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.

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; and   a 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; and   means 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.