Semiconductor photodetector
First Claim
1. A method for detecting a light signal of a predetermined wavelength by two photon absorption using an optically pumped photodetector, the method comprising:
- providing the detector in the form of a resonator adapted to resonate in response to the light signal of the predetermined wavelength, the resonator having a plurality of spaced apart active semiconductor regions at locations substantially corresponding to anti-nodes of a resonating electromagnetic field, each active region defining a conduction band and at least one valence band, the conduction band defining with the corresponding valence band closest thereto an energy bandgap,selecting the material of the active regions so that the energy bandgap of each active region is such that the photon energy of the light signal of the predetermined wavelength is less than half of the energy gap of the bandgap,pumping the active regions with a pump light beam, the photon energy of which is not less than the energy gap of the band gap of each active region less the photon energy of the light signal of the predetermined wavelength, so that when the light signal of the predetermined wavelength is received simultaneously with the pump light beam a photon is absorbed by each active region from each of the light signal and the pump light beam to transfer an electron across the energy bandgap from the valence band to the conduction band of the corresponding active region,directing the light signal into the active regions, andmonitoring the voltage across the active regions for detecting a change in voltage indicative of the light signal being of a predetermined wavelength.
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Accused Products
Abstract
A semiconductor photodetector (1) for detecting short duration laser light pulses of predetermined wavelength in a light signal (2) comprises a micro-resonator (3) of vertical Fabry-Perot construction having a Bragg mirror pair, namely, a front mirror (5) and a rear mirror (6) with an active region (8) located between the front and rear mirrors (5,6). An N-type substrate (11) supports the rear mirror (6). The light signal (2) is directed into the active region (8) through the front mirror (5) while a pump beam (17) is directed into the active region (8) at an end (18) thereof. The spacing between the front and rear mirrors (5,6) is such as to cause light of the predetermined wavelength to resonate between the mirrors (5,6). The semiconductor material of the active region (8) is selected so that one photon from each of the light signal (2) and the pump beam (17) are required to transfer one electron from a valence band (21) of the active region (8) across a bandgap (22) to a conduction band (20) so that the active region operates on the principle of Two-Photon Absorption. On the active region (8) being simultaneously subjected to the pump beam and light of the predetermined wavelength in the light signal (2) electrons are transferred by Two-Photon Absorption from the valence band (21) to the conduction band (20), thus causing a change in the voltage developed across the active region (8). The change in voltage is detected between an electrode (15) on the substrate (11) and electrodes (8) on the front mirror (5) thereby indicating the presence of light of the predetermined wavelength in the light signal (2).
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Citations
22 Claims
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1. A method for detecting a light signal of a predetermined wavelength by two photon absorption using an optically pumped photodetector, the method comprising:
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providing the detector in the form of a resonator adapted to resonate in response to the light signal of the predetermined wavelength, the resonator having a plurality of spaced apart active semiconductor regions at locations substantially corresponding to anti-nodes of a resonating electromagnetic field, each active region defining a conduction band and at least one valence band, the conduction band defining with the corresponding valence band closest thereto an energy bandgap, selecting the material of the active regions so that the energy bandgap of each active region is such that the photon energy of the light signal of the predetermined wavelength is less than half of the energy gap of the bandgap, pumping the active regions with a pump light beam, the photon energy of which is not less than the energy gap of the band gap of each active region less the photon energy of the light signal of the predetermined wavelength, so that when the light signal of the predetermined wavelength is received simultaneously with the pump light beam a photon is absorbed by each active region from each of the light signal and the pump light beam to transfer an electron across the energy bandgap from the valence band to the conduction band of the corresponding active region, directing the light signal into the active regions, and monitoring the voltage across the active regions for detecting a change in voltage indicative of the light signal being of a predetermined wavelength. - View Dependent Claims (4, 5, 6, 7, 8, 9, 15, 21)
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2. A method for operating an optical switch comprising a semiconductor photodetector, whereby the semiconductor photodetector is adapted for absorbing light of a predetermined wavelength and comprises:
- a resonator adapted to resonate in response to a light signal of light of the predetermined wavelength, the resonator comprising;
a pair of spaced apart mirrors, a non-active region located between the mirrors, and a plurality of spaced apart active regions located in the non-active region for receiving the light signal and a pump light beam, the active regions being provided in the non-active region at locations corresponding to anti-nodes of an electromagnetic field resonating between the mirrors, each active region defining a conduction band and at least one valence band, the conduction band of each active region defining with the corresponding valence band closest to the conduction band an energy bandgap, the width of the energy bandgap being such as to require absorption of more than one photon to effect transition of one electron from the valence band to the conduction band, so that when the light signal of the predetermined wavelength is received by each active region simultaneously with the pump light beam, a photon is required from each of the light signal and the pump light beam to transfer an electron across the energy bandgap from the valence band to the conduction band of each active region to produce a detectable voltage change across the active regions indicative of the light signal of the predetermined wavelength, the optical switch is being responsive to the voltage change produced across the active regions of the resonator in response to light of the predetermined wavelength being absorbed by the photodetector for outputting an electrical signal, the method comprising;directing a light beam comprising a plurality of co-propagating signals of respective different wavelengths at the photodetector, and monitoring the output of the optical switch for detecting an electrical signal indicative of the light beam comprising a light signal of the predetermined wavelength. - View Dependent Claims (3, 10, 11, 12, 13, 14, 16, 17, 18, 19, 20, 22)
- a resonator adapted to resonate in response to a light signal of light of the predetermined wavelength, the resonator comprising;
Specification