Parametric generation and characterization of femtosecond mid-infrared pulses in ZnGeP_2

Abstract

Ultrafast mid-infrared (IR) coherent radiation plays an important role in strong-field physics, wherein the use of longer wavelengths has reduced the optical intensities needed to drive light-matter interactions by orders of magnitude in comparison to near-IR radiation. Optimizing parametric interactions for generation and characterization of mid-IR pulses is an enabling step for those applications. We report on the production of >50 µJ femtosecond pulses centered at 5 µm in a two-stage optical parametric amplifier (OPA) based on ZnGeP, a high-performance optical material in this spectral region. The OPA is pumped by an ultrafast 2-µm source. Amplified pulses have been characterized by parametric upconversion, enabling the use of standard silicon detectors. A numerical model of the system has been developed and tested to control dispersion, group-velocity mismatch, and off-axis parametric fluorescence. The source architecture is suitable for production of mJ-level mid-IR ultrafast pulses without the use of chirped-pulse amplification, where convenient pumping could be realized directly by mid-IR laser sources based on materials such as Cr:ZnSe or Cr:ZnS.

Towards Terawatt Sub-Cycle Long-Wave Infrared Pulses via Chirped Optical Parametric Amplification and Indirect Pulse Shaping

“…For example, an OPA in ZGP generated 53  μ J, 700 fs laser pulses at 5  μ m when pumped by another OPA at around 2  μ m24; an OPCPA in ZGP generated 100  μ J, 69 fs (calculated transform limit) laser pulses at 5.3  μ m when pumped by a Ho:YAG CPA at 2.09  μ m26; another OPCPA in ZGP generated 200  μ J, 360 fs laser pulses at 7  μ m when pumped by a Ho:YLF CPA at 2  μ m25. Here we simulate the OPCPA discussed in the last section to generate 4–12  μ m idler pulses.…”

“…We have previously experimentally demonstrated 3 mJ, CEP-stable two-cycle pulses from 1.2  μ m to 2.2  μ m with the highest 18% pump-to-signal conversion efficiency22 and numerically demonstrated for the first time a robust approach for generation of mJ-level, CEP-stable, two-cycle pulses from 2.4  μ m to 4.0  μ m23. Recently, rapid progress has been made on the generation of short-pulse mid-IR laser sources around 5  μ m or above242526. However, the compression of such pulses down to the transform limit has remained a great challenge due to lack of higher-order phase control over broadband mid-IR.…”

Bandwidth Control in 5-µm Pulse Generation by Double-Chirped Optical Parametric Amplification

“…The 2 μm OPA system uses a two-stage mixed phase-matching scheme based on BBO crystals to produce mid-IR pulses with a pulse energy of 2.2 mJ and a pulse duration of 42 fs [27]. Previous work on 5 μm pulse production has shown that the use of a 60 fs pump pulse at 2 μm generates higher pulse energy with better conversion efficiency due to an increased pulse-splitting length in the second OPA stage [28]. The 5 μm parametric source uses two ZGP crystals with dimensions of 10 × 10 × 1.0 mm 3 and 10 × 10 × 1.5 mm 3 in the first and second OPA stage, respectively.…”

Toward terawatt few-cycle pulses via optical parametric chirped-pulse amplification with oxide crystals

“…Given the lack of traditional laser amplifiers beyond 3 µm, the common method is to convert an intense near-IR laser to the mid-IR spectral region via nonlinear frequency conversion, such as difference-frequency generation (DFG) and optical parametric amplification (OPA). Table 1 lists the typical ultrafast lasers in the mid-IR and long-wave IR ranges, which are generated by DFG or OPA based on different nonlinear crystals [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] . Limited by the detrimental effects of nonlinear self-focusing and optical damage, these IR pulses have relatively low nJ to sub-mJ energies.…”