An exciting new paper by Liang Gao et al. in nature shows a way to take a movie of a single pulse of light. This opens up the ability to see non-repeatable events such as nuclear explosions, optical rogue waves or gravitational waves. These events happen on the femtosecond (10-15s) timescale that are one off events.
Before we get into the nuts and bolts of how it works here are the amazing movies they captured of a single pulse of light.
Light hitting a mirror will be reflected at the same angle it approaches the mirror. Something else you can see if the evanescent field (light tunnels through the material) which decays away exponentially over time. We can use this to perform spectroscopy on a surface.
Light will travel slower in a lower refractive index material here is a comparison of air and resin where the light in the resin is travelling slower.
Refraction occurs at the surface of a lower refractive index material and a higher refractive index material.
This is my favourite, Seeing the glow of molecules after they have been excited. They capture a phenomenon called fluorescence where light of a higher energy (green in this case) is absorbed by the molecule (Rhodamine) the excited molecules loses some of that energy to vibrations and then drops down to the ground state emitting lower energy light (red).
Here are all of the different experiments.
So how does it work. Here is my basic explanation feel free to correct me in the comments. Firstly an ultrafast laser pulse is needed these are generated using special laser cavities that bounce a laser pulse inside a cavity hundreds of times each time they destructively interfere inbetween pulses and constructively interfere only for a few femtoseconds - if you have ever made a diffraction pattern in on a wall (spatially) think of this as a diffraction pattern in time (temporally). The camera used is quite similar to the old CRT TVs but in reverse instead of electrons being scanned over a phosphorous screen that converts the electrons to light. Light hits a phosphorous screen where the photons of light are converted to electrons these are accelerated towards a camera sensor like in a cellphone and an image is created. However you apply a voltage ramp across the path of the electrons so they are deflected depending on when they arrive (you reduce the voltage as a function of time). This means electrons from light that arrived earlier will be deflected more by the electric field than electrons from light that arrives near the end. You can think of this as sophisticated light painting where you get a blur of colour by keeping the shutter open on a camera.
Here is a schematic of the optics used.
Gao, L.; Liang, J.; Li, C.; Wang, L. V. Nature 2014, 516, 74–77.