Circularly Polarized Photoluminescence characteristics of emiters placed on a nanophotonic platform

"Circular dichroism The differential transmittance measurements were carried out in a custom-made optical setup. A white-light tungsten halogen lamp (Ocean Optics, HL-2000-HP, FL, USA) is coupled to a silver reflective collimator (RC08SMA-P01, Thorlabs) and used as an excitation light source. The light beam is passed through a Glan-Thompson Calcite Polarizer (GTH10M, Thorlabs) and directed to a super achromatic quarter wave-plate (SAQWP05M-700, Thorlabs) oriented at ±π/4 compared to the polarization direction on a rotation mount (ELL14, Thorlabs) to obtain a circularly polarized light beam. The optical elements are automatically controlled by custom software (LabView NXG). The sample is positioned at the focal plane of a pair of 4x objectives (RMS4X, NA = 0.1, Olympus). Finally, the transmitted light is fiber-coupled to a spectrometer (Ocean Optics, QEPro-FL). Steady-state circularly polarized photoluminescence Chiral photoluminescence is characterized using the same optical elements as for the dichroic transmittance but reversed in order. First, the emitted chiral photoluminescence is directed to a quarter wave-plate (10RP52-1B, Newport) oriented at ±π/4 and then to a linear polarizer (20LP-VIS-B, Newport), filtering one of the circular components. The excitation source consisted of a 200ps pulsed laser source (LDH-P-C-405 laser driven with a PDL 800B driver with 5–80 MHz repetition rate)) with its wavelength peak at 405nm. In the case of the unpolarized excitation study, the light source used for excitation was an unpolarized LED centered at 405nm (M405L4, Thorlabs) coupled to a 4x (RMS4X, NA=0.1, Olympus) objective used to collimate the diverging emitted beam and refocused with an achromatic 50mm lens upon the metasurface. Time-resolved circularly polarized photoluminescence The optical set-up used for the time-resolved photoluminescence was PicoQuant Time Correlated Single Photon Counting system (Time Harp 260 PICO board, 25 ps temporal resolution; PMA Hybrid 40 detector, 250 ps response time; 405 nm LDH-P-C-405 laser driven with a PDL 800B driver with 5–80 MHz repetition rate) equipped with a compact monochromator (Solar Laser Systems). Photoluminescence lifetimes were retrieved using the PicoQuant FluoFit Pro software, and fitting the PL decay data accounting for instrument response function."