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Design considerations of photonic lanterns for diffraction-limited spectrometry

Lin, Jonathan and Jovanovic, Nemanja and Fitzgerald, Michael P. (2021) Design considerations of photonic lanterns for diffraction-limited spectrometry. Journal of the Optical Society of America B, 38 (7). A51-A63. ISSN 0740-3224. doi:10.1364/josab.423664.

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The coupling of large telescopes to astronomical instruments has historically been challenging due to the tension between instrument throughput and stability. Light from the telescope can either be injected wholesale into the instrument, maintaining high throughput at the cost of point-spread function (PSF) stability, or the time-varying components of the light can be filtered out with single-mode fibers (SMFs), maintaining instrument stability at the cost of light loss. Today, the field of astrophotonics provides a potential resolution to the throughput-stability tension in the form of the photonic lantern (PL): a tapered waveguide that can couple a time-varying and aberrated PSF into multiple diffraction-limited beams at an efficiency that greatly surpasses direct SMF injection. As a result, lantern-fed instruments retain the stability of SMF-fed instruments while increasing their throughput. To this end, we present a series of numerical simulations characterizing PL performance as a function of lantern geometry, wavelength, and wavefront error (WFE), aimed at guiding the design of future diffraction-limited spectrometers. These characterizations include a first look at the interaction between PLs and phase-induced amplitude apodization (PIAA) optics. We find that Gaussian-mapping beam-shaping optics can enhance coupling into 3-port lanterns but offer diminishing gains with larger lanterns. In the y and J band (0.97–1.35 µm) region, with moderately high WFE (∼10% Strehl ratio), a 3-port lantern in conjunction with beam-shaping optics strikes a good balance between pixel count and throughput gains. If pixels are not a constraint, and the flux in each port will be dominated by photon noise, then larger port count lanterns will provide further coupling gains due to a greater resilience to tip-tilt errors. Finally, we show that lanterns can maintain high operating efficiencies over large wavelength bands where the number of guided modes at the lantern entrance drops, if care is taken to minimize the attenuation of weakly radiative input modes.

Item Type:Article
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URLURL TypeDescription Paper ItemConference Paper
Lin, Jonathan0000-0001-8542-3317
Jovanovic, Nemanja0000-0001-5213-6207
Fitzgerald, Michael P.0000-0002-0176-8973
Additional Information:© 2021 Optical Society of America. Received 25 February 2021; revised 20 May 2021; accepted 21 May 2021; posted 24 May 2021 (Doc. ID 423664); published 17 June 2021. The authors thank G. Ruane for providing the PIAA lens design. The authors would also like to thank C. Betters, S. Leon-Saval, and B. Norris for valuable discussions on photonic lanterns, as well as O. Guyon for his insight on various components of the numerical model. Funding: Heising-Simons Foundation (2020-1821). Data Availability: Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request. The authors declare no conflicts of interest.
Funding AgencyGrant Number
Heising-Simons Foundation2020-1821
Issue or Number:7
Record Number:CaltechAUTHORS:20210804-155110109
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Official Citation:Jonathan Lin, Nemanja Jovanovic, and Michael P. Fitzgerald, "Design considerations of photonic lanterns for diffraction-limited spectrometry," J. Opt. Soc. Am. B 38, A51-A63 (2021); DOI: 10.1364/josab.423664
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110146
Deposited By: Tony Diaz
Deposited On:04 Aug 2021 18:15
Last Modified:01 Oct 2021 22:26

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