Ultrafast nonlinear optical response of Fano resonances in gallium arsenide under high magnetic field
- Univ. of California, Berkeley, CA (United States). Dept. of Physics
Fano interference results from the coupling between a discrete energy level and a continuum of states whose energies overlap. In the linear absorption spectrum, a Fano resonance manifests itself in an asymmetric lineshape with a minimum at the energy where the contributions of the discrete state and the continuum interfere destructively. Using femtosecond spectroscopy, the authors study for the first time, the dynamics of the coherent emission from Fano resonances and compare it to that from an isolated Lorentzian line. They find that despite the very narrow frequency lineshape, the coupling to the continuum induces an almost instantaneous nonlinear optical response. Experiments are carried out in bulk GaAs, where an applied magnetic field leads to the formation of discrete magneto-exciton states. The higher-order magneto-excitons energetically overlap with the 1-dimensional continua of states with k parallel to the field and Fano resonances are formed. The zero field absorption spectrum of the sample shows that the heavy hole (hh) and light hole (lh) exciton resonances are split due to uniaxial strain. The typical Fano lineshape is clearly observed both for hh and lh magneto-excitons at B = 10T. The temporal behavior of the polarization stimulated from Fano and Lorentzian resonances is studied by transient four-wave-mixing (FWM) experiments with co-circularly polarized 100-fs pulses.
- Research Organization:
- Lawrence Berkeley Lab., CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 10179382
- Report Number(s):
- LBL--35201; CONF-9405219--6; ON: DE94018181
- Country of Publication:
- United States
- Language:
- English
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