Generation of Coherent Phonons in a CdTe Single Crystal Using an Ultrafast Two-Phonon Laser-Excitation Process

Abstract

The detection-energy dependence of a coherent phonon in a (001) CdTe crystal, generated by ultrashort laser pulses with the center energy transparent or opaque to the sample, is investigated using a spectrally resolved pump-probe method. At the excitation in the transparent region, the detection-energy dependence of the phonon amplitude has two peaks at the energy shifted by one times the phonon energy of CdTe from the center energy of the probe pulses. On the other hand, the amplitude in the opaque region shows two peaks at the energy shifted by about two times the phonon energy. This difference occurs even though the observed energies of the coherent phonons in both regions are the same as that of the longitudinal optical phonon of CdTe. The energy shifts in the detection-energy dependence imply that the emission and absorption of one phonon and two phonons in the transparent and opaque regions, respectively, are implicated in coherent phonon generation. In this study, the detection-energy dependence is examined from the viewpoint of the third-order nonlinear susceptibility based on the impulsive stimulated Raman scattering process under nonresonant and resonant conditions.

Coherent Excitation of Optical Phonons in GaAs by Broadband Terahertz Pulses

“…Excitation and control of coherent optical phonons has been studied extensively last few decades as a tool to investigate dynamical properties of materials1617181920. Coherent phonons have been excited with optical laser pulses via various mechanisms including impulsive stimulated Raman scattering (ISRS)162122, displacive excitation of coherent phonons (DECP)2324 and screening of the surface field182526. Due to the large energy difference between the phonons and the photons in optical frequency range, the electric field of the excitation pulse interacts with electrons, and indirectly couples to nuclei in optical excitation processes.…”

Ultrafast quenching of electron–boson interaction and superconducting gap in a cuprate superconductor

“…The dynamics of electrons and atoms interacting with intense, and ultrashort optical pulses is one of the emerging fields in physics. Strong optical pulses have been used as powerful tools to measure the electron-phonon interaction in solids [1,2], to investigate fundamental dynamical processes in semiconductors [3,4], and to modulate the lattice structure of solids by creating dynamical states with new properties [5][6][7][8]. These methods are particularly exciting in the context of correlated materials, where intense optical fields can drive a transition from an insulating to a metastable metallic phase [9], can induce transient signatures of superconductivity [10], can lead to anisotropic modulation of the electron-phonon coupling [11], and can disentangle the different dynamics in governing the superconducting and pseudogap phase of cuprates [12][13][14][15].…”

Influence of pulse width and detuning on coherent phonon generation

“…Coherent phonons are widely used to study phonon dynamics for a wide variety of materials such as semimetals, [1][2][3][4][5] semiconductors, [6][7][8][9][10][11][12][13] superconductors, [14][15][16][17] and topological insulators, [18][19][20][21] with pump-probe type time-resolved reflectivity measurements. An ultrashort pump pulse coherently excites optical phonons which oscillate in phase and modulate the electric susceptibility.…”