Fig. 1. Transparent regions and damage thresholds of commonly used nonlinear crystals. The full (color) bar marks the transparent regions at zero (half) transmittance. The black, red and blue bars correspond to conventional oxide crystals, new langasite oxide crystals and semiconductor crystals, respectively. The green circles mark the damage thresholds with 10 ns pulses at $2.05~\unicode[STIX]{x03BC}\text{m}$ for the ZGP crystal and 10 ns pulses at 1064 nm for other crystals. Most of the data come from the book, D. N. Nikogosyan, Nonlinear Optical Crystals: A Complete Survey (Springer, New York, 2006). Other data for langasite oxides come from Refs. [45–48] and [51].

Fig. 2. PM for noncollinear OPCPA pumped by 1030 nm laser. (a) Type-II ($e_{p}\rightarrow o_{s}+e_{i}$) PM in $XY$ plane of $\text{LiGaS}_{2}$ crystal; (b) Type-I ($o_{p}\rightarrow e_{s}+e_{i}$) PM in LGN crystal; (c) Type-II ($o_{p}\rightarrow e_{s}+o_{i}$) PM in LGN crystal. $\unicode[STIX]{x1D6FC}$ is the intersecting angle between pump and mid-IR beams inside the crystal; $\unicode[STIX]{x1D6FC}=0^{\circ }$ corresponds to the collinear configuration.

Fig. 3. Schematic setup of the proposed $5.2~\unicode[STIX]{x03BC}\text{m}$ TW-class OPCPA system based on oxide LGN crystals. All of the hardware devices in the gray background are commercially available. The reflection-induced losses in the LGN crystals and Si plate are neglected. Three OPCPA stages are pumped with the same intensity of $50~\text{GW}/\text{cm}^{2}$.

Fig. 4. PM properties of Type-II collinear intrapulse DFG. (a) The attainable signal (blue) and idler (red) wavelengths under the condition of $\text{GVM}_{si}=0$. In the calculation, the PM angle $\unicode[STIX]{x1D703}$ (green) is varied with the pump wavelength. (b) The phase-matched signal (blue) wavelength, idler (red) wavelength and the corresponding $\text{GVM}_{ps}$ (black) at $\unicode[STIX]{x1D703}=59.50^{\circ }$.

Fig. 5. (a) Schematic of intrapulse DFG for passive CEP stability. (b) Calculated mid-IR idler intensity as a function of the polarization angle $\unicode[STIX]{x1D711}$. The inset in (b) illustrates the definition of the angle $\unicode[STIX]{x1D711}$. The calculation parameters are $\unicode[STIX]{x1D706}_{p}=770~\text{nm}$, $\unicode[STIX]{x1D706}_{s}=904~\text{nm}$, $\unicode[STIX]{x1D706}_{i}=5.2~\unicode[STIX]{x03BC}\text{m}$, $\unicode[STIX]{x1D703}=59.50^{\circ }$, $L=0.1~\text{mm}$ and $I_{0}=1~\text{TW}/\text{cm}^{2}$.

Fig. 6. Simulation results for intrapulse DFG. (a) Input pump (black) and signal (red) spectral components. (b) Idler efficiency versus LGN crystal length. Inset shows the idler beam profile at $L=0.7~\text{mm}$. (c) Output mid-IR idler spectrum (solid) and phase (dashed) at $L=0.7~\text{mm}$. (d) Output idler pulse before (black) and after (red) dispersion compensation with GDD of $652~\text{fs}^{2}$ and TOD of $-5.84\times 10^{3}~\text{fs}^{3}$. The blue curve shows the FTL pulse. The parameters used in the simulation are $\unicode[STIX]{x1D706}_{p}=770~\text{nm}$, $\unicode[STIX]{x1D706}_{s}=904~\text{nm}$, $\unicode[STIX]{x1D706}_{i}=5.2~\unicode[STIX]{x03BC}\text{m}$, $\unicode[STIX]{x1D703}=59.50^{\circ }$, $I_{p0}=0.75~\text{TW}/\text{cm}^{2}$ and $I_{s0}=0.25~\text{TW}/\text{cm}^{2}$.

Fig. 7. Simulation results for the three-stage OPCPA. (a) Evolution of the mid-IR pulse energy in the first (green), second (red) and third (blue) OPCPA stages. (b) Evolution of chirped mid-IR pulse duration with amplification. The black curve represents the input chirped pulse. (c) Evolution of mid-IR spectrum with amplification. The black curve represents the input mid-IR spectrum. (d) FTL pulses after OPCPA-3 (blue) and seed mid-IR pulses before stretching (black). (e) Pump beam profile output from the first (left), second (middle) and third (right) OPCPA stages. (f) Mid-IR beam profile output from the first (left), second (middle) and third (right) OPCPA stages.