Spontaneous parametric down conversion(SPDC)and second harmonic generation(SHG)represent two of the most significant nonlinear optical effects.However,in previous studies,the two were studied separately,and a comparative study of the differences and connections between them is lacking.This paper presents a comparative study of the spectral distributions of SPDC and SHG in the perspective of the frequency domain.The study employs periodically poled potassium titanyl phosphate(PPKTP)crystal and lithium borate(LBO)crystal as examples.Theoretical calculations and experimental measurements indicate that the spectral distribution functions of both can be obtained by the product of the pump envelope function(PEF)and the phase matching function(PMF).However,in SHG,the PEF and PMF are single-variable functions with a limited spectral tuning range,while in SPDC,the PEF and PMF are two-variable functions with a larger tuning range.This study provides a deeper understanding of the spectra of SPDC and SHG,as well as guidance on selecting the appropriate spectral width for experimental purposes.
维普
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