Efficient propagation of light through the atmosphere requires the compensation of phase distortions induced by the atmosphere, thermal lensing, thermal blooming, or aero-optics. We have developed a deformable mirror engineered to compensate these aberrations while reflecting high power radiation with minimal heating and thermally induced distortion. We present the results of a multi-year effort to address many of the challenges with existing state-of-the-art designs while reducing cost, complexity, and manufacturing time.
Polymer membrane deformable mirrors offer a low-cost alternative to conventional technology in a wide variety of
adaptive optics or laser beam shaping applications. In this paper we evaluate the suitability of two different kinds of
polymer membrane deformable mirrors for laser machining. We present results showing that a 12.5-mm diameter
nitrocellulose membrane fails near 400 microns of motion. We present results from a demonstration of a high peak
power beam shaping and show a new compact laser beam shaping system using a polymer membrane deformable
mirror. We evaluate the effect of Q-switched laser radiation on polymer membranes at 355nm and 1060nm.
Effective application of membrane deformable mirrors requires understanding of the operating
characteristics of these devices. Using custom developed hardware and software tools, we were able to
quantify the temporal and spatial response characteristics of a membrane deformable mirror. Temporal
characteristics were analyzed using a frequency sweep stimulus while measuring the DM response on a
feedback photodiode. Spatial characteristics of the DM were analyzed in terms of its ability to reproduce
Zernike polynomials of increasing order using a variety of actuator patterns. We present here both the
techniques for performing these measurements and the results from simulation and the laboratory.
The performance of laser machining systems can often be improved by adjusting the intensity profile of the
beam on the target. Shaping a laser intensity profile can be efficiently accomplished by adjusting the
spatial phase of the beam before propagating the beam a distance to the target. Beam shaping can be
accomplished with passive diffractive elements, but this technique is only capable of creating a single
intensity profile and is usually very sensitive to the input beam characteristics. Beam shaping with active
optical elements like deformable mirrors can enable the system to achieve multiple shapes and compensate
for non-ideal input beams, but can be very expensive. We present here a demonstration of laser beam
shaping with low-cost membrane deformable mirrors.
Metric adaptive optics systems search over a set of wavefront modes or commands to actuators to
optimize a system performance metric like Strehl ratio or brightness. These systems have been explored
for many decades and have been thought to be unreliable due to local minima in the metric space. It has
been shown that some modes match well with no local minima to a given metric, but they rely on the
ability of a mirror to create reliable replicas of the search modes. We present here a study of the most
common implementation of metric adaptive optics that involves searching over the actuator command
space while evaluating an intensity-based metric. We map an error space relating a common metric to
actuator commands and statistically analyze the error function to determine the quantity and location of the
The application of adaptive optics has been hindered by the cost, size, and complexity of the systems. We describe here
progress we have made toward creating low-cost compact turn-key adaptive optics systems. We describe our new low-cost
deformable mirror technology developed using polymer membranes, the associated USB interface drive
electronics, and different ways that this technology can be configured into a low-cost compact adaptive optics system.
We also present results of a parametric study of the stochastic parallel gradient descent (SPGD) control algorithm.