Two-state negative feedback avalanche diode having a control element for determining load state
View Patent ↗A negative feedback avalanche diode for detecting the receipt of a single photon is described. The photodetector comprises a load element having two load states, one characterized by high impedance and the other characterized by low impedance. The load state of the load element is controlled by a control signal generated within the negative feedback avalanche diode itself.
1. A negative feedback avalanche detector comprising:
a single-photon avalanche diode;
a load element having a first load state and a second load state, the first load state being higher impedance than the second load state; and
a control element operable for providing a control signal that determines the load state of the load element;
wherein the load element and control element collectively define a load for the single-photon avalanche diode, and wherein the load element switches between the first load state and second load state based on a control signal generated within the negative feedback avalanche detector.
2. The negative feedback avalanche detector of claim 1 wherein the control signal is based on a signal provided by the single-photon avalanche photodiode.
3. The negative feedback avalanche detector of claim 2 wherein the control signal is based on a first current through the single-photon avalanche photodiode.
4. The negative feedback avalanche detector of claim 1 wherein the control element comprises a resistor, and wherein the control signal is based on a first current from the single-photon avalanche photodiode, the first current being a portion of the avalanche current, and wherein at least a portion of the first current passes through the resistor.
5. The negative feedback avalanche detector of claim 1 wherein the load element comprises a transistor.
6. The negative feedback avalanche detector of claim 1 wherein the single-photon avalanche photodiode, the load element, and the control element are monolithically integrated.
7. The negative feedback avalanche detector of claim 1 wherein the single-photon avalanche photodiode is dimensioned and arranged to detect a single photon having a wavelength equal to or greater than 1000 nm.
8. The negative feedback avalanche detector of claim 1 wherein the control element and the load element collectively define a delay element.
9. The negative feedback avalanche detector of claim 1 wherein the control element comprises at least one element selected from the group consisting of a resistor, a reactive element, and a transistor.
10. A method comprising:
generating a first current in response the receipt of a first photon at a negative feedback avalanche photodiode;
providing a first portion of the first current to a load element, wherein the load element has a first load state and a second load state, and wherein the first load state is higher impedance that the second load state, and further wherein the load state of the load element is based on a first control signal;
providing a second portion of the first current to a control element;
providing the first control signal from the control element, the first control signal being based on the second portion.
11. The method of claim 10 further comprising providing the control element and the load element such that the load element switches from the first load state to the second load state in response to an increase in the magnitude of the first current and the load element switches from the second load state to the first load state in response to a decrease in the magnitude of the first current.
12. The method of claim 11 wherein the control element and load element are provided such that (1) the load element switches from the first load state to the second load state after a first time delay after the increase in the magnitude of the first current and (2) the load element switches from the second load state to the first load state occurs after a second time delay after the decrease in the magnitude of the first current.
13. The method of claim 10 further comprising providing the load element such that the load element includes a transistor.
14. The method of claim 10 further comprising providing the control element such that it includes a resistor.
15. The method of claim 10 further comprising providing the control element such that it includes a reactive element.
16. The method of claim 10 further comprising providing the control element such that it includes an active element.