All-optical single-photon detector

A method of detecting an incidence of a single photon onto a device, comprising:

• applying a probe light onto a device having a bandgap, wherein the device includes a P-N junction maintained in a reverse bias and adapted to initiate an avalanche mode of freeing valence electrons and holes based on incidence of a single photon thereon, and wherein the probe light is configured to apply energy less than the bandgap;
• receiving the reflected probe light from the device by a probe light detector;
• applying a single photon from a control beam to the device from a control beam;
• detecting changes in the device by the probe light detector as the device goes into an avalanche regime,
• wherein the changes correspond to a time delay between the incidence of the single photon onto the device causing a change in concentration of free electrons and holes in the device.

A method of detecting modulations of optical properties of a device, comprising:

• applying a probe light onto a device having a bandgap, wherein the device includes a P-N junction maintained in a reverse bias and adapted to initiate an avalanche regime of freeing valence electrons and holes based on the incidence of a single photon thereon, and wherein the probe light is configured to apply energy less than the bandgap;
• receiving reflected probe light from the device by probe light detector;
• applying a single photon from a control beam to the device;
• detecting fast modulations in the reflected probe light as the device initiates an avalanche regime, wherein the modulations correspond to changes in the device in response to the incidence of the single photon.