The vortex fiber nulling mode of the Keck Planet Imager and Characterizer (KPIC)

Abstract

The Keck Planet Imager and Characterizer (KPIC) is an upgrade to the Keck II adaptive optics system that includes an active fiber injection unit (FIU) for efficiently routing light from exoplanets to NIRSPEC, a highresolution spectrograph. Towards the end of 2019, we will add a suite of new coronagraph modes as well as a high-order deformable mirror. One of these modes, operating in K-band (2.2µm), will be the first vortex fiber nuller to go on sky. Vortex Fiber Nulling (VFN) is a new interferometric method for suppressing starlight in order to spectroscopically characterize exoplanets at angular separations that are inaccessible with conventional coronagraph systems. A monochromatic starlight suppression of 6 × 10 −5 in 635 nm laser light has already been demonstrated on a VFN testbed in the lab. A polychromatic experiment is now underway and coupling efficiencies of < 5×10 −4 and ∼ 5% have been demonstrated for the star and planet respectively in 10% bandwidth light. Here we describe those experiments, the new KPIC VFN mode, and the expected performance of this mode using realistic parameters determined from on-sky tests done during the KPIC commissioning.

Vortex fiber nulling for exoplanet observations: conceptual design, theoretical performance, and initial scientific yield predictions

“…These practical trade-offs have led our team to adopt the pupil-plane version for current laboratory testing 6 and future plans for on-sky deployment, 31 despite the fact that our first VFN paper 5 concentrated on the focalplane approach. The remainder of this paper pertains to the pupil-plane version, but most of the theoretical performance properties also apply in the focal-plane case.…”

“…While multi-aperture fiber nulling has been demonstrated on sky using the 200-inch Hale Telescope at Palomar Observatory 28 and preparation is underway for the first on-sky demonstration of VFN as part of the Keck Planet Imager and Characterizer (KPIC) instrument, [29][30][31] in the following we present conceptual design trades, theoretical performance, and estimated scientific yield of a VFN mode operating in the near-infrared on the future Thirty Meter Telescope (TMT) Multi-Object Diffraction-limited High-resolution Infrared Spectrograph (MOD-HIS) instrument. 32 Specifically, we will show that it is feasible to detect >10 known planets with integration times of tens of hours and potentially search for rocky planets in the habitable zones of nearby stars.…”

Detecting and characterizing close-in exoplanets with vortex fiber nulling

“…This was done using a supercontinuum white light source (NKT Photonics SuperK EXTREME) and tunable filter (NKT Photonics SuperK VARIA) to programmatically vary the wavelength and bandwidth of the source. As mentioned in last year's conference, 21 the system performed well. A null of 4.5 × 10 −4 with a simultaneous peak planet coupling of 4.5% was achieved at 10% bandwidth centered around 790 nm.…”

The Keck Planet Imager and Characterizer: demonstrating advanced exoplanet characterization techniques for future extremely large telescopes (Conference Presentation)

“…To enhance the starlight suppression for the FIU arm and hence really demonstrate HDC, the 1000 element DM, as well as several coronagraphs, 15 an atmospheric dispersion compensator and pupil shaping optics will be installed upstream of the fiber feed during a later phase of the project. 16…”

“…• Phase II: This involves replacing the base FIU optics with the same optical layout with other modules that improve planet throughput and suppress starlight to reduce the required integration time. 15,16 In addition, the PyWFS will be facilitized. This not only includes preparing the PyWFS for routine operation, but a replacement of the roof prisms for ones optimized for the NIR as well as steering capabilities on the input field steering mirrors to allow for offsetting for calibration.…”