Photodetector comprising coupled fabry-perot resonators

A photodetector comprising:

• a substrate, which is reflective to electromagnetic radiation incident on the photodetector;
• electrode portions, which are supported by the substrate, and which have respective surfaces facing away from the substrate, referred to as upper surfaces and located at a common level of spacing from said substrate;
• portions of an electrically insulating material, which are located between the electrode portions and the substrate, so as to electrically insulate each electrode portion from the substrate;
• and
• at least one portion of a photoconductive material, which is arranged to be in electrical contact with two of the electrode portions which are adjacent, at least two of the electrode portions and the substrate being intended to collect a photodetection current when the photodetector is in use, characterized in that a first and a second of the electrode portions which are adjacent delimit therebetween, parallel to the substrate, a volume into which, when the photodetector is in use, the radiation penetrates in order to be reflected by the substrate, forming a first Fabry-Perot resonator between said substrate and the level of the upper surfaces of the electrode portions,
• and in that the second electrode portion and a third of the electrode portions, which is located on a side of said second electrode portion opposite said first electrode portion, delimit therebetween, parallel to the substrate, another volume into which, when the photodetector is in use, the radiation also penetrates to be reflected by the substrate, forming a second Fabry-Perot resonator between said substrate and the level of the upper surfaces of the electrode portions,
• the first and second Fabry-Perot resonators being designed to generate standing-wave components that propagate perpendicular to the substrate when the photodetector is in use, and in that the photodetector has the following features /1/ to /3/:
• /1/ a width of the first Fabry-Perot resonator, measured between the first and second electrode portions parallel to the substrate, is different from a width of the second Fabry-Perot resonator, measured between the second and third electrode portions also parallel to the substrate, so that the first and second Fabry-Perot resonators have respective individual resonance wavelength values, effective for the radiation incident on the photodetector, which are different, with respective values of an individual resonance quality factor of the first and second Fabry-Perot resonators such that, on one wavelength axis of the incident radiation, the following individual resonance intervals:
• [λri·(1−3/Qi);
• λri(1+3/Qi)], have an overlap, where i is equal to 1 or 2 to designate the first or second Fabry-Perot resonator, respectively, and λri and Qi are respectively the wavelength and quality factor values of the individual resonance of the Fabry-Perot resonator i;
• /2/ a sum of the widths of the first and second Fabry-Perot resonators with the width of the second electrode portion, measured parallel to the substrate between the volumes of the first and second Fabry-Perot resonators, is adapted to produce a coupling between said first and second Fabry-Perot resonators, by being less than a resonance wavelength value relative to the coupling, known as the coupling resonance wavelength, which is effective for the radiation incident on the photodetector, and which results from interference between at least three waves, including:
• a first wave resulting from the reflection of incident radiation on the substrate;
• a second wave emerging from the first Fabry-Perot resonator, resulting from a superposition of several wave components, among which at least one of said wave components has made at least one round trip within the volume of the second Fabry-Perot resonator;
• and
• a third wave emerging from the second Fabry-Perot resonator, resulting from another superposition of several other wave components, among which at least one of said other wave components has made at least one round trip within the volume of the first Fabry-Perot resonator;
• and
• /3/ the photoconductive material is absorbent for the coupling resonance wavelength, and the portion of said photoconductive material is located in or on at least one of the volumes of the first and second Fabry-Perot resonators.