performing distance measurement and 3D imaging, comprising:

• a modulated light source for transmitting a light pulse to a target object;
• a processor;
• and
• a receiving unit comprising one or more phase-sensitive photo-detectors for detecting photons generated by a received light reflected from the target object, wherein each individual phase-sensitive photo-detector comprises:
• a semiconductor substrate doped with a first conductive type of dopant;
• two or more guided regions formed in the semiconductor substrate and doped with the first conductive type of dopant;
• a photo sensing region disposed between the two or more guided regions for sensing an impinging photon from the received light by generating photo carriers;
• and
• two or more detection regions formed in the semiconductor substrate and doped with a second conductive type of dopant,
• wherein:
• the two or more guided regions are respectively connected to power sources to apply an electric potential across the two or more guided regions for controlling a detectivity of the impinging photon;
• and
• the photo sensing region is provided to form at least a pn junction between the two or more guided regions that is reverse biased so as to reduce or prevent a leakage path between the two or more guided regions,
• wherein the photo sensing region comprises three or more sub-regions,
• wherein any two adjacent sub-regions are doped with different conductive type of dopants selected from the first and the second conductive type of dopants such that at least two pn junctions are formed for the three or more sub-regions,
• wherein the at least two pn junctions are configured to be reverse biased such that their depletion regions merge to fully deplete the photo sensing region,
• wherein the individual phase-sensitive photo-detector further comprises an isolation region forming a ring-like surrounding structure arranged to surround the two or more guided regions and the two or more detection regions, so as to isolate the two or more guided regions and the two or more detection regions from the semiconductor substrate, and wherein the isolation region is doped with the second conductive type of dopant opposite to the first conductive type.