Fig. 1. (a) Illustration of generation of narrowband idler from broadband pump and signal with an equal linear chirp. (b) Normalized phase-matching efficiency of a 10 mm type I (phase-matching angle: 20°) BBO. Δk is the propagation constant difference, and L is the ZGP crystal length.

Fig. 2. (a) Input pump (blue) and signal (red) spectra. (b) Input pump (blue) and signal (red) pulse shapes in the case of an initial pump and signal chirp of 10000  fs2. (c) Output idler spectra under different pump and signal chirps. (d) Output idler pulse shapes in the case of an initial pump and signal chirp of 10000  fs2 (blue) and transform limited idler pulse shape (red).

Fig. 3. Schematic setup of DC-OPA.

Fig. 4. (a) Input pump spectrum. (b) Output signal spectrum. (c) Measured output idler spectrum (solid red line) and simulated output idler spectrum (dotted black line).

Fig. 5. Energy stability and beam profile (inset figure) of the idler.