Surface and average volume temperature measurements in semitransparent media based on multispectral thermotransmittance

Temperature plays an essential role in maintaining the performance of microsystems, which calls for three-dimensional mapping of heat sources, hot spots and thermal properties. In this context, infrared (IR) thermography provides information for opaque materials but faces limitations when applied to semitransparent samples such as microfluidic chips or semiconductor materials in the IR range. In this article, we present temperature maps obtained for the surface and average volume of two semitransparent samples with a detection limit of 1 K. To achieve such measurements, we demonstrated that thermotransmittance signals can be decomposed into two parts: the first originating from interfaces and the second originating from the volume. We quantified the contributions of both components by combining contactless measurements with a heat transfer model. We then validated the method using two Borofloat glass samples with different thicknesses. We were able to discriminate the contributions of surface and volume temperatures by performing spectroscopic thermotransmittance measurements at wavelengths ranging from 3100 to 3400 nm due to the different spectral behaviors of these two components. This new technique is an important improvement for temperature measurements using IR cameras in semitransparent media.