Multi-section tunable laser with differing multi-element mirrors

• US 4,896,325 A
• Filed: 08/23/1988
• Issued: 01/23/1990
• Est. Priority Date: 08/23/1988
• Status: Expired due to Term

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Coldren, Larry A.
• Primary Examiner(s): Scott, Jr., Leon
• Application Number:
  US07/235,307
• Time in Patent Office: 518 Days
• Field of Search: 372/101, 372/20, 372/92, 372/99, 372/102, 372/29, 372/32, 372/38
• US Class Current: 372/20
• CPC Class Codes: H01S 5/06256 with DBR-structure
• CPC Class Codes: H01S 5/1215 Multiplicity of periods
• CPC Class Codes: H01S 5/125 Distributed Bragg reflector [DBR] lasers

Abstract

An improvement for allowing selective tuning of the emitted beam over a broad bandwidth to a diode laser having an active section for creating a light beam by spontaneous emission over a bandwidth around some center frequency and for guiding and reflecting the light beam between a pair of mirrors bounding the active on respective ends thereof to create an emitted beam of laser light. The mirrors each have narrow, spaced reflective maxima with the spacing of the reflective maxima of respective ones of the mirrors being different whereby only one the reflective maxima of each of the mirrors can be in correspondence and thereby provide a low loss window at any time. The preferred mirrors each include a plurality of discontinuities to cause the narrow, spaced reflective maxima wherein the spacing of the discontinuities of one mirror is different from the spacing of the discontinuities of the other mirror so as to cause the wavelength spacing of the maxima to be different. Additionally, the preferred embodiment includes a vernier circuit operably connected to the mirrors for providing an electrical signal to the mirrors which will cause continuous tuning within a desired frequency band, an offset control circuit operably connected to the mirrors for providing a voltage signal to the mirrors which will shift the reflective maxima of the mirrors into alignment at a desired frequency mode, and a phase control circuit for adjusting the laser mode wavelength to be in correspondence with the low loss window.

Claims

1. In a diode laser having an active section for creating a light beam by spontaneous emission over a bandwidth around some center frequency and for guiding and reflecting the light beam between a pair of mirrors bounding the active section on respective ends thereof to create an emitted beam of laser light, the improvement to allow selective tuning of the emitted beam comprising:

the mirrors each having spaced reflective maxima points providing a maximum reflection of an associated wavelength with the spacing of said reflective maxima points of the respective mirrors being different whereby only one said reflective maxima of each of the mirrors can be in correspondence with a wavelength of the created lightbeam and thereby provide a low loss window at any time.

2. The improvement to a diode laser of claim 1 and additionally comprising:

mirror means for adjusting a wavelength at which said reflective maxima points of the respective mirrors occur whereby the wavelength of said low loss window and therefore the frequency of the emitted beam can be adjusted.

3. The improvement to a diode laser of claim 2 and additionally comprising:

phase shifter means for adjusting the round trip cavity phase between the pair of mirrors and thus a lasing mode wavelength of the diode laser.

4. The improvement to a diode laser of claim 3 and additionally comprising:

means for adjusting said phase shifter means in combination with said means for adjusting the wavelength at which said reflective maxima points of the respective mirrors occurs whereby the wavelength of said low loss window and the lasing mode wavelength of the diode laser can be adjusted in synchronism to provide selective tuning over a broad bandwidth.

5. The improvement to a diode laser of claim 3 wherein:

an index of refraction of said phase shifter means, the two mirrors and an active section are each changeable independently as a function of an electrical signal applied thereto.

6. The improvement to a diode laser of claim 3 wherein:

(a) said phase shifter means, the two mirrors and an active section each have an electrode connected thereto for applying an electrical signal thereto; and

,

(b) the index of refraction of said phase shifter means, the two mirrors and the active section are each changeable independently as a function of said electrical signal applied to said electrode thereof.

7. The improvement to a diode laser of claim 1 wherein:

the mirrors each include a plurality of discontinuities which cause said reflective maxima points, the spacing of said discontinuities of one mirror being different from the spacing of said discontinuities of the other mirror so as to cause a wavelength spacing of said reflective maxima points to be different in respective ones of the mirrors.

8. The improvement to a diode laser of claim 7 and additionally comprising:

mirror means for adjusting an optical spacing of said discontinuities of the respective mirrors whereby the wavelength of said low loss window and therefore the frequency of the emitted beam can be adjusted.

9. The improvement to a diode laser of claim 8 wherein said means for adjusting the optical spacing of said discontinuities comprises:

(a) vernier control circuit means connected to the mirrors for providing an electrical signal to the mirrors which causes continuous tuning within a desired frequency band; and

,

(b) offset control circuit means connected to the mirrors for providing a electrical signal to the mirrors which shifts said reflective maxima points of the mirrors into alignment at a desired frequency mode.

10. The improvement to a diode laser of claim 9 and additionally comprising:

(a) phase shifter means for adjusting the round trip cavity phase between the pair of mirrors and thus a lasing mode wavelength of the diode laser; and

,

(b) phase control circuit means operated in synchronism with said vernier control circuit means for aligning the wavelength of the lasing mode wavelength of the diode laser to be the same as the wavelength of said low loss window.

11. An improved tunable diode laser comprising:

(a) active section semiconductor means for creating a light beam by spontaneous emission over a bandwidth around some center frequency and for guiding said light beam between opposed ends thereof to create an emitted beam of laser light; and

,

(b) a pair of mirrors bounding said active section semiconductor means on respective ones of said opposed ends thereof, said mirrors each having spaced reflective maxima points providing a maximum reflection of an associated wavelength with the spacing of said reflective maxima points of respective ones of said mirrors being different whereby only one said reflective maxima of each of said mirrors can be in correspondence with a wavelength of the created lightbeam and thereby provide a low loss window at any time.

12. The improved tunable diode laser of claim 11 and additionally comprising:

mirror means for adjusting a wavelength at which said reflective maxima points of respective ones of said mirrors occurs whereby the wavelength of said low loss window and therefore the frequency of said emitted beam can be adjusted.

13. The improved tunable diode laser of claim 12 and additionally comprising:

phase shifter means for adjusting the round trip cavity phase between said mirrors and thus a lasing mode wavelength of the diode laser.

14. The improved tunable diode laser of claim 13 and additionally comprising:

means operably connected for adjusting said phase shifter means in combination with said means for adjusting the wavelength at which said reflective maxima of respective ones of said mirrors occurs whereby the wavelength of said low loss window and the lasing mode wavelength of the diode laser can be adjusted in synchronism to provide selective tuning over a broad bandwidth.

15. The improved tunable diode laser of claim 13 wherein:

an index of refraction of said phase shifter means, said mirrors and said active section semiconductor means are each changeable independently as a function of an electrical signal applied thereto.

16. The improved tunable diode laser of claim 13 wherein:

(a) said phase shifter means, said mirrors and said active section semiconductor means each have an electrode connected thereto for applying an electrical signal thereto; and

,

(b) the index of refraction of said phase shifter means, said mirrors and said active section semiconductor means are each changeable independently as a function of said electrical signal applied to said electrode thereof.

17. The improved tunable diode laser of claim 11 wherein:

said mirrors each include a plurality of discontinuities causing said reflective maxima points, the spacing of said discontinuities of one said mirror being different from the spacing of said discontinuities of the other said mirror so as to cause the wavelength spacing of said reflective maxima points to be different in respective ones of said mirrors.

18. The improved tunable diode laser of claim 17 and additionally comprising:

means for adjusting an optical spacing of said discontinuities of respective ones of said mirrors occurs whereby the wavelength of said low loss window and therefore the frequency of said emitted beam can be adjusted.

19. The improved tunable diode laser of claim 18 wherein said means for adjusting an optical spacing of said discontinuities comprises:

(a) vernier control circuit means connected to said mirrors for providing an electrical signal to said mirrors which causes continuous tuning within a desired frequency band; and

,

(b) offset control circuit means operably connected to said mirrors for providing a electrical signal to said mirrors which shifts said reflective maxima of said mirrors into alignment at a desired frequency mode.

20. The improved tunable diode laser of claim 19 and additionally comprising:

(a) phase shifter means for adjusting the round trip cavity phase between said mirrors and thus a lasing mode wavelength of the diode laser; and

,

(b) phase control circuit means operated in synchronism with said vernier control circuit means for aligning the wavelength of the lasing mode wavelength of the diode laser to be the same as the wavelength of said low loss window.

21. A diode laser which can be operated at selectably variable frequencies covering a wide wavelength range comprising:

(a) active section semiconductor means for creating a light beam by spontaneous emission over a bandwidth around some center frequency and for guiding said light beam between opposed ends thereof;

(b) gain control means connected to said active section semiconductor means for supplying an electrical signal to said active section semiconductor means which causes said active section semiconductor means to have gain sufficient to overcome losses and create an emitted beam of laser light;

(c) a pair of mirrors bounding said active section semiconductor means on respective ones of said opposed ends thereof, said mirrors each having spaced reflective maxima points providing a maximum reflection of an associated wavelength with the spacing of said reflective maxima points of respective ones of said mirrors being different whereby only one said reflective maxima of each of said mirrors can be in correspondence with a wavelength of the created lightbeam and thereby provide a low loss window at any time, said mirrors each including a plurality of discontinuities to cause said reflective maxima, the spacing of said discontinuities of one said mirror being different from the spacing of said discontinuities of the other said mirror so as to cause the spacing of said reflective maxima to be different in respective ones of said mirrors; and

,

(d) means operably connected to said mirrors for independently adjusting an index of refraction of said phase shifter means, said mirrors and said active section semiconductor means.

22. The diode laser of claim 21 wherein said adjusting means comprises:

(a) said phase shifter means, said mirrors and said active section semiconductor means each have an electrode connected thereto for applying an electrical signal thereto; and

,

(b) means for applying independent electrical signals to respective ones of said electrodes thereby causing an index of refraction of said phase shifter means, said mirrors and said active section semiconductor means to be changed independently as a function of said electrical signal applied to said electrode thereof.

23. The diode laser of claim 21 wherein said adjusting means includes:

(a) vernier control circuit means operably connected to said mirrors for providing a voltage signal to said mirrors which causes continuous tuning within a desired frequency band; and

,

(b) offset control circuit means connected to said mirrors for providing a voltage signal to said mirrors which shifts said reflective maxima of said mirrors into alignment at a desired frequency mode.

24. The diode laser of claim 23 and additionally comprising:

(a) phase shifter semiconductor means disposed between said active section semiconductor means and one of said mirrors for adjusting the round trip cavity phase between said mirrors and thus a lasing mode wavelength of the diode laser; and

,

(b) phase control circuit means operated in synchronism with said vernier control circuit means for aligning the wavelength of the lasing mode wavelength of the diode laser to be the same as the wavelength of said low loss window.

25. The improvement to a diode laser of claim 23 and additionally comprising:

phase shifter means for adjusting the round trip cavity phase between the pair of mirrors and thus a lasing mode wavelength of the diode laser.

26. In a diode laser having,

active section semiconductor means for creating a light beam by spontaneous emission over a bandwidth around some center frequency and for guiding the light beam between opposed ends thereof;

gain control means connected to the active section semiconductor means semiconductor means for supplying an electrical signal to the active section semiconductor means semiconductor means which will cause the active section semiconductor means semiconductor means to provide gain to overcome losses and create an emitted beam of laser light;

a pair of mirrors bounding the active section semiconductor means semiconductor means on respective ones of the opposed ends thereof, the mirrors each having spaced reflective maxima points providing a maximum reflection of an associated wavelength with the spacing of the reflective maxima points of respective ones of the mirrors being different whereby only one the reflective maxima points of each of the mirrors can be in correspondence with a wavelength of the created lightbeam and thereby provide a low loss window at any time, the mirrors each including a plurality of discontinuities causing the reflective maxima points, the spacing of the discontinuities of one mirror being different from the spacing of the discontinuities of the other mirror so as to cause a wavelength spacing of the reflective maxima points to be different in respective ones of the mirrors; and

,

phase shifter semiconductor means disposed between the active section semiconductor means and one of the mirrors for adjusting the round trip cavity phase between the mirrors and thus a lasing mode wavelength of the diode laser, the method of operation at selectably variable frequencies covering a wide wavelength range comprising the steps of;

(a) connecting vernier control circuit means to the mirrors to provide a selectably adjustable electrical signal to the mirrors which can cause continuous tuning within a frequency band;

(b) connecting offset control circuit means to the mirrors to provide an electrical signal to the mirrors which can shift the reflective maxima of the mirrors into alignment at a desired frequency mode;

(c) connecting phase control circuit means to the phase shifter semiconductor means to adjust the round trip cavity phase between the mirrors;

(d) using the offset control circuit means to shift the reflective maxima of the mirrors into alignment at a desired frequency mode;

(e) using the vernier control circuit means to tune the laser within a frequency band adjacent the frequency mode selected by the offset control circuit means; and

,

(f) using the phase control circuit means in synchronism with the vernier control circuit means to align the wavelength of the lasing mode wavelength of the diode laser to be the same as the wavelength of said low loss window.

27. The method of claim 26 wherein said step (e) of using the phase control circuit means in synchronism with the vernier control circuit means comprises the steps of:

(a) connecting an output from the vernier control circuit means to the phase control circuit means; and

,

(b) using a signal output from the vernier control circuit means to control the phase control circuit means.