Coherent Excitation of Optical Phonons in GaAs by Broadband Terahertz Pulses

Abstract

Coherent excitation and control of lattice motion by electromagnetic radiation in optical frequency range has been reported through variety of indirect interaction mechanisms with phonon modes. However, coherent phonon excitation by direct interaction of electromagnetic radiation and nuclei has not been demonstrated experimentally in terahertz (THz) frequency range mainly due to the lack of THz emitters with broad bandwidth suitable for the purpose. We report the experimental observation of coherent phonon excitation and detection in GaAs using ultrafast THz-pump/optical-probe scheme. From the results of THz pump field dependence, pump/probe polarization dependence, and crystal orientation dependence, we attributed THz wave absorption and linear electro-optic effect to the excitation and detection mechanisms of coherent polar TO phonons. Furthermore, the carrier density dependence of the interaction of coherent phonons and free carriers is reported.

Dynamics of Time Evolution of Quantum Oscillator Excitation by Electromagnetic Pulses

“…Parameter  is determined by equality (2). It should be noted that in contrast to (1), expression (11) presents the result in explicit form as a function of parameter  and numbers of stationary states (m, n).…”

“…A quantum harmonic oscillator is a unique physical model that can be analytically described when interacting with a perturbation of an arbitrary value outside the framework of perturbation theory [1,2]. On the other hand, the development of the methods of generation of ultra-short laser pulses (USP) [3,4] makes it relevant to consider the interaction of such pulses with various targets [5][6][7][8][9][10] including oscillatory systems [11,12]. So, in a previous work of the authors [12], the excitation of a quantum oscillator for the entire duration of the USP was considered, depending on the pulse duration and the frequency detuning of its carrier frequency from the own frequency of the oscillator and arbitrary value of electric field amplitude in the pulse.…”

Broadband electrically tunable VO2‑Metamaterial terahertz switch with suppressed reflection

“…The terahertz (THz) region of the electromagnetic (EM) spectrum has attracted enormous interest to investigate fundamental physical phenomena at meV energy scales . Additionally, interest has expanded to the applied realm as advances in THz technologies enable applications in wireless communications, security, imaging, and biosensing, among others.…”

“…The terahertz (THz) region of the electromagnetic (EM) spectrum has attracted enormous interest to investigate fundamental physical phenomena at meV energy scales. [1][2][3][4][5][6] Additionally, interest has expanded to the applied realm as advances in THz technologies enable applications in wireless communications, 7,8 security, 9 imaging, 10 and biosensing, 11 among others. With the proliferation of THz technologies, there is a continuing demand for better means of modulating and otherwise manipulating THz light.…”

Excitation of coherent optical phonons in iron garnet by femtosecond laser pulses

“…Excitation and detection of coherent phonons have attracted significant scientific interest over the past few decades, as they can be employed to investigate the dynamic properties of various materials, from metals to dielectrics. [1][2][3][4][5][6][7][8][9][10][11] Impulsive stimulated Raman scattering (ISRS) provides a unique approach to study the dynamics of coherent phonons through inelastic scattering of a single femtosecond laser pulse. 12 ISRS can be used for the selective excitation of coherent phonons by choosing the proper polarization of the pump pulses.…”