NICI's currently installed AO system.
At the present time, the 85-element wavefront sensors used in Hokupa'a-85 and NICI have the most number of channels of any system built at UH. In fact, these systems are only second in number of channels to the 188 element AO system on Subaru.
UH's AO lab is now working on a high order 200 - 300 channel AO system with the ability to achieve low-light imaging. AO systems are often limited by the need to observe bright objects. Adaptive optics tries to recover the resolving power of large apertures to the degree that system noise sources permit. Functionally, however, we must use information (i.e. photons), generally from the target itself, to restore diffraction-limited performance. This need to consume photons for wave front sensing imposes its own limits on the observation. Almost universally, observations are limited not because the object is too faint to see, but because it is too faint to correct. Curvature adaptive optics is intrinsically more efficient in terms of the number of channels needed for a given level of correction, so it is able to extend AO correction to fainter objects.
In our AO systems, each wavefront sensing channel images light onto a set of optical fibers that each feed a photon-counting avalanche photo diode. Having photon-counting detectors on each channel enables low light operation and allows noiseless channel combination, improving faint source response. By increasing the number of wavefront sensing channels, the ability to detect faint objects is increased.
Certain challenges arise in building an AO system with such a high number of wavefront sensing channels, such as a small minimum radius of curvature. Our group is working to address these challenges and construct a 200 - 300 element system with a corresponding deformable mirror.
Site design: Katie Whitman; Header graphic design: Banana Grafeeks