Abstract
Extended coupled-wave analysis of optical parametric chirped-pulse amplification (OPCPA) reveals regimes whereby high-peak-power few-cycle pulses can be generated in the long-wavelength infrared (LWIR) spectral range. Broadband OPCPA in suitable nonlinear crystals pumped at around 2 μm and seeded either through the signal or the idler input is shown to enable the generation of high-power field waveforms with pulse widths shorter than two field cycles within the entire LWIR range.
Highlights
Technologies enabling the generation of electromagnetic field waveforms as short as a few field cycles are on the cutting edge of modern optical science [1]
All the three ZGP crystals are oriented at an angle θ = 52.9о in the considered optical parametric chirped pulse amplification (OPCPA) scheme to phase match the parametric amplification of the 7.0-μm seed
An eoe OPCPA process in three AGSe crystals with θ = 48.8о seeded with negatively chirped 3.3-ps pulses at 2.34 μm [Figs. 7(a)–7(e)], on the other hand, delivers an idler-wave output centered at λ3 ≈16 μm [Fig. 7(b)] with an energy of about 0.28 mJ [Fig. 7(e)] and a spectrum corresponding to a transform-limited pulse width of 100 fs [Fig. 7(b)], which corresponds to 1.9 field cycles
Summary
Technologies enabling the generation of electromagnetic field waveforms as short as a few field cycles are on the cutting edge of modern optical science [1]. The second scheme of broadband OPCPA examined in this work [scheme II in Fig. 1(b)] is seeded through the signal field This version of OPCPA does not require an additional stage for seed generation since a suitably red-shifted seed can be generated through a frequency broadening of the pump field in the bulk of mid-IR transparent solid or via soliton selffrequency shift in a properly designed optical fiber, e.g., a photonic-crystal fiber [36,37]. Nonlinear phase shifts and spatial self-action may become a significant factor, especially for high peak powers of the pump field, these effects are not included in Eq (1) With such an approach we seek to identify, through a transparent physical analysis, the key limitations on short-pulse LWIR generation due to the dispersion of nonlinear materials that seem best suited for OPCPA in the LWIR range. As our analysis presented below shows, Eqs. (6) and (7) provide accurate predictions for the asymptotic upper-bound limit for the signal and idler energies [dotted lines in Figs. 2–11], serving as a guide that helps choose the crystal thickness for each OPCPA stage
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