A. G. Stepanov

Effect of intense chirped pulses on the coherent phonon generation in Te

The authors have studied the influence of chirped laser pulses on the coherent phonon generation in single crystal Te. They have shown that the pulse chirp affects the amplitude of coherent phonons with A1 symmetry in the case of intense excitation only. By varying the chirp of an intense exciting pulse, the authors demonstrated that negatively chirped pulses are almost twice more effective in the creation of lattice coherence than positively chirped pulses.

Spectral modifications of femtosecond laser pulses induced by phase-matched optical rectification in lithium niobate

We report experimental observations of the spectral modifications of ultrashort laser pulses caused by the generation of terahertz (THz) radiation via phase-matched optical rectification in LiNbO3. The measured red-shift and narrowing of the laser pulse spectra are in good agreement with the description of the THz generation in terms of difference frequency mixing. Moreover, we propose and demonstrate a new method for evaluating the absolute energy of the THz pulse generated via high-efficiency optical rectification. The method is based on analyzing the observed laser pulse spectral modifications. Abilities to obtain >100% optical-to-THz quantum conversion efficiency are discussed.

Spectral modifications of femtosecond laser pulses induced by high-efficiency optical rectification

We report experimental observations of the spectral modifications of ultrashort laser pulses caused by the generation of terahertz (THz) radiation via phase-matched optical rectification in LiNbO3. The measured red shift and narrowing of the laser pulse spectra is in a good agreement with the consideration of the THz generation processes in terms of difference frequency mixing. Moreover, we propose and demonstrate a new method for evaluating the absolute energy of the THz pulse generated via high-efficiency optical rectification. The method is based on analyzing the laser pulse spectral modifications. Abilities to obtain >100% optical-to-THz quantum conversion efficiency are discussed.

Effect of phase modulation of a laser pulse on the generation of a coherent totally symmetric phonon in a tellurium single crystal

The effect of phase modulation (resulting in a chirp of an ultrashort laser pulse) on the generation of a coherent A1 phonon in Te was studied. The amplitude of coherent oscillations was found to depend on the sign and value of the pulse chirp: the oscillation amplitude decreases as the chirp increases. For a positive chirp, this effect is twofold stronger than for a negative one. The frequency-resolved response of a bandwidth-limited pulse was studied, which revealed the difference of oscillations and the relaxation response for the Stokes and anti-Stokes frequencies. The detected phenomena can be used for coherent control of lattice dynamics.