Full diagnostics and optimization of time resolution for time- and angle-resolved photoemission spectroscopy

Abstract

Achieving a high time resolution is highly desirable for revealing the electron dynamics and light-induced phenomena in time- and angle-resolved photoemission spectroscopy (TrARPES). Here, we identify key factors for achieving the optimum time resolution, including laser bandwidth and optical component induced chirp. A full diagnostic scheme is constructed to characterize the pulse duration and chirp of the fundamental beam, second harmonic, and fourth harmonic, and prism pairs are used to compensate for the chirp. Moreover, by using a Sb2Te3 film as a test sample, we can achieve a high test efficiency for the time resolution during the optimization process. An optimized time resolution of 81 fs is achieved in our TrARPES system with a high repetition rate tunable from 76 to 4.75/n MHz.

Ultrafast time- and angle-resolved photoemission spectroscopy with widely tunable probe photon energy of 5.3-7.0 eV for investigating dynamics of three-dimensional materials

“…1). We would like to point out that in our previous setup [11] where the FHG is achieved by passing the SH through the BBO crystal directly without generating significant chirp, compression of SH is not so critical, while in the current setup, the SH passes through a large-size prism made of fused silica with a length of 15 mm before the KBBF crystal, and the chirp is significant. For example, a 50 fs SH pulse at 400 nm is elongated to 95 fs after passing through the prism.…”

“…The time resolution is obtained by analyzing the temporal evolution of photoexcited electrons at high energy measured on Sb 2 Te 3 , which is dominated by the direct photoexcitation [11]. Figure 5(a) shows the images measured as a function of energy and delay time.…”

“…5(b) shows a fast rising edge. Fitting the data by a Gaussian function convolved with the product of the step function and single-exponential function allows to extract the time resolution [11]:…”

“…Timeand angle-resolved photoemission spectroscopy (TrARPES) [3,4] has been a powerful technique for capturing the ultrafast carrier dynamics and photo-induced phase transitions with energy-, momentum-and time-resolution. In the past decades, major progress has been made in TrARPES instrumentation, including extending the pump wavelength to midinfrared [5] or terahertz [6], improving the energy resolution or time resolution [7][8][9][10][11] etc. Developments in the probe source using high harmonic generation (HHG) [12][13][14], or free electron laser [15] with a higher probe photon energy have also been achieved.…”

Light-Tunable Surface State and Hybridization Gap in Magnetic Topological Insulator MnBi$_8$Te$_{13}$

“…The photo-excited electronic states can be better revealed in the differential images in Fig. 3 38 where ∆t is the width of the rising edge and τ is the relaxation time. The relaxation time of the photo-excited electrons in the BCB increases from 1.25 to 1.88 ps when moving towards the Fermi energy and increases from 0.98 to 1.31 ps for photo-excited holes, which is similar to the relaxation time ranging from 1.16 to 1.69 ps for for photo-excited electrons and 1.23 to 1.31 ps for photo-excited holes of the SS.…”