Thermally Activated, Variable Blazed Grating for Coherent Beam Steering
Abstract
The ability to perform non-mechanical optical beam steering is of critical importance in laser communication and remote sensing; it is as vital as a phased-array antenna is for RADAR. Directed energy transmission and direction-selective reception increase performance and produce tactical advantage in DoD applications. However, specific geometric features of non-mechanical beam steering devices must be designed in proportion to the wavelength of the monochromatic light to be steered. Also, the ability to handle higher energies by reducing the energy per unit requires large areas of uniform properties on the micrometer scale. These challenges have been addressed in the past using liquid crystals (LC) to produce a peak steering angle of 4 degrees, albeit limited by problems due to the fringing field effect. Recent advances in micro-fabrication techniques, including the synthesis and manipulation of certain electro- and thermo-optic materials, hold new opportunities for efficient beam steering solutions. The objective of this thesis research is to demonstrate thermally controllable beam steering, and enable further investigation of efficiency and response time and their dependence on geometry. The design, fabrication and performance of such a thermally-activated, nonmechanical beam steering device is demonstrated for the first time herein. The elastomeric media, polydimethlyoxane (PDMS), was used as the active, phase-controlling agent. Its temperature-dependent index of refraction was employed in a reflection-mode device by depositing it on a stair-step-approximated, blazed grating. The periodic nature of the device contains the reflected beam within discrete, angular orders. The proofof- concept device is modeled, tested and analyzed to explain its observed performance. Angular control of up to 1.2 degrees has been experimentally demonstrated. This approach promises simplicity of design and fabrication without thelarger,
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 2007
- Accession Number
- ADA469501
Entities
People
- Matthew T. Johnson
Organizations
- Air Force Institute of Technology