Abstract
Wavefront sensing and control are important for enabling one of the key advantages of using large apertures, namely higher angular resolution. Pyramid wavefront sensors are becoming commonplace in new instrument designs owing to their superior sensitivity. However, one remaining roadblock to their widespread use is the fabrication of the pyramidal optic. This complex optic is challenging to fabricate due to the pyramid tip, where four planes need to intersect at a single point. Thus far, only a handful of these have been produced due to the low yields and long lead times. To address this, we present an alternative implementation of the pyramid wavefront sensor which relies instead on two roof prisms. Such prisms are easy and inexpensive to source. We demonstrate the successful operation of the roof prism pyramid wavefront sensor on an 8 m class telescope, at visible and near-infrared wavelengths, for the first time using a SAPHIRA HgCdTe detector without modulation for a laboratory demonstration, and elucidate how this sensor can be used more widely on wavefront control test benches and instruments.
Highlights
Implementation of new telescopes with increasing apertures is driven by the desire to increase the collecting area and sensitivity of an instrument, and to improve the angular resolution of the telescope
We demonstrate the successful operation of the roof prism pyramid wavefront sensor on a 8-m class telescope, at visible and near infrared wavelengths —for the first time using a SAPHIRA HgCdTe detector without modulation for a laboratory demonstration, and elucidate how this sensor can be used more widely on wavefront control test benches and instruments
Instead of computing the slopes of the wavefront as it is commonly done for most pyramid wavefront sensor (PyWFS), the algorithm uses the whole image of the sensor, and multiplies it by a control matrix using a bank of Graphics Processing Units (GPUs) to get the Deformable Mirror (DM) command directly
Summary
Implementation of new telescopes with increasing apertures is driven by the desire to increase the collecting area and sensitivity of an instrument, and to improve the angular resolution of the telescope. If the PyWFS is modulated, which is the more typical case when used at visible wavelengths, the dynamic range of the sensor can be extended, thereby mitigating the need for an upstream AO system, but reducing at the same time the sensitivity to low-order modes The benefits of such a wavefront sensor were realized early on and it has far been employed in several world-class AO facilities including LBTAO (Esposito et al 2011), MagAO (Close et al 2013) and SCExAO (Jovanovic et al 2015).
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