Cross-Polarization-Extinction Enhancement and Spin-Orbit Coupling of Light for Quantum-Dot Cavity Quantum Electrodynamics Spectroscopy
Petr Steindl, J. A. Frey, Justin Norman, John Edward Bowers, Dirk Bouwmeester, W. Löffler · Physical Review Applied · 2023
Resonant laser spectroscopy is essential for the characterization, operation, and manipulation of single-quantum systems such as semiconductor quantum dots. The separation of the weak resonance fluorescence from the excitation laser is key for high-quality single- and entangled-photon sources. This is often achieved by cross-polarization laser extinction, which is limited by the quality of the optical elements. Recently, it was discovered that Fresnel-reflection birefringence in combination with single-mode filtering counteracting spin-orbit-coupling effects enables a three-order-of-magnitude improvement of polarization extinction [Benelajla et al., Phys. Rev. X 11, 021007 (2021)]. Here, we demonstrate this method for cross-polarization-extinction enhancement in cryogenic confocal microscopy of a resonantly excited semiconductor quantum dot in a birefringent optical microcavity, and observe a $10\ifmmode\times\else\texttimes\fi{}$ improvement of the single-photon contrast.