Miniaturized Nd-YAG laser as photoelastic transducer for small forces sensing

LABORATOIRE COMMUN DE METROLOGIE, LNE-CNAM, 61 rue du Landy, case I36 - 93210, La Plaine Saint-Denis, France

^a Email de correspondance de l’auteur : naceur.khelifa@cnam.fr

Abstract

Measurement and traceability of small forces (< 0.5 N) to the International System of Units (SI) remain a challenge for research and industry. For this purpose, we have developed a force sensor based on the photoelastic effect in a solid-state laser. At lower stress levels the induced shift in frequency between the two orthogonal polarizations, associated to a longitudinal laser mode, is proportional to the intensity of the force acting on the laser medium. From theoretical predictions, we show that high sensitivities can be obtained with miniaturized monolithic Nd-YAG laser. A short description of the used photoelastic force sensors is reported with a focus on his static response with an inventory of influencing parameters. The sensitive element of the force sensor is a plan-plan cylindrical monolithic Nd-YAG laser (2 mm in length and 3 mm in diameter). The overall uncertainty, estimated from beat frequencies measurements, comes mainly from reproducibility. Accordingly, with this kind of sensor it is possible to achieve high sensitivity required for measuring of small forces at the level of micronewton, but it still, at least for actual size sensor, more suitable for measurement in the range from 100 µN to more than 1 N.