Mr. Maodong Gao Profile

Maodong Gao

at Caltech

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Publications (3)

Proceedings Article | 17 March 2023 Presentation

Advanced high-Q resonators for next-generation frequency microcombs

Kerry Vahala, Zhiquan Yuan, Maodong Gao, QingXin Ji, Yan Yu, Leo Wu, Joel Guo, Mario Paniccia, Warren Jin, Heming Wang, John Bowers

Proceedings Volume PC12425, PC1242501 (2023) https://doi.org/10.1117/12.2656088

KEYWORDS: Resonators, Semiconductor lasers, Physics, Optical resonators, Nonlinear optics

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Proceedings Article | 29 August 2022 Poster + Paper

An all-photonic, dynamic device for flattening the spectrum of a laser frequency comb for precise calibration of radial velocity measurements

Nemanja Jovanovic, Pradip Gatkine, Boqiang Shen, Maodong Gao, Nick Cvetojevic, Katarzyna Ławniczuk, Ronald Broeke, Charles Beichman, Stephanie Leifer, Jeffrey Jewell, Gautam Vasisht, Dimitri Mawet

Proceedings Volume 12188, 121885D (2022) https://doi.org/10.1117/12.2630301

KEYWORDS: Waveguides, Frequency combs, Modulation, Calibration, Spectrographs, Precision calibration, Polarization, Velocity measurements, Light sources, Chemical elements

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Laser frequency combs are fast becoming critical to reaching the highest radial velocity precisions. One shortcoming is the highly variable brightness of the comb lines across the spectrum (up to 4-5 orders of magnitude). This can result in some lines saturating while others are at low signal and lost in the noise. Losing lines to either of these effects reduces the precision and hence effectiveness of the comb. In addition, the brightness of the comb lines can vary with time which could drive comb lines with initially reasonable SNR’s into the two regimes described above. To mitigate these two effects, laser frequency combs use optical flattener’s. Flattener’s are typically bulk optic setups that disperse the comb light with a grating, and then use a spatial light modulator to control the amplitude across the spectrum before recombining the light into another single mode fiber and sending it to the spectrograph. These setups can be large (small bench top), expensive (several hundred thousand dollars) and have limited stability. To address these issues, we have developed an all-photonic spectrum flattener on a chip. The device is constructed from optical waveguides on a SiN chip. The light from the laser frequency comb’s output optical fiber can be directly connected to the chip, where the light is first dispersed using an arrayed waveguide grating. To control the brightness of each channel, the light is passed through a Mach-Zehnder interferometer before being recombined with a second arrayed waveguide grating. Thermo-optic phase modulators are used in each channel before recombination to path length match the channels as needed. Here we present the results from our first generation prototype. The device operates from 1400-1800 nm (covering the H band), with 20, 20 nm wide channels. The device was mounted on a PCB board to enable electrical control of the active elements and tested in the laboratory. It was demonstrated that the Mach- Zehnder’s allowed for nearly 40 dBs of dynamic modulation of the spectrum, which is greater than that offered by most spatial light modulators. With a smooth spectrum light source (superluminescent light source), we reduced the spectral variation to 3 dBs, limited by the properties of the components used. On a laser frequency comb which had strong modulations at high spatial frequencies, we still managed to reduce the modulation to 5 dBs. These devices are of the order of a US quarter and could play a significant role in future PRV and EPRV initiatives.

Proceedings Article | 29 August 2022 Presentation + Paper

Innovations and advances in instrumentation at the W. M. Keck Observatory, vol. II

Marc Kassis, Steve Allen, Carlos Alvarez, Ravinder Banyal, Robert Bertz, Charles Beichman, Aaron Brown, Matthew Brown, Gerald Cabak, Kevin Bundy, Sylvain Cetre, Jason Chin, Mark Chun, Will Deich, Richard Dekany, Jacques Delorme, Mark Devenot, Greg Doppmann, Michael Fitzgerald, Jason Fucik, Grant Hill, Philip Hinz, Bradford Holden, Andrew Howard, Maodong Gao, Steve Gibson, Percy Gomez, Colby Gottschalk, Peter Gillingham, Tucker Jones, Nemanja Jovanovic, Evan Kirby, Quinn Konopacky, Shanti Krishnan, Renate Kupke, James Larkin, Stephanie Leifer, Hilton Lewis, Scott Lilley, Jessica Lu, James Lyke, Nick MacDonald, Eduardo Marin, Matt Matuszewski, Dimitri Mawet, Rosalie McGurk, Maxwell Millar-Blanchaer, Reston Nash, Craig Nance, James Neill, John O'Meara, Eliad Peretz, Claire Poppett, John Mather, Matthew Radovan, Mitsuko Roberts, Sam Ragland, Kodi Rider, Constance Rockosi, Dale Sandfor, Boqiang Shen, Charles Steidel, Sunil Simha, Andy Skemer, Deno Stelter, Avinash Surendran, James Thorne, Ben McCarney, Kyle Lanclos, Ashley Baker, Ryan Rubenzahl, Arpita Roy, Sam Halverson, Jerry Edelstein, Christopher Martin, Maureen Savage, Dale Sandford, Stephanie Sallum, Josh Walawender, Peter Wizinowich, Kyle Westfall, Kerry Vahala, Shelley Wright, Truman Wold, Sherry Yeh

Proceedings Volume 12184, 1218405 (2022) https://doi.org/10.1117/12.2628630

KEYWORDS: Adaptive optics, Spectrographs, Exoplanets, Sensors, Spectroscopy, Imaging systems, Telescopes, Planets, Cameras, Observatories

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