Fang Shi

Design and field tests of an 8-W sum-frequency laser for adaptive optics

The design and characteristics of an 8 watt diode laser pumped version of the sum frequency laser designed for astronomy is described together with an outline of field test undertaken on the NOAO Vacuum Telescope Tower at Sac Peak. Optical pumping effects were shown to increase the return by a factor of 2.5 subarcsecond beacons were produces with a brightness equal to a 9.2 magnitude star with 1.2 watts incident at the sodium layer under sodium abundance column density of 5 X 109 atoms/cm2.

Investigation of wavefront estimators using the Wavefront Control Experiment at Yerkes Observatory

The Wavefront Control Experiment (WCE) is a zonal adaptive optics system that has been used to test many different matrix wavefront reconstructors. This has influenced the choice of reconstructors for experiments conducted using the Wavefront Control Experiment at Yerkes Observatory, at the Starfire Optical Range 1.5 m telescope, and the Chicago Adaptive Optics System (ChAOS) at the Apache Point 3.5 m telescope. The matrices are generated from a Macintosh software package, called A+, with a graphics user interface. The mathematical basis of many of the reconstructors is outlined, along with our experience using them, and thoughts about future reconstructor concepts.

Performance of ChAOS on the Apache Point Observatory's 3.5-m telescope

The Chicago Adaptive Optics System has been installed on the 3.5 meter ARC telescope at Apache Point for two years. Strehl improvements of 12 are obtained at 0.85 microns in 1- 2 arcsecond seeing. The major limitation in performance is set by the telescope vibrations.

Description of the Chicago Adaptive Optics System (ChAOS)

This paper describes some of the history and the current design of the Chicago Adaptive Optics System (ChAOS). ChAOS is a facility AO system using a sodium layer laser beacon which is due to be permanently mounted on a 3.5 meter ARC telescope located at Apache Point New Mexico. First light is expected in 1995.

Horizontal adaptive optics research at Yerkes Observatory

Horizontal adaptive optics research has been conducted at Yerkes Observatory since the first tests in 1994. This includes the study of wavefront reconstruction techniques, isoplanatic angle measurements, branch points in the phase function, and combined adaptive optics and phase diversity experiments.

Increasing the useful field-of-view of an adaptive optics system

The size of the corrected field of view of an adaptive optics system is though to be a severe limitation on the usefulness of an adaptive optics system. We show that under good seeing conditions the useful field of view is an order of magnitude larger than the field predicted by the classical isoplanatic angle. The corrected field of view is experimentally shown to increase when using spatially degraded wavefront corrections. Two methods of spatially degrading the wavefront were tested: low-order modal wavefront reconstructions and the use of a low-altitude Rayleigh wavefront reference beacon. In both cases the on- axis performance is sacrificed for an increased field of view.

Adaptive optics research at Yerkes Observatory

We summarize the history and our current and planned adaptive efforts using the telescopes at Yerkes Observatory.

Coupling efficiency of starlight to low-order-mode optical fibers using adaptive optics: rationale and experiments using the Wavefront Control Experiment

Planetary detection using doppler shifts requires very high resolution spectrographs which are stable over periods of years. Single or low order mode optical fibers have advantages in this application since they produce spatially scrambled Gaussian input illumination and diffraction limited size input image for spectrograph slit. Very high resolution spectroscopy is thus possible with modest dimensions of the spectrograph. This results in greatly lowering the cost of spectrograph and increasing the stability. However, adaptive optics system is needed to improve the light coupling efficiency. This paper reviews the potential of this technique and presents some preliminary laboratory experiments with the Wavefront Control Experiment (WCE). Plans of future experiment after installing the WCE in a Coude room of a 40 degree(s) reflector telescope at Yerkes Observatory are also presented.