Very broad gain bandwidth parametric amplification in nonlinear crystals at critical wavelength degeneracy

Angular dispersion compensation for ultra-broadband pulses by using a cascaded prism and hollow-core fiber configuration

In this paper, we report that the angular dispersion of the output pulses in a nonlinear process can be efficiently compensated by using a cascaded prism(s) and short hollow-core fiber (HCF) configuration. Here, the prism(s) is used to suppress the angular dispersion and transform it into spatial chirp, while the HCF is used for removing this spatial chirp and the residual angular dispersion, which can also significantly improve the beam quality. The feasibility of this novel method is numerically and experimentally investigated with the ultra-broadband idler pulses centered at 1250 nm wavelength and generated by an LBO crystal based non-collinear optical parametric amplifier. The proof-of-principle experiment shows that the angular dispersion can be effectively removed and ultra-broadband idler pulses with good spectral quality and spatial profile can be obtained. The total transmission efficiency in the experiment is around 67% and the measured M x2 and M y2 can reach 1.12 and 1.04, respectively. To the best of our knowledge, this is the first reported ultra-broadband angular dispersion compensation scheme combining prism(s) and HCF, which can remarkably eliminate the angular dispersion while simultaneously possesses high efficiency, good spectral and beam spatial quality.

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.

Numerical analysis of the DKDP-based high-energy optical parametric chirped pulse amplifier for a 100 PW class laser

An optical parametric chirped pulse amplifier (OPCPA) based on a large-aperture DKDP crystal and pumped by a 10 kJ level Nd:glass laser can serve as the final amplifier for a 100 PW level laser. A comprehensive numerical investigation on such a high-energy OPCPA is presented in this work. The effects on the efficiency-bandwidth product induced by the deuteration level, absorption loss, temperature variation, and optimization of zero-phase-mismatch wavelength (ZPMW) are analyzed in detail. Based on the analysis above, a three-dimensional numerical simulation taking into account the effects of pumping depletion, diffraction, and walk-off shows that, by optimization of ZPMW, broadband (over 210 nm spectral width in FWHM) and high efficiency (${\gt}37\%$) amplification can be realized in the DKDP crystal even with a moderate deuteration level of 70%, which can relax the requirement of a high deuteration level in a large-aperture DKDP crystal. The numerical analysis can provide meaningful guidance for the design and construction of 100 PW class laser systems.

PT symmetry and antisymmetry by anti-Hermitian wave coupling and nonlinear optical interactions

Light propagation in systems with anti-Hermitian coupling, described by a spinor-like wave equation, provides a general route for the observation of antiparity-time (PT) symmetry in optics. Remarkably, under a different definition of parity operator, a PT symmetry can be found as well in such systems. Such symmetries are ubiquitous in nonlinear optical interactions and are exemplified by considering modulation instability in optical fibers and optical parametric amplification.

Non-collinear spectral coherent combination of ultrashort laser pulses

Non-collinear spectral coherent combining (NCSCC) of ultrashort pulses is analyzed. 2D modeling of the electromagnetic field is performed in case of NCSCC using two or three pulses with different wavelengths. In the case of two pulses, a potentially unwanted spatio-temporal structure of the field appears, corresponding to spatial and temporal modulation of the pulse. By using NCSCC of three 62 fs long pulses with different spectral composition, such spatial-temporal coupling is eliminated and the combined pulse duration in the focal region drops to less than half. The method is scalable to a large number of ultrashort pulses.

Optical parametric gain and bandwidth in highly nonlinear tellurite hybrid microstructured optical fiber with four zero-dispersion wavelengths

The parametric amplification gain and bandwidth in highly nonlinear tellurite hybrid microstructured optical fiber (HMOF) are simulated based on four wave mixing process. The fiber core and cladding materials are made of TeO(2)–Li(2)O–WO(3)–MoO(3)–Nb(2)O(5) and TeO(2)–ZnO–Na(2)O–P(2)O(5) glass, respectively. The fiber has four zero-dispersion wavelengths and the chromatic dispersion is flattened near the zerodispersion wavelengths. A broad gain bandwidth as wide as 1200 nm from 1290 to 2490 nm can be realized in the near infrared window by using a tellurite HMOF as short as 25 cm.