MatCalorie™: Absorption Measurement for Laser Optics Application Note

Author: Christopher Lee – R&D Manager

Absorption coefficients of optical components in high-power applications are an important parameter in determining the quality of optical components. Optical components with higher absorption coefficients absorb a larger proportion of the optical beam which may result in thermal runaway. This phenomenon affects the quality of laser beams, undermining the quality of laser machining processes. As such, it is important for end-users to employ optical components with small absorption coefficients.

Operation Principle

MatCalorie™ is the world’s first commercial absorption measurement system for optical components. In compliance with the ISO standard, this instrument is based on the principle of calorimetry where the optical component is illuminated by a collimated laser beam. A portion of the laser energy is absorbed and converted to heat which manifests as the temperature of the optical component rises under testing.

The system is fully automated and customizable to laser operating wavelengths at 1um and 10.6um calorimetric measurements to determine the total (surface and bulk) absorption coefficient of relatively thin samples (2mm-9mm). It is operational in transmission and in 0/45° reflection modes.

The key specifications are listed in table 1:

ModelMat’C-1umMat’C-10umMat’C-1um-10um
Laser SourceYAGCO2YAG & CO2
Wavelength1 μm9.4/10.6 μm1 & 10.6 μm
Power~10 W~10 W~10 W
Stability<10%<3%< 3% & <10%
AlignmentVisible beamVisible beamVisible beam
SamplesTransmission windows, focusing lens, reflective
mirrors, etc.
Transmission windows, focusing lens, reflective
mirrors, etc.
Transmission windows, focusing lens, reflective
mirrors, etc.
Absorption
Resolution
0.01%0.01%0.01%
Table 1. Key specifications of MatCalorie™

The key indicative feature of our product is the design of the vacuum chamber which allows for its compact size. Other features include automated functions to provide a turn-key solution for absorption coefficient measurements on the factory floor. The laser calorimetry design is based on duo-sensors differential thermal measurements. Multi-effect scattering elimination has been achieved by a miniaturized chamber design. A three-point algorithm has been implemented in the software. The improvements of the developed calorimetry system over competitive technologies, albeit non-commercially available, are high in resolution, simplicity, and cost-effectiveness. The innovation has been featured by SPIE in 2014.

Laser Calroimetry 1
Figure 1. Mid-IR MatCalorie equipment

Applications

The system now boasts industry 4.0 capability, integrating system data as feedback to determine the health of the components in the system. This technology ensures maximal functionality for absorption measurement.

Laser Calroimetry 3
Figure 2. MatCalorie GUI

The system could be used in but not limited to the following application scenarios:

  • Bulk absorption of new or unique materials.
  • Bulk absorption of material used in 3D additive manufacturing.
  • Coating quality and substrate characterization in manufacturing processes.
  • Applicable Materials: ZnSe/Fused Silica/Copper Mirror/Diamond/Polished Steel etc.

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