Characterization of emission from thermo-optical tweezers during spontaneous self-assembly

It is well known that thermo-optical tweezers leads to deposition of continuous patterns on substrates mediated by Marangoni convection currents around micro-bubbles. While performing the deposition, we also find that there is an accompanying emission. On first look, one would expect this to be thermal broadband emission. However, the spectrum of emission seems to start from green and extend all the way to near infra red. Such peak wavelengths would correspond to 3000 K or even higher. Generation of such high temperatures at the local hot spot would melt the glass substrate. However, such melting facets have never been seen. Thus we speculate that the emission is actually two photon fluorescence from the incident light on the deposited pattern. Soft Oxometallate material is known to exhibit photoluminescence in the green-red region of spectrum. This kind of emission is also observed in carbon nanotubes when incident with a focused 1064 nm light, the origin of which appears to be similar multiphoton fluorescence processes.