Ultrafast cavity switching : a novel ressource for solid-state CQED

It has been known since the 80’s that the optical modes and optical response of semiconductor microcavities can be changed in a transient and reversible way through a modification of the refractive index of the semiconductor... [ view full abstract ]

It has been known since the 80’s that the optical modes and optical response of semiconductor microcavities can be changed in a transient and reversible way through a modification of the refractive index of the semiconductor matrix. Initially developed in view of all-optical data processing and computing, “cavity switching” induced by the electrical injection of free carriers is nowadays widely used for the reconfiguration of photonic circuits.
In the context of CQED, cavity switching appears as a very powerful tool enabling to tailor the spontaneous emission properties of embedded emitters, through a dynamic control of the emitter-cavity mode detuning [1].
As a first example, we present recent switching experiments performed on micropillars containing collections of QDs. We observe large switching amplitudes (by as much as 20 linewidth), as well as differential switching of the pillar modes [2], using ultrafast optical carrier injection. By filtering the micropillar emission within a narrow spectral window, we observe ultrashort spontaneous emission pulses (down to 4ps!), which are generated by the QDs during their transient coupling with the cavity mode. Cavity switching acts here as a way to switch on and off the QD spontaneous emission into the cavity channel. In clear contrast to Fourier-transform laser pulses of similar duration, such pulses display a much shorter coherence time, as highlighted e.g. by transmission experiments through scattering media.
Recent theoretical advances also highlight the huge interest of cavity switching for CQED. For instance, single photons with a tailored time-envelope can be generated by a single quantum dot (QD) in a state-of-the-art microcavity, with a high efficiency and fidelity, by adjusting in real-time the magnitude of the Purcell effect [1,3]. This is noticeably the case for Gaussian time-envelopes and time reversed-exponential envelopes, both important resources for photonic quantum information processing.

[1] H. Thyrrestrup et al, Opt. Exp. 21, 23130 (2013).
[2] H. Thyrrestrup et al, Appl. Phys. Lett. 105, 111115 (2014).
[3] G. Hornecker et al, SPIE Optics and Optoelectronics 2015, Prag, doi:10.1117/12.2178991; E Peinke et al, under review