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.