Paper 13100-256
Efficient broad band, high resolution (R~30,000) photonic spectrographs realized through cascading
20 June 2024 • 17:30 - 19:00 Japan Standard Time | Room G5, North - 1F
Abstract
Arrayed waveguide gratings (AWGs) offer a promising photonic architecture to miniaturize astronomical spectrographs by several orders of magnitudes. However, the overlapping spectral orders in an AWG need to be separated using bulk-optics cross-dispersion to retrieve the full spectrum, which reduces the photonic advantage. In this paper, we present experimental results from a proof-of-concept cascaded AWG setup, which eliminates the need for bulk-optics cross-dispersion. A low-resolution, high-FSR AWG (channel spacing ~ 8.75 nm , FSR ~ 200 nm) splits the input spectrum into coarse channels which are then dispersed at high-resolution (R ~ 30,000, FSR ~ 12 nm) using the fine AWG. Thus, the entire spectrum across ~200 nm can be imaged using one coarse AWG and a stack of fine AWGs, one corresponding to each coarse channel. Both coarse and fine AWGs are built using doped-SiO2 platform. The peak efficiencies of the low- and high-resolution chips are ~80% and ~40%, respectively, thus giving a total peak efficiency of 32% for the cascaded AWG. This high-efficiency cascaded AWG demonstration paves the way for a fully integrated photonic spectrograph for ground- and space-based telescopes.
Presenter
Pradip R. Gatkine
Caltech (United States)
Pradip Gatkine is NASA Hubble Fellow at Caltech. He received his PhD in Astronomy from the University of Maryland in July 2020. His photonic research includes the development of next-generation astrophotonic instrumentation for large telescopes. He is currently developing high-resolution astrophotonic arrayed waveguide grating (AWG) spectrographs for astronomical telescopes. He led an Astro-2020 white paper on astrophotonics in the next decade. He also co-led the Astrophotonics Roadmap, a comprehensive vision document on challenges in all aspects of astrophotonics that need to be resolved in the next 10 years. He is starting as an Assistant Prof. of Physics and Astronomy at Univ of California Los Angeles (UCLA) in March 2024.