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1、Laser basicsOptics, Eugene Hecht, Chpt. 13;Optical resonator tutorial: http:/ oscillationLaser is oscillatorLike servo with positive feedback Greater than unity gainRuby laser exampleLaser turn-on and gain saturationLaser gain and lossesGain decreases as output power increases Saturation2021/8/252Fa
2、bry-Perot cavity for feedbackHigh reflectivity mirrorsLow loss per round tripMust remember resonance conditionsround trip path is multiple of l2021/8/253High reflectivity Fabry-Perot cavityBoundary conditionsfield is zero on mirrorsMultiple wavelengths possibleagrees with resonance conditionsLaser l
3、ongitudinal modesClassical mechanics analogMulti-mode laserFabry-Perot boundary conditionsMultiple resonant frequencies2021/8/254Single longitudinal mode lasersInsert etalon into cavityUse low reflectivity etalonlow loss2021/8/255Laser transverse modesWave equation looks like harmonic oscillatorEx:
4、E = E e -iwtSeparate out z dependence Solutions for x and y are Hermite polynomialsFrequencies of transverse modesTransverse laser modes2021/8/256Single transverse mode lasersPut aperture in laserCreate loss for higher order modesMulti-longitudinal Multi-transverse&long. Single mode 2021/8/257Gaussi
5、an beamsZero order mode is GaussianIntensity profile:beam waist: w0confocal parameter: zfar from waistdivergence angle Gaussian propagation2021/8/258Power distribution in GaussianIntensity distribution:Experimentally to measure full width at half maximum (FWHM) diameterRelation is dFWHM = w 2 ln2 1.
6、4 wDefine average intensityIavg = 4 P / (p d2FWHM)Overestimates peak: I0 = Iavg/1.42021/8/259Resonator optionsBest known - planar, concentric, confocalConfocal uniquemirror alignment not criticalposition is criticaltransverse mode frequencies identicalTypes of resonatorsSpecial cases2021/8/2510 刚才的发言，如刚才的发言，如有不当之处请多指有不当之处请多指正。谢谢大家！正。谢谢大家！2021/8/2511
