Tailored index single mode optical amplifiers and devices and systems including same

• US 7,027,475 B1
• Filed: 09/14/2001
• Issued: 04/11/2006
• Est. Priority Date: 04/11/2000
• Status: Expired due to Fees

• Current Assignee: Coherent Inc (Coherent Corp.)
• Original Assignee: Nuvonyx, Inc.
• Inventors: Faircloth, Brian O., Zediker, Mark S., Haake, John M., Priest, James A., Bott, Eric E.
• Primary Examiner(s): Harvey, Mingun Oh
• Assistant Examiner(s): Nguyen, Tuan N.
• Application Number:
  US09/951,778
• Time in Patent Office: 1,670 Days
• Field of Search: 372 43- 50, 372/75, 372/18, 372/69, 372/71, 372/3, 372/32, 372/92, 372/64, 372/96, 359/279, 385/136
• US Class Current: 372/50.1
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/122 Basic optical elements, e.g. light-guiding paths
• CPC Class Codes: G02B 6/1228 Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305
• CPC Class Codes: G02B 6/13 Integrated optical circuits characterised by the manufacturing method
• CPC Class Codes: H01S 3/2383 Parallel arrangements
• CPC Class Codes: H01S 5/0071 for beam steering, e.g. using a mirror outside the cavity to change the beam direction
• CPC Class Codes: H01S 5/0085 for modulating the output, i.e. the laser beam is modulated outside the laser cavity
• CPC Class Codes: H01S 5/026 Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers stabilisation of output H01S5/06
• CPC Class Codes: H01S 5/0268 Integrated waveguide grating router, e.g. emission of a multi-wavelength laser array is combined by a "dragon router"
• CPC Class Codes: H01S 5/0655 Single transverse or lateral mode emission
• CPC Class Codes: H01S 5/1014 Tapered waveguide, e.g. spotsize converter H01S5/1064 takes precedence
• CPC Class Codes: H01S 5/106 varying thickness along the optical axis
• CPC Class Codes: H01S 5/1064 varying width along the optical axis
• CPC Class Codes: H01S 5/22 having a ridge or stripe structure
• CPC Class Codes: H01S 5/222 having a refractive index lower than that of the cladding layers or outer guiding layers
• CPC Class Codes: H01S 5/2231 with inner confining structure only between the active layer and the upper electrode
• CPC Class Codes: H01S 5/227 Buried mesa structure ; Striped active layer
• CPC Class Codes: H01S 5/4012 Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms
• CPC Class Codes: H01S 5/4031 Edge-emitting structures
• CPC Class Codes: H01S 5/50 Amplifier structures not provided for in groups H01S5/02 - H01S5/30

Abstract

A semiconductor laser device includes a tailored index single mode power amplifier. A high-power laser system can be produced by connecting several of the tailored index single mode power amplifiers in parallel. In an exemplary case, a phase shifting device can be optically coupled to each of the tailored index single mode power amplifiers; the phase shifting devices can be controlled to ensure that the laser beams output by the tailored index single mode power amplifiers are both phase aligned and wavefront matched.

Claims

1. A semiconductor laser device, comprising:

an optical phased array having N optical power amplifiers optically coupled to one another in parallel,

wherein each of the N power amplifiers comprises a tailored index single mode guided power amplifier,

wherein N is an integer greater than or equal to 2,

wherein each of the N tailored index single mode power amplifiers comprises a buried rib structure, and

wherein each of the N tailored index single mode power amplifiers exhibits a continuous taper in the index profile.

2. The semiconductor device as recited in claim 1, wherein each of the N tailored index single mode power amplifiers:

exhibits a discontinuous variation in the index profile that produces a cumulative predetermined index profile.

3. The semiconductor device as recited in claim 1, wherein the current profile applied to the amplifier structures is varied to tailor the index of the power amplifier.

4. The semiconductor device as recited in claim 1, further comprising:

a heat sink,

wherein the tailored index step of the power amplifiers is provided by varying the thermal impedance characteristic of the junction at the heat sink.

5. The semiconductor device as recited in claim 1, wherein the tailored index step of the power amplifiers is provided by implanting impurities in regions of the semiconductor device adjacent to the power amplifier.

6. The semiconductor device as recited in claim 1,

wherein the N power amplifiers are disposed in an array of M×

R power amplifiers,

wherein M and R are both positive integers, and

wherein N is equal to the product of M times R.

7. The semiconductor laser device as recited in claim 6,

wherein the N power amplifiers receive an input signal from a single master oscillator, and

wherein the N output beams are coherent with respect to one another.

8. The semiconductor laser device as recited in claim 6,

wherein a first M of the N power amplifiers receives an input beam from an R^th master oscillator,

wherein a second M of the N power amplifiers receives an input beam from an R^th-1 master oscillator, and

wherein all of the output beams generated by the first M of the N power amplifiers are coherent with respect to one another but incoherent with respect to the output beams generated by the second M of the N power amplifiers.

9. The semiconductor device as recited in claim 1, further comprising:

an optical device for optimizing the fill factor of the phased array output beam synthesized from the outputs of the N power amplifiers.

10. The semiconductor device as recited in claim 1, further comprising:

N phase modulators optically coupled to the N power amplifiers, respectively; and

a control system controlling the N phase modulators to thereby phase align each output signal generated by the N power amplifiers.

11. The semiconductor device as recited in claim 10, wherein the control system implements a hill climbing algorithm.

12. The semiconductor device as recited in claim 10, wherein the control system implements an interferometric phase control algorithm.

13. The semiconductor device as recited in claim 1, further comprising:

at least one of N phase modulators and N-1 phase modulators optically coupled to at least one of N and N-1 of the N power amplifiers, respectively; and

a control system controlling the at least one of N phase modulators and the N-1 phase modulators to thereby phase align each output signal generated by the at least one of N and the N-1 of the N power amplifiers.

14. The semiconductor device as recited in claim 13, wherein the control system implements a hill climbing algorithm.

15. The semiconductor device as recited in claim 13, wherein the control system implements an interferometric phase control algorithm.

16. A high power laser system comprising a plurality of the semiconductor laser devices recited in claim 1.

17. The high power laser system as recited in claim 16, wherein the phased aligned output of the semiconductor laser device is transmitted by a single optical fiber.

18. An integrated semiconductor device which generates N phase aligned, wavefront matched laser beams from N amplified laser beams, comprising:

N phase modulators receiving an input beam from a master oscillator and generating N phase shifted laser beams;

N tailored index single mode power amplifiers receiving the N phase shifted laser beams and generating the N amplified laser beams;

a phase sensor generating N sensor signals indicative of the phase of the individual N amplified laser beams; and

a controller for controlling the phase of each of the N amplified laser beams responsive to the N sensor signals, respectively, to thereby generate the N phase aligned, wavefront matched laser beams,

wherein N comprises a positive integer.

19. The integrated semiconductor device as recited in claim 18, wherein each of the N tailored index single mode power amplifiers comprises a buried rib structure.

20. An integrated semiconductor device which generates N phase aligned, wavefront matched laser beams from N amplified laser beams, comprising:

N-1 phase modulators receiving an input beam from a master oscillator and generating N-1 phase shifted laser beams;

N tailored index single mode power amplifiers receiving the N-1 phase shifted laser beams and the input beam and generating the N amplified laser beams;

a phase sensor generating N-1 sensor signals indicative of the phase of the individual N-1 amplified laser beams; and

a controller for controlling the phase of each of the N-1 amplified laser beams responsive to the N-1 sensor signals, respectively, to thereby generate the N phase aligned, wavefront matched laser beams,

wherein N comprises a positive integer greater than or equal to 2.

21. The integrated semiconductor device as recited in claim 20, wherein each of the N tailored index single mode power amplifiers comprises a buried rib structure.

22. A semiconductor laser system, comprising:

N tailored index single mode power amplifiers;

L phase modulators optically coupled to the input ports of L of the N tailored index single mode power amplifiers;

an optical device which launches the output of the N tailored index single mode power amplifiers into an optical fiber to thereby generate a coherent beam;

a phase sensor for generating respective electrical signals indicative of phase and wavefront characteristic each of L of the N coherent beams; and

a controller electrically coupled to the L phase modulators for permitting the L phase modulators to match the phase and wavefront of the L of the N coherent beams to one another,

wherein L and N are positive integers and N is greater than or equal to L.

23. The semiconductor laser system as recited in claim 22, further comprising:

an optical tap for routing a predetermined portion of the N coherent beams to a sensor output port; and

a power sensor optically coupled to the sensor output port for measuring the output of the semiconductor laser system.

24. The semiconductor laser system as recited in claim 22, wherein each of the N tailored index single mode power amplifiers comprises a buried rib structure.

25. A two-dimensional semiconductor laser array, comprising:

an optical phased array having N power amplifiers optically coupled to one another in parallel,

wherein each of the N power amplifiers comprises a tailored index single mode guided power amplifier,

wherein the N power amplifiers are disposed in R linear arrays of power amplifiers, each linear array including M power amplifiers,

wherein M and R are both positive integers; and

N is equal to the product of M times R,

wherein the N power amplifiers receive an input beam from a single master oscillator, and

wherein the N output beams are coherent with respect to one another.

26. The two-dimensional semiconductor laser array as recited in claim 25,

wherein an R^th linear array of power amplifiers receives an input beam from an R^th master oscillator,

wherein an R^th-1 linear array of power amplifiers receives an input beam from an R^th-1 master oscillator, and

wherein all of the output beams generated by the R^th linear array of power amplifiers are coherent with respect to one another but incoherent with respect to the output beams generated by the R^th-1 linear array of power amplifiers.

27. The two-dimensional semiconductor laser array as recited in claim 25, wherein each of the N tailored single mode power amplifiers comprises a buried rib structure.

28. A semiconductor device comprising:

an optical phased array having N output amplifiers,

wherein each of the output amplifiers comprises a tailored index single mode power amplifier, the N output amplifiers are disposed on a single substrate,

wherein N comprises an integer equal to or greater than 2,

wherein each of the N tailored index single mode power amplifiers comprises a buried rib structure, and

wherein each of the N tailored index single mode power amplifiers exhibits a continuous taper in the index profile.

29. A laser system comprising:

an optical phased array of N tailored index single mode amplifiers;

at least one of N and N-1 phase modulators disposed upstream of selected ones of the N tailored index single mode amplifiers;

an optical signal source producing an optical signal, said optical signal being sent to said at least one of N an N-1 phase modulators;

a distribution network for distributing the optical signal to the selected ones of the at least one of N and N-1 phase modulators;

a controller for generating at least one of N and N-1 control signals;

interface circuitry for applying the at least one of N and N-1 control signals to the at least one of N and N-1 phase modulators to effect control; and

means for measuring a parameter characteristic of selected ones of the output signals produced by the N tailored index single mode amplifiers,

wherein N comprises an integer equal to or greater than 2, and

wherein each of the N tailored index single mode power amplifiers comprises a buried rib structure.

30. The laser system as recited in claim 29, wherein the N tailored index single mode amplifiers, the at least one of N and N-1 phase modulators, and a portion of the distribution network are supported by a single support element.

31. The laser system as recited in claim 30, wherein the distribution network includes a free space portion.

32. The laser system as recited in claim 29, wherein the N tailored index single mode amplifiers, the at least one of N and N-1 phase modulators, a portion of the distribution network, and the interface circuitry are supported by a single support element.

33. The laser system as recited in claim 29, wherein the N tailored index single mode amplifiers, the at least one of N and N-1 phase modulators, a portion of the distribution network, the controller, and the interface circuitry are supported by a single support element.

34. The laser system as recited in claim 29, wherein the N tailored index single mode amplifiers, the at least one of N and N-1 phase modulators, a portion of the distribution network, the controller, the optical signal source, and the interface circuitry are supported by a single support element.

35. The laser system as recited in claim 29,

wherein the measuring means measures the near-field phase pattern produced by the N tailored index single mode amplifiers, and

wherein the controller optimizes the far-field emission of the N tailored index single mode amplifiers by appropriately controlling the N-1 phase modulators associated with the N tailored index single mode amplifiers.

36. The laser system as recited in claim 29,

wherein the measuring means generates measurement signals representing the relative phases of the output signals of the N tailored index single mode amplifiers to one of each other and a common phase reference signal, and

wherein the controller optimizes the far-field emission of the N tailored index single mode amplifiers by appropriately controlling the N-1 phase modulators associated with the N tailored index single mode amplifiers.

37. The laser system as recited in claim 29,

wherein the measuring means measures the power generated by the N tailored index single mode amplifiers incident on a remote target, and

wherein the controller maximizes the power from the N tailored index single mode amplifiers incident on the target by appropriately controlling the N-1 phase modulators associated with N tailored index single mode amplifiers.

38. The laser system as recited in claim 29,

wherein the measuring device measures the power coupled from the semiconductor device into an optical fiber, and

wherein the controller maximizes the power from the N tailored index single mode amplifiers coupled into the optical fiber by appropriately controlling the N-1 phase modulators associated with the N tailored index single mode amplifiers.