@article {Fischer:2016:0736-2935:6376,
title = "Miniaturized all-optical Sound Pressure Sensor",
journal = "INTER-NOISE and NOISE-CON Congress and Conference Proceedings",
parent_itemid = "infobike://ince/incecp",
publishercode ="ince",
year = "2016",
volume = "253",
number = "2",
publication date ="2016-08-21T00:00:00",
pages = "6376-6382",
itemtype = "ARTICLE",
issn = "0736-2935",
url = "https://ince.publisher.ingentaconnect.com/content/ince/incecp/2016/00000253/00000002/art00066",
author = "Fischer, Balthasar",
abstract = "The membrane-free optical microphone, an alternative concept to measure sound pressure, will be presented. A laser beam locked to a millimeter-sized Fabry-P{\’e}rot interferometer experiences a change in wavelength if the pressure inside the interferometer is altered by a sound wave.
The resulting change in back reflection of the laser is measured by a photo diode, thus providing a direct measurement of the sound pressure. It is important to mention, that the system operates without any moving parts. Hence, the measured signal is not a result of a mechanically moving or
deformable mirror, but a consequence of the change in the medium's density itself, and its related change of refractive index. Therefore, this sensor principle is free from mechanical resonances and allows for a linear frequency response expanding over 1MHz in air and over 25MHz in liquids.
The talk compares operation in gaseous and liquid media and addresses potential contributions of internal structure-borne movements of the mirrors. It is shown that, even if Eigenmodes of the mechanical sensor structure are excited by sound pressure, their contribution is 3 orders of magnitude
below the contribution of the refractive index change, and may therefore be neglected. Several applications are presented.",
}