Research On Coating Of 590 Nm Laser Resonator Cavity Based On Yb:LCB Crystal

The self-frequency-doubled laser crystal has both laser and nonlinear optical properties,and can complete the laser and frequency doubling process in a single crystal device.The laser fabricated by this kind of crystal has the advantages of simple structure,small volume and good stability,which can meet the demand of modern information society for highly integrated optoelectronic devices.By coating optical films on the surface of self-frequency-doubled crystal,the self-frequency doubling effect can be coupled and matched more effectively,thus making the output of new-wavelength laser possible.Based on the properties of Yb:LCB,the LCB crystal is excited by 976 nm light to generate 1180 nm Raman light,and the 590 nm laser can be obtained by oscillating 1180 nm in the resonant cavity.Many studies have been carried out on the growth and application of LCB crystals at home and abroad,but little research has been reported on the coating of LCB crystals.Based on the characteristics of LCB crystal and the basic theory of optical film,Ta₂O₅ and Si O₂ were selected as coating materials,and the initial film system of resonant cavity is discussed and designed.The influence of repetition period,interference levels on the spectral characteristics and electric field intensity distribution was analyzed,and the design and optimization of the resonant cavity film system were completed.The ion assisted vacuum deposition technology was used to fabricate the film.Combined with the characteristics of surface defects and deposition process,the surface spray point problem of Ta₂O₅ thin film was analyzed.It was found that the degassing was insufficient in the pre-melting process,which was prone to splash and form surface defects.By establishing the path model and optimizing the electron beam path,it is ensured that the electron beam effectively runs the trajectory covering the entire crucible material surface,and the material can be fully pre-melted,thus reducing the surface defects of the film.The relationship between refractive index,surface roughness and ion source bias of Ta₂O₅ thin films was studied.As the bias voltage increases from 90 V to 140 V,the refractive index increases first,and then it is no longer obvious after a certain point.The film roughness decreases first and then increases.The combination of optical monitoring and quartz crystal control is adopted,which the thickness of the film is monitored by optical control,and the deposition rate is monitored by crystal oscillator,so that the thickness of the film system can be accurately controlled.The transmittance spectrum of single-sided coated LCB crystal was tested.The average reflectance of input surface at 560?590 nm was R=99.68%,the average transmittance at 970?1100 nm was 92.98%,and the average reflectance at1120?1180 nm was R=99.78%.The average transmittance of the output surface at560?590 nm was T=92.55%,the average reflectivity at 970?985 nm was R=99.75%,the average transmittance at 1020?1100 nm was T=92.17%,and the average reflectivity at 1130?1180 nm was R=99.79%.The prepared Yb:LCB crystal device realized the milliwatt-level 590 nm laser output.