Monolithic power monitor and wavelength detector
View Patent ↗Monolithic single and/or dual detector structures are fabricated on the emitting surface of a VCSEL and/or on a lens or glass substrate configured to be positioned along the axis of emission of an optical light source. Each monolithic detector structure includes one or two PIN detectors fabricated from amorphous silicon germanium with carbon doping or amorphous germanium with hydrogen doping. The monolithic detectors may additionally include various metallization layers, buffer layers, and/or anti-reflective coatings. The monolithic detectors can be grown on 1550 NM VCSELs used in optical transmitters, including lasers with managed chirp and TOSA modules, to reduce power and real estate requirements of the optical transmitters, enabling the optical transmitters to be implemented in long-reach SFP+ transceivers.
1. A monolithic dual detector structure for detecting the optical power and wavelength of light emitted by an optical light source, the structure comprising:
a first detector structure, the first detector structure having selectively doped areas that provide PIN junctions of a photovoltaic device, the first detector structure further having a sufficiently small optical absorption coefficient, within an optical wavelength range, that limits absorption by the first detector structure to a corresponding small fractional amount of light being emitted by an optical light source;
a periodic structure on the first detector, the periodic structure being attuned to a particular wavelength within the optical wavelength range such that the periodic structure is substantially transmissive for light of the particular wavelength and variably less transmissive for light of different wavelengths; and
a second detector structure on a second buffer layer on the periodic structure, the second detector structure having selectively doped areas that provide PIN junctions of a photovoltaic device, the second detector structure further having a sufficiently small absorption coefficient, within the optical wavelength range, that limits absorption by the second detector structure to a corresponding small fractional amount of light being emitted by the optical light source;
wherein the combination of the first detector structure, periodic structure, second buffer layer, and second detector structure is sufficiently thin to be substantially transmissive of light of the particular wavelength propagating therethrough.
2. The monolithic dual detector structure of claim 1 , wherein the first detector structure is on a first buffer layer, further comprising:
a first anti-reflective coating layer between the first buffer layer and the first detector structure;
a second anti-reflective coating layer between the first detector structure and the periodic structure; and
a third anti-reflective coating layer on the second detector.
3. The monolithic dual detector structure of claim 2 , wherein the first buffer layer and the second buffer layer include one or more of the following materials:
polyimide, silicon oxide, and nitride.
4. The monolithic dual detector structure of claim 1 , wherein the periodic structure is shaped as an etalon or a distributed Bragg reflector minor and includes multiple periodic layers of one or more oxide materials.
5. The monolithic dual detector structure of claim 1 , wherein each of the first detector structure and the second detector structure include one or more of amorphous silicon germanium with carbon doping or amorphous germanium with hydrogen doping.
6. The monolithic dual detector structure of claim 5 , wherein the first detector structure, the second detector structure, or both, are further doped with phosphorous.
7. The monolithic dual detector structure of claim 1 , wherein the monolithic dual detector structure is fabricated on one or more of:
the emitting surface of a vertical cavity surface emitting laser along its axis of light emission;
an optical lens configured to be positioned along an axis of light emission of an optical light source, wherein the optical lens is positioned such that the monolithic dual detector structure fabricated on the optical lens is also positioned along the axis of light emission; and
a substrate configured to be positioned between an optical light source and an optical lens along an axis of emission of the optical light source, wherein the substrate is positioned such that the monolithic dual detector structure fabricated on the substrate is also positioned along the axis of light emission.
8. The monolithic dual detector structure of claim 1 , wherein each of the first detector structure and the second detector structure include a plurality of metallization layers.
9. The monolithic dual detector structure of claim 1 , further comprising, a latched garnet, a plurality of polarizers, and a doped glass plate configured to act as an integrated collimating lens, wherein the latched garnet, plurality of polarizers, and doped glass plate are coupled between the first detector structure and the periodic structure.
10. The monolithic dual detector structure of claim 1 , further comprising control lines coupled to the periodic structure, wherein the application of an electrical current or voltage to the periodic structure through the control lines alters the dielectric function of the periodic structure thereby altering the transmissivity of the periodic structure such that the periodic structure can function as a variable optical attenuator.