Electronic frequency stabilization of microwave oscillators.
TL;DR: Two circuits for use to control the frequency of a microwave oscillator by an external high Q cavity are described, and a technique by which the frequency‐stabilization systems could be used to investigate the structure of microwave absorption spectra is suggested.
Abstract: Two circuits for use to control the frequency of a microwave oscillator by an external high Q cavity are described. One of the circuits uses a microwave equivalent of the frequency discriminator, in conjunction with a d.c. amplifier. The other uses the cavity in a special circuit that provides an intermediate‐frequency signal that is a measure of the difference between the frequencies of the oscillator and cavity. This allows the use of an intermediate‐frequency amplifier. The resulting stability of the oscillators is such that audible beat frequencies can be produced between two oscillators at 10,000 Mc/sec. The resultant signal can be frequency modulated at audiofrequencies, with stabilization acting throughout the modulation cycle. A technique by which the frequency‐stabilization systems could be used to investigate, with high resolution, the structure of microwave absorption spectra is suggested.
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TL;DR: In this article, the authors describe a new and highly effective optical frequency discriminator and laser stabilization system based on signals reflected from a stable Fabry-Perot reference interferometer.
Abstract: 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.
3,393 citations
TL;DR: In this article, the Pound-Drever-Hall laser frequency stabilization (PDSH) was introduced for the first time, and the intended audience is both the researcher learning the technique for their first time and the teacher who wants to cover modern laser locking in an upper-level physics or electrical engineering course.
Abstract: 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.
1,218 citations
TL;DR: In this paper, a linear polarizer or Brewster plate is placed inside the reference cavity, so that the reflected light acquires a frequency-dependent elliptical polarization, which can provide the error signal for electronic frequency stabilization without any need for modulation techniques.
941 citations
TL;DR: In this article, a short historical perspective and survey of the frequency modulation spectroscopy work performed to date is presented, and theoretical lineshapes for a variety of experimental conditions are given.
Abstract: Frequency modulation (FM) spectroscopy is a new method of optical heterodyne spectroscopy capable of sensitive and rapid measurement of the absorption or dispersion associated with narrow spectral features. The absorption or dispersion is measured by detecting the heterodyne beat signal that occurs when the FM optical spectrum of the probe wave is distorted by the spectral feature of interest. A short historical perspective and survey of the FM spectroscopy work performed to date is presented. Expressions describing the nature of the beat signal are derived. Theoretical lineshapes for a variety of experimental conditions are given. A signal-to-noise analysis is carried out to determine the ultimate sensitivity limits.
518 citations
TL;DR: In this paper, an external cavity is used to enhance the molecular response to the light field, and an external FM technique is applied for shotnoise-limited signal recovery, and a perfect match between the FM sideband frequency and the cavity free spectral range makes the detection process insensitive to the laser-frequency noise relative to the cavity, and, at the same time, overcomes the cavity bandwidth limit.
Abstract: We consider several highly sensitive techniques commonly used in detection of atomic and molecular absorptions. Their basic operating principles and corresponding performances are summarized and compared. We then present our latest results on the ultrasensitive detection of molecular overtone transitions to illustrate the principle and application of the cavity-enhanced frequency-modulation (FM) spectroscopy. An external cavity is used to enhance the molecular response to the light field, and an FM technique is applied for shotnoise-limited signal recovery. A perfect match between the FM sideband frequency and the cavity free spectral range makes the detection process insensitive to the laser-frequency noise relative to the cavity, and, at the same time, overcomes the cavity bandwidth limit. Working with a 1.064-mm Nd:YAG laser, we obtained sub-Doppler overtone resonances of C2HD, C2H2, and CO2 molecules. A detection sensitivity of 5 3 10 213 of
400 citations
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TL;DR: In this paper, the absorption of electromagnetic waves in the one-half cm wave-length range has been measured for both pure and mixed mixtures as a function of pressure, and the measured values are in agreement with the theory of Van Vleck both as regards the absolute value of the absorption (which is as great as 67 db/km at the band center for pure mixtures at a pressure of one atmosphere) and the dependence on pressure.
Abstract: The absorption of electromagnetic waves in the one-half cm wave-length range has been measured for ${\mathrm{O}}_{2}$ and ${\mathrm{O}}_{2}$-${\mathrm{N}}_{2}$ mixtures as a function of pressure. The apparatus employs a klystron oscillator, crystal-rectifier frequency-multiplier, wave guide absorption path, and crystal detector. The measured values are in agreement with the theory of Van Vleck both as regards the absolute value of the absorption (which is as great as 67 db/km at the band center for pure ${\mathrm{O}}_{2}$ at a pressure of one atmosphere) and the dependence on pressure.
63 citations