Miniaturized, high temperature black body radiation source

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Technology abstract

Miniaturized thermal radiation sources are important for miniaturized optical instruments, such as micro spectrometer. To have sufficient sensitivity of the instrument the number of photons emitted by the radiation source should be as high as possible. In miniaturized sources, with reduced surface area, this can be obtained by increasing the specific radiation power. The low thermal mass of the system and the laser heating are ideal for a fast switching black body radiator.

Technology Description

Miniaturized thermal radiation sources are important for miniaturized optical instruments, such as micro spectrometer. To have sufficient sensitivity of the instrument the number of photons emitted by the radiation source should be as high as possible. In miniaturized sources, with reduced surface area, this can be obtained by increasing the specific radiation power.

In case of thermal radiation sources this is obtained by increasing the temperature of the radiator. In the new miniaturized thermal radiation source, presented here, a tiny piece of ceramic, the absorber emitter, is heated with laser radiation.

The ceramic is made of silicon carbide, selected because of the high temperature and temperature shock stability of this material. The emission and absorption coefficient of radiation depends on the intrinsic properties of silicon carbide, but depends also on the structure of the surface of the absorber/emitter. A number of small cavities, drilled into the surface of the absorber/ emitter, increase the absorption and emission coefficient. This structuring is used in that parts of the surface where laser radiation should be absorbed or thermal radiation should be emitted.

The low thermal mass of the absorber/ emitter and the laser heating are ideal conditions for a fast switching black body radiator.

Figure 1 shows a drawing of the high temperature black body radiation source with the absorber/ emitter heated with laser radiation. Hexagonal arranged blind holes in the surface area of the absorber/ emitter form a black body radiator. Diameter of a single blind hole: 40 µm. A thin sheet of zirconium oxide with low thermal conductivity is used to fix the absorber/ emitter in its housing.

In figure 2 is shown a picture of the absorber/ emitter made of silicon carbide mounted in a fixing structure with low thermal conductivity. The hexagonal arranged blind holes are visible in the centre of the absorber/ emitter.

Figure 3 shows the measured specific radiation power of the absorber emitter with a clear maximum in the centre, due to the blind holes in the surface.

Innovations & Advantages

Miniature high power black body radiator with the absorber/ emitter made of ceramic. The ceramic, silicon carbide, is very stable, ideal for a long working service. Independent from the intrinsic optical properties of the ceramic, the optical properties of the absorber/ emitter are adjusted by structuring the surface of the absorber/ emitter with blind holes. The low thermal mass of the absorber/ emitter and the laser heating are ideal conditions for a fast switching blackbody radiator.

Current and Potential Domains of Application

The miniaturized, high temperature black body radiation source is applicable as:

  • optical micro spectrometer
  • gas sensor