Toward direct optical excitation of excitonic many-body effects using intense thermal states

Abstract

Quantum spectroscopy in solids directly detects nonlinear changes created exclusively by quantum fluctuations of light. So far, it has been realized only by projecting a large set of measurements with a coherent-state laser to a specific quantum-light response. We present two complementary experimental approaches to realize intense and ultrafast thermal-state sources. We investigate the effects of continuous excitation from a superluminescent diode (SLD) as well as an ensemble-averaging technique using phase-modulated pulses. By measuring excitonic nonlinearities in gallium arsenide, we demonstrate that the experimentally realized thermal-state source produces significantly reduced many-body nonlinearities compared to a coherent-state excitation. We also review experimental approaches toward future realization of quantum spectroscopy with thermal states.