# Ultrafast Mid-IR Laser Pulses Generation via Chirp Manipulated Optical Parametric Amplification
## 5 Prospects and Conclusions  
The BBP-OPA scheme has been proven capable of generating microjoule broadband tunable pulses in the IR region. More detailed results will be needed to further confirm this concept. Meanwhile, the potential of the proposed scheme is not limited to the present results. Broadband pump pulses with energy from several tens microjoule to the millijoule level has been realized with various techniques including the multi-plate scheme and HCF compression. Utilizing such pulses in a BBP-OPA scheme enables the generation of a more intense supercontinuum that supports few-cycle pulse duration.  
On the other hand, the achieved spectra are limited to 2100 nm due to the spectrometer in our lab. Since the idler bandwidth is insensitive to the phase-matching condition, tuning the idler frequency as well as the signal is feasible by simply rotating the nonlinear crystal and changing the pump-seed delay. Considering the absorption of BBO crystal in the Mid-IR region, other nonlinear crystals such as AGS, LN or LT can be introduced owing to their higher transmission range up several microns, which will allow more efficient conversion in the Mid-IR spectral region.  
The ultrashort pulses generated from chirp manipulated OPA can be a powerful tool in a number of related researches owing to its unique characteristics over commercially available Ti:sapphire lasers, including longer carrier wavelength, broader spectral bandwidth, and shorter pulse duration. The low requirement on a multi-plate scheme allows BBP generation with a wide variety of initial laser energy of only several tens to hundreds \(\upmu\)J. With the reported conversion efficiency, \(\upmu\)J-level few-cycle Mid-IR pulses can be directly obtained from a single-stage BBP-OPA pumped by a laser system with moderate pulse energy, which can benefit applications that do not require the ultrahigh energy of femtosecond laser pulses [115; 116; 117; 118; 119].  
In particular, femtosecond IR pulses have been widely employed in ultrafast spectroscopy to investigate the carrier dynamics in semiconductor structures using pump-probe measurements [120; 121; 122]. Due to the wavelength tunability of chirp manipulated OPA accompanied with the ultrashort pulse duration, the generated pulses with lower photon energy compared to Ti:sapphire laser can be helpful in probing the carrier relaxation process. The widely variable photon energy provided by the tunable Mid-IR laser might uncover essential information about the evolution during the decay of excited states at different energy levels.  
In conclusion, we introduced the chirp manipulated optical parametric amplification scheme in this paper and reviewed some of the results on the latest developments. The superb energy scalability of DC-OPA is a promising route to fully utilize the hundreds millijoule energy of a Ti:sapphire laser in an OPA system. In addition, the dual-chirped geometry allows the simultaneous manipulation of the pump and seed chirps, which can also remarkably benefit the gain bandwidth of the system. The broadband pumped OPA shows potential in generating an intense supercontinuum and few-cycle pulses spanning the whole IR spectral region, which we believe will contribute to the future developments of ultrafast optics and strong field physics.  
[PERSON] and [PERSON] wrote the paper, [PERSON] and [PERSON] carried out the theoretical investigations, [PERSON] designed the experiments, [PERSON] and [PERSON] performed the experiments and the measurements described in the manuscript. All the authors reviewed and provided comments on the manuscript.  
This work is supported by grant (No. 11574101, 11627809, 11774111) from National Natural Science Foundation of China.  
The authors declare no conflict of interest.