Laser-to-fiber coupling
View Patent ↗Our wafer scale processing techniques produce chip-laser-diodes with a diffraction grating ( 78 ) that redirects output light out the top ( 88 ) and/or bottom surfaces. Generally, a diffraction grating ( 78 ) and integrated lens-grating ( 78 ) are used herein to couple light from the chip to an output fiber ( 74 ), and the lens-grating ( 78 ) is spaced from the diffraction grating ( 76 ). Preferably the diffraction grating ( 76 ) and integrated lens grating ( 78 ) are also used to couple light from the output fiber ( 74 ) back to the active region of the chip. The integrated lens-grating ( 78 ) can be in a coupling block ( 82 ). The use of a coupling block ( 82 ) can eliminate “facet-type damage”. A coupling block ( 82 ) is generally used herein to couple light from the chip to an output fiber ( 74 ), and preferably to couple feedback reflected from the fiber ( 74 ) back to the chip.
1. A method of horizontally generating light within a semiconductor structure, and diffracting at least a portion of the generated light out of said structure and into an optical fiber, said method comprising:
providing a semiconductor substrate having a substrate with a bottom surface and having a lower metal contact on at least a portion of said substrate bottom surface;
providing a core layer containing an active-region, a waveguide region longitudinally-displaced from an active and a passive region with an adjacent passive-end facet, said core layer being over said substrate;
providing a top cladding layer on said core layer; providing a top electrode layer over said top cladding layer,
providing a top metal contact on a portion of said top electrode layer over said active region;
providing grating fingers extending down into said top cladding layer over at least a portion of said waveguide region to provide a diffraction grating;
providing an integrated lens-grating wherein the lens-grating is spaced by at least one-hundred wavelengths from the top grating from the diffraction grating;
providing a coupling block with an optical fiber attached, said coupling block connected to said semiconductor substrate; and
applying a voltage between said top and lower metal contacts, whereby light is generated in said active region and at least a portion of the generated light is diffracted out of at least one of said cladding upper surface and said substrate bottom surface, and focused into said fiber by said lens-grating.
2. The method of claim 1 , wherein said lens-grating is on said substrate bottom.
3. The method of claim 1 , wherein said lens-grating is in said coupling-block.
4. The method of claim 1 , wherein said diffraction grating and integrated lens-grating are also used to couple light from the output fiber back to the active region of the semiconductor substrate.
5. The method of claim 1 , wherein an upper buffer layer is provided between said top cladding layer and said core and a lower buffer layer is provided between said substrate and said core.
6. A semiconductor laser diode, said laser diode comprising:
a semiconductor substrate;
a core layer comprising an active region and a waveguide region on said substrate, said waveguide region being longitudinally-displaced from an active region, and wherein said active region comprises at least one quantum well;
an upper cladding layer on said core layer;
a diffraction grating comprising grating fingers extending down into said top cladding layer over at least a portion of said waveguide region;
an integrated lens-grating wherein the lens-grating is spaced by at least one-hundred wavelengths from the diffraction grating; and
a coupling block connected to said semiconductor substrate and to an optical fiber.
7. A method of fabricating a light-generating semiconductor structure, said structure having top and bottom surfaces, said method comprising:
providing a semiconductor substrate;
providing a core layer containing an active-region, and a waveguide region longitudinally-displaced from an active region, said core layer being over said substrate;
providing a top cladding layer on said core layer;
providing a diffraction grating on said top cladding layer over at least a portion of said waveguide region;
providing an integrated lens-grating integrated into said diffraction grating or on said bottom surface or in a coupling block cut from a glass wafer and attached to an optical fiber, said semiconductor substrate, or both; and
providing at least one grating in said coupling block, wherein the at least one grating is selected from the group consisting of: a resonance-grating to reflect light back to the active region, a fiber-diffraction-grating to diffract light into the fiber along the fiber axis, a diffraction-grating to diffract light into the coupler and then into the fiber, the lens-gating, and a beam-shaping grating.
8. The method of claim 7 , wherein an output fiber is provided and said lens-grating directs an output beam into said fiber.
9. The method of claim 8 , wherein the fiber is a single-mode fiber.
10. The method of claim 8 , wherein a coupling-block having opposing faces is provided and one coupling-block opposing face is attached to the fiber and the other opposing face is attached to the semiconductor structure.
11. The method of claim 10 , wherein an integrated lens-grating is within the coupling-block.
12. The method of claim 8 , wherein the diffraction grating diffracts light both upwards and downwards and an integrated reflector directs both upwards and downwards refracted light through the integrated lens-grating into the fiber.
13. The method of claim 8 , wherein the diffraction grating diffracts light both upwards and downwards and a topside integrated reflector directs upwards refracted light through the integrated lens-grating into the fiber.
14. The method of claim 10 , wherein the fiber is attached to the coupling-block by a thermosetting optically-transparent adhesive which was applied to the coupling-block and/or the fiber and dried without being cured, and wherein the fiber is then placed in contact with the coupling block, and the thermosetting adhesive is then cured to bond the fiber to the coupling block.
15. The method of claim 10 , wherein the semiconductor structure is attached to the coupling-block by a thermosetting optically-transparent adhesive which was applied to the coupling-block and/or the semiconductor structure and dried without being cured, and wherein the semiconductor structure is then placed in contact with the coupling block, and the thermosetting adhesive is then cured to bond the semiconductor structure to the coupling block.
16. The method of claim 15 , wherein the thermosetting adhesive is cured to bond the semiconductor structure to the coupling block at a position of essentially a maximum value of light intensity in the fiber by UV curing.
17. The method of claim 8 , wherein the lens-grating is spaced by at least one-hundred wavelengths from the diffraction grating.
18. The semiconductor laser diode of claim 6 , wherein the coupling block contains the integrated lens-grating.
19. The semiconductor laser diode of claim 6 , wherein the integrated lens-grating is on a bottom of the semiconductor substrate.
20. The semiconductor laser diode of claim 6 , wherein the coupling block contains at least one grating selected from the group consisting of: a resonance-grating to reflect light back to the active region, a fiber-diffraction-grating to diffract light into the fiber along the fiber axis, a diffraction-grating to diffract light into the coupler and then into the fiber, the lens-grating, and a beam-shaping grating.