Abstract
The coherence spike of femtosecond laser pulses in the reflection-type pump-probe measurements has been systematically studied in the semiconductor (100) InP. By varying the setup of the pump-probe measuring system, i.e. the polarizations of pump and probe pulses, the incident angles of pump and probe beams, and the interval of delay time between pump and probe pulses, the dramatic changes in the strength of coherence spike could be clear observed. Furthermore, the proposed methods to remove the coherence spike from the transient reflectivity curves have been demonstrated in the time-domain measurements.
Highlights
The pump-probe technique has been applied to the time-resolved measurements over past decades
Eichler et al further explained it by diffraction from a transient grating induced by interference of the pump and probe beams [3]. They provided very important basic principles for the generation of the coherence artifact. This coherence artifact could be found in most time-resolved spectroscopy[4]-[7] and disturbs the analysis of relaxation dynamics to determine the amplitude of signal near zero delay and relaxation time from the trace of ΔR/R or ΔT /T
Wang et al [4] revealed that the controversy in lifetime of p-like excited state of the hydrated electron is due to the existence of a coherence spike at zero delay time in pump-probe spectroscopic kinetics traces
Summary
The pump-probe technique has been applied to the time-resolved measurements over past decades. In order to understand the reaction mechanisms or the electronic structure of the excited states in media, measuring the characteristics of lifetime is widely adopted by scientists This pump-probe technique is of increasing interest in solid state physics, where it is used for studying metals, semiconductors, superconductors, and other materials. Wang et al [4] revealed that the controversy in lifetime of p-like excited state of the hydrated electron is due to the existence of a coherence spike at zero delay time in pump-probe spectroscopic kinetics traces. After removing this spike effect, they could obtain the intrinsic lifetimes of the two incompletely relaxed states in bulk water are 180 ± 30 and 545 ± 30 fs. We report the systematical studies for the origin of the coherence spike in reflection-type pump-probe measurements and further demonstrate the effective methods for removing it
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