- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Coherently controlled generation of single-cycle terahertz pulses from a thin layer of nonlinear medium with low-frequency resonances
摘要： We propose a scheme to generate single-cycle terahertz (THz) pulses via reflection of an optical femtosecond pulse train from a thin layer of nonlinear resonant medium. Our method is based on the coherent control of low-frequency oscillations and free induction decay in the medium. The specific single-cycle shape of generated THz pulses requires a plane wave front and detection in the near field. Our theoretical results pave the way to a new, simple, and highly efficient way to generate single-cycle waveshape-tunable THz pulses.
关键词： nonlinear resonant medium,coherent control,single-cycle waveshape-tunable,free induction decay,terahertz pulses
更新于2025-09-23 15:19:57
-
How pump–probe differential reflectivity at negative delay yields the perturbed-free-induction-decay: theory of the experiment and its verification
摘要： We present a simple but mathematically complete first-principles theory for the pump–probe differential reflectivity experiment at negative delay (probe preceding the pump) to show how it gives information about the perturbed-free-induction-decay of coherent polarization. The calculation, involving the optical Bloch equations to describe the induced polarization and the Ewald–Oseen idea to calculate the reflected signal as a consequence of the free oscillations of perturbed dipoles, also explicitly includes the process of lock-in detection of a double-chopped signal after it has passed through a monochromator. The theory giving a closed form expression for the measured signal in both time and spectal domains is compared with experiments on high quality GaAs quantum well sample. The dephasing time inferred experimentally at 4 K compares remarkably well with the inverse of the absorption linewidth of the continuous-wave photoluminescence excitation spectrum. Spectrally-resolved signal at negative delay calculated from our theoretical expression nicely reproduces the coherent spectral oscillations observed in our experiments, although exact fitting of the experimental spectra with the theoretical expression is difficult on account of multiple resonances.
关键词： pump–probe theory and experiment,perturbed-free-induction-decay,optical Bloch equations,Ewald–Oseen extinction theorem,excitonic polarization dephasing
更新于2025-09-09 09:28:46