马赫-曾德尔干涉仪频谱特性及入射视场展宽技术研究

Mach-Zehnder interferometer spectral characteristics and incident field of view widening technology

马赫-曾德尔干涉仪(MZI)具有光学能量利用率高、便于视场展宽等优点,在光学滤波、鉴频等方面具有广泛的应用。然而,在实际应用中MZI频谱会受到各种因素的影响而导致性能下降。从理论上导出了在考虑入射光发散角2θ_(0)和谱宽Δν的影响下,MZI干涉频谱的理论表达式,并定量分析了其对MZI频谱的影响。结果表明:MZI的光程差l越大,其频谱受Δν的影响越显著,l与入射光波长λ比值越大,其频谱受θ_(0)的影响越显著;当λ=355 nm,l=3 cm时(第1种情形),Δν=10 GHz和θ_(0)=4.5 mrad将分别使条纹对比度K降至2.8%和16.3%;当λ=532 nm,l=59 cm时(第2种情形),Δν=0.5 GHz和θ_(0)=1.25 mrad将分别使K降至3.2%和15%。为减小发散角的影响,从理论上进一步研究了棱镜式视场展宽技术。结果表明:若补偿棱镜厚度d和折射率n满足d=nl/(n􀀀1),对应第1种情形,θ_(0)=50 mrad时K仍高于93.1%,θ_(0)=70 mrad时K将降至33.3%;在第2种情形下,θ_(0)=25 mrad时K仍高于94.0%,θ_(0)=35 mrad时K将降至37.6%。若d依据不同θ_(0)取不同最优值时,在第1种情形下,θ_(0)=70 mrad时K仍高于92.1%;而在第2种情形下,θ_(0)=35 mrad时K仍高于94.4%。

In view of the advantages of high utilization of optical energy and easy field of view broaden-ing,Mach-Zehnder interferometer(MZI)has a wide range of applications in optical filtering,frequency discrimination,and so on.However,in practical applications,its spectrum will be affected by various fac-tors,resulting in performance degradation.In this work,the theoretical expressions of MZI interference spectrum are derived considering the influence of divergence angle 2θ_(0) and spectrum width Δν of incident light,and then their influence on MZI spectrum is analyzed quantitatively.The results show that the larger the optical path difference l of MZI is,the more significant the influence of Δν on its spectrum is,and the greater the ratio of l to incident light wavelengthλis,the more significant the influence of θ_(0) on its spectrum is.When λ=355 nm and l=3 cm(the first case),Δν=10 GHz and θ_(0)=4.5 mrad will reduce the fringe contrast K to 2.8% and 16.3%,respectively.And when λ=532 nm,l=59 cm(the second case),Δν=0.5 GHz and θ_(0)=1.25 mrad will reduce K to 3.2% and 15%,respectively.In order to reduce the influence of the beam divergence angle,the prism field broadening technique is further studied theoretically.The results show that if the thickness d and refractive index n of the compensation prism meet the conditions of d=nl/(n-1),in the first case,K is still higher than 93.1% when θ_(0)=50 mrad,and K will drop to 33.3% even when θ_(0)=70.In the second case,K is still higher than 94.0%when θ_(0)=25,and K will drop to 37.6% when θ_(0)=35 mrad.If d takes different optimal values according to differentθ_(0),in the first case,K is still higher than 92.1% when θ_(0)=70 mrad.And in the second case,K is still higher than 94.4% when θ_(0)=35 mrad.