Monitoring and control assembly for wavelength stabilized optical system

• US 6,233,263 B1
• Filed: 06/04/1999
• Issued: 05/15/2001
• Est. Priority Date: 06/04/1999
• Status: Expired due to Term

• Current Assignee: NeoPhotonics Corporation (Lumentum Holdings Inc.)
• Original Assignee: BANDWIDTH9
• Inventors: Yuen, Wupen, Chang-Hasnain, Constance J., Dato, Renato, Kner, Peter, Li, Gabriel S., Worland, Philip, Yu, Rang-Chen
• Primary Examiner(s): Scott, Jr., Leon
• Application Number:
  US09/326,126
• Time in Patent Office: 711 Days
• Field of Search: 372/32, 372/28, 372/26, 372/9, 372/33, 372/20, 372/23, 372/29, 372/38
• US Class Current: 372/32
• CPC Class Codes: H01S 5/0078 for frequency filtering
• CPC Class Codes: H01S 5/0208 Semi-insulating substrates
• 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 5/0264 for monitoring the laser-output
• CPC Class Codes: H01S 5/0422 with n- and p-contacts on the same side of the active layer
• CPC Class Codes: H01S 5/0683 by monitoring the optical output parameters
• CPC Class Codes: H01S 5/0687 Stabilising the frequency of the laser
• CPC Class Codes: H01S 5/18366 Membrane DBR, i.e. a movable DBR on top of the VCSEL

Abstract

A monitoring and control assembly for an optical system includes a tunable laser. The laser generates a divergent output beam along an optical axis. A first photodetector is provided. A wavelength selective filter is tilted at an angle relative to the optical axis that provides an angular dependence of a wavelength reflection of the wavelength selective filter and directs the reflected output beam towards the first photodetector.

Claims

1. A monitoring and control assembly for an optical system, comprising:

a tunable laser selected from a VCSEL or an edge emitter generating a divergent output beam along an optical axis, the laser including an active region with first and second opposing reflectors that define a laser gain cavity;

a first photodetector positioned outside of the laser gain cavity; and

an adjustable wavelength selective filter that splits the output beam into a transmitted portion and a reflected portion, the adjustable wavelength selective filter being positioned at an angle θ

relative to the optical axis to provide an angular dependence of a wavelength reflection of the wavelength selective filter and direct the reflected output beam towards the first photodetector, wherein the wavelength selective filter provides wavelength selectivity by changing the angle θ and

a ratio of the transmitted and reflected portions is a function of wavelength of output beam and the angle θ

.

2. The system of claim 1, wherein the first photodetector is positioned in a lateral direction relative to the laser.

3. The optical system of claim 1, wherein an output face of the tunable laser is coplanar with a face of the first photodetector.

4. The optical system of claim 1, wherein an output face of the tunable laser is non-coplanar with a face of the first photodetector.

5. The optical system of claim 1, wherein the first photodetector is distanced from the tunable laser.

6. The system of claim 1, further comprising:

a second photodetector positioned adjacent to the first photodetector, wherein two different parts of the output beam are incident on the first and second photodetectors and a change in wavelength from the laser is converted to a difference in transmission detected by the first and second photodetectors.

7. The system of claim 6, further comprising:

a control loop coupled to the first and second photodetectors and the laser, the control loop providing a feedback of a difference signal generated by the first and second photodetectors in response to a change in wavelength of the laser.

8. The system of claim 7, wherein the system is programmable.

9. The system of claim 7, further comprising:

a control source coupled to the laser and the control loop, the control source providing wavelength stabilization of the laser in response to a change in wavelength of the laser.

10. The assembly of claim 6, wherein the laser, the first photodiode and the second photodiode form a monolithically integrated chip.

11. The assembly of claim 6, wherein the laser, the first photodiode and the second photodiode form an integral assembly.

12. The assembly of claim 1, wherein the laser and the first photodiode form a monolithically integrated chip.

13. The assembly of claim 1, wherein the wavelength selective filter is a Fabry-Perot etalon.

14. The assembly of claim 1, wherein the laser and the wavelength selective filter are positioned on a common substrate.

15. The assembly of claim 1, wherein the first photodiode is one photodiode included in an array of photodiodes.

16. The assembly of claim 15, wherein the laser and the array of photodiodes form a monolithically integrated chip.

17. The assembly of claim 1, wherein the laser is a semiconductor laser.

18. The assembly of claim 1, wherein the laser is an output face of a semiconductor laser.

19. The assembly of claim 1, wherein the angle of the wavelength selective filter is adjustable to provide wavelength tunability.

20. The assembly of claim 1, wherein the laser comprises:

a cantilever apparatus for tuning resonance wavelength of a Fabry-Perot cavity, the Fabry-Perot cavity including a bottom reflecting member and a top reflecting member.

21. The assembly of claim 20, wherein the Fabry-Perot cavity comprises:

an electrically responsive substrate;

a support block positioned on the electrically responsive substrate; and

a cantilever structure including a base section resting on the support block, a deformable section extending above the electrically responsive substrate and creating an air gap between the deformable section and the electrically responsive substrate, and an active head positioned at a predetermined location on the deformable section and including at least a portion of the top reflecting member.

22. The assembly of claim 21, wherein the laser further comprises:

an electrical tuning contact disposed on the cantilever structure for applying a tuning voltage V_t to produce a downward electrostatic force F_d between the electrical tuning contact and the electrically responsive substrate, wherein the size of the air gap is altered and a resonant wavelength is tuned.

23. The assembly of claim 22, wherein the laser further comprises:

an oxidation layer disposed within one of the reflecting members, the oxidation layer having been partially oxidized so that a small aperture of unoxidized remains to provide optical and current confinement.

24. The assembly of claim 20, wherein the Fabry-Perot cavity comprises:

an electrically responsive substrate;

a support block positioned on the electrically responsive substrate; and

a cantilever structure including a base section resting on the support block, a deformable section extending above the electrically responsive substrate and creating an air gap between the deformable section and the electrically responsive substrate, and an active head positioned at a predetermined location on the deformable section and including at least a portion of the top reflecting member.

25. The assembly of claim 24, wherein the laser catcher comprises:

a electrical tuning contact disposed on the cantilever structure for applying a tuning voltage V_t to produce a downward electrostatic force F_d between the electrical tuning contact and the electrically responsive substrate, wherein the size of the air gap is altered and a resonant wavelength is tuned.

26. The assembly of claim 25, wherein the laser further comprises:

an oxidation layer disposed within one of the reflecting members, the oxidation layer having been partially oxidized so that a small aperture of unoxidized remains to provide optical and current confinement.

27. A monitoring and control assembly for an optical system, comprising:

a tunable laser selected from a VCSEL or an edge emitter generating a divergent output beam along an optical axis, the laser including an active region with first and second opposing reflectors that define a laser gain cavity;

a collimating optical element positioned along the optical axis;

a pair of photodetectors each positioned outside of the laser gain cavity; and

a wavelength selective filter including a Fabry-Perot Etalon with a distributed thickness to provide a positional dependence of a wavelength reflection or transmission of the filter and transmit or reflect the beam towards the pair of detectors.

28. The system of claim 27, further comprising:

a control loop coupled to the first and second photodetectors and the laser, the control loop providing a feedback of a difference signal generated by the first and second photodetectors in response to a change in wavelength of the laser.

29. The system of claim 28, wherein the system is programmable.

30. The system of claim 28, further comprising:

a control source coupled to the laser and the control loop, the control source providing wavelength stabilization of the laser in response to a change in wavelength of the laser.

31. The assembly of claim 27, wherein the first and second photodiodes are positioned on a common substrate.

32. The assembly of claim 27, wherein the laser is a semiconductor laser.

33. The assembly of claim 27, wherein the laser is an output face of a semiconductor laser.

34. The assembly of cl aim 27, wherein the laser comprises:

a cantilever apparatus for tuning resonance wavelength of a Fabry-Perot cavity, the Fabry-Perot cavity including a bottom reflecting member and a top reflecting member.