Superfluorescence in magnetized quantum wells (collaboration with J. Kono group)

Quantum optical phenomena have played a major role in our understanding of the interaction of light with atomic systems. In particular, superfluorescence (SF) is one of most exotic cooperative phenomena known in quantum optics. In SF, an incoherently prepared system of N inverted atoms develops macroscopic coherence self-consistently through a subtle quantum process starting from vacuum fluctuations. The resultant macroscopic dipole decays superradiantly producing a burst of coherent radiation. Superfluorescence has been observed in atomic gases and rarefied impurities in crystals. Cooperative spontaneous recombination (superfluorescence) of electron-hole plasmas in semiconductors has been a challenge to observe due to ultrafast decoherence. We show that superfluorescence can be achieved in quantum-confined semiconductor systems and present experimental evidence for superfluorescence from high-density photoexcited electron-hole plasmas in quantum wells under high magnetic fields (>20 T). At a critical magnetic field strength and excitation fluence, we observe a clear transition in the band-edge photoluminescence from omnidirectional output to a randomly directed but highly collimated beam. Changes in the linewidth, carrier density, and magnetic field scaling of the emission spectra correlate precisely with the onset of random directionality and are consistent with cooperative recombination [1,2].

In our most recent studies, pump-probe spectroscopy and streak-camera data reveal ultrafast disappearance of carriers from Landau levels accompanied by an outburst of radiation, in striking agreement with the expected development of superfluorescence process (Nature, to be submitted).

[1] Y. D. Jho, X. Wang, X. Wei, J. Kono, D. H. Reitze, A. A. Belyanin, V. V. Kocharovsky, Vl. V. Kocharovsky and G. S. Solomon, Cooperative Recombination of a Quantized Electron-Hole Plasma, Phys. Rev. Lett., 96, 237401 (2006); selected for the July 2006 issue of Virtual Journal of Ultrafast Science; http://arxiv.org/abs/cond-mat/0601483

[2] Y. D. Jho, X. Wang, X. Wei, J. Kono, D. H. Reitze, A. A. Belyanin, V. V. Kocharovsky, Vl. V. Kocharovsky and G. S. Solomon, Superfluorescence from Dense Electron-Hole Plasmas under High Magnetic Fields: Spectral Behavior and Dependence on Strain and Pulse Duration, J. Modern Optics, v. 53, no. 16/17, 2325 (2006); http://arxiv.org/abs/cond-mat/0607022