We analyze the generation of external cavity frequency - doubling with knbo3 crystal theoretically . in order to get the second - order nonlinear conversion from 858nm to 429nm with knbo3 , we use non - critical type - i phase - matching to avoid the walk - off effect the corresponding optimum focusing condition is as followings : double refraction parameter b = 0 , focus parameter = 2 . 84 , optimum phase mismatch parameter = 0 . 574 . based on the theoretical analysis and numerical calculations , we obtain the ideal nonlinear conversion coefficient about 1 . 45 % / w with crystal length of 7mm and 2 . 07 % / w with crystal length of 10mm at the phase - matching temperature around 23 . 50c 根據(jù)對(duì)其倍頻原理及性能的分析討論,在用該晶體完成波長從858nm到429nm的二階非線性轉(zhuǎn)換時(shí),采用非臨界相位匹配條件(此時(shí)無離散效應(yīng),對(duì)應(yīng)的雙折射參數(shù)b = 0 ,共焦長度為= 2 . 84 ,最佳相位失配因子為= 0 . 574 ) ,在相位匹配溫度約為23 . 5時(shí),理論上通過計(jì)算得到理想情況下非線性轉(zhuǎn)換系數(shù)約為1 . 45 / w (長度為7mm ) , 2 . 07 / w (長度為10mm ) 。
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