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.

http://jila1.nickersonm.com/papers/Laser%20Phase%20and%20Frequency%20Stabilization%20Using%20an%20Optical%20Resonator.pdf

Laser phase and frequency stabilization using an optical resonator

The goal of the Laser Interferometer Gravitational-Wave Observatory (LIGO) Project is to detect and study astrophysical gravitational waves and use data from them for research in physics and astronomy. LIGO will support studies concerning the nature and nonlinear dynamics of gravity, the structures of black holes, and the equation of state of nuclear matter. It will also measure the masses, birth rates, collisions, and distributions of black holes and neutron stars in the universe and probe the cores of supernovae and the very early universe. The technology for LIGO has been developed during the past 20 years. Construction will begin in 1992, and under the present schedule, LIGO's gravitational-wave searches will begin in 1998.

/pdf/ligo-the-laser-interferometer-gravitational-wave-observatory-1ru47xyhtr.pdf

LIGO: The Laser Interferometer Gravitational-Wave Observatory.

The detection and measurement of gas concentrations using the characteristic optical absorption of the gas species is important for both understanding and monitoring a variety of phenomena from industrial processes to environmental change. This study reviews the field, covering several individual gas detection techniques including non-dispersive infrared, spectrophotometry, tunable diode laser spectroscopy and photoacoustic spectroscopy. We present the basis for each technique, recent developments in methods and performance limitations. The technology available to support this field, in terms of key components such as light sources and gas cells, has advanced rapidly in recent years and we discuss these new developments. Finally, we present a performance comparison of different techniques, taking data reported over the preceding decade, and draw conclusions from this benchmarking.

/pdf/optical-gas-sensing-a-review-4uaf589xiq.pdf

Optical gas sensing: a review

This paper is an introduction to an elegant and powerful technique in modern optics: Pound–Drever–Hall laser frequency stabilization. This introduction is primarily meant to be conceptual, but it includes enough quantitative detail to allow the reader to immediately design a real setup, suitable for research or industrial application. The intended audience is both the researcher learning the technique for the first time and the teacher who wants to cover modern laser locking in an upper-level physics or electrical engineering course.

http://www.jila1.nickersonm.com/papers/An%20introduction%20to%20Pound-Drever-Hall%20laser%20frequency%20stabilization.pdf

An introduction to Pound–Drever–Hall laser frequency stabilization

In-fibre Bragg grating (FBG) sensors are one of the most exciting developments in the field of optical fibre sensors in recent years. Compared with conventional fibre-optic sensors, FBG sensors have a number of distinguishing advantages. Significant progress has been made in applications to strain and temperature measurements. FBG sensors prove to be one of the most promising candidates for fibre-optic smart structures. This article presents a comprehensive and systematic overview of FBG sensor technology regarding many aspects including sensing principles, properties, fabrication, interrogation and multiplexing of FBG sensors. It is anticipated that FBG sensor systems will be commercialized and widely applied in practice in the near future due to the maturity of economical production of FBGs and the availability of cost effective interrogation and multiplexing techniques.

https://iopscience.iop.org/article/10.1088/0957-0233/8/4/002/pdf

In-fibre Bragg grating sensors

In these two lectures we will discuss principles underlying the development of some laser interferometer gravitational radiation detectors, some of the techniques being devised to overcome the many experimental problems, and results obtained so far in experimental work at the University of Glasgow and the California Institute of Technology. We also hope to give some indication about possible long-term prospects, as well as presenting some new ideas bearing on these problems.

Gravitational Wave Detectors Using Laser Interferometers and Optical Cavities: Ideas, Principles and Prospects

Most of the techniques being developed for detection of gravitational radiation involve sensing the small strains in space associated with the gravitational waves by looking for changes in the apparent distance between two (or more) test masses. In many of the experimental searches performed so far the detectors consisted of massive aluminium bars, the metal near the ends of the bars acting as the test masses, and impulsive strains induced in the bars were searched for. Thetrain sensitivity of such experiments has been in the range 10−16 to 10−18 for pulses of duration of order 1 millisecond, the limits usually being set by thermal noise in the bar, and transducer and amplifier sensitivity. Current predictions of gravitational waves to be expected from various types of astrophysical sources suggest that strain sensitivities some three orders of magnitude better than these are likely to be required for detection of gravitational wave bursts from known types of sources at a useful rate, although indecd signals may be present over a wide frequency range — from 10 kHz to 10−4 Hz or lower. (A good summary is given in the proceedings of a conference on “Sources of Gravitational Radiation” [1]). Work on bar gravity wave detectors is continuing; but an alternative approach is to use widely separated and nearly free test masses, and monitor changes in their separation by optical interferometry techniques. This method shows considerable promise for both high sensitivity and wide bandwidth and frequency coverage. At the sensitivity levels required absolute length measurements would be difficult, but a comparison of two baselines perpendicular to one another, which may be affected in opposite senses by a gravitational wave travelling in a suitable direction, provides a practical alternative. Early experiments of this type were carried out at Hughes Laboratories [2] using a simple Michelson interferometer to monitor separations between ree test masses suspended in vacuum. The displace- ment sensitivity of such an arrangement may be improved by causing the light in each arm of the interferometer to travel back and forth many times between mirrors attached to the test masses, and a multireflection system of this type using Herriott delay lines was proposed by R. Weiss [3]. Experimental work on multireflection Michelson interferometers for gravity wave detection has been carried out at MIT, the Max-Planck Institute at Munich, and the University of Glasgow.

Optical Cavity Laser Interferometers for Gravitational Wave Detection

A Gravity-Wave Detector Using Optical Cavity Sensing

As outlined in the preceding talk by Dr Thorne, there are many possible sources of
gravitational radiation, ranging from the interactions of supermassive black holes
to supernova explosions of stars. Detection of such radiation could give information
which cannot be obtained otherwise, for example on events occurring in the cores
of stellar systems, and could also provide important clues on the existence, nature
and behaviour of black holes.

G. M. Ford

Papers

Laser phase and frequency stabilization using an optical resonator

Gravitational Wave Detectors Using Laser Interferometers and Optical Cavities: Ideas, Principles and Prospects

Optical Cavity Laser Interferometers for Gravitational Wave Detection

A Gravity-Wave Detector Using Optical Cavity Sensing

Gravitational wave detectors