Abstract

Ultrafast coherent spectroscopy techniques such as four-wave mixing rely on nonlinearities in the optical properties, that may produce time reversal or a χ⁽³⁾. Consequently, relatively high excitation powers are needed to produce a sufficient signal-to-noise ratio. Here we present a new ultra-sensitive technique based on the Doppler effect that allows for coherent spectroscopy without the need of a nonlinearity. We demonstrate our technique by measuring the quantum beat between the light- and heavy-hole excitons in a quantum well at extremely low excitation powers.

© 1996 IEEE