Single-shot pump-probe technique by the combination of an echelon and a grating with a time window of 109 ps

Abstract

In this study, using only a single pulse, pump-probe measurement with a large time window of more than 100 ps is implemented. A commercial grating is used to encode a time window of ~ 56 ps in a single pulse; therefore, there is no need for machining customization. In addition, in this technique, the grating surface is accurately imaged, eliminating the image blur problem caused by phase differences in previous echelon-based techniques. Moreover, to make full use of the grating surface and obtain a larger time window, a simple reflection echelon is combined that matches the grating in the time window. This combination encoding strategy results in a total time window of ~ 109 ps and maintains accurate imaging of the grating surface. This time window is an order of magnitude greater than the maximum reported values of the echelon encoding strategy and the angle beam encoding strategy. To demonstrate this single-shot pump-probe technique, the two-photon absorption process of ZnSe and the excited-state absorption process of a symmetrical phenoxazinium bromine salt were studied. The possibility of further improving the experimental setup is also discussed.

Dual-grating single-shot pump-probe technique

“…The pixels along the grating of the output laser pulse and can be attributed to pulse broadening due to the angular spectral dispersion of the grating, as well as time blurring by the angular crossing of the pump and probe beams. In addition, there are small upward spikes on either side of the TPA valley, which may be related to the two-beam coupling of the chirped pulse due to the nonlinear refractive coefficient of the material [19,20], which was also observed in previous TPA measurements at a wavelength of 515 nm [17]. In addition, after the ultrafast TPA process was completed, the transmittance of ZnSe did not fully recover to the initial value, as can be observed in Fig.…”

“…Maintaining accurate imaging of the grating surface also eliminates the phase difference problem that exists in the echelon encoding strategy. In addition, compared with our previously reported echelon and grating combination encoding strategy [17], there are several advantages: i) there is no need for echelon customization, and a large time window can be achieved by using only the combination of commercial gratings; ii) this technique always encodes the time-delay in the direction of the grating length. In this way, similar to the echelon encoding strategy and the angle beam encoding strategy, spectral decomposition can be carried out in the spatial dimension orthogonal to the grating length; therefore, single-shot transient absorption spectroscopy with a large time window can be achieved.…”

Dual-grating single-shot pump-probe technique

“…Maintaining accurate imaging of the grating surface also eliminates the phase difference problem in the echelon encoding strategy. In addition, compared with the echelon and grating combination encoding strategy [17], there are several advantages: i) there is no need for echelon customization, and a large time window can be achieved by using only the combination of commercial gratings; ii) this technique always encodes the time-delay in the direction of the grating length. In this way, similar to the echelon encoding strategy and the angle beam encoding strategy, spectral decomposition can be carried out in the spatial dimension perpendicular to the grating length; therefore, single-shot transient spectroscopy with a large time window can be achieved.…”

Dual grating single-shot pump-probe technique

“…Compared to the angular beam encoding strategy, this strategy does not require a large sample area. In our previous work [17], we reported a single-shot pump-probe technique that uses a combination encoding strategy of a commercial grating and a simple echelon to achieve a time window of 109 ps, which effectively eliminates the phase difference problem of the echelon encoding strategy. To the best of our knowledge, this is the first study to achieve a time window of more than 100 ps using a spatial encoding strategy.…”