Meaning
Measurement procedure for determining the absolute absorption loss of optical components by monitoring temperature changes during laser irradiation. Heat conversion from light energy is quantified by laser calorimetry, which is required for high-power laser systems where tiny losses cause thermal lensing. This technique provides higher sensitivity than ratiometric power measurements for very low absorption materials.
Thermal Response
Sensors attached to the edge of the sample record the temperature rise while a laser of known power passes through the center. Once the laser is turned off, the cooling rate is observed to account for heat transfer to the surrounding environment. Laser calorimetry calculates the absorption by correlating the slope of the heating curve with the mass and specific heat of the component.
A stable thermal environment is necessary to prevent noise from masking the small temperature changes.
Accuracy Condition
Isolating the sample from drafts and external heat is necessary.
Quality Validation
Optics suppliers use this method to audit the cleanliness of their polishing and coating processes. If laser calorimetry reveals absorption levels above the design specification, it usually indicates sub-surface damage or chemical residues from the fabrication step. Identifying these flaws early prevents the catastrophic failure of lenses during the final power-up of a multi-kilowatt industrial system.
