External cavity laser

Abstract

Embodiments of systems and methods are provided for a tunable laser device. The tunable laser device may include a diffraction grating connected to a pivot arm that pivots the diffraction grating about a pivot point to tune the laser device. In pivoting the diffraction grating about the pivot point, both the wavelength to which the diffraction grating is tuned and the length of the optical cavity may be changed. The length of the pivot arm may be selected to reduce the number of mode hops of the tunable laser device when tuning the laser device over its tuning range.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates an exemplary laser system, in accordance with embodiments of methods and systems of the present invention;

FIGS. 2A and 2B provide a simplified diagram for illustrating a Littrow angle, in accordance with embodiments of methods and systems of the present invention;

FIG. 3 illustrates a simplified exemplary laser system where the pivot point is located directly below the intercept point on the transmission grating, in accordance with embodiments of methods and systems of the present invention;

FIG. 4 provides an exemplary plot illustrating mode number, versus wavelength over the tuning range for an exemplary laser system for various lengths of the pivot arm, in accordance with embodiments of methods and systems of the present invention;

FIG. 5 provides an exemplary plot illustrating mode number, versus wavelength over the tuning range for an exemplary laser system for various lengths of the pivot arm between Pmin and Pmax, in accordance with embodiments of methods and systems of the present invention;

FIG. 6 illustrates a simplified exemplary laser system illustrating various positions for locating the pivot point of a pivot arm, in accordance with embodiments of methods and systems of the present invention;

FIG. 7 illustrates an exemplary laser system in which the alignment of the laser system's components may be adjusted, in accordance with embodiments of methods and systems of the present invention;

FIGS. 8A and 8B illustrate an exemplary pivot arm with an attached transmission grating, in accordance with embodiments of methods and systems of the present invention;

FIGS. 9A and 9B illustrate an exemplary mount, transmission grating and first portion of a pivot arm, in accordance with embodiments of methods and systems of the present invention.

Claims

1. A laser system comprising: a highly reflecting surface;a light source which provides light;a lens which collimates the light to provide a collimated coherent light beam;a diffraction grating which reflects at least a portion of a wavelength of light of the collimated coherent light beam towards the light source; anda pivot arm connected to the diffraction grating, wherein the pivot arm is configured to pivot the diffraction grating to thereby adjust the wavelength of light reflected by the diffraction grating towards the light source as well as adjusting an optical path length for the laser system.

2. The laser system of claim 1, wherein the pivot arm rotates about a rotational axis located at a pivot length spaced from the diffraction grating to adjust the reflected wavelength of light such that a length between the diffraction grating and the light source is adjusted when the diffraction grating is pivoted.

3. The laser system of claim 2, wherein the pivot length is selected to minimize the number of mode hops across a tuning range of the laser system.

4. The laser system of claim 2, wherein the pivot length is selected to be between a calculated minimum pivot length and a maximum pivot length, wherein the minimum pivot length is calculated using a change in Littrow angle for rotating the diffraction grating from a center wavelength to a longest wavelength for the laser system and the maximum pivot length is calculated using a change in Littrow angle for rotating the diffraction grating from the center wavelength to a shortest wavelength for the laser system.

5. The laser system of claim 2, wherein the rotational axis is located on a line determined to pass through a calculated point located directly below a point on the diffraction grating at which the coherent light beam intercepts the diffraction grating, and wherein the line is at an angle corresponding to a Littrow angle for the diffraction grating when the laser system is tuned to a center wavelength.

6. The laser system of claim 1, wherein coherent light source and the lens are located on a moveable assembly to adjust a position of the coherent light source and lens with respect to the diffraction grating.

7. The laser system of claim 1, wherein the pivot arm comprises at least first, second and third axes of rotation about which at least a portion of the pivot arm may pivot.

8. A method for generating a coherent light beam comprising the following steps: (a) providing a collimated coherent light beam; and(b) pivoting a pivot arm connected to a diffraction grating to adjust a position of the diffraction grating, thereby adjusting a wavelength of light of the collimated coherent light beam reflected by the diffraction grating as well as adjusting an optical path length for the laser system.

9. The method of claim 8, wherein the pivot arm rotates about a rotational axis located at a pivot length spaced from the diffraction grating to adjust the reflected wavelength of light such that a length of an optical cavity is adjusted when the diffraction grating is pivoted.

10. The method of claim 9, wherein the pivot arm adjusts the position of the diffraction grating in a range of positions from a first position, to a second position, the first and second positions corresponding to a minimum wavelength of light and a maximum wavelength of light reflected by the diffraction grating, and wherein the pivot length is selected to minimize the number of mode hops across a tuning range.

11. The method of claim 9, wherein the pivot length is selected to be between a calculated minimum pivot length and a maximum pivot length, wherein the minimum pivot length is calculated using a change in Littrow angle for rotating the diffraction grating from a center wavelength to a longest wavelength for the laser system and the maximum pivot length is calculated using a change in Littrow angle for rotating the diffraction grating from the center wavelength to a shortest wavelength for the laser system.

12. The method of claim 9, wherein the rotational axis is located on a line determined to pass through a calculated point located directly below a point on the diffraction grating at which the coherent light beam intercepts the diffraction grating, and wherein the line is at an angle corresponding to a Littrow angle for the diffraction grating at a center wavelength.

13. The method of claim 8, wherein the provided collimated coherent light beam is provided using a coherent light source and a lens, and wherein the coherent light source and lens are located on a moveable assembly, the method further comprising the step of: adjusting a position of the moveable assembly to adjust the position of the coherent light source and lens with respect to the diffraction grating.

14. The method of claim 8, wherein the pivot arm comprises at least a first, second and third axes of rotation about which at least a portion of the pivot arm may pivot.

15. A laser system for generating a coherent light beam comprising: means for providing a collimated coherent light beam;means for reflecting at least a portion of a wavelength of light of the collimated coherent light beam; andmeans for adjusting a position of the reflecting means to thereby adjust a wavelength of light of the collimated coherent light beam reflected by the reflecting means as well as adjusting an optical path length for the laser system.

16. The system of claim 15, wherein the adjusting means comprises means for rotating the reflecting means about a rotational axis located at a pivot length spaced from the reflecting means to adjust the reflected wavelength of light such that a length of an optical cavity is adjusted when the reflecting means is rotated about the rotational axis.

17. The system of claim 16, wherein the adjusting means adjusts the position of the reflecting means in a range of positions from a first position to a second position, the first and second positions corresponding to a minimum wavelength of light and a maximum wavelength of light reflected by the reflecting means; and wherein the pivot length is selected to minimize the number of mode hops across a tuning range for the laser system.

18. The system of claim 16, wherein the pivot length is selected to be between a calculated minimum pivot length and a maximum pivot length, wherein the minimum pivot length is calculated using a change in Littrow angle for rotating the reflecting means from a center wavelength to a longest wavelength for the laser system and the maximum pivot length is calculated using a change in Littrow angle for rotating the reflecting means from the center wavelength to a shortest wavelength for the laser system.

19. The system of claim 16, wherein the rotational axis is located on a line determined to pass through a calculated point located directly below a point on the reflecting means at which the coherent light beam intercepts the reflecting means, and wherein the line is at an angle corresponding to a Littrow angle for the reflecting means at a center wavelength.

20. The system of claim 15, further comprising means for adjusting, with respect to the reflecting means, a position of the collimated coherent light beam providing means.

21. The system of claim 15, wherein the adjusting means comprises at least a first, second and third axes of rotation about which at least a portion of the pivoting means may pivot.