Theoretical Consideration on Potential and Scalability of Optical Rotors based on a pn-Junction Rod

Abstract

This paper theoretically investigates how a Si pn-junction rod offers the potential to develop rotating motion. An analytical steady state solution of excess carrier concentration of the Si rod is derived from the continuity equation. The solution is given by a non-linear differential equation. Numerical calculation results strongly suggested that a 200 µm-long Si rod should rotate with the acceleration of ~103 m/s2 under the illumination of 1 W/cm2. This is very good performance. It is also shown that this performance holds even for nano-scale rod rotors. It is expected that such rotors will suit various medical test chips that have no battery.

Keywords

• pn junction
• rod
• light illumination
• rotation
• carrier generation
• recombination
• power generation