Dual-chirped difference frequency generation(DFG)is an advantageous technique for generating the broadband midinfrared(IR)idler wave,which is inaccessible by a population-inversion-based laser system.In principle,the ...Dual-chirped difference frequency generation(DFG)is an advantageous technique for generating the broadband midinfrared(IR)idler wave,which is inaccessible by a population-inversion-based laser system.In principle,the generated idler wave may even suffer a spectrum broadening compared with the driving pulsed lasers if the pump and signal waves are oppositely chirped.However,broadband phase-matching is always the determining factor for the resulting efficiency and the bandwidth of the generated idler wave.In this study,specific to an oppositely dual-chirped DFG scheme,we derive the precondition to realize broadband frequency conversion,wherein a negative(1/υp-1/υi)/(1/υs-1/υi),in terms of the correlation coefficient of the group velocity(σ),is necessary.However,most birefringence bulk crystals can only provide the required material dispersions in limited spectral regions.We show that the periodically poled lithium niobate crystal that satisfies an inactive Type-II(eo-o)quasi-phase-matching condition has a stable negativeσand exerts the expected broadband gain characteristic across an ultra-broad idler spectral region(1.7-4.0µm).Finally,we propose and numerically verify a promising DFG configuration to construct a tunable mid-IR spectrum broader based on the broadband phase-matched oppositely dual-chirped DFG scheme.展开更多
基金This work was supported in part by the National Natural Science Foundation of China(No.61505113)Natural Science Foundation of Guangdong Province(No.2020A1515010541)Science and Technology Project of Shenzhen(Nos.JCYJ20180305124930169,JCYJ20190808143419622 and ZDSYS201707271014468).
文摘Dual-chirped difference frequency generation(DFG)is an advantageous technique for generating the broadband midinfrared(IR)idler wave,which is inaccessible by a population-inversion-based laser system.In principle,the generated idler wave may even suffer a spectrum broadening compared with the driving pulsed lasers if the pump and signal waves are oppositely chirped.However,broadband phase-matching is always the determining factor for the resulting efficiency and the bandwidth of the generated idler wave.In this study,specific to an oppositely dual-chirped DFG scheme,we derive the precondition to realize broadband frequency conversion,wherein a negative(1/υp-1/υi)/(1/υs-1/υi),in terms of the correlation coefficient of the group velocity(σ),is necessary.However,most birefringence bulk crystals can only provide the required material dispersions in limited spectral regions.We show that the periodically poled lithium niobate crystal that satisfies an inactive Type-II(eo-o)quasi-phase-matching condition has a stable negativeσand exerts the expected broadband gain characteristic across an ultra-broad idler spectral region(1.7-4.0µm).Finally,we propose and numerically verify a promising DFG configuration to construct a tunable mid-IR spectrum broader based on the broadband phase-matched oppositely dual-chirped DFG scheme.
