Efficient parametric conversion from 106 to 38 μm by an aperiodically poled cascaded lithium niobate

Abstract

We experimentally demonstrated an efficient optical parametric oscillator (OPO) with high parametric conversion from 1.0645 to 3.8 μm. An aperiodically poled magnesium oxide doped lithium niobate wafer was designed and fabricated as the nonlinear crystal of the OPO. A linearly polarized acousto-optic Q-switched Nd:YVO4 laser was used as the pump source. High pump-to-idler conversion efficiency of 18.5% was achieved with a slope efficiency of up to 21.5%. When compared with a periodically poled channel fabricated on the same wafer, under the condition of output coupler optimized for the periodically poled lithium niobate based OPO, an improvement of slope efficiency by 28.3% from 15.2% to 19.5% and total efficiency by 12.5% from 13.6% to 15.3% under the highest pump power of 11 W was realized for the pump-to-idler conversion.

Efficiency-enhanced mid-wave infrared beam generation at 3.8 μm with a seeded optical parametric generator

“…Our model calculations show that it is possible to reach and exceed the mid-wave infrared conversion efficiencies achieved using the OPOs based on APMgLN crystals that were recently reported in the literature. 18,19 In fact, we find that devices based on gratings with lengths 75 mm or larger can provide conversion efficiencies of 18% or larger; provided that the relative strengths of the OPA processes, pump power levels, and pump beam waist radii are correctly chosen.…”

“…The diameter of this circular area is chosen to be typically 3 times of the diameter of the pump beam at the exit surface of the crystal. For each time slice, Equations (15)- (18) are integrated along the length of the APMgLN crystal using the Cash-Karp Runge-Kutta algorithm 28 to determine the beam intensity corresponding to each field at the exit of the crystal. We calculate Hankel and inverse Hankel transforms at each location along z during the integration process.…”

“…In order to achieve higher overall conversion efficiencies, it is usually preferable to use a single bulk crystal or a single grating where two or more processes take place by employing simultaneous phase matching (SMPM) [12][13][14][15][16][17][18][19][20] rather than cascading multiple processes in separate bulk crystals or separate gratings. Frequency conversion using SMPM also reduces the system complexity.…”

“…14 In idler efficiency enhancement with SMPM, two optical parametric amplification (OPA) processes are simultaneously phase matched within a single crystal or a single grating. [16][17][18][19][20] When pumped by a laser source, the signal is amplified and the idler is generated as a result of the first OPA process (OPA-1), the signal acts as the pump for the second OPA process (OPA-2) and the idler conversion efficiency is enhanced as a result of OPA-2 along with the generation of a difference-frequency (DF) output. Recently, OPOs based on aperiodic gratings that were designed with the method given in Ref.…”

“…13 were employed for mid-wave infrared beam generation using idler efficiency enhancement with SMPM. 18,19 However, no attempt was made for the optimization of the relative strengths of the simultaneously phase-matched processes. Injection-seeded idler efficiency-enhanced OPGs (IEE-OPGs) with optimized relative strengths for the two simultaneously phase-matched processes were recently proposed.…”