Monolithically integrated infrared transceiver
A Schottky diode is monolithically integrated into the core of an infrared semiconductor laser (e.g., a quantum cascade laser) to create a heterodyned infrared transceiver. The internal mode field of the infrared semiconductor laser couples to an embedded Schottky diode and can mix the infrared fields to generate a response at the difference frequency.
1. A monolithically integrated infrared transceiver, comprising:
an infrared semiconductor laser, comprising
a bottom cladding layer,
a layered semiconductor heterostructure active region, comprising two or more different semiconductor layers, on the bottom cladding layer, and
a top cladding layer, comprising a plurality of doped semiconductor layers, on the active region, thereby providing a laser waveguide between the top and bottom cladding layers for confinement of a mode field of the infrared semiconductor laser therein; and
a Schottky diode, comprising a rectifying metal contact recessed into the top cladding layer such that the mode field couples to the depletion region of the diode.
2. The infrared transceiver of claim 1 , wherein the mode field comprises at least one mode having a frequency of greater than 10 THz (less than 30 μm wavelength).
3. The infrared transceiver of claim 2 , wherein the at least one mode has a frequency between 10 and 300 THz (between 30 and 1 μm wavelength).
4. The infrared transceiver of claim 1 , wherein mixing occurs between at least two modes of the mode field to provide an intermediate frequency output signal at the diode.
5. The infrared transceiver of claim 4 , wherein the at least two modes comprises two or more laser modes, one or more laser modes and externally received infrared radiation, one or more laser modes and infrared radiation generated by non-linear mechanisms in the laser, or one or more laser modes and other frequencies generated by non-linear rectification in the Schottky diode.
6. The infrared transceiver of claim 5 , wherein the externally received infrared signal is received by an end facet or sidewall of the laser waveguide, or through a top or bottom cladding layer of the laser waveguide.
7. The infrared transceiver of claim 5 , wherein the externally received infrared signal is received by an infrared antenna structure connected to the Schottky diode.
8. The infrared transceiver of claim 1 , wherein the diode rectifies a single laser mode of the mode field to provide a DC electrical response proportional to the laser power.
9. The infrared transceiver of claim 1 , wherein the infrared semiconductor laser comprises a quantum cascade laser.
10. The infrared transceiver of claim 1 , wherein the infrared semiconductor laser comprises a ring geometry laser, a photonic crystal later, or a nano-laser.
11. The infrared transceiver of claim 1 , wherein the layered semiconductor heterostructure active region comprises GaAs, AlAs, InAs, GaN, AlN, InN, GaSb, AlSb, InSb or alloys thereof.
12. The infrared transceiver of claim 1 , wherein the doping of the top-most doped semiconductor layers of the top cladding layer is tailored to bring the mode field of the infrared semiconductor laser close to the rectifying metal contact of the Schottky diode.
13. The infrared transceiver of claim 12 , wherein the top-most doped semiconductor layers have doping of less than 1×10 19 cm −3 .
14. The infrared transceiver of claim 1 , wherein the rectifying metal contact is recessed into the top cladding layer to contact a semiconductor layer having a doping of less than 1×10 18 cm −3 .
15. The infrared transceiver of claim 1 , wherein the rectifying metal contact comprises titanium.
16. The infrared transceiver of claim 1 , wherein the rectifying metal contact has a cross-sectional dimension of greater than 1 micron.
17. The infrared transceiver of claim 1 , wherein the laser waveguide comprises a ridge structure.
18. The infrared transceiver of claim 17 , further comprising at least one additional Schottky diode to form an array of mixers on the top of the ridge structure.
19. The infrared transceiver of claim 1 , further comprising a coplanar RF waveguide or microstrip line on the laser waveguide.
20. The infrared transceiver of claim 1 , further comprising at least one additional infrared semiconductor laser, each with at least one Schottky diode, wherein the mode field of the at least one additional infrared semiconductor laser couples to the depletion region of the at least one Schottky diode to provide an array of infrared transceivers.