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 4. Integration of 2&3 5. Conclusions
MAPPING ATMOSPHERES NASA/NOAA Crossfield et al. 2014
MEASURE PLANET SPIN a Relative position ( ) 1.0 0.5 0.0 0.5 Stellar velocity Star position Planet position b CC signal 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 Lyot stop Tip-tilt mirror Corner cube Tracking CCD lens Fiber aligner Objective lens SM fiber Overhead view of the fiber injection unit
PERFORMANCE OF FIU planet suppressed star Fiber coupling efficiency of ~60%-70% achieved beacon image Proves to be a simple and smoothly repeatable design 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? Image of our speckle field taken with the tracking CCD Improves SNR of planet image/spectra
h = 0.5h 0 (1+cos(2π Rcos(θ-q)/x 0 + αlp)) h 0 : maximum poke height q: angle of sinusoid x 0 : actuators/cycle (spatial freq. = numact/x 0 ) αlp: phase delay Pupil Plane Focal Plane Fourier transform π/2 Fourier transform 0
SPECKLE NULLING: IN ACTION (~3λ/d, pi/2)
suppression factor ~ 11 (3λ/D speckle)
suppression factor ~ 8 (2λ/D speckle)
suppression factor ~ 6 (4λ/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; optimal params: 90nm & 3.14rads Suppression: ~ 100; optimal params: 80nm & 2.83rads
CONCLUSIONS NEXT STEPS The FIU works! High coupling efficiencies could be achieved Speckle nulling with a SM fiber will improve contrast for the planet Automate planet coupling process with piezo actuators Full-scale High-Contrast Spectroscopy Testbed (HCST) 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.
REFERENCES C. Marois, B. Macintosh, T. Barman, B. Zuckerman, I. Song, J. Patience, D. Lafreniere, R. Doyon, Direct Imaging of Multiple Planets Orbiting the Star HR 8799, Science, Volume 322, Issue 5906, pp. 1348- (2008). Crossfield, I. J. M., Biller, B., Schlieder, J. E., Deacon, N. R., Bonnefoy, M., Homeier, D., Allard, F., Buenzli, E., Henning, T., Brandner, W., Goldman, B., and Kopytova, T., A global cloud map of the nearest known brown dwarf, Nature 505, 654 656 (Jan. 2014). D. Mawet, P. Wizinowich, R. Dekany, M. Chun, D. Hall, S. Cetre, O. Guyon, J.K. Wallace, B. Bowler, M. Liu, G. Ruane, E. Serabyn, R. Bartos, J. Wang, G. Vasisht, M. Fitzgerald, A. Skemer, M. Ireland, J. Fucik, J. Fortney, I. Crossfield, R. Hu, B. Benneke, Keck Planet Imager and Characterizer: concept and phased implementation, Proc. SPIE 9909, Adaptive Optics Systems V, 99090D, (Jul. 2016). Snellen, I. A. G., Brandl, B. R., de Kok, R. J., Brogi, M., Birkby, J., and Schwarz, H., Fast spin of the young extrasolar planet β Pictoris b, Nature 509, 63 65 (May 2014). Snellen, I., de Kok, R., Birkby, J. L., Brandl, B., Brogi, M., Keller, C., Kenworthy, M., Schwarz, H., and Stuik, R., Combining high-dispersion spectroscopy with high contrast imaging: Probing rocky planets around our nearest neighbors, A&A 576, A59 (Apr. 2015). Benneke, B., Strict Upper Limits on the Carbon-to-Oxygen Ratios of Eight Hot Jupiters from Self- Consistent Atmospheric Retrieval, arxiv.org, 7655 (Apr. 2015).