The measurement of very small light forces has wide applications in many fields of physics. A common measurement method for small force detection is the determination of changes in the dynamic behavior of mechanical oscillators, either in amplitude or in frequency. The detection of slowly varying forces mostly requires long period oscillators, such as a torsion pendulum. We demonstrate the application of a macroscopic, low-noise, torsion balance oscillator for the detection of radiation pressure forces at the femto-Newton level. The system is “precooled” (removing excess seimic noise) to be only thermal noise limited. The demonstrated force sensitivity reaches the thermal limit.
© 2008 Optical Society of America
Instrumentation, Measurement, and Metrology
Original Manuscript: December 12, 2007
Revised Manuscript: February 4, 2008
Manuscript Accepted: February 5, 2008
Published: March 5, 2008
F. Mueller, S. Heugel, and L. J. Wang, "Femto-Newton light force measurement at the thermal noise limit," Opt. Lett. 33, 539-541 (2008)