Frequency doubled fiber laser

• US 5,974,059 A
• Filed: 03/04/1997
• Issued: 10/26/1999
• Est. Priority Date: 03/04/1997
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Dawson, Jay W.
• Primary Examiner(s): Davie, James W.
• Application Number:
  US08/811,183
• Time in Patent Office: 966 Days
• Field of Search: 372/6, 372/20, 372/22, 372/32, 372/92, 372/102
• US Class Current: 372/6
• CPC Class Codes: G02F 1/37 for second-harmonic generation G02F1/3532 takes precedence
• CPC Class Codes: H01S 3/0675 Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
• CPC Class Codes: H01S 3/1312 by controlling the optical pumping
• CPC Class Codes: H01S 3/139 by controlling the mutual position or the reflecting properties of the reflectors of the cavity , e.g. by controlling the cavity length

Abstract

A system for lasing includes a diode laser array for emitting light of wavelength λ₀, a tunable Bragg grating fiber laser connected to the diode laser array for emitting single mode light of wavelength 2*λ_vis, a cladding pumped power amplifier connected to the diode laser array and the tunable Bragg grating fiber laser, and a second harmonic generator, including an optical cavity and crystal, connected to the cladding pumped power amplifier for emitting light of wavelength λ_vis. The second harmonic generator is maximized, thereby maximizing emission of the light of wavelength λ_vis, by control electronics connected to the tunable Bragg grating fiber laser, the cladding pumped power amplifier, and the second harmonic generator. The control electronics stabilize the amplitude of the light of wavelength 2*λ_vis, emitted by the tunable Bragg grating fiber laser and lock the frequency of the light of wavelength 2*λ_vis to the optical cavity resonance.

Claims

1. A system for lasing, comprising:

a diode laser array for emitting light of wavelength λ

₀ ;

a tunable Bragg grating fiber laser connected to the diode laser array for emitting single mode light of wavelength 2*λ

_vis ;

a cladding pumped power amplifier connected to the diode laser array and the tunable Bragg grating fiber laser;

a second harmonic generator, including an optical cavity having an optical cavity resonance, connected to the cladding pumped power amplifier for emitting light of wavelength λ

_vis ; and

control electronics coupled to detect output from the second harmonic generator and tune the Bragg grating fiber laser to match the optical cavity resonance

thereby maximizing emission of the light of wavelength l_vis.

2. The system of claim 1,

wherein the control electronics are connected to the tunable Bragg grating fiber laser, the diode laser array, and the second harmonic generator;

and further wherein the control electronics stabilize the amplitude of the light of wavelength 2*λ

_vis emitted by the tunable Bragg grating fiber laser and lock the frequency of the light of wavelength 2*λ

_vis to the optical cavity resonance.

3. The system of claim 2, further comprising a means for tuning the tunable Bragg grating fiber laser by straining and compressing.

4. The system of claim 3, wherein the means includes a piezoelectric material.

5. The system of claim 3, wherein the means is temperature dependent.

6. The system of claim 3, wherein the control electronics control the means for tuning and the diode laser array.

7. The system of claim 6, wherein the control electronics comprise:

a first photodetector, connected to the tunable Bragg grating fiber laser, for detecting the light of wavelength 2*λ

_vis emitted by the tunable Bragg grating fiber laser and converting the light to a first electric current;

a proportional-differential-integral control circuit, connected to the first photodetector and to the means for tuning, for receiving the first electric current and outputting first control signals to the means for tuning.

8. The system of claim 6, wherein the control electronics comprise:

a second photodetector, connected to the second harmonic generator, for detecting the light of wavelength 2*λ

_vis emitted by the second harmonic generator and converting the light to a second electric current;

a demodulating circuit, connected to the second photodetector, for demodulating the second electric current;

a proportional-integral-differential control circuit, connected to the demodulating circuit and the diode laser array, for receiving the second electric current, as demodulated, and outputting second control signals to the diode laser array.

9. The system of claim 7, further comprising:

a second photodetector, connected to the second harmonic generator, for detecting the light of wavelength 2*λ

_vis emitted by the second harmonic generator and converting the light to a second electric current;

a demodulating circuit, connected to the second photodetector, for demodulating the second electric current;

a proportional-integral-differential control circuit, connected to the demodulating circuit and the diode laser array, for receiving the second electric current, as demodulated, and outputting second control signals to the diode laser array.

10. A method of lasing, comprising the steps of:

emitting light of wavelength λ

₀ ;

passing a first portion of the emitted light to a tunable fiber laser;

passing a second portion of the emitted light to a power amplifier;

tuning the tunable fiber laser to emit single lasing mode light of wavelength 2*λ

_vis ;

emitting single lasing mode light of wavelength 2*λ

_vis by the tunable fiber laser;

propagating the single lasing mode light through a core of a clad optical fiber;

propagating the second portion of the emitted light through a cladding of the clad optical fiber;

mode matching the light propagated through the clad optical fiber to a resonance of an optical cavity; and

emitting a laser beam by a crystal within the optical cavity.

11. The method of claim 10, further comprising the step of:

controlling an amplitude of the single lasing mode light to stabilize the amplitude to 2*λ

_vis and to lock the frequency of the single lasing mode light to the resonance of the optical cavity.

12. The method of claim 11, wherein the step of controlling comprises the steps of:

photodetecting the single lasing mode light;

converting the detected single lasing mode light to a first electric current; and

proportionally-differentially-integrally controlling the step of emitting light of wavelength λ

₀ based on the first electric current.

13. The method of claim 11, wherein the step of controlling comprises the steps of:

photodetecting the laser beam;

converting the detected laser beam to a second electric current;

demodulating the second electric current by comparing the second electric current to a reference sinusoidal oscillation; and

proportionally-integrally-differentially controlling the step of tuning based on the demodulated second electric current.

14. The method of claim 12, wherein the step of controlling comprises the steps of:

photodetecting the laser beam;

converting the detected laser beam to a second electric current;

demodulating the second electric current by comparing the second electric current to a reference sinusoidal oscillation; and

proportionally-integrally-differentially controlling the step of tuning based on the demodulated second electric current.

15. A lasing system, comprising:

means for emitting light of wavelength λ

₀ ;

a tunable fiber laser connected to the means for emitting light, for receiving a first portion of the emitted light;

a power amplifier connected to the means for emitting light, for receiving a second portion of the emitted light;

means, connected to the tunable fiber laser, for tuning the tunable fiber laser to emit single lasing mode light of wavelength 2*λ

_vis ;

an optical fiber having a core and a clad, connected to the tunable fiber laser and the means for emitting, for propagating the single lasing mode light through the core and propagating the second portion of the emitted light through the clad;

a second harmonic generator, connected to the optical fiber, including an optical cavity of a resonance and a crystal in the optical cavity;

means, connected to the optical fiber, for mode matching the light propagated through the optical fiber to the resonance of the optical cavity;

wherein the crystal emits a laser beam.

16. The lasing system of claim 15, further comprising:

controls, connected to the tunable fiber laser, the means for emitting, and the second harmonic generator, for controlling an amplitude of the single lasing mode light to stabilize the amplitude to 2*λ

_vis and to lock the frequency of the single lasing mode light to the resonance of the optical cavity.

17. The method of claim 16, wherein the controls comprise:

means for photodetecting the single lasing mode light, connected to the tunable fiber laser;

means for converting the detected single lasing mode light to a first electric current, connected to the means for photodetecting; and

means for proportionally-differentially-integrally controlling the step of emitting light of wavelength λ

₀ based on the first electric current, connected to the means for emitting.

18. The lasing system of claim 16, wherein the controls comprise:

means for photodetecting the laser beam, connected to the second harmonic generator;

means for converting the detected laser beam to a second electric current, connected to the means for photodetecting the laser beam;

means for demodulating the second electric current by comparing the second electric current to a reference sinusoidal oscillation, connected to the means for converting; and

means for proportionally-integrally-differentially controlling the means for tuning based on the demodulated second electric current, connected to the means for proportionally-integrally-differentially controlling and the means for tuning.

19. The lasing system of claim 17, wherein the controls comprise:

means for photodetecting the laser beam, connected to the second harmonic generator;

means for converting the detected laser beam to a second electric current, connected to the means for photodetecting the laser beam;

means for demodulating the second electric current by comparing the second electric current to a reference sinusoidal oscillation, connected to the means for converting; and

means for proportionally-integrally-differentially controlling the means for tuning based on the demodulated second electric current, connected to the means for proportionally-integrally-differentially controlling and the means for tuning.

20. The system of claim 15, wherein the crystal is selected from the group consisting of KTP, LBO, LiNbO₃ and MgO:

LiNbO₃.

21. The system of claim 15, wherein λ

_vis is less than about 800 nm and greater than about 400 nm and λ

₀ is less than about 2*λ

_vis.

22. The system of claim 15, wherein the means for tuning comprises a piezoelectric piece and means connected to the piezoelectric piece, for selectively varying a voltage applied to the piezoelectric piece.