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About me
Hi! I am a postdoc at Leiden University in the group of Professor Sebastiaan Haffert. My research interests lie in optical and near-infrared instrumentation for the detection, imaging, and spectroscopy of exoplanets. Specifically, I look for ways to reduce contamination from starlight, both in hardware, through instrument design and wavefront sensing and control, and in data post-processing with statistical methods.
Previously, I obtained a PhD in Physics at Caltech (in the Exoplanet Technology Lab led by Professor Dimitri Mawet), an MS in Aeronautics and Astronautics from MIT, and a BS in Physics from Caltech. I was a recipient of the NSF Graduate Research Fellowship.
Email: xin[at]strw.leidenuniv.nl
Github: yinzi-xin
ORCID: https://orcid.org/0000-0002-6171-9081
Mode-sorting coronagraphy
During my PhD, I proposed the Photonic Lantern Nuller (PLN) instrument concept for the efficient detection and spectroscopic characterization of exoplanets within the diffraction limit - a regime inaccessible to conventional coronagraphs. Accessing closer-in separations would greatly increase the expected number of detectable planets, which scales inversely with the inner working angle. The PLN is a cross-aperture nuller that works by injecting light into a Mode-Selective Photonic Lantern (MSPL), leveraging the spatial symmetries of the device to cancel out on-axis starlight while letting off-axis planet light through. It was inspired by the Vortex Fiber Nuller concept - however, a PLN retains more of the planet flux than the VFN because of its multiple ports, and can achieve higher sensitivity to planets.
The PLN has been characterized in the lab in monochromatic and broadband light. Its performance has been improved with wavefront sensing and control techniques, and it has been demonstrated on-sky at the Subaru Telescope.
First-author publications
Efficient Detection and Characterization of Exoplanets within the Diffraction Limit: Nulling with a Mode-selective Photonic Lantern: ApJ (Open Access)
Laboratory demonstration of a Photonic Lantern Nuller in monochromatic and broadband light: arXiv, JATIS
Implicit electric field conjugation with a Photonic Lantern Nuller: arXiv, JATIS
Wavefront sensing and control
Speckle nulling is an established technique for destructively interfering starlight with itself by using a deformable mirror (DM) to modulate the phase of the light. In Fall 2022, I led the the effort to perform the first on-sky demonstration of speckle nulling through a single-mode fiber with the Keck Planet Imager and Characterizer (KPIC) instrument. It is also the first demonstration of speckle nulling that uses a high-resolution spectrograph simultaneously for wavefront sensing and for science-grade spectra.
Because techniques like speckle nulling and implicit electric field conjugation rely on a series of probes on the DM, we may be able to constrain the level of coherent starlight based on how it interferes with the probes. Improving constraints on the coherent light may be helpful in removing the effects of leaked starlight on the data.
First-author publications
On-sky Speckle Nulling through a Single-Mode Fiber with the Keck Planet Imager and Characterizer: arXiv, JATIS
Implicit electric field conjugation with a Photonic Lantern Nuller: arXiv, JATIS
Data post-processing and analysis
Post-processing of coronagraphic data should take advantage of as many sources of information as it can to disentangle residual starlight from planet signal. I showed that the instrumental sensitivity of a coronagraph to wavefront error is one such source of information, and can be used to derive robust observables — a simple way to implement an instrument-motivated prior that improves the signal-to-noise ratio of planet signals.
First-author publications
Coronagraphic Data Post-processing Using Projections on Instrumental Modes: ApJ (Open Access)
Other
The Deformable Mirror Demonstration Mission (DeMi) is a cubesat developed by the STARLab at MIT. It operated from 2020 to 2021 and tested a Microelectromechanical (MEMS) Deformable Mirror in space for the first time, raising its technology readiness level from 5 to 9. I was partly responsible for aligning the payload optics, and I also wrote and tested the wavefront control algorithm, which was successfully used in orbit (see Morgan et al. 2022 for details).