Science

A portion of our research efforts are based around optical cavities. These are a way to confine and trap radiation within small physical structures, such that the electric field builds up very strongly. Such strong electric fields enable one to obtain micro-lasing, for example, or build very tiny optical sensors in which the strong electric field is used to measure the properties of the surrounding medium.

The following few pages are a lesson on how these optical resonances form. They come from some general interest talks I've given in the past few years, although perhaps a bit more technical. In future, I hope one day to add other lessons talking about different aspects of the things we're interested in, such as quantum dots or biolasing.

Lesson 1: Resonances

lesson 2    lesson 3    lesson 4    lesson 5

In our research, we study "optical" resonances called whispering gallery modes. To understand this strange-sounding phenomenon, we can discuss something called "resonance" first. Resonances are super-common in everyday life and explain all kinds of fundamental phenomena, including chemical bonds, subatomic particles, musical instruments, and even the tides in the Bay of Fundy.

Resonances go all the way back to what most of us learned in first-year or high-school physics. The simplest example is the standing wave on a string. These are special waves that appear to remain stationary, and have very large amplitudes. They're actually made from many traveling waves running back and forth along the string and interfering with each other. The first four standing waves on a string are shown below. In each case, the string is oscillating with a specific frequency. The only "allowed" frequencies at which a standing wave on a string can form are for integer multiples of the first allowed frequency.

 

 

Note that each resonance has nodes - that is, regions on the string that aren't moving. The two blue dots are nodes, but all of the waves except the first one have additional nodes halfway between the regions of highest oscillation.

On to lesson 2.