Nonlinear Optical Properties Research Of Novel Nonlinear Optical Crystal RbBe₂BO₃F₂

RbBe₂BO₃F₂（RBBF） is a novel nonlinear optical crystal with deep ultravioletoutput capacity, which theoretical researches of optical properties have not beenreported yet. In this paper, the theoretical research of nonlinear optical properties ofRBBF crystal and the optical properties of RBBF optical parametric oscillator （OPO）have been simulated, for conducting the experimental work. The main researchcontents in this paper include:Firstly, according to the law of energy and momentum conservation and thedispersion equation of RBBF crystal, phase-matching angle, nonlinear effectivecoefficient, walk-off angle, and permitted parametric of second harmonic generation（SHG） for RBBF crystal in type-I and type-II phase-matching have analyzed bytheoretical simulation, and compared with KBe₂BO₃F₂（KBBF） crystal. It is presentedthat the RBBF crystal has the ability to produce the deeply UV harmonic generation,and has a smaller walk-off angle and larger permitted parametric. Meanwhile,theoretical research of SHG conversion efficiency of RBBF crystal has beenprocessed. The conversion efficiency in type-I and type-II phase-matching has beensimulated which the pump radiation is of plane wave and Gaussian beam. When thepumped radiation is of plane wave, the conversion efficiency of RBBF in type-I SHGcould be as high as100%when the polarization ratio reaches0.8, the conversionefficiency of RBBF in type-II SHG could be as high as78%. When the pumpedradiation is of Gaussian beam, the conversion efficiency of RBBF in type-I SHGcould be as high as70%when the polarization ratio reaches0.9064, the conversionefficiency of RBBF in type-II SHG could be as high as80%. The feature, functionand application method of “Parametric calculation software of KBBF group crystal”has been introduced. Users could use this software to calculate the phase-matchingangle, nonlinear effective coefficient, walk-off angle, permittrd parametic and theconversion efficiency of SHG of KBBF group crystal.Secondly, theoretical researches of the third harmonic generation of the RBBFcrystal have been processed. According to the law of energy and momentumconservation and the dispersion equation of RBBF crystal, phase-matching angle,nonlinear effective coefficient, walk-off angle, and permitted parametric of thirdharmonic generation （THG） for RBBF crystal in type-I and type-II phase-matchinghave analyzed by theoretical simulation, and compared with KBBF crystal. It ispresented that RBBF crystals have the ability to produce the deeply UV harmonic generation. In type-I phase-matching, the shortest wavelength of THG is approximate160nm, in type-II（1） phase-matching, the shortest wavelength of THG is approximate187.7nm. We compareed with KBBF crystal, although the effective nonlinearcoefficient of RBBF crystal is small, but it has an advantage of walk-off angle, andpermitted parametric.Finally, the theoretical researches of the angle tuning curves of the RBBF crystaloptical parametric oscillator in type-I and type-II phase-matching have been processed,and compared it with KBBF and CsBe₂BO₃F₂（CBBF） crystal. The results shows that,in type-I phase-matching, when the wavelength of pump light reach to213nm and266nm, the tunability of RBBF crystal is preferably, in type-II phase-matching, whenthe wavelength of pump wavelength reach to266nm and355nm, the tunability ofRBBF crystal is preferably. The performance of angle tuning properties of RBBFcrystal is worse than that of KBBF, then better than that of CBBF crystal.