Atmospheric-compensation experiments in strong-scintillation conditions.

Most atmospheric-turbulence-compensation experiments have been performed under weak-scintillation conditions; conventional phase-conjugate adaptive-optics systems usually provide good correction for these conditions. We have performed an experiment over a 5.5-km horizontal propagation path to explore the efficacy of conventional adaptive optics in strong-scintillation conditions. The experimental results showed a significant degradation in correction as the scintillation increased. The presence of branch points in the phase appears to be the primary reason for the degradation in correction as the scintillation increases.

Experimental demonstration of atmospheric compensation using multiple synthetic beacons.

We present experimental results that demonstrate real-time, atmospheric-turbulence compensation of a bright star with the use of two synthetic beacons. Each beacon was used to measure the phase aberrations over only part of the telescope aperture, a configuration that is suitable for reducing focal-anisoplanatism error. To our knowledge, this is the first demonstration of atmospheric compensation with the use of multiple synthetic beacons.

Experimental observation of thermal-blooming phase-compensation instability.

We have made the first experimental observations to our knowledge of thermal-blooming phase-compensation instability. We identified the instability by impressing a spatial intensity modulation on the laser beam and watching this modulation grow as thermal-blooming compensation was performed with a 69-channel phaseconjugate adaptive-optics system.

Aberrations of the perfect grating rhomb.

The aberrations caused by a perfect grating rhomb beam sampler are calculated for a diverging beam. In the geometric optics limit a tilt does not appear, whereas astigmatism and higher-order aberrations are introduced by a perfect grating rhomb.

Thermal-blooming compensation using the CLASP system.

A closed-loop system for phase compensation of thermal blooming has been designed and tested. This system-called CLASP for closed-loop adaptive single parameter-is a single-mode outgoing-wave dither system. CLASP has demonstrated stable convergence to the optimum thermal-blooming-correction amplitude in a laboratory experiment.

Thermal-blooming compensation: experimental observations using a deformable-mirror system.

A laboratory experiment has demonstrated the effectiveness of compensating for forced-convection-dominated cw thermal blooming by using a deformable mirror to add phase corrections to the laser beam. In agreement with theoretical predictions, the peak focal-plane irradiance has been increased by a factor of 3 under severely bloomed conditions.