Kugel Tobias, Okazaki Daiki, Arai Ko, Ashihara Satoshi
Appl Opt. 2022 Feb 1;61(4):1076-1081. doi: 10.1364/AO.446473.
Amid the increasing potential of ultrafast mid-infrared (mid-IR) laser sources based on transition metal doped chalcogenides such as Cr:ZnS, Cr:ZnSe, and Fe:ZnSe lasers, there is a need for direct and sensitive characterization of mid-IR mode-locked laser pulses that work in the nanojoule energy range. We developed a two-dimensional spectral shearing interferometry (2DSI) setup to successfully demonstrate the direct electric-field reconstruction of Cr:ZnS mode-locked laser pulses with a central wavelength of 2.3 µm, temporal duration of 30.3 fs, and energies of 3 nJ. The reconstructed electric field is in reasonable agreement with an independently measured intensity autocorrelation trace, and the quantitative reliability of the 2DSI measurement is verified from a material dispersion evaluation. The presented implementation of 2DSI, including a choice of nonlinear crystal as well as the use of high-throughput dispersive elements and a high signal-to-noise ratio near-IR spectrometer, would benefit future development of ultrafast mid-IR lasers and their applications.
在基于过渡金属掺杂硫族化物（如Cr:ZnS、Cr:ZnSe和Fe:ZnSe激光器）的超快中红外（mid-IR）激光源潜力不断增加的背景下，需要对工作在纳焦耳能量范围内的中红外锁模激光脉冲进行直接且灵敏的表征。我们开发了一种二维光谱剪切干涉测量（2DSI）装置，成功地展示了对中心波长为2.3 µm、时间持续时间为30.3 fs且能量为3 nJ的Cr:ZnS锁模激光脉冲的直接电场重建。重建的电场与独立测量的强度自相关迹线合理吻合，并且通过材料色散评估验证了2DSI测量的定量可靠性。所展示的2DSI实现方式，包括非线性晶体的选择以及高通量色散元件和高信噪比近红外光谱仪的使用，将有利于超快中红外激光器及其应用的未来发展。
