Photon Thermalization and Condensation in a Quantum Well Open Microcavity

The thermalization of light and its ground state condensation has been extensively explored in recent years [1], with the link between laser action and Bose Einstein condensation of a thermalized photon gas in an open microcavity [2, 3] opening new ways to understand laser system. In this talk we report thermalization and condensation of light in a semiconductor quantum well weakly coupled to an open microcavity system [4]. This system consists of half a vertical external cavity surface emitting laser, constructed on GaAs with an InGaAs quantum well emitting near 925 nm, with a piezo controlled external spherical dielectric mirror positioned to achieve low cavity mode orders with well-defined transverse modes. We present evidence of cavity photon thermalization and since we have used a single quantum well with minimized absorption, , to match the cavity loss, , we explore the influence of thermalization coefficient, . This level of control allows us to compare our data to recent theory on photon condensation in semiconductor systems [5]. In the condensation regime, we identify a region of ground state mode stability with good thermalization . Meanwhile regions of poor thermalization , and at high operation power, show multi-mode or higher order spatial mode lasing, which is consistent with the theory of dye-based condensates [6, 7]. We also assess the strength of photon-photon interactions and find a normalized interaction parameter, . Since this value increases with quantum well number, this system is promising for the possibility of observing rich interaction physics.<br/><br/><b>References</b><br/><br/>[1] J. Bloch, <i>et al</i>, Nature Reviews Physics 4, 470 (2022)<br/>[2] J. Klaers <i>et al</i>, Nature Physics <b>6</b>, 512 (2010)<br/>[3] J. Klaers <i>et al.,</i> Nature <b>468</b>, 545 (2010)<br/>[4] R. C. Schofield <i>et al.,</i> arXiv:2306.15314 (2023)<br/>[5] A. Loirette-Pelous & J-J.Greffet, Laser & Photonics Rev.,<b>17</b>, 2300366 (2023)<br/>[6] H. Heston <i>et al</i>, Phys. Rev. Lett., <b>120</b>, 040601 (2018)<br/>[7] J.D. Rodrigues, <i>et al</i>, Phys. Rev. Lett. <b>126</b>, 150602 (2021)