Motivation
The purpose of this research is to determine how well we can use a TI Digital MicroMirror Device (DMD) to control and manipulate optical wavefronts.
Our main goal in this project is to determine the feasibility of using this DMD chip in Adaptive Optics, in particular, uplink Laser Guide Star correction.
In Adaptive Optics, a reference wavefront is usually required in order to correct for atmospheric aberrations.
This wavefront is usually provided by a very bright star (Guide Star) that is within close proximity of the area of sky under study.
However, a bright enough Guide Star will not always be available for this purpose. In such a case, a Laser Guide Star is created.
A Laser Guide Star (LGS) is essentially an artificial star used in Astronomical Adaptive Optics imaging.
The LGS is formed by directing a powerful laser beam into the atmosphere, where it travels 90km to the sodium rich mesosphere.
The energy from laser beam then excites the sodium atoms, emitting very bright light at 589 nm.
A bright light source is then created, which could then act as an artificial Guide Star. However, this technique is greatly limited by atmospheric aberrations since the laser's wavefront will get distorted as it travels through the atmosphere.
In effect, this will diffuse the collimated beam of light, making the LGS smudged and disfigured instead of being sharp and focused.
Theories suggest that if we knew exactly how the atmosphere distorts the laser's wavefront we could effectively correct the wavefront before it is sent into the atmosphere. In other words, if knew exactly how the atmosphere will distort the wavefront, we could apply the exact opposite effect to wavefront before sending it into atmosphere. This would effectively neutralize the effect of atmospheric distortion, making for a much more defined and focused LSG.
To do this though, we would need a device that has the capacity to manipulate an optical wavefront to a very high degree of accuracy. We think that our TI Digital Micro-Mirror Device (DMD) has such capabilities. This project will seek to test and demonstrate the DMD's capability of performing such this task.
The ability to adeptly control optical wavefronts also has potentially many different applications of science. Fields such as medical imaging and laser communication use laser techniques that heavily rely on wavefront control. We hope that our technique of wavefront control using the DMD chip will find useful implementations in these fields as well.
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