Highly-sensitive quantitative thermal microscopy using gold nano-particles as heat sources

Thermal imaging based on Quadriwave Lateral Shearing Interferometry (QWLSI) is able to measure temperature fields from the temperature-induced refractive index changes of the medium surrounding a heat source. The conventional arrangement employed a continuous wave laser source to illuminate nano-particles and a wavefront analyzer (SID4Bio) to perform QWLSI. With this arrangement, a resolution of 1°C is achieved on the temperature variation measurement. We present a system implementing a synchronous detection modality. By modulating the laser source locked-in with the SID4Bio camera we get rid of the low-frequency noise and so increase the sensitivity of the temperature variation measurement.