What is a halogen light source?

A halogen light source is a technologically improved incandescent lamp that mostly has a bulb made of quartz glass and is filled with halogen gas. It generates light with a thermal energy distribution.
As with conventional incandescent lamps, light is generated by causing tungsten wire to glow. It operates at a temperature (above 2800 k) that is significantly higher than with incandescent lamps (approx. 2100 k) and therefore emits more intense light with a greater proportion of blue and green. Due to the quartz glass of the bulb, the increased heat is not as easily emitted into the environment. The spectrum of a halogen light source corresponds very closely to that of a black body.

Because atoms at these temperatures are constantly evaporating from the tungsten wire, the bulb is filled with a halogen gas. Tungsten halides are formed. These decompose again close to the hot filament, causing the metal atoms to attach themselves again to the filament. The metal wire virtually repairs itself.

Due to the high temperature of the tungsten wire, halogen light sources emit a light spectrum that begins in the near-UV range, has its maximum at around 1 µm and extends to around 3 µm. As a result, halogen light sources are suitable for many applications in spectroscopy. However, their luminance is low compared to LED or plasma light sources. The choice of filling gas can influence the light spectrum.