In situ Tuning of Optical Modes in Single Semiconductor Microcavities by Laser Heating

We employ a focused laser beam both as an optical probe and as a tool to tune in situ the spectral position of modes of semiconductor optical microcavities containing quantum dots (QDs) as emitters. Laser-heating of a microcavity placed inside a cryostat is used either to locally enhance the refractive index or to controllably desorbs cryogettered gases. The latter approach allows us to controllably blue-shift the modes of GaAs microdisks. Transverse-electric (TE) and transverse-magnetic (TM) modes are observed to shift at different rates. An analytic calculation suggests that this behavior is due to an effective reduction of the disk thickness upon heating. The method can be used to bring into resonance optical modes with the emission lines of embedded QDs and may be applied to tune the coupling in photonic molecules consisting of closely spaced optical resonators.