A small displacement sensor for dynamically measuring small forces is presented. Employing a coupled-cavity laser configuration constructed with a moving external mirror, this sensor provides high sensitivity with a minimum detectable displacement of 0.8 nm, independently of the lasing wavelength, while the lasing state is mechanically stabilized by a negative-feedback loop to maintain a constant external-cavity length. The sensor is shown to be of great use for detecting extremely small distortions in a stiff cantilever, reflecting transient variations in small friction forces in mechanical systems.
© 1998 Optical Society of America
Yoshitada Katagiri and Kiyoshi Itao, "Dynamic Microforce Measurement by Distortion Detection with a Coupled-Cavity Laser Displacement Sensor Stabilized in a Mechanical Negative-Feedback Loop," Appl. Opt. 37, 7193-7199 (1998)