Laser Doppler vibrometer

Abstract: We describe a new and highly effective optical frequency discriminator and laser stabilization system based on signals reflected from a stable Fabry-Perot reference interferometer. High sensitivity for detection of resonance information is achieved by optical heterodyne detection with sidebands produced by rf phase modulation. Physical, optical, and electronic aspects of this discriminator/laser frequency stabilization system are considered in detail. We show that a high-speed domain exists in which the system responds to the phase (rather than frequency) change of the laser; thus with suitable design the servo loop bandwidth is not limited by the cavity response time. We report diagnostic experiments in which a dye laser and gas laser were independently locked to one stable cavity. Because of the precautions employed, the observed sub-100 Hz beat line width shows that the lasers were this stable. Applications of this system of laser stabilization include precision laser spectroscopy and interferometric gravity-wave detectors.

Abstract: Keywords: anemometrie a : laser ; anemometrie ; optique ; laser : Doppler Reference Record created on 2005-11-18, modified on 2016-08-08

Abstract: Preface.- Introduction.- Basic Measuring Principles.- Fundamentals of Light Propagation and Optics.- Light Scattering from Small Particles.- Signal Generation in Laser Doppler and Phase Doppler Systems.- Signal Detection, Processing and Validation.- Laser Doppler Systems.- Phase Doppler Systems.- Further Particle Sizing Methods Based on the Laser Doppler Technique.- Fundamentals of Data Processing.- Processing of Laser Doppler Data.- Processing of Phase Doppler Data.- Choice of Particles and Particle Generation.- System Design Considerations.- Appendix.- Bibliography.- Index.

Abstract: In this letter, we present the microfabrication and application of arrays of silicon cantilever beams as microresonator sensors with nanoscale thickness to detect the mass of individual virus particles. The dimensions of the fabricated cantilever beams were in the range of 4–5 μm in length, 1–2 μm in width and 20–30 nm in thickness. The virus particles we used in the study were vaccinia virus, which is a member of the Poxviridae family and forms the basis of the smallpox vaccine. The frequency spectra of the cantilever beams, due to thermal and ambient noise, were measured using a laser Doppler vibrometer under ambient conditions. The change in resonant frequency as a function of the virus particle mass binding on the cantilever beam surface forms the basis of the detection scheme. We have demonstrated the detection of a single vaccinia virus particle with an average mass of 9.5 fg. These devices can be very useful as components of biosensors for the detection of airborne virus particles.