Temperature dependence of the photothermal laser cooling efficiency for a micro-cantilever

The relationship between the photothermal cooling efficiency of a micro-cantilever's mechanical mode and the environmental temperature is studied. The micro-cantilever and a polished fiber end form a low finesse Fabry—Perot (FP) cavity. Experimental results in a temperature range from 77 K to 298 K show that temperature has an obvious influence on photothermal cooling efficiency. The photothermal cooling efficiency, η_ph, at 100 K is 10 times that at 298 K. This accords well with the theoretical analysis that the high photothermal cooling efficiency can be achieved when photothermal response time, τph, and mechanical resonant frequency, ω₀, are close to the optimal photothermal cooling condition ω₀τ_ph = 1. Our study provides an important approach for high effective photothermal cooling and high-sensitivity measurement for force microscopy. (condensed matter: electronic structure, electrical, magnetic, and optical properties)