An Analysis Of The Photothermal Drive Of A Quartz Force Sensor

Abstract

This paper investigates the feasibility of running a quartz force sensor with an optical drive.The general theory behind optical (strictly speaking, photothermal) driving of a resonant structure is presented and this is used in conjunction with empirical results obtained from an existing system to clarify problem areas and to suggest improvements. A straightforward method for optical reading is briefly described.

Optical vibrating quartz crystal pressure sensor using frustrated-total-internal-reflection readout technique

“…The system relies upon the modulation of light by very small movements of the resonanting element (as compared to reflective readout systems-Mallalien et al [19], Jones et al [20]). …”

“…Conversion efficiencies of up to 10 percent have been achieved with (in contrast to Dreulesaint et al) an overall power consumption of a few multiwatts. The publication of Mallalien et al [19] shows a theoretical analysis of a photothermal drive of a crystal and proposes a reflective modulation read-out system.…”

Optical microresonator sensor systems

“…10 The sensing mechanism depended on a steel cantilever bending in response to loads applied to its free end, so changing the axial stress in a three-beam quartz oscillator bonded to the surface nearby. A thin nichrome layer backing the quartz served to absorb energy from an incident intensity-modulated optical beam, creating a thermal modulation and so, in turn, a mechanical vibration.…”