A unique range of continuous wave laser sources spanning the entire spectral range, from 210 nm to 10.8 μm, is one of the most important assets of the Optical Radiation Measurement group. The main purpose of the facility is to provide radiant power stabilised radiation as well as irradiance-stabilised radiation to measure accurately the characteristics of detectors and associated instrumentation.

Tunable radiation from the facility is also widely used to measure the transmission of optical components - filters, crystals, lenses and so on - making use of the accurately known wavelengths, high spectral radiance and fine spectral resolution available from laser radiation.

Available laser power outputs range from watts down to picowatts and can be focused to diffraction limited spots for high spatial resolution work. The group has also developed novel methods of processing the Gaussian output profile of the lasers to produce beams which are spatially uniform in irradiance, as well as monochromatic and depolarised. Output powers can be stabilised to one part in 100 000, resulting in an extremely stable source.

Laser sources include all the standard commercially available lasers together with many custom designed sources to provide a nearly continuous spectrum from the UV to the mid-IR. Recent additions include a Cr⁴⁺ laser. This laser produces radiation from 1.38 μm to 1.55 μm, wavelengths suitable for fibre optic communications, but with power levels of several hundred milliwatts.

The suite of lasers is often used to generate high stability, monochromatic lights sources for use in a wide range of experiments. NPL has developed a unique technology to turn laser radiation into a uniform, non-coherent monochromatic light source.