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

Abstract

In this paper, we model the performance of a device with a simple architecture for high-power mid-wave infrared beam generation at a wavelength of 3.8 microns. The device is a seeded idler efficiency-enhanced optical parametric generator (IEE-OPG) based on an aperiodically poled MgO-doped LiNbO3 (APMgLN) grating pumped by a high-repetition rate nanosecond-pulsed 1064-nm laser and seeded by a low-power 1478-nm distributed feedback diode laser. In the IEE-OPG, two optical parametric amplification (OPA) processes, OPA-1 and OPA-2, are simultaneously phase matched in a single APMgLN grating. The signal at 1478 nm is amplified and the idler at 3800 nm is generated as a result of OPA-1, the signal acts as the pump for OPA-2 and the conversion efficiency of the idler is enhanced as a result of OPA-2. Also, a difference-frequency beam at 2418 nm is generated.We characterized the device performance using a realistic model that takes the diffraction of the beams into account. We designed multiple aperiodic gratings with varying relative strengths of OPA-1 and OPA-2. For various crystal lengths, optimum relative strengths of the two processes and input pump power levels for achieving the maximum mid-wave infrared conversion efficiency and output power are determined.Efficiency-enhanced mid-wave infrared beam generating optical parametric oscillators (OPOs) based on APMgLN gratings were reported before. However, no attempt was made for the optimization of the relative strengths of the simultaneously phase-matched processes in these devices. Our model calculations show that it is possible to reach and exceed the mid-wave infrared conversion efficiencies of these OPOs by correctly choosing the design parameters of the seeded OPGs based on relatively long APMgLN gratings.

Idler-efficiency-enhanced long-wave infrared beam generation using aperiodic orientation-patterned GaAs gratings

“…Furthermore, it is possible to adjust the relative height of these two peaks; hence the relative strength of the processes can be adjusted. It was recently shown that the maximum output efficiency or power can be achieved by optimizing the relative strength of OPA 1 and OPA 2 processes in an idler-efficiency-enhanced seeded OPG [27,28].…”

“…The achievable power conversion efficiencies for the conversion of the well-established 2 μm laser sources, such as a Tm:fiber laser pumped Ho:YAG laser, a Tm,Ho:fiber laser, or a Tm,Ho:YLF laser, into the relatively long wavelength region of 8-12 μm are rather low due to the relatively small quantum efficiencies (25%-17% corresponding to the conversion of a 2 μm pump to an 8 μm idler and a 2 μm pump to a 12 μm idler, respectively). One solution is the use of cascaded optical parametric amplification (OPA) processes for the enhancement of the conversion efficiency of the idler, whose wavelength is in the 8-12 μm band in our case, compared to what is achievable by a single OPA process [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. In such a device, 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).…”

“…In order to achieve higher overall conversion efficiencies, rather than cascading OPA 1 and OPA 2 in separate gratings, it is preferable to employ a single grating in which both processes take place by means of simultaneous phase matching (SMPM) [20][21][22][23][24][25][26][27][28][30][31][32][33]. SMPM increases the effective interaction length dedicated to each nonlinear process.…”

“…Furthermore, in an idler-efficiency-enhanced device employing SMPM, it is highly desirable to adjust the relative strength of the processes involved to an optimum value by means of the grating design method so that the output conversion efficiency or power is maximized. In [27,28], the design of aperiodically poled MgO-doped LiNbO 3 (APMgLN) gratings for an idlerefficiency-enhanced mid-wave infrared (3.8 μm) beam generating seeded OPG were reported. The design with the optimum relative strength of OPA 1 and OPA 2 processes was determined at a given pump power for maximum output efficiency or power.…”

“…In this method some of the domain walls are discarded considering the minimum domain length (D min ) that is achievable in the production process. In [27,28], this method was used for designing aperiodic gratings for an idler-efficiency-enhanced mid-wave infrared beam generating seeded OPG.…”