New photothermal deflection technique to discriminate between heating and cooling

•Microscopic of CdSe/ZnS using anti-Stokes luminescence was confirmed.•Newly proposed photothermal deflection technique does not require multiple lasers.•Deflection of probe beam with respect to pump beam is an indicator of cooling.

Photothermal deflection spectroscopy (PDS) is a highly sensitive and precise technique that is used to measure the optical absorption and thermal characteristics of a sample. While most applications of PDS utilize a heating beam, laser cooling of solids, or optical refrigeration as it is sometimes called, use this technique to determine if a laser is cooling or heating a sample. Current PDS methods for laser cooling require multiple laser wavelengths in both the Stokes and anti-Stokes region to ensure that cooling is occurring. This can cause problems if lasers must be changed or no lasers in the desired wavelength are available. Herein, we present a photothermal deflection technique that uses the deflection of the probe laser to determine if microcooling is occurring inside a sample.