Advanced Methods of Semiconductor Research Seminar – Tuesday 2nd of June 2026
We cordially invite you to Advanced Methods of Semiconductor Research Seminar on Tuesday 2nd of June 2026 at 13:15 in room 321, building A-1, where there will be delivered a lecture:
Photon condensation in semiconductor microcavities under optical excitation
by Aasooda Malik
from Department of Experimental Physics, Wroclaw Tech
The lecture abstract is attached below.
Photon Bose-Einstein condensation (BEC) in the absence of external trapping mechanism provides a unique environment for investigating macroscopic quantum phenomena under nonequilibrium settings. In this trapless regime, condensation takes place without spatial limitations, allowing for better insight into thermalization processes and interaction effects that influence the formation of a photon condensate. We performed a number of experiments by varying pump spots and detunings and our study seeks to understand how varying excitation wavelengths influence the formation and characteristics of photon BECs.
In this study, we explore the phase diagram of photon Bose–Einstein condensation within a planar semiconductor microcavity subjected to quasi-homogeneous excitation. Experiments were performed on a GaAs-based λ-microcavity with InGaAs quantum wells as the active medium and AlAs/AlGaAs distributed Bragg reflectors (DBRs), emitting around 920 nm. The sample, produced through molecular beam epitaxy, was cooled to cryogenic temperatures (~77 K) to perform photon BEC and (~4K) for exciton polariton experiments respectively.
I will present experimental investigation on the condensation of exciton polaritons in a microcavity structure in which the cavity resonance remains almost constant at different places allowing systematic tuning of the exciton-photon detuning across the sample. We verified strong coupling in the sample by probing different positions on the sample. We observed condensation across a range of detunings, demonstrating tunability of the system.
In the second part of the presentation, I will describe investigations of the effect of excessive excitation energy on the thermalization and condensation of the photon gas. Here, the experiments were conducted at three excitation wavelengths – 796 nm, 818 nm, and 842 nm – associated with the first, second, and third Bragg reflectivity minima of the cavity. By methodically altering the pump power and excitation wavelength, we investigate the energy shifts of the photons to deduce the influence of the excessive free-carrier nonlinearities vs. the Kerr-like nonlinearity to set new lower boundaries on the estimates of the photon-photon interaction constant.
