Visible-far-infrared pump-probe spectroscopy on carriers and excitons in GaAs/AlGaAs multiple quantum wells

Abstract

Far-infrared spectroscopy is a powerful tool in the study of low-energy excitations in solids, such as magnons, phonons, and electronic transitions in semiconductor quantum structures. With the recent development of picosecond pulsed FIR sources, such as those based on laser-driven photoconductive antennas, a new class of nonequilibrium phenomena can be studied in the FIR. We focus on picosecond experiments in which a nearvisible laser 'pump' pulse creates an excitation that is monitored by time-delayed FIR 'probe' pulses. We present a new experimental scheme using an unamplified 790-890 nm tunable Ti:sapphire laser and advanced photoconductive antenna technology. An ultrafast photoconductive transmitter and receiver antenna form the THz beam system, which is used to generate and detect the FIR probe pulse. The pump pulses are derived from the laser.