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Day 1: OSA Materials for Optomechanical Actuation Incubator

Michael Forkner, OSA & SPS

This OSA Incubator has the intriguing title of Materials for Optomechanical Actuation. Optomechanical actuation is the act of turning light (electro-magnetic energy) into mechanical work. This most commonly calls to mind photovoltaics and solar cells. Solar cells take the energy of the sun and converts it into electricity, which then in turn can be used to do mechanical work. The use of electricity as a mediator is currently the easiest and most efficient way to do mechanical work from light, but there are several other ways light can do mechanical work. The Hosts for this program Chris Bardeen, University of California Riverside; Antti Makinen, Office of Naval Research; Peter A. Morrison, Office of Naval Research; and Ravi Shankar, University of Pittsburgh hope to explore a few of these areas.  
One way is to use the fact that photons, though massless, carry momentum. Any object that absorbs photons will also absorb their momentum. This momentum is so small that normally we would never notice, but by using optical resonators and accurate measurement devices, photon momentum can be used as an optomechanical actuator. Another, stronger way for photons to perform mechanical work is through the transfer of the photon’s energy into thermal energy. When photons are absorbed, some of their energy is typically converted to heat. The heat absorbed can cause a gradient and this temperature gradient can do work by bending or distorting a material mechanically. 

However, possibly the most exciting method for optomechanical actuation is using photon absorption to initiate nuclear rearrangements. One way this happens is when a photon excites a molecule into a different physical configuration, which shrinks or grows the molecule in some direction.  This change creates a large amount of force that can be used to do work. With this method, it is possible to shine light on a material to create stresses that result in macroscopic shape changes, such as 90 degree bends, as well as to reverse the effect when the light is removed.  This creates a new way to do work in a system without a flow of electricity.
During the program introduction, Incubator host Dr. Chris Bardeen brought up some questions for the field of optomechanical actuation: How do we asses and compare photomechanical materials? Are there new materials that can provide qualitative improvements in stability, reversibility, and force generation or should we focus on improving known materials? What are the appropriate Figures of Merit for these materials?
This Incubator program was designed to help answer these and other questions. Throughout day one, speakers discussed what materials systems they are working with, what Figures of Merit they have thought about and what limitations they have seen. By sharing their research results and viewpoints with other specialists in their field, they have been able to explore common problems work towards the best solutions.
Day 2 of this OSA Incubator will provide more insight into the answers to the questions Dr. Bardeen posed. Stay tuned!

Kaushik Bhattachary, California Institute of Technology, discussing a aontinuum perspective of actuating with light.

Pance Naumov, New York University, Abu Dhabi, kicks off his presentation on Quantification and Modeling of Dynamic Effects in Molecular Crystals discussing natural actuators. 
Image for keeping the session alive