Fig. 1. Schematic of the OPCPA setup. DL, delay line; TFP, thin film polarizer at 1064 nm; DM, dichroic mirror; BS, beam splitter; HWP, half-wave plate; WLC, white-light continuum; Sa, sapphire; RM, roof mirror; IR, image relay; OAP, off-axis parabolic mirror; VDF, variable density filter; T, telescope; PC, computer.

Fig. 2. Spectrum evolution through the OPCPA system. Insert, near-field beam profile after the second KTA crystal, as measured by a pyroelectric thermal camera (PyroCAM) with a spatial resolution of $80~\unicode[STIX]{x03BC}\text{m}$.

Fig. 3. Energy fluctuation of compressed pulses at 1450 nm.

Fig. 4. Temporal characterization of the compressed pulse. (a) Measured and (b) retrieved SHG-FROG traces; (c) reconstructed pulse envelope (blue), which is 60 fs (FWHM), phase (green) and its TL pulse (red); (d) reconstructed spectrum (blue), phase (green) and measured spectrum (red) obtained by a near-infrared spectrometer (NIR-Quest from Ocean Optics).

Fig. 5. (a) Amplified signal energy as a function of pump energy (seed energy fixed) of the first (insert) and the second OPA stages. (Black) Seed energy fixed at $30~\unicode[STIX]{x03BC}\text{J}$. (Red) Seed energy fixed at $55~\unicode[STIX]{x03BC}\text{J}$. (b) Amplified signal (black dots) and idler (red dots) energies as functions of pump energy in the second OPA stage (the energy of the first amplified signal is fixed at 4.9 mJ).