## 2 Experimental Setup  
The 1937-nm pump pulses used in our scheme were derived from an updated version of the Tm:YAP regenerative amplifier [48], operating under a 10-kHz repetition rate. Figure 1 depicts the schematic of the experimental setup. The regenerative amplifier was capable of providing 0.122 mJ of pulse energy with a 360-fs pulse duration after 45 round trips, at a crystal temperature of \(-20\,^{\circ}\)C. The regenerative amplifier chamber was purged with nitrogen to reduce the effect of absorption from the water molecules [48; 49]. The output pulses of the amplifier were recorded with a resolution of 0.04 nm using a spectrum analyzer (Yokogawa-AQ6375 by Yokogawa Meters & Instruments Corporation, Tokyo, Japan). Figure 2 depicts the obtained spectrum. Using an infrared beamsplitter, 15 \(\upmu\)J of the compressed amplified pulses after 45 round trips were selected and loosely focused into a 3-mm YAG plate to generate the supercontinuum. The residual part of the pump from the beam splitter was focused into a 2-mm BBO crystal (cut at \(\theta=20^{\circ}\)) to generate the second harmonic (SH) with 10% efficiency, which will be used for characterizing the phase of the generated SC later on. The full spectrum of the supercontinuum was collected in its entirety, right after generation, and was sent to be recorded by switching between two spectrum analyzers (Yokogawa-AQ6315 and Yokogawa-AQ6375) and a home-built Fourier transform spectrometer (liquid nitrogen-cooled InSb photoconductive detector) depending on the wavelength region. The responses from the detectors were corrected, and as can be seen from Figure 3, the limits of the spectrum of the SC expanded into MIR region, reaching 4-mm boundaries. Detailed knowledge of the phase of the SC plays a pivotal role in applications such as OPA, especially when designing the parameters to maximize OPA systems' performance. For this reason, a pulse characterization system was constructed in our design. The biggest obstacle in characterizing SC pulses arises from the fact that they have in general an ultra-broad bandwidth and very low energy. For this reason, the choice of the characterization system would require adequate considerations. Due to the substantial drawbacks of the second harmonic generation frequency-resolved optical gating method (SHG-FROG) when the subject pulses are too weak to obtain efficient second harmonic signal generation or when the required phase-matching angle for SHG of the pulses would be very large (corresponding to extremely thin non-linear medium), such systems would be rendered inapplicable as the characterization system. While electro-optic sampling schemes have the capability to obtain the properties of the SC pulses, their complexity and technical sophistication would not be deemed suitable for the purpose of our study [50]. XFROG is well known for its capabilities to characterize  
Figure 1: Schematic design of the experimental setup. LD, laser diode. BS, beam splitter. FM, folding mirror. PC, Pockels cell. SCG, supercontinuum generation. SFG-XFROG, sum-frequency generation cross-correlation frequency-resolved optical gating. Figure 2: Recorded spectrum of the amplified pulses from the Tm:YAP regenerative amplifier using 23.5 W of absorbed power, operating under 10 kHz and \(-20\,^{\circ}\)C.  
complicated pulses [51; 52], and since it is based on the nonlinear interaction of a reference pulse, it can be used to measure low energy pulses with a broad bandwidth. Therefore, it was chosen to characterize the SC in our design. To characterize a pulse using XFROG, a well-defined reference pulse is required. Although it would be straightforward to use a part of the seed pulse before SC generation as the reference pulse, we chose to use its second harmonic pulse instead because the initial pulse had a very featured spectral profile, and the SH pulses in general exhibited a much cleaner profile. The SH pulses were characterized using a second-harmonic generation FROG (SHG-FROG).