1. Free-Space Communication for Autonomous Sensors using Grating Light Modulators
David R. Pedersen, Michael H. Guddal
University of California, Davis
Olav Solgaard
Stanford University

2. Outline Summary of Year 1 Milestones Improvements in GLM design
Developed, modeled and characterized GLM
Demonstrated free-space optical link using GCC modulator
Improvements in GLM design
Reduce angle dependence and dispersion
Increase damping
No interference with plasma => “buried” GLM
Year 2 Milestones
Integrate micromachined GLM with on-board power
Buried GLM, through-the-wafer interconnects, wafer bonding

3. GCC Communication Link

4. High Contrast GLM Reduced Angle dependence Reflective State
Diffractive State
Increased damping

5. Full-wafer Grating Light Modulators
Period: 10
Gap: 10um
Beam Width: 10um
Substrate/Beam Spacing: 2um
Beam Length: 200um to 600um
Beams: Doped low stress polysilicon Insulating Material: PSG

6. Lay out
Each line: 2mm open-circuit region etched to the substrate and aligned with the front
Front
Backside contact to the substrate
Back

7. Buried Grating Light Modulators - Technology Development
DRIE trenches for interconnects
and corner-cube reflectors
Oxidation-smoothed
TIR surface
AR-coating
GLM aperture

8. Autonomous Sensor Wafer with Buried GLMs

9. Conclusion Met Year 1 Milestones: Full-wafer fabrication process
Fabricated and tested micro-machined GLMs
Demonstrated free-space communication
Full-wafer fabrication process
Year 2 Milestones
Integrate micromachined GLMs with on-board power, sensors, and electronics sources
Technology development
Buried GLMs
Through-the-wafer interconnects
Wafer bonding