The High Brightness Study Of Semiconductor Laser Based On Beam Combining

Solid state laser has the problems of large volume,low efficiency and short life.It produces large amounts of waste heat during its process of working.The accumulation of waste heat decreases electro-optic conversion efficiency and reduces the output beam quality.These will affect the properties of solid state lasers.At present,the requirements of the output power and the brightness of lasers become higher and higher in many fields,and the solid state lasers can not meet the requirements.Compared with the solid state laser,the semiconductor laser has the advantages of high efficiency,small size,low cost and long service life.Thus,the current research has been focused on the brightness of the high semiconductor laser.The power and brightness of a single semiconductor laser is limited,so an array of multiple lasers is required.However,since the"smile"effect exists in the array and the bending degree increases with the current,the beam quality is poor.This paper makes use of the beam combining method to achieve high brightness output of the single tube semiconductor laser.The beam combining technology includes coherent beam combination and incoherent beam combination.The former,which is sensitive to environmental temperature,the precision of device and the phase of the laser,is difficult to achieve.The latter can be easily achieved and it includes space beam combination,polarized beam combination and wavelength beam combination.Space beam combination combines the beams emitted by different light sources into a high energy beam through mirrors.The new wavelength beam combination,spectrum beam combination,combines beams of different wavelengths into one beam through external cavity feedback.The interval between the wavelengths can be lower than 0.1nm and its beam quality is close to a single tube’s.This paper uses single tube semiconductor laser as the light source and utilizes the spectrum beam combination technology which contains a transmission grating,to keep the combined single tube locked in different wavelengths.The beams passing through the output coupling mirror are in the same direction.This improves the beam quality and combines multiple single beams.The focusing lens has achieved its optimal design via an optical simulation software,ZEMAX,by unfolding the light path.In the direction of the fast axis,the focusing lens can reach the diffraction limit.This reduces the impacts of aberrations on the external cavity feedback.This paper summarizes a concrete method to improve the electro-optic efficiency.Six single tubes with front cavity surface plating film are used in this study.For each single tube,the output power is 10W and the wavelength is 975nm.After spectrum beam combination,the beams are coupled into the optical fiber which has a core radium of 105μm and a NA of 0.17.Finally,the continuous laser pulses are obtained.The power is40.85W,the spectral linewidth is 2.9nm and the brightness is 19.58 MW/(cm~2·sr).The obtained high brightness semiconductor laser fiber coupling module has the characteristics of high brightness,narrow linewidth and can be used in the field of pumped high energy fiber laser.