Wavelength beam combining device including output control unit for controlling light source unit to have variable output

Abstract

A wavelength beam combining device includes: a laser diode stack comprising a plurality of stacked laser diode bars, wherein each laser diode bar comprises a plurality of laser diodes arranged laterally in a row; a light condensing member; a diffraction grating; a resonator mirror; and an output control unit configured to control each of the laser diode bars such that, in every possible mode in which the output control unit controls each laser diode bar to operate such that one or more of the laser diodes emit laser beams and one or more of the laser diodes do not emit laser beams, the one or more laser diodes that emit laser beams are located inward of the one or more laser diodes that do not emit laser beams.

What is claimed is: 
     
         1 . A wavelength beam combining device comprising:
 a laser diode stack comprising a plurality of stacked laser diode bars, wherein each laser diode bar comprises a plurality of laser diodes arranged laterally in a row, wherein each laser diode is configured to emit a laser beam with a predetermined wavelength width;   a light condensing member comprising a cylindrical lens configured to condense the laser beams emitted from the laser diode stack, wherein an optical axis plane of the light condensing member is aligned with an optical axis plane of centermost ones of the plurality of laser light sources of each laser diode bar;   a diffraction grating on which the laser beams condensed by the light condensing member are incident;   a resonator mirror disposed in an optical path of a diffracted beam from the diffraction grating, the resonator mirror having an optical axis aligned with an optical axis of the diffracted beam; and   an output control unit configured to control each of the laser diode bars so as to operate in at least (i) a first mode, in which all of the plurality of laser diodes emit laser beams, and (ii) a second mode, in which, among the plurality of laser diodes, at least laser diodes located farthest from the centermost laser diode do not emit laser beams, and others of the plurality of laser diodes emit laser beams, such that an output of the wavelength beam combining device during the second mode is lower than an output of the wavelength beam combining device during the first mode;   wherein the output control unit is configured such that, in every possible mode in which the output control unit controls each laser diode bar to operate such that one or more of the laser diodes emit laser beams and one or more of the laser diodes do not emit laser beams, the one or more laser diodes that emit laser beams are located inward of the one or more laser diodes that do not emit laser beams.   
     
     
         2 . The wavelength beam combining device according to  claim 1 , wherein:
 the output control unit is configured to turn on a current flowing through the laser diodes in each laser diode bar in a plurality of steps including:
 a first step in which at least the centermost laser diode emits a laser beam, laser diodes located farthest from the centermost laser diode do not emit laser beams, and laser diodes adjacent to the laser diodes located farthest from the centermost laser diode do not emit laser beams, 
 a second step in which the laser diode bar operates in the second mode, such that at least laser diodes located farthest from the centermost laser diode do not emit laser beams, and others of the plurality of laser diodes emit laser beams, and 
 a third step in which the laser diode bar operates in the first mode, such that all of the plurality of laser diodes emit laser beams. 
   
     
     
         3 . The wavelength beam combining device according to  claim 2 , wherein:
 the plurality of stacked laser diode bars include:
 a first laser diode bar, 
 a second laser diode bar located above the first laser diode bar, and 
 a third laser diode bar located below the first laser diode bar; and 
   in the first and second steps, a quantity of laser diodes in each of the second and third laser diode bars that emit laser beams is less than a quantity of laser diodes in the first laser diode bar that emit laser beams.   
     
     
         4 . The wavelength beam combining device according to  claim 1 , wherein:
 the output control unit is configured to turn off a current flowing through the laser diodes in each laser diode bar in a plurality of steps including:   a first step in which the laser diode bar operates in the second mode, such that at least laser diodes located farthest from the centermost laser diode do not emit laser beams, and others of the plurality of laser diodes emit laser beams,   a second step in which at least the centermost laser diode emits a laser beam, laser diodes located farthest from the centermost laser diode do not emit laser beams, and laser diodes adjacent to the laser diodes located farthest from the centermost laser diode do not emit laser beams, and   a third step in which none of the plurality of laser diodes emit laser beams.   
     
     
         5 . The wavelength beam combining device according to  claim 4 , wherein:
 the plurality of stacked laser diode bars include:
 a first laser diode bar, 
 a second laser diode bar located above the first laser diode bar, and 
 a third laser diode bar located below the first laser diode bar; and 
   in the first and second steps, a quantity of laser diodes in each of the second and third laser diode bars that emit laser beams is less than a quantity of laser diodes in the first laser diode bar that emit laser beams.   
     
     
         6 . The wavelength beam combining device according to  claim 1 , further comprising:
 a collimator disposed between the laser diode stack and the light condensing member and configured to collimate the laser beams emitted from the laser diodes into substantially parallel beams.   
     
     
         7 . The wavelength beam combining device according to  claim 6 , wherein:
 the collimator comprises a lens array of collimation lenses that are arranged laterally in a row.   
     
     
         8 . The wavelength beam combining device according to  claim 1 , wherein:
 the resonator mirror is a partially reflecting mirror configured to reflect a portion of the diffracted beam.   
     
     
         9 . The wavelength beam combining device according to  claim 1 , wherein:
 each laser diode bar comprises a rear mirror, and   the resonator mirror and the rear mirror of each laser diode bar form an external resonator.   
     
     
         10 . The wavelength beam combining device according to  claim 1 , wherein:
 the output control unit comprises a switch.   
     
     
         11 . The wavelength beam combining device according to  claim 10 , wherein:
 the switch is a four-step switch.