Researchers at NIST have developed a new technique using optical fiber taper waveguides to efficiently collect and measure the optical properties of single solid-state quantum emitters, such as quantum dots in semiconductors. The technique offers a factor of ten efficiency improvement compared to traditional methods using lenses, with efficiencies approaching 70% when combined with specially-designed on-chip waveguides.
The fiber taper waveguide system allows for straightforward interfacing with high-performance optical sources, detectors, and other elements. It can be used for resonant spectroscopy, providing better spectral and temporal resolution while revealing different physical behaviors. The technique has been optimized for various geometries and material systems, including colloidal quantum dots and single molecules embedded in thin dielectric films.
NIST is collaborating with colleagues at the University of Rochester to implement the technique for single semiconductor quantum dots. The work involves developing a customized low-temperature optical characterization setup that combines traditional free-space microphotoluminescence measurements with fiber-based photoluminescence and transmission spectroscopy in an environment cooled to about 6 K.
Additionally, NIST researchers are working with colleagues at the ITL on using frequency upconversion to address challenges of single emitter spectroscopy at near-infrared wavelengths. The technique can be used for single-photon level detection and connecting different quantum systems operating at different energies.
Keywords: single emitters, fluorescence centers, quantum dots, fiber taper waveguide, frequency upconversion
