A low noise laser interferometry readout for challenging acceleration measurements in space (original) (raw)

A laser interferometer accelerometer for vibration sensitive cryogenic experiments

Measurement Science and Technology

Monitoring motion originating from ultra low-temperature cooling systems like cryocoolers is important for vibration sensitive cryogenic experiments like KAGRA. Since no high sensitivity commercial cryogenic accelerometers are available, we developed a compact self-calibrating accelerometer with a Michelson interferometer readout for cryogenic use. Change in calibration factor and drop in interferometer output originating from temperature drop were the main concerns which were tackled. Sensitivity of 3.38 × 10 − 11 m/ H z at 1 Hz was achieved at 300 K. The accelerometer was tested inside the KAGRA cryostat; showed stable operation down to 12 K in 0.1–100 Hz band with only 1% visibility drop. Our accelerometer can be employed in low vibration cryogenic environment for a multitude of applications.

Inertial Grade Laser Accelerometer Practicability and Basic Experiments

2003

A novel laser accelerometer is introduced, its physical principle and main characteristics are explained, and preliminary experimental results are presented. The accelerometer utilizes two Nd:YAG laser crystals and a common proof mass which operate in push-pull mode. The main advantages of the described laser accelerometer are wide measuring range which covers 9 decades up to 100 m/s², very high linearity over measuring range and excellent dynamics (20 kHz bandwidth). In comparison to servo accelerometers, these results represent a high- performance sensor. The measurement uncertainty and precision analysis have been carried out according to GUM guidelines. The analysis shows that the relative uncertainty in sensitivity of the laser accelerometer amounts to 10 -6 .

Differential laser interferometer for nanometer displacement measurements

AIAA Journal, 1995

A dual beam differential laser interferometer/vibrometer measurement system was developed for studying the steady-state and dynamic behavior of low-weight high-performance mechanical systems. This newly developed optical system employs many optical and mechanical design tactics to achieve design targets such as nanometer displacement accuracy, ease of use, capability of measuring untreated structural surfaces, high-measurement bandwidths, and large-dynamic ranges. Both the optical/mechanical configurations and the design approaches adopted are discussed in detail. A flying slider and thin-film disk system currently used in the disk drive industry were used as the testbed to verify the capabilities of this newly developed nanometer structural displacement/velocity measurement system.

Laser displacement sensor with application to gravitational radiation detection

Applied Optics, 1980

The principles of operation of a novel laser displacement sensor are described. The intended application of the sensor is to measure displacements induced by gravitational radiation. The laser sensor is composed of three coupled cavities, defined by two laser mirrors and the mirrors of a Fabry-Perot etalon placed inside the laser cavity. The laser is forced to oscillate in two longitudinal modes by a Fox-Smith internal mode selector. It is shown that the laser system can be made to operate in a condition where the beat frequency between these modes has an enhanced sensitivity to relative displacements between the etalon mirrors. A He-Ne laser displacement sensor was constructed, and a displacement sensitivity of 4.6 X 1012 Hz/cm was obtained. This value is shown to be in good agreement with the value predicted by a theoretical analysis of the sensor performance.

A Tutorial on Laser Interferometry for Precision Measurements

— Laser interferometers have found wide usage in a variety of precision measurement applications. The ability to gain precise position information with minimal change to the dynamics of the device being measured has a large set of advantages. This allows interferometer systems to be used in feedback loops for precision systems. This paper presents a tutorial on laser interferometers, their use in precision motion feedback systems, the issues faced by such systems, and some of the solutions that have been applied to these issues.

Interferometric readout of a monolithic accelerometer, towards the fm/ rtHz resolution

The European Gravitational wave Observatory Virgo is undergoing an upgrade to increase its strain sensitivity to about 3x10^24 1/rtHz in the detection band of 10 Hz –10 kHz. The upgrade for this detector necessitates seismically isolating sensing optics in a vacuum environment that were on an optical bench outside vacuum in previous Virgo configurations. For this purpose, Nikhef has designed and built the five compact isolators, called MultiSAS. To measure the residual motion of the optical components and the transfer function of the isolator in full assembly, no (commercial) sensor is available that has sufficient sensitivity. A novel vibration sensor has been built at Nikhef that features an interferometric readout for a horizontal monolithic accelerometer. It will be able to measure in the vicinity of the fm/rtHz regime from 10 Hz onwards. Current results show unprecedented (self) noise levels around 35 fm/rtHz from 25 Hz onwards. In spite of these excellent results, it is still higher than the modeled noises. Several possible unmodeled noise sources and possible solutions have been identified.

Fiber interferometer combining sub-nm displacement resolution with miniaturized sensor head

25th International Conference on Optical Fiber Sensors

The presented interferometer concept enables high-accuracy target displacement measurement in difficult accessible locations and the development of small fiber optic sensor to measure other physical parameters e.g. pressure, vibration, gravity force, etc.. Furthermore, this configuration is basically insensitive to disturbances to the lead fiber between the passive sensor head and the measurement system including the electro-optical parts and the detection interferometer. Two test setups are built and tested to demonstrate the feasibility of high-speed measurement up to 50 kHz, low system drift of ~0.5 nm over 500 s and a low displacement noise level down to 2.8 pm/√ Hz.

Vibration compensating beam scanning interferometer for surface measurement

Applied Optics, 2008

Light beam scanning using a dispersive element and wavelength tuning is coupled with fibre-optic interferometry to realize a new surface measurement instrument. The instrument is capable of measuring nano-scale surface structures and form deviation. It features active vibration compensation and a small optical probe size that may be placed remotely from the main apparatus. Active vibration compensation is provided by the multiplexing of two interferometers with near common paths. Closed loop control of a mirror mounted on a piezoelectric transducer is used to keep the path length stable. Experiments were carried out due deduce the effectiveness of the vibration compensation and the ability to carry out a real measurement in the face of large environmental disturbance.

Laser diode interferometer used for measuring displacements in large range with a nanometer accuracy

Optics and Laser Technology, 2001

In this paper, the displacement of an object is measured with a photothermal phase-modulating laser diode interferometer. A feedback control system is designed to reduce the measurement errors caused by the uctuations in the optical wavelength of the laser diode and the vibrations of the optical components in the interferometer. A new method is proposed to enlarge the measuring range of displacement. Using this method, the measuring range is enlarged from half wavelength to nearly 125 m and the measurement accuracy is about 1 nm. The simulation and experimental results have shown the usefulness of the method and the feedback control system.