Temperature- and wavelength-insensitive parametric amplification enabled by noncollinear achromatic phase-matching

Optical modification of nonlinear crystals for quasi-parametric chirped-pulse amplification

Quasi-parametric chirped-pulse amplification (QPCPA), which features a theoretical peak power much higher than those obtained with Ti:sapphire laser or optical parametric chirped-pulse amplification, is promising for future ultra-intense lasers. The doped rare-earth ion used for idler dissipation is critical for effective QPCPA, but is usually not compatible with traditional crystals. Thus far, only one dissipative crystal of Sm3+-doped yttrium calcium oxyborate has been grown and applied. Here we introduce optical means to modify traditional crystals for QPCPA applications. We theoretically demonstrate two dissipation schemes by idler frequency doubling and sum-frequency generation with an additional laser. In contrast to absorption dissipation, the proposed nonlinear dissipations ensure not only high signal efficiency but also high small-signal gain. The demonstrated ability to optically modify crystals will facilitate the wide application of QPCPA.

Simultaneously Wavelength- and Temperature-Insensitive Mid-Infrared Optical Parametric Amplification with LiGaS2 Crystal

Ultrafast mid-infrared (mid-IR) lasers with a high pulse repetition rate are in great demand in various fields, including attosecond science and strong-field physics. Due to the lack of suitable mid-IR laser gain medium, optical parametric amplifiers (OPAs) are used to generate an ultrafast mid-IR laser. However, the efficiency of OPA is sensitive to phase mismatches induced by wavelength and temperature deviations from the preset points, which thus limits the pulse duration and the average power of the mid-IR laser. Here, we exploited a noncollinear phase-matching configuration to achieve simultaneously wavelength- and temperature-insensitive mid-IR OPA with a LiGaS2 crystal. The noncollinearity can cancel the first-order dependence of phase matching on both wavelength and temperature. Benefitting from the thermal property of the LiGaS2 crystal, some collinear phase-matching solutions derived from the first-order and even third-order wavelength insensitivity have comparatively large temperature bandwidths and can be regarded as approximate solutions with simultaneous wavelength and temperature insensitivity. These simultaneously wavelength- and temperature-insensitive phase-matching designs are verified through numerical simulations in order to generate few-cycle, high-power mid-IR pulses.

Temperature-insensitive broadband optical parametric chirped pulse amplification based on a tilted noncollinear QPM design

Ultrafast pulsed laser of high intensity and high repetition rate is the combined requisite for advancing strong-field physics experiments and calls for the development of thermal-stable ultrafast laser systems. Noncollinear phasing matching (PM) is an effective solution of optimizing the properties of optical parametric chirped pulse amplification (OPCPA) to achieve broadband amplification or to be temperature-insensitive. But as a cost, distinct noncollinear geometries have to be respectively satisfied. In this paper, a noncollinear quasi-phase-matching (QPM) scheme of both temperature- and wavelength-insensitive is presented. With the assistance of the design freedom of grating wave vector, the independent noncollinear-angle requirements can be simultaneously realized in a tilted QPM crystal, and the temperature-insensitive broadband amplification is achieved. Full-dimensional spatial-temporal simulations for a typical 1064 nm pumped mid-IR OPCPA at 3.4 µm are presented in detail. Compared with a mono-functional temperature-insensitive or broadband QPM scheme, the presented QPM configuration shows a common characteristic that simultaneously optimizes the thermal stability and the gain spectrum. Broadband parametric amplification of a ∼40 fs (FWHM) pulsed laser is achieved with no signs of gain-narrowing. Both of the beam profiles and the amplified spectra stay constant while the temperature is elevated by ∼100°C. Finally, influence of the QPM grating errors on the gain spectrum is discussed.

Stable ultra-broadband gain spectrum with wide-angle non-collinear optical parametric amplification

Comparing with the non-collinear optical parametric amplification (NOPA), the gain bandwidth could be significantly enhanced by the wide-angle NOPA (WNOPA), i.e., with a divergent signal (WNOPA-S) or pump (WNOPA-P). In a uniaxial crystal, the spectral symmetry/asymmetry of WNOPA is introduced. In WNOPA-S, the ultra-broadband gain spectrum can be obtained in two phase-matching directions at both sides of the pump, however, the output is heavily angularly dispersed. In WNOPA-P, although the gain bandwidth enhancement is only achieved in one phase-matching direction, i.e., on the opposite side of the crystal axis, it is free of angular dispersion. The stabilities of the gain spectrum in NOPA and in WNOPA-P are experimentally compared and theoretically analyzed. Compared with NOPA, WNOPA-P supports an even broader and more stable gain spectrum, and compared with WNOPA-S, WNOPA-P is angular-dispersion-free. The conversation efficiency of WNOPA-P is the same as NOPA. We suppose WNOPA-P is ideally suitable for the amplification of stable ultra-broadband few-cycle pulse lasers.

Comprehensive analyses of the thermal insensitive noncollinear phase-matching for power scalable parametric amplifications

Thermal-induced phase-mismatch distortion, which will dramatically deteriorate the efficient energy transfer, has become a critical obstacle to power scaling of optical parametric amplifiers. To ease this efficiency deterioration, the noncollinear optical parametric amplification (OPA) configuration widely employed to achieve broadband phase-matching (PM) may also serve as a promising approach to optimize the temperature acceptance. In this paper, starting from the noncollinear wave-vector equations, a required thermo- and angle-relationship analogous to that of noncollinear broadband PM is firstly inferred. Based on the presented mathematical criterion, we have explored the potential spectral boundaries of this ingenious temperature insensitive OPA scheme. Full-dimensional simulations of two types of typical OPA processes were quantitatively discussed. Compared with traditional collinear PM designs, the presented noncollinear PM configurations show significant common characteristics on improving the temperature acceptance and subsequently the overall amplification efficiency. For a typical high power parametric process of the 532 nm pumped near-IR OPA at 800 nm especially, incredible temperature bandwidth exceeding 8000 °C was obtained while a YCOB (xz plane) crystal is adopted. What is more, it can also be applied to ameliorate the gain-spectrum thermo-instability of OPA.