%0 Journal Article
%A Cao, Qian
%A Kärtner, Franz
%A Chang, Guoqing
%T Towards high power longwave mid-IR frequency combs: power scalability of high repetition-rate difference-frequency generation
%J Optics express
%V 28
%N 2
%@ 1094-4087
%C Washington, DC
%I Optica
%M PUBDB-2020-00333
%P 1369 - 1384
%D 2020
%X Frequency combs in the mid-IR wavelength are usually implemented by difference-frequency generation (DFG) that mixes pump pulses and signal pulses. Different from most optical parametric amplifiers that operate at a typical low repetition rate of <0.1 MHz, mid-IR frequency combs require that pump/signal pulse repetition rate must be at least as high as tens of MHz (normally >30 MHz). The DFG mixing high repetition rate (HRR) pulses limits the allowed pulse energy to prevent crystal damage. In this paper, we numerically investigate HRR DFG with a focus on the energy scalability of idler pulses. We show that HRR DFG–unlike optical parametric amplifiers–may operate in the linear regime, in which the idler pulse energy scales linearly with respect to the pump/signal pulse energy. Our simulation results suggest an efficient approach to energy scaling the idler mid-IR pulses in a HRR DFG: increase the signal pulse energy to the same level as the pump pulse energy. We also show that DFG seeded by pump/signal pulses at ∼2-µm range benefits from reduced group-velocity mismatch and exhibits better idler energy scalability. For example, 44.2-nJ pulses at 9.87 µm can be achieved by mixing 500-nJ, 2.0-µm pump pulses and 100-nJ, 2.508-µm signal pulses in a 2-mm-thick GaSe crystal. At the end of this paper, we show that such high-energy signal pulses can be derived from the pump pulses using a recently invented fiber-optic method. Therefore, implementation of high-power (>2 W) longwave mid-IR frequency combs is practically feasible.
%F PUB:(DE-HGF)16
%9 Journal Article
%$ pmid:32121849
%U <Go to ISI:>//WOS:000513232200046
%R 10.1364/OE.28.001369
%U https://bib-pubdb1.desy.de/record/434790