External cavity laser method and apparatus with orthogonal tuning of laser wavelength and cavity optical path length

• US 20050135439A1
• Filed: 01/13/2005
• Published: 06/23/2005
• Est. Priority Date: 07/06/2001
• Status: Active Grant

• Current Assignee: Alejandro D. Farinas, Andrew Daiber, Hua Li, William B. Chapman
• Original Assignee: Alejandro D. Farinas, Andrew Daiber, Hua Li, William B. Chapman
• Inventors: Li, Hua, Daiber, Andrew, Farinas, Alejandro D., Chapman, William B.
• Granted Patent: US 7,218,652 B2
• Time in Patent Office: Days
• US Class Current: 372/20
• CPC Class Codes: H01S 3/105 by controlling the mutual position or the reflecting properties of the reflectors of the cavity , e.g. by controlling the cavity lengthH01S3/10076, H01S3/13 take precedence
• CPC Class Codes: H01S 3/1055 one of the reflectors being constituted by a diffraction grating
• CPC Class Codes: H01S 3/1062 using a controlled passive interferometer, e.g. a Fabry-Perot etalon
• CPC Class Codes: H01S 5/0222 Gas-filled housings
• CPC Class Codes: H01S 5/0617 using memorised or pre-programmed laser characteristics
• CPC Class Codes: H01S 5/0687 Stabilising the frequency of the laser
• CPC Class Codes: H01S 5/141 using a wavelength selective device, e.g. a grating or etalon H01S5/146 takes precedence

Abstract

An external cavity laser apparatus and method wherein wavelength or channel selection is carried independently from adjustment of external cavity optical path length. The apparatus comprises a wavelength or channel selector tuner and an external cavity tuner, wherein the wavelength tuner is uncoupled from the external cavity tuner. The tuning mechanisms for wavelength selection and cavity optical path length are configured to operate independently or orthogonally with respect to each other. The wavelength tuner may operate according to a first, channel selection signal, while the external cavity tuner operates according to a second, external cavity adjustment signal. The wavelength tuner and external cavity tuner may operate under the control of the same, or of separate controllers. The channel selection signal may be derived from a look-up table of adjustment parameter data accessed by a controller, and the external cavity adjustment signal may be derived from an error signal from a detector configured to measure external cavity loss.

Claims

1-19. -19. (canceled)

20. A method for tuning an external cavity laser, comprising:

(a) tuning a channel selector with a first tuning element according to a first wavelength selection signal; and

(b) tuning an external cavity optical path length with a second tuning element according to a second cavity mode error signal;

(c) said tuning said channel selector carried out independently from said tuning said external cavity optical path length.

21. The method of claim 20, wherein said first wavelength selection signal is derived independently from said second cavity mode signal.

22. The method of claim 20, wherein said tuning by said first tuning element is carried out substantially orthogonally with respect to said tuning by said second tuning element.

23. The method of claim 20, further comprising:

(a) controlling said first tuning element with a first controller; and

(b) controlling said second tuning element with a second controller.

24. The method of claim 20, further comprising:

(a) deriving said first, wavelength selection signal from a stored look-up table of adjustment parameter data; and

(b) deriving said second, cavity mode error signal from output from a sensor configured to monitor external cavity loss associated with said external cavity optical path length.

25. The method of claim 24, wherein said deriving said second, cavity mode error signal comprises monitoring voltage modulation across a gain medium associated with said external cavity.

26. The method of claim 24, wherein said deriving said second, cavity mode error signal comprises introducing a frequency modulation to said external cavity optical path length, said frequency modulation detectable by said sensor.

27. A laser apparatus, comprising:

(a) first tuning means for locking a laser onto a peak of a first passband, the first passband representing a laser mode;

(b) second tuning means for adjusting optical path length to lock the laser onto a peak of a second passband, the second passband representing a laser channel, and

(c) means for unlocking the laser channel from the peak of the second passband while the laser mode is maintained locked onto the first passband;

28. The laser apparatus of claim 27, further comprising:

(a) means for deriving a wavelength selection signal for said first tuning means; and

(b) means for deriving an optical path length signal for said second tuning means;

(c) said wavelength signal deriving means operable independently from said optical path length signal deriving means.

29. The laser apparatus of claim 27, wherein said first tuning means comprises wavelength selection control means for actuating a channel selector according to signals derived from optical output of said laser.

30. The laser apparatus of claim 29, wherein said second tuning means comprises external cavity control means for actuating a reflector according to signals derived from voltage monitored across a gain medium of said laser.