Helium-cadmium laser
The helium-cadmium lasers are metal vapor gas lasers for the blue and near UV spectral range .
- Power: 10… 200 mW
- Coherence length : approx. 30 cm
- Wavelengths : 325.0 nm (UV), 353.6 nm (UV) and 441.6 nm (blue)
- Applications: basic research, materials science, medical technology
- Cost: approx. € 12,000 for a new device
Helium-cadmium lasers consist of a vacuum-tight welded tube filled with helium and cadmium metal vapor . They emit in the blue or ultraviolet spectral range and, before the introduction of diode lasers with similar wavelengths, were almost the only continuously and reasonably economically operable laser sources in the blue and UV range. Two wavelengths of the helium-cadmium plasma can be used to generate the laser beam, the 325 and the 442 nm line. However, the plasma emits many more lines that are often disruptive and can be filtered out using a combination of prisms.
A helium-cadmium laser has a typical service life of around 10,000 hours. Due to its high cost, it is mostly only found in scientific institutions. Because of its high beam quality and coherence length compared to diode lasers, it is sometimes indispensable for examinations in the near ultraviolet spectral range.
With its typical performance, the helium-cadmium laser has laser protection class 3B and its beam must neither get into the eye nor should the skin be brought into the laser beam. Its 325 nm laser spot itself is invisible, but it causes fluorescence on many materials , which can be seen as a brightly shining blue spot. The 442 nm laser line is visible as blue light.
Typical applications are holography , spectroscopy or cancer prevention techniques.