A key avenue to improving the precision of radial velocity measurements is by using photonic devices to collect the light from the focal plane and delivering the beams to the slit of spectrograph via a single-mode fiber. Single-mode fibers have the favorable property that they allow light to propagate in a single energy distribution characterized by a Gaussian shape with a flat wavefront which is temporarily stable and independent of changes to the injection. These properties mean that the point spread function delivered to the input slit of a spectrograph is highly stable with time and independent of changes to the injection which is currently a key limitation to precision radial velocity measurements and known as "Modal Noise". Further light delivery via single-mode fibers is the key requirement to realize long baseline interferometers such as the Optical Hawaiian Array for Nanoradian Astronomy.
Injecting into single-mode fibers efficiently is inherently difficult because it requires closely matching the intensity and wavefront of the focused beam to that supported by the fiber. The atmosphere is currently the key roadblock to efficient injection. However, extreme adaptive optics systems such as Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system currently being commissioned will enable high order wavefront correction and make efficient coupling into single-mode fibers possible. In addition, pupil apodization optics used for coronagraphy, known as phase induced amplitude apodization lenses also present in the SCExAO instrument, allow for close matching of the intensity distributions.
We report on the progress and lessons learnt on developing an efficient single-mode injection unit within the SCExAO instrument. As part of the PANDORA project we aim to use this injection and combine it with several other photonic technologies to enable high precision radial velocity measurements in new and innovative ways.
|Title of host publication||Ground-Based and Airborne Instrumentation for Astronomy V|
|Editors||Suzanne K. Ramsay, Ian S. McLean, Hideki Takami|
|Place of Publication||Washington, DC|
|Number of pages||8|
|Publication status||Published - 2014|
|Event||Ground-Based and Airborne Instrumentation for Astronomy V - Montreal, Canada|
Duration: 22 Jun 2014 → 26 Jun 2014
|Name||Proceedings of SPIE|
|Publisher||SPIE-INT SOC OPTICAL ENGINEERING|
|Other||Ground-Based and Airborne Instrumentation for Astronomy V|
|Period||22/06/14 → 26/06/14|
- Extreme adaptive optics
- Modal noise
- photonic lanterns
- Precision radial velocity measurements
- Pupil apodization
- Single-mode fiber