Advanced LIGO subsystems
are the organizational units of the overall project. Follow the links below to view the mission and progress of each subsystem.
|Auxiliary Optics||Core Optics|
|Data Acquisition||Data and|
LIGO Technology Development and Migration
Explore the menu of case study links (left) to view impacts of LIGO technology across the broader science and engineering community.
|Technology Transfer Case Studies|
|LIGO Technology Migration|
|Adaptive Beam Shaping|
|High Power Modulator|
|Diode Pumped Laser|
|Vacuum Cable Clamp|
|Interferometric Displacement Sensor|
|Oxide Bonding Techniques|
|Fast Chirp Transform|
|Blind Data Search Method|
|Distributed Identity Management|
|Holographic Quantum Geometry|
|Technology Type: Lasers
A Novel Approach to Very High Performance Stabilization of Laser Frequency
Prior to the development of RF Reflection Locking, the use of very high-finesse optical cavities as stable references to which lasers could be locked in frequency was limited by the control bandwidth achievable, and hence by the resulting stability possible. Then a key development transformed the field. It was demonstrated that high-frequency phase modulation of the light directed toward the optical cavity, together with coherent detection of the light reflected from the optical cavity, resulted in the generation of a useful error signal over a wide detuning bandwidth around the cavity resonance. This signal also gave a proportional response to relative phase fluctuations above the cavity linewidth. It was found that these features could be effectively used to implement very wideband and high-gain servo control.
The promise of this approach was announced in the "Pound-Drever-Hall" publication (1) from the Joint Institute for Laboratory Astrophysics in the US (where the interest was mainly for precision measurements), and the University of Glasgow in Scotland (where interest was driven by the requirements of interferometric gravitational-wave detectors). For a decade the technique remained of largely academic interest. Then, numerous practical applications stimulated its adoption in a wide range of technical areas and markets.
The use of RF Reflection Locking -- or Pound-Drever-Hall (PDH) locking, as it has become known -- is now widespread in many fields, including spectroscopy, chip and reticule inspection, precision standards definition, optical frequency standards, space borne metrology applications, development and testing of ultra-low-loss mirrors, frequency reference cavities, fiber optic sensing and nonlinear laser frequency conversion.
The benefits from this research have influenced the growth of companies such as Toptica and Sacher Lasertechnik in Europe, and Advanced Thin Films and Vescent Photonics in the US; the development of a range of fast photo detectors and modulators from New Focus; advances in communication and metrology systems provided by precise frequency control of infrared fiber lasers by NP Photonics, and the generation of EUV light from modelocked visible lasers. Other developments not yet near-market have also been aided. Indeed the technique underpins almost all advances in frequency metrology, fundamental measurement, and any field in which lasers must be controlled in frequency, such as ultra-stable optical clocks, and dissemination of laser frequency standards.
1. Laser Phase and Frequency Stabilization using an Optical Resonator R.W.P. Drever, J.L. Hall, F.V. Kowalski, J. Hough, G.M. Ford, A.J. Munley and H. Ward Appl. Phys. B 31, 97-105 (1983)
Photos courtesy of Caltech, John Hall and Leo Holberg.
Explore Advanced LIGO
Instrumentation and Astrophysics
An Overview of the Upgrades
The International Partnership
LIGO Technology Transfers
LIGO Scientific Collaboration