Study On The Frequency-Doubled Blue/Green External-Cavity Surface-Emitting Lasers

As a new type of semiconductor laser,vertical-external-cavity surface-emitting lasers combine advantages of solid state lasers and vertical-cavity surface-emitting semiconductor lasers,and can produce high output power and good beam quality.The flexible external cavity structure allows placing a nonlinear crystal in the cavity to achieve the intra-cavity frequency-doubling,so to expand the wavelength of the laser.This paper briefly introduces the history of the vertical-external-cavity surface-emitting lasers,summarizes its advantages,and discusses current research progress and the application prospect of frequency-doubled external-cavity surface-emitting lasers.Basic theories about the device structure,the work principle and the gain chip design of external-cavity surface-emitting lasers are introduced.In addition,the coupling wave equation of second harmonic was solved using the small signal model.The related theories about the principle of second harmonic generation and the conversion efficiency of frequency doubling are explained.Then,the influence factors on the frequency doubling conversion efficiency are analyzed,the nonlinear characteristics of the crystal are described,and the selection of the nonlinear crystal in intra-cavity frequency-doubling is optimized.The thermal effect of vertical-external-cavity surface-emitting lasers is analyzed.In the experiment of liquid capillary bonding,the influence of surface cleanliness on the bonding strength is studied,and a SiC heatsink is capillary bonded on a gain chip successfully by the use of methanol as the bonging liquid.In the experiment of substrate removing,the acid corrosion and alkaline corrosion are investigated contrastively,and the GaAs substrate of the gain chip is removed smoothly by the use of alkaline corrosion.Frequency-doubled blue vertical-external-cavity surface-emitting lasers with the straight linear cavity and V-shaped cavity are built,and characteristics of the gain chip and output performances of the laser are obtained.The fundamental wavelength is966 nm and its full width at half maximum is 5 nm.The measured M~2 factors of blue light in x and y direction are about 1.04 and 1.01,respectively.The output powers of two lasers with different cavity structures are compared and analyzed,and the disadvantages of the straight linear cavity and the advantages of the V-shaped cavity are presented.The output power of the blue light is210 mW at 483 nm wavelength,and the spectral linewidth is 2.5 nm when the absorbed pump power is 3.5 W and the heatsink temperature is 13.5?.A compact and miniaturized frequency-doubled green light external-cavity surface-emitting laser is also built.Characteristics of the gain chip and output performances of the laser are obtained.The fundamental wavelength is 1096 nm and its full width at half maximum is 1 nm.The output power of the green laser is 135.5mW at 548 nm wavelength,and the spectral linewidth is 0.5 nm when the absorbed pump power is 3.8 W and the heatsink temperature is 12.5?.