Coherent Phonon Dynamics in Semiconductors
Author | : Feng He (Ph. D.) |
Publisher | : |
Total Pages | : 254 |
Release | : 2018 |
ISBN-10 | : OCLC:1242439330 |
ISBN-13 | : |
Rating | : 4/5 (30 Downloads) |
Download or read book Coherent Phonon Dynamics in Semiconductors written by Feng He (Ph. D.) and published by . This book was released on 2018 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ultrafast pump-probe spectroscopy is a powerful experimental technique to study the light-matter interaction and ultrafast dynamics in solids. In many semiconductors, under ultrafast laser irradiation, phonons (quantized lattice vibrations) with both temporal and spatial coherence can be generated conveniently. When a stronger laser pulse excites coherent phonons that induce refractive index change, and thus the reflectivity change of the materials, the time-dependent phonon dynamics can be detected by a delayed probe pulse. The generation and detection of coherent phonons provide an opportunity to understand the fundamental physics between light and matter interaction, as well as a path to manipulate other physical processes, for applications such as sound amplification stimulated emission (SASER), phonon mode manipulation, ultrafast phase switching, superconductivity enhancement and manipulation of magnetism1−5. This thesis presents a series of time-resolved studies of coherent phonons in three semiconductor systems, including bulk CdSe, Bi2Te3/Sb2Te3 superlattice and GaAs/AlAs superlattice. In bulk CdSe, a material extensively studied for quantum dot photoelectronics, coherent phonons serve as the probe for the reversible ultrafast melting. In Bi2Te3/Sb2Te3 superlattice, a material system used for thermoelectrics, the coherent thermal phonons are excited directly and are found to be selectively filtered in the superlattice structure compared with bulk materials. In GaAs/AlAs superlattice, a quantum well structure for photodetectors and lasers, a strong quantum coherent coupling among different phonon modes is observed. A similar coherent coupling between photons and phonons has been used to induce and enhance superconductivity [superscript 6,7] and mimic the magnetic field8. However, direct observation of nonlinear phonon coupling is rare. Moreover, a novel technique based on surface plasmon resonance has been implemented into the pump-probe spectrometer to improve detection efficiency