Abstract
Intense femtosecond pulses generated from Chirped Pulse Amplification (CPA) and Optical Parametric Amplification (OPA)-based laser systems enable us to monitor electron motion across various energy regimes with greater time resolution. By studying the multi-photon processes occurring during ultrafast-laser-matter interactions, we can decipher the electronic and optical properties of matter.
To achieve this, we conducted experiments in two main directions: the generation of shorter laser pulses and the high-harmonic spectroscopy of solid-state media.
In the first direction, we applied the multiplate spectral broadening technique to the second harmonic generation (SHG) of a 1030 nm pulse (centered at 515 nm) and a few-cycle 800 nm pulse. High harmonic generation (HHG) measurements from the compressed 515 nm pulse demonstrate the effectiveness and potential of this convenient technique.
In the second direction, we began with HHG experiments on bulk-state materials. From scratch, we constructed a comprehensive solid-HHG setup that works well with different bulk-state targets and supports measurements along multiple dimensions, including common static and dynamic measurements. Notably, dynamic measurements from crystalline SiO2 (quartz) demonstrate that information on electron-phonon coupling and phonon-phonon scattering can be fully extracted and reconstructed via time-resolved high harmonic spectroscopy.
Next, we extended our research to 2D-state materials. A new setup has been built and upgraded several times. Equipped with high-precision imaging and high-efficiency signal generation and collection units, this 2D-target-specialized setup is highly adaptable to different 2D-state samples. Additionally, to achieve the cleanest measurements, we tested various ideas, including using free-standing 2D samples and performing experiments under different geometries. Both static and time-resolved measurements on different types of 2D-state samples have been performed and more experiments are undertaken.
Anyone interested is welcome to attend.