Berkeley Sensor & Actuator Center Smart dust Active Laser Transmitter (SALT) Matthew Last, Kris Pister Berkeley Sensor and Actuator Center

Berkeley Sensor & Actuator Center Free-space Communication Low-frequency Beam Steering (DC -> 1kHz) Smart dust Active Laser Transmitter (SALT)

Berkeley Sensor & Actuator Center Free-Space Communication using Agile Beamsteering What do we gain over RF? –High Antenna Gain Excellent performance: low power, long range, high bit rate 1mrad, 1mW beam = 318 kW /steradian Isotropic 1mW radiator = 80  W/steradian  Antenna gain of 152 dB for typical laser –No spectrum regulation issues –SDMA (Space-Division, Multiple Access) with imaging receivers –Only simple baseband modulation necessary (OOK)

Berkeley Sensor & Actuator Center Free-Space Communication using Agile Beamsteering (2) When to use? –Need Line of Sight –Need Clear Weather (no fog) At what cost? –Tight alignment tolerances –Only point-to-point networks (no broadcasting) –Unidirectional links yield asymmetrical networks

Berkeley Sensor & Actuator Center Long Range, Low Power Crosslinks (a)5.2 km Berkeley Marina (b)15.3 km Coit Tower (c)21.4 km Twin Peaks 3 mW optical power: And plenty of power to go further…

Berkeley Sensor & Actuator Center Current Work

Berkeley Sensor & Actuator Center Performance: Mechanical Angle of Deflection Unactuated (Probe Tip) Actuated (Thermal) In-plane 45 degrees11 degrees Out-of-plane Untested28 degrees

Berkeley Sensor & Actuator Center Actuation Power - 1 st Generation

Berkeley Sensor & Actuator Center Actuation Power – 2 nd Generation

Berkeley Sensor & Actuator Center 2 nd Generation Mirror Pictures:

Berkeley Sensor & Actuator Center Ongoing Projects: Lenses and lens systems –vary lens diameter –lens quality evaluation? Laser diode mount Prototype laser transmitter system (laser diode -> collimating lens -> 2-DOF mirror)

Berkeley Sensor & Actuator Center More Pictures:

Berkeley Sensor & Actuator Center Fun Numbers: divergence = 1.22 /d –1mm 650nm .79 mrad divergence –1mrad 650nm .79mm aperture 1mW 1mrad emitter puts out 40 times more power/steradian than a 100 W bulb