At the Gemini front end is a high power, ultra-short pulse, high repetition-rate laser. It uses titanium-doped sapphire (TiS) as its active material, and works at 800 nm in the near infra-red part of the spectrum, just outside the region visible to the human eye. Experiments on Gemini produce bright, coherent x-ray sources, or energetic beams of electrons and protons.
The pulses from the Gemini front end are so short that they are like sheets of light energy thinner than a human hair, which in addition can be focused to a spot a few thousandths of a millimetre across. The energy they contain is thus delivered to a very small target extremely quickly, allowing experimenters to study the way matter behaves under extreme conditions of temperature and pressure.
The Gemini laser can deliver thirty times as much energy in each of two beams. With 30 joules on target in two beams, an intensity greater than 1021 W cm-2 and a repetition rate of three shots per minute, the extreme concentration of energy possible with Gemini makes it one of the most intense lasers in the world.