Investigations of a coherently driven semiconductor optical cavity QED system

Abstract

Chip-based cavity quantum electrodynamics (QED) devices consisting of a self-assembled InAs quantum dot (QD) coupled to a high quality factor GaAs microdisk cavity are coherently probed through their optical channel using a fiber taper waveguide. We highlight one particularly important aspect of this all-fiber measurement setup, which is the accuracy to which the optical coupling level and optical losses are known relative to typical free-space excitation techniques. This allows for precise knowledge of the intracavity photon number and measurement of absolute transmitted and reflected signals. Resonant optical spectroscopy of the system under both weak and strong driving conditions are presented, which when compared with a quantum master equation model of the system allows for determination of the coherent coupling rate between QD exciton and optical cavity mode, the different levels of elastic and inelastic dephasing of the exciton state, and the position and orientation of the QD within the cavity. Pump-probe measurements are also performed in which a far offresonant red-detuned control laser beam is introduced into the cavity. Rather than producing a measurable ac-Stark shift in the exciton line of the QD, we find that this control beam induces a saturation of the resonant system response. The broad photoluminescence spectrum resulting from the presence of the control beam in the cavity points to sub-bandgap absorption in the semiconductor, and the resulting free-carrier generation, as the likely source of system saturation.

Cavity-Enhanced Real-Time Monitoring of Single-Charge Jumps at the Microsecond Time Scale

“…It could also be assisted by the presence of discrete states in neighboring material defects or quantum dots. We point out that sub-band-gap absorption, leading to charge fluctuations stemming from photoexcited free carriers, has already been reported in a cavity-QED device [29].…”

Superradiant decay and dipole-dipole interaction of distant atoms in a two-way cascaded cavity QED system

“…These include monolithic microtoroids and microdisks, whose whispering-gallery modes may couple to free atoms via their evanescent fields [3][4][5][6][7][8][9], or quantum dots embedded in the resonators themselves [10][11][12][13]. Highly efficient input and output is achieved by overlapping the evanescent fields of tapered optical fibers with the resonator modes.…”

Microtoroidal cavity QED with fiber overcoupling and strong atom-field coupling: A single-atom quantum switch for coherent light fields

“…Additionally, the ultra-small volumes of the WGM's supported by these monolithic structures lead to very large single photon electric fields and, consequently, very large atom-field coupling strengths, g, which may exceed dissipative rates in the system. In fact, this regime of strong coupling cavity QED has now been demonstrated experimentally for both a single alkali atom in the evanescent field of a microtoroidal [23] or microbottle [27] resonator and for a single quantum dot embedded in a microdisk resonator [42,43].…”