Subwavelength Grating Bandpass Filter for On-Chip hBN Single Photon Emitter Selection
Chris Whittington
Vanderbilt University, Nashville, Tennessee, USA _______________________________________
Hexagonal boron nitride (hBN) hosts a wide range of bright single photon emitters (SPEs) that hold promise for room-temperature quantum information systems (QIS) applications. The majority of research in this area over the past decade has been focused on characterizing the SPEs as well as exploring methods for their reliable and deterministic formation. However, as the hBN SPE platform continues to mature, there exists a need to integrate these photon sources on-chip to provide the ability to route photons and enable them to perform logic functions or other QIS operations. While the basic waveguide architecture needed for on-chip control of light has existed for decades, a key component that needs to be considered for a QIS platform containing on-chip hBN SPEs is a compact and efficient way to select the desired single photon emission wavelength among the multitude of emission wavelengths that can be emitted from defects in hBN. To address this issue, we report a compact silicon nitride subwavelength grating (SWG) bandpass filter that is engineered to precisely filter out a specified SPE wavelength, as shown in Fig 1. The dimensions of the SWG filter determine both the center wavelength and bandwidth of the filter. Fig. 1(c) shows a SWG filter designed to select the Group I emitter at 602 nm (2.06 eV), which is in close proximity to 583 nm (2.13 eV) and 633 nm (1.96 eV) emitters. We will discuss how SPEs produced on an hBN flake using a focused ion beam are pre-characterized with photoluminescence microscopy to understand the location and spectral properties of the SPEs before the hBN flake is transferred onto the SWG bandpass filter. The filtered 602 nm single photons will be routed on-chip before being coupled off-chip for characterization via g(2) autocorrelation measurements. We suggest that our SWG filter design demonstrates a simple method to select, preserve, and route hBN single photons on-chip for quantum applications.
Email: Christopher.Whittington@Vanderbilt.Edu