Ultimate fast optical switching of a planar microcavity in the telecom wavelength range

Applied Physics Letters (Impact Factor: 3.52). 02/2011; 98. DOI: 10.1063/1.3580615
Source: arXiv

ABSTRACT We have studied a GaAs-AlAs planar microcavity with a resonance near 1300 nm
in the telecom range by ultrafast pump-probe reflectivity. By the judicious
choice of pump frequency, we observe a ultimate fast and reversible decrease of
the resonance frequency by more than half a linewidth due to the instantaneous
electronic Kerr eff?ect. The switch-on and switch-off? of the cavity is only
limited by the cavity storage time of ?tcav = 0.3ps and not by intrinsic
material parameters. Our results pave the way to supra-THz switching rates for
on-chip data modulation and real-time cavity quantum electrodynamics.

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    ABSTRACT: We present ultrafast reflectivity measurements on the dynamics of optically excited free carriers in semiconductor microcavities. We observe that the relaxation dynamics of the switched cavity is strongly frequency dependent, which points towards multiple carrier populations. The interest in ultrafast all-optical switching of nano-photonic structures has rapidly increased due to the inherent speed of the process. This not only promises new developments in information technology [1-3] but also a better understanding in fundamental electrodynamics as well as in ultrafast cavity QED [4]. The fastest mechanisms for switching are, as recently shown, the electronic Kerr effect [5] and, as more commonly used, the excitation of free carriers [2,3,5-9]. Despite all studies on switching with free carriers, there is still a debate on the dynamics and the recombination processes in these nano-photonic structures. Here, we explore the dynamics of a semiconductor microcavity, which is switched by optically excited free carriers. Our experiments are performed on the well-known GaAs-AlAs planar semiconductor microcavity system over a wide frequency range. To track the dynamics of the relaxation of the switched cavity, we keep the pump frequency constant at ωpu=5000 cm-1 (λpu=2000 nm) to ensure two-photon absorption in the GaAs layers, while the probe frequency was scanned. Using this scheme, we are able to resolve the time dependent spectral response of the cavity (Fig. 1(b)). We observe that the relaxation process of the cavity, driven by the recombination of free carriers, shows a strong spectral dependence. The latter cannot be explained assuming a single population model for the free carriers in the GaAs of the Bragg-stack and the λ-layer.
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    ABSTRACT: This paper deals with Metropolis Monte Carlo analysis of the all-optical switching. The laser-induced magnetization dynamics with various laser pulse fluencies and durations are followed by analysis of probable transitions occurred in the sample. The calibration of Monte Carlo steps with physical time was performed by comparison with a reference dynamics described by Landau-Lifshitz-Bloch equation. For an accurate description it was necessary to consider a four-temperature model by analyzing the dynamics of electrons, spins, lattice and environment temperature. All-optical switching conditions were synthesized in a phase diagram that outlines switching and non-switching regions as well as an unpredictable switching region.
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    ABSTRACT: We theoretically study the interaction between dual cavity modes in a planar photonic microcavity structure in the optical communication wavelength range. The merging and splitting of cavity mode is analyzed with realistic microcavity structures. The merging of dual cavity resonance into a single cavity resonance is achieved by changing the number of layers between the two cavities. The splitting of single cavity resonance into dual cavity resonance is obtained with an increase in the reflectivity of mirrors in the front and rear side of the microcavity structure. The threshold condition for the merging and splitting of cavity mode is established in terms of structural parameters. The physical origin of the merging of dual cavity modes into a single cavity resonance is discussed in terms of the electric field intensity distribution in the microcavity structure. The microcavity structure with dual cavity modes is useful for the generation of entangled photon pairs, for achieving the strong-coupling regime between exciton and photon, and for high resolution multi-wavelength filters in optical communication.

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