Can You Trap Light?

Concept Form

The “light trap” is an invention which slows down and traps light into a rolled up Nautillus shell or cylinder for the purpose of retaining light throughout the day inside the device and time-offsetting the release of the light by the number of daylight hours so that the first ray of light entering the device at dawn is the first ray of light released by the device at sunset (it is a passive streetlight or car headlamp technology). The functionality can be achieved by depositing an effective BEC on the surface of a thin film sheet and rolling up the effective BEC-thin film composite; there are variations of an enclosed or open system as well as using an actual BEC or Fabry-Perot cavities for the light trap aspect.

1. Bose Einstein Condensate

   Utilizing a BEC to slow down light is a theoretically viable idea, however current technology does not allow for its commercialization at this time.  From the paper, A high-flux BEC source for mobile atom interferometers (2015, New J. Phys.), a BEC is generated by loading a cold atomic beam into a chip that first traps atoms using laser-cooling and then magnetic traps them for about 1.6s. Approximately, 105 rubidium-87 atoms can be produced at a 1 Hz rate. Unfortunately, this experimental chip is not ideal for our light trap application as it would take considerable experimentation and effort to integrate this with a light source to slow its velocity. The original proposed idea of an effective BEC sol gel however would have worked well in this scenario but it only has a lifetime on the order of picoseconds (see Room-temperature Bose–Einstein condensation of cavity exciton–polaritons in a polymer (2014, Nature)).

   Another idea for the light trap invention was to use a convex lens to focus a large amount of light into a single point. At the focal point a concave lens will be put to straighten the rays out. Now all of the light is concentrated down to a single point. We will bounce the light at various angles so it goes from being initially vertical to almost completely horizontal. By reducing the area of the device we can use a small amount of Bose-Einstein Condensate to slow it down as the light bounces off of a nearly perfectly reflective surface back and forth through it.  Doing so will allow us to trap the light for a period of time.

2. Other Light Trapping Methods
   • We could use some other material other than a BEC that will slow down light (even glass slows down light 33%). This could be used instead or we could come up with a Fabry–Pérot interferometer where we can have the light going almost completely sideways to increase the path of the light so it takes another 8 hours or so to hit the ground; placed inside a house, it could catch light from outside and release it at night thus naturally brightening the house circumventing electrical lighting.
   • If this is something we pursue in the future it cannot be in an environment where the temperature changes since this will make the material expand or contract and if it isn’t accurate down to the nanoscale the device won’t work.
   • Since destructive interference destroys the light rays, it is an intricate geometry problem to determine the minimally destructive internal trapping structure.