THE EFFECT OF MESA DIMENSIONS ON MEMS DIAPHRAGMS FOR FABRY-PEROT INTERFEROMETER-BASED FIBER OPTIC SENSORS

In this study, the effects of mesa dimensions on sensor response in diaphragm-based FabryPerot fiber optic sensors (FOSs) were investigated in detail. Mesa diaphragms, also called centerembossed diaphragms, have been discussed sufficiently in the literature, but the effect of mesa thickness on sensor performance has not been discussed in detail. Moreover, there is no precise analytical solution for such diaphragms. For this reason, diaphragms with different thicknesses and radii were selected, and the deflection and frequency responses of the diaphragm according to the applied acoustic pressure were analyzed using the ANSYS software, depending on whether the mesa is thinner or thicker than the diaphragm. If the thickness of the mesa is smaller than the thickness of the diaphragm, the center deflection changes drastically. However, if the thickness of the mesa is two times greater than the thickness of the diaphragm, there is no significant change in the deflection results. Similarly, if the mesa thickness is thinner than the diaphragm, the sensor’s frequency response changes drastically with increasing mesa radius. In cases where the mesa thickness is larger than the diaphragm thickness, the frequency response changes less. According to the results, mesa dimensions should be considered when designing a mesa diaphragm-based Fabry-Perot FOS

High Temperature Sapphire Optical Fiber Sensor

A sapphire fiber optic sensor for ultra-high temperature is developed, which owns the advantages of high temperature tolerance and compact. The detecting fiber is manufactured by fusing the sapphire fiber for detector head. The developed infrared radiation light is detected and the high temperature optical fiber sensor is placed in the ultra-high temperature furnace. The sensor signal will be transmitted to the display device through a photoelectric conversion module, and data acquisition module. As a result, the temperature response sensitivity is 2.292 uV1/2/K The measurement results show that the repeatability of the sensor is good. The maximum temperature measured by the sensor is 1823 K. The sensor can withstand 10 hours at high temperature and the error is less than 1 %. The development of common optical fiber sensor can stably exist at high-temperature. The sensor owns the advantage of simple, compact, easy to fabricate, what’s more, it can tolerate ultrahigh temperature for a long time

Design, suspension and optical characterization of the beam splitter and output mode cleaner for the AEI 10 m prototype

Gravitational wave detectors are highly sensitive instruments to measure gravitational waves. To increase their observation time and decrease maintenance and upgrade periods, newly developed improvements need to be tested thoroughly. The AEI 10 m prototype is a testing facility for potential upgrades to gravitational wave detectors, providing an extremely low noise environment. The sub-SQL interferometer at the AEI 10 m prototype is a Fabry-Perot Michelson interferometer. Once set up, it will measure differential length changes between its interferometer arms limited by the standard quantum limit (SQL). This will allow techniques to surpass the SQL in gravitational wave detectors to be tested. This thesis presents the design and implementation of various subsystems for the sub-SQL interferometer at the AEI 10 m prototype. Aluminum gallium arsenide (AlGaAs) test mass mirror coatings promise reduced coating Brownian noise. Nonetheless, it remained to be shown that the thickness uniformity and damage threshold of AlGaAs coatings fulfill the requirements of gravitational wave detectors. Here, the thickness uniformity RMS was measured to be 0.41 ±0.05 nm, and the lower limit for the laser-induced damage threshold of the mirrors was measured to be 64 ±5 MW/cm2. A scatter measurement device is set up to characterize optics for the AEI 10 m prototype. It provides bidirectional reflection distribution function measurements of high-quality optics. It can measure optics with a total integrated scattering of below 0.01 ppm. The beam splitter of the sub-SQL interferometer and its triple-suspension were designed. The optical requirements of the beam splitter are defined and discussed. Its shape and a split coating are designed to reduce the power in arising ghost beams. The beam splitter’s triple suspension was built, and its resulting performance was evaluated, fulfilling the set requirements. An output mode cleaner for the sub-SQL interferometer was designed and built, in- cluding its double suspension. The design focuses on reducing optical losses while fulfilling the mode filter requirements. Its losses were measured to be 0.1 ±0.4 % while fulfilling the required mode filter performance based on an output beam profile of aLIGO

Optical Sensors

This book is a compilation of works presenting recent developments and practical applications in optical sensor technology. It contains 10 chapters that encompass contributions from various individuals and research groups working in the area of optical sensing. It provides the reader with a broad overview and sampling of the innovative research on optical sensors in the world

UW Imaging of Seismic-Physical-Models in Air Using Fiber-Optic Fabry-Perot Interferometer

A fiber-optic Fabry-Perot interferometer (FPI) has been proposed and demonstrated for the ultrasound wave (UW) imaging of seismic-physical models. The sensor probe comprises a single mode fiber (SMF) that is inserted into a ceramic tube terminated by an ultra-thin gold film. The probe performs with an excellent UW sensitivity thanks to the nanolayer gold film, and thus is capable of detecting a weak UW in air medium. Furthermore, the compact sensor is a symmetrical structure so that it presents a good directionality in the UW detection. The spectral band-side filter technique is used for UW interrogation. After scanning the models using the sensing probe in air, the two-dimensional (2D) images of four physical models are reconstructed

UW Imaging of Seismic-Physical-Models in Air Using Fiber-Optic Fabry-Perot Interferometer

A fiber-optic Fabry-Perot interferometer (FPI) has been proposed and demonstrated for the ultrasound wave (UW) imaging of seismic-physical models. The sensor probe comprises a single mode fiber (SMF) that is inserted into a ceramic tube terminated by an ultra-thin gold film. The probe performs with an excellent UW sensitivity thanks to the nanolayer gold film, and thus is capable of detecting a weak UW in air medium. Furthermore, the compact sensor is a symmetrical structure so that it presents a good directionality in the UW detection. The spectral band-side filter technique is used for UW interrogation. After scanning the models using the sensing probe in air, the two-dimensional (2D) images of four physical models are reconstructed

The Design of the Keck Observatory and Telescope

This report describes the design of the Ten Meter Telescope and Observatory. Since 1977 the University of California has been actively designing a ten meter telescope for visible and infrared ground-based astronomy. The University of California and the California Institute of Technology have now joined in a collaboration to construct and operate this telescope and observatory. A generous gift of seventy million dollars to Caltech from the W. M. Keck Foundation, announced in January 1985, will provide funds for the construction of the facility. In recognition the facility will be named the W. M. Keck Telescope and Observatory. The University of California will provide funds for its operation. We expect construction to be completed by 1990. The design of the telescope and observatory continues to be improved as the detailed design progresses. The description given here is current as of January 1985. Although many design details will change before construction, this description is accurate in the general concept and in many particulars. The details of the design are described in an ongoing series of Reports and Technical Notes. An index to this series is given in the Reference Section of this report

Sixteenth International Laser Radar Conference, Part 1

This publication contains extended abstracts of papers presented at the 16th International Laser Radar Conference. One-hundred ninety-five papers were presented in both oral and poster sessions. The topics of the conference sessions were: (1) Mt. Pinatubo Volcanic Dust Layer Observations; (2) Global Change/Ozone Measurements; (3) GLOBE/LAWS/LITE; (4) Mesospheric Measurements and Measurement Systems; (5) Middle Atmosphere; (6) Wind Measurements and Measurement Systems; (7) Imaging and Ranging; (8) Water Vapor Measurements; (9) Systems and Facilities; and (10) Laser Devices and Technology. This conference reflects the breadth of research activities being conducted in the lidar field. These abstracts address subjects from lidar-based atmospheric investigations relating to global change to the development of new lidar systems and technology