Nanostructured <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mrow><mml:mi>Ga</mml:mi><mml:mi>As</mml:mi></mml:mrow></mml:math>/(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>Al</mml:mi><mml:mo>,</mml:mo><mml:mi>Ga</mml:mi></mml:math>)<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>As</mml:mi></mml:math> Waveguide for Low-Density Polariton Condensation from a Bound State in the Continuum
Fabrizio Riminucci, Vincenzo Ardizzone, Luca Francaviglia, M. Lorenzon, C. Stavrakas, Scott Dhuey, A. Schwartzberg, Simone Zanotti, Dario Gerace, Kirk Baldwin, L. N. Pfeiffer, Giuseppe Gigli, D. Frank Ogletree, A. Weber-Bargioni, Stefano Cabrini, D. Sanvitto
Abstract
Exciton-polaritons are hybrid light-matter states that arise from strong coupling between an exciton resonance and a photonic cavity mode. As bosonic excitations, they can undergo a phase transition to a condensed state that can emit coherent light without a population inversion. This aspect makes them good candidates for thresholdless lasers, yet short exciton-polariton lifetime has made it difficult to achieve condensation at very low power densities. In this sense, long-lived symmetry-protected states are excellent candidates to overcome the limitations that arise from the finite mirror reflectivity of monolithic microcavities. In this work we use a photonic symmetry-protected bound state in the continuum coupled to an excitonic resonance to achieve state-of-the-art polariton condensation threshold in a $\mathrm{Ga}\mathrm{As}$/($\mathrm{Al},\mathrm{Ga}$)$\mathrm{As}$ waveguide. Most important, we show the influence of fabrication control and how surface passivation via atomic layer deposition provides a way to reduce exciton quenching at the grating sidewalls.