A FIBER INJECTION UNIT FOR EXOPLANET SPECTROSCOPY Presenter: Wenhao - PowerPoint PPT Presentation

A FIBER INJECTION UNIT FOR EXOPLANET SPECTROSCOPY Presenter: Wenhao Xuan Mentor: Dimitri Mawet Collaboratorsrs: Garreth Ruane, James Kent Wallace, Daniel Echeverri, Michael Randolph Marois et al. 2008 (2010)

OUTLINE 1. Science Objectives (Exoplanet Characterization) & Context 2. Building the Fiber Injection Unit 3. Speckle Nulling Experiments Integration of 2&3 4. Conclusions 5.

MAPPING ATMOSPHERES NASA/NOAA Crossfield et al. 2014

MEASURE PLANET SPIN a b 1.0 Stellar velocity 0.5 Relative position ( ″ ) CC signal Star position 0.0 Planet position –0.5 –1.0 –60 –40 –20 0 20 40 –100 –50 0 50 Velocity (km s –1 ) Velocity (km s –1 ) Snellen et al. 2014

EXOPLANET SPECTRA Konopacky et al. 2013

KECK PLANET IMAGER AND CHARACTERIZER (KPIC) Mawet et al. 2016

HIGH-CONTRAST IMAGING + HIGH-RESOLUTION SPECTROSCOPY Elimination of modal noise. Bypasses speckle noise calibration issues (Snellen et al. 2015). Spectrograph receives less background noise. Spectrograph more compact (conservation of étendue).

SINGLE-MODE TRANSMISSION OF PLANET E-field amplitude profiles for the guided modes of a multi-mode fiber. Credits to RP Photonics. One single propagation mode (LP 01 ) Very low losses Coupling efficiency hinged on entrance beam quality & alignment

A BRIEF INTRODUCTION TO ADAPTIVE OPTICS & CORONAGRAPHY

PROTOTYPING THE FIU Tip-tilt Lyot stop mirror Tracking CCD Corner cube lens Objective lens Fiber aligner SM fiber Overhead view of the fiber injection unit

PERFORMANCE OF FIU “planet” suppressed Fiber coupling efficiency of “star” ~60%-70% achieved Proves to be a simple and smoothly repeatable design beacon image Image of star, planet and beacon taken by the tracking CCD

SPECKLE NULLING BASICS What? — Blobs of residual starlight in final image plane that result from wavefront aberrations How? — Generate anti-speckle by imposing sinusoids on the deformable mirror & interfere it with existing speckle Why? — Improves SNR of planet image/spectra Image of our speckle field taken with the tracking CCD

h = 0.5h 0 (1+cos(2 π Rcos( θ -q)/x 0 + α lp)) h 0 : maximum poke height • q: angle of sinusoid • x 0 : actuators/cycle (spatial freq. = numAct/x 0 ) • α lp: phase delay • Pupil Plane Focal Plane π /2 Fourier transform 0 Fourier transform

SPECKLE NULLING: IN ACTION (~3 λ /d, pi/2)

suppression factor ~ 11 (3 λ /D speckle)

suppression factor ~ 8 (2 λ /D speckle)

suppression factor ~ 6 (4 λ /D speckle)

INTEGRATION: SPECKLE NULLING @ FIBER (WORK IN PROGRESS) Besides intensities from CCD, we record power with a photodiode Expect increased suppression of speckle noise through SM fibers Results?

CCD RESULTS V.S. PHOTODIODE RESULTS Suppression: ~ 9; Suppression: ~ 100 ; optimal params: 90nm & 3.14rads optimal params: 80nm & 2.83rads

CONCLUSIONS NEXT STEPS Automate planet coupling The FIU works! process with piezo actuators High coupling efficiencies could be achieved Full-scale High-Contrast Spectroscopy Testbed Speckle nulling with a SM fiber (HCST) will improve contrast for the planet On-sky demonstration W.M. Keck Observatory

COMING SOON! Planned layout of future HCST

ACKNOWLEDGEMENTS Special thanks to Dimitri Mawet, Garreth Ruane, James Kent Wallace for their invaluable mentorship, Daniel Echeverri and Michael Randolph for being such talented lab partners, and Elodie Choquet, Ji Wang, Reed Riddle, Jason Fucik, Patrick Murphy, Judy McClain for their constant support and assistance.

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