Cooperative recombination of electron-hole pairs in semiconductor quantum wells under quantizing magnetic fields

Abstract

We present results of detailed investigations of light emission from semiconductor multiple quantum wells at low temperatures and high magnetic fields excited by intense femtosecond laser pulses. The intensity and linewidth as well as the directional and statistical properties of photoemission strongly depended on the magnetic field strength and pump laser fluence. We also investigated the effects of spot size, temperature, excitation geometry, and excitation pulse width on the emission properties. The results suggest that the initially incoherent photoexcited electron-hole pairs spontaneously form a macroscopic coherent state upon relaxation into the low-lying magnetoexcitonic states, followed by the emission of a superfluorescent burst of radiation. We have developed a theoretical model for superfluorescent emission from semiconductor quantum wells, which successfully explained the observed characteristics.

Superradiant Lasing and Collective Dynamics of Active Centers with Polarization Lifetime Exceeding Photon Lifetime

“…(Here the term "superfluorescence" is used instead of the more common term "SR" because in many experimental and theoretical works the latter implies that there is some preliminary coherent resonant pulse initiating a collective spontaneous emission.) Similar observations are made for the superfluorescent recombination in semiconductor samples with modest inhomogeneous broadening of active particles, which include free electrons and holes in magnetized GaAs quantum wells [21,22], degenerate electronhole gas in semiconductors [29], excitons in ZnTe crystals [10,34], and In-centers in Cd 0.8 Zn 0.2 T e crystals [13]. Based on CW pumping, the class D lasers are expected [31] to have variety of operation regimes, rich multi-mode spectra, and flexible pulse profiles, which are promising for the pulse shaping technologies and the pulse processing in "information optics" [18,39,45].…”

Renormalized energies of superfluorescent bursts from an electron-hole magnetoplasma with high gain in InxGa1−xAs quantum wells

“…Using intense femtosecond laser pulses, we excited e-h pairs at ultrahigh densities and observed bright and sharp emission lines. 13,14 At the highest field and excitation ranges, strong Landau quantization and Fermi degeneracy increased the density of states and suppressed decoherence, leading to the emergence of intense and coherent pulses of light, or SF bursts, as we recently reported. 15 In the present study, we examined the influence of many-body interactions on the light emission processes of e-h pairs in the presence of gain, through a detailed magnetic field (B) dependent study of the energies of the SF lines.…”

“…A right angle microprism (1 mm 2 area) redirected the in-plane emission from the edge of the sample to the fiber. [13][14][15] A quartztungsten-halogen lamp was used for white-light transmission measurements. For low and high excitation PL studies, a 25-mW He-Ne laser and an amplified Ti:sapphire laser were used, respectively.…”

Superfluorescence from photoexcited semiconductor quantum wells: Magnetic field, temperature, and excitation power dependence

“…At higher temperatures, many mechanisms can destroy the coherent state, among which the electron-phonon scattering is dominant. Therefore, the SF observability condition that the cooperative frequency should be larger than the dephasing rate 29 is not easily satisfied at high temperatures. In addition, high temperature would broaden the quasi-Fermi edge of the Fermi-Dirac distribution, destroying the quantum degeneracy condition, necessary for gain enhancement at the Fermi-edge in an e-h system.…”