Author
Charles H. Townes
Other affiliations: University of California, University of California, Santa Cruz, Space Sciences Laboratory ...read more
Bio: Charles H. Townes is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Infrared Spatial Interferometer & Interferometry. The author has an hindex of 62, co-authored 345 publications receiving 19318 citations. Previous affiliations of Charles H. Townes include University of California & University of California, Santa Cruz.
Papers published on a yearly basis
Papers
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11 Oct 1965
TL;DR: In this paper, an OPTICAL FREQUENCY ELECTROMAGNETIC BEAM is used to generate its own waveguide, for direct energy generation through a selected area of a selected medium.
Abstract: AN OPTICAL FREQUENCY ELECTROMAGNETIC BEAM IS MAINTAINED AT A POWER LEVEL SUCH THAT ELECTROSTRICTIVE QUALITIES OF A SELECTED MEDIUM IS ALTERED CAUSING THE BEAM TO GENERATE ITS OWN WAVEGUIDE, FOR DIRECTING ENERGY THROUGH SUCH MEDIUM.
1 citations
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01 Jan 1989TL;DR: In this article, the authors made 55″ resolution maps of the 158 µm [CII] emission line in the region of the curved, thermal filaments and the +20/+50 kms-1 molecular clouds in Sgr A.
Abstract: We have made 55″ resolution maps of the 158 µm [CII] emission line in the region of the curved, thermal filaments and the +20/+50 kms-1 molecular clouds in Sgr A. The [CII] emission is spatially well correlated with the radio continuum in the filaments. The large intensity of the [CII] radiation excludes shocks as the origin of the ionization and we conclude that the curved filaments are most likely photo-ionized HII regions at the surface of dense molecular clouds. Our [CII] maps of the +20/+50 kms-1 clouds indicate that the +50 kms-1cloud is close to ( 30pc).
1 citations
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01 Jan 1997TL;DR: The Infrared Spatial Interferometer (ISI) of the University of California at Berkeley is a two telescopes interferometer operating in the infrared (9-12 microns) as discussed by the authors.
Abstract: The Infrared Spatial Interferometer (ISI) of the University of California at Berkeley is a two telescopes interferometer operating in the infrared (9–12 microns). Many late type stars and their circumstellar dust shell have been observed and modelled. Several results have been obtained: location of the inner radii of the dust shell, physical conditions in the dust formation zone, optical depth of the shell, diameters of some evolved stars, location of SiO masers by regard to the dust (Danchi et al. 1994a, Greenhill et al. 1995).
1 citations
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TL;DR: The size and variability of the photospheres of several late-type stars has been probed using 11 micron heterodyne interferometry as discussed by the authors, which yielded diameter measurements accurate to about 1% for α Ori and o Cet, an supergiant and a mira variable.
Abstract: The size and variability of the photospheres of several late-type stars has been probed using 11 micron heterodyne interferometry High resolution observations performed during the years 1999 - 2001 yielded diameter measurements accurate to about 1% for α Ori and o Cet, an supergiant and a mira variable Narrow bandwidths (017 cm -1 ) and high resolution spectra were used to avoid molecular lines Observations were made at several different wavelengths, sometimes purposely overlapping an observed spectral feature In all cases, the 11 micron sizes are larger than previously measured visible and near-infrared diameters The discrepancies will be discussed In addition, a variation of the diameter of Mira with phase has been observed
1 citations
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TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.
Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …
33,785 citations
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TL;DR: In this paper, the authors consider the atomic dynamics and the optical response of the medium to a continuous-wave laser and show how coherently prepared media can be used to improve frequency conversion in nonlinear optical mixing experiments.
Abstract: Coherent preparation by laser light of quantum states of atoms and molecules can lead to quantum interference in the amplitudes of optical transitions. In this way the optical properties of a medium can be dramatically modified, leading to electromagnetically induced transparency and related effects, which have placed gas-phase systems at the center of recent advances in the development of media with radically new optical properties. This article reviews these advances and the new possibilities they offer for nonlinear optics and quantum information science. As a basis for the theory of electromagnetically induced transparency the authors consider the atomic dynamics and the optical response of the medium to a continuous-wave laser. They then discuss pulse propagation and the adiabatic evolution of field-coupled states and show how coherently prepared media can be used to improve frequency conversion in nonlinear optical mixing experiments. The extension of these concepts to very weak optical fields in the few-photon limit is then examined. The review concludes with a discussion of future prospects and potential new applications.
4,218 citations
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01 Jan 1963TL;DR: In this article, it was shown that the semiclassical theory, when extended to take into account both the effect of the field on the molecules and the effects of the molecules on the field, reproduces the same laws of energy exchange and coherence properties as the quantized field theory, even in the limit of one or a few quanta in the field mode.
Abstract: This paper has two purposes: 1) to clarify the relationship between the quantum theory of radiation, where the electromagnetic field-expansion coefficients satisfy commutation relations, and the semiclassical theory, where the electromagnetic field is considered as a definite function of time rather than as an operator; and 2) to apply some of the results in a study of amplitude and frequency stability in a molecular beam maser. In 1), it is shown that the semiclassical theory, when extended te take into account both the effect of the field on the molecules and the effect of the molecules on the field, reproduces almost quantitatively the same laws of energy exchange and coherence properties as the quantized field theory, even in the limit of one or a few quanta in the field mode. In particular, the semiclassical theory is shown to lead to a prediction of spontaneous emission, with the same decay rate as given by quantum electrodynamics, described by the Einstein A coefficients. In 2), the semiclassical theory is applied to the molecular beam maser. Equilibrium amplitude and frequency of oscillation are obtained for an arbitrary velocity distribution of focused molecules, generalizing the results obtained previously by Gordon, Zeiger, and Townes for a singel-velocity beam, and by Lamb and Helmer for a Maxwellian beam. A somewhat surprising result is obtained; which is that the measurable properties of the maser, such as starting current, effective molecular Q, etc., depend mostly on the slowest 5 to 10 per cent of the molecules. Next we calculate the effect of amplitude and frequency of oscillation, of small systematic perturbations. We obtain a prediction that stability can be improved by adjusting the system so that the molecules emit all their energy h Ω to the field, then reabsorb part of it, before leaving the cavity. In general, the most stable operation is obtained when the molecules are in the process of absorbing energy from the radiation as they leave the cavity, most unstable when they are still emitting energy at that time. Finally, we consider the response of an oscillating maser to randomly time-varying perturbations. Graphs are given showing predicted response to a small superimposed signal of a frequency near the oscillation frequency. The existence of "noise enhancing" and "noise quieting" modes of operation found here is a general property of any oscillating system in which amplitude is limited by nonlinearity.
3,928 citations
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TL;DR: In this method, non-linear susceptibility tensors are introduced which relate the induced dipole moment to a power series expansion in field strengths and the various experimental observations are described and interpreted in terms of this formalism.
Abstract: Recent advances in the field of nonlinear optical phenomena are reviewed with particular empphasis placed on such topics as parametric oscillation self-focusing and trapping of laser beams, and stimulated Raman, Rayleigh, and Brillouin scattering. The optical frequency radiation is treated classically in terms of the amplitudes and phases of the electromagnetic fields. The interactions of light waves in a mterial are then formulated in terms of Maxwell's equations and the electric dipole approximation. In this method, non-linear susceptibility tensors are introdueed which relate the induced dipole moment to a power series expansion in field strengths. The tensor nature and the frequency dependence of the nonlinearity coefficients are considered. The various experimental, observations are described and interpreted in terms of this formalism.
3,893 citations
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TL;DR: Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, the Nordtvedt effect in lunar motion, and frame-dragging.
Abstract: The status of experimental tests of general relativity and of theoretical frameworks for analyzing them is reviewed and updated. Einstein’s equivalence principle (EEP) is well supported by experiments such as the Eotvos experiment, tests of local Lorentz invariance and clock experiments. Ongoing tests of EEP and of the inverse square law are searching for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, the Nordtvedt effect in lunar motion, and frame-dragging. Gravitational wave damping has been detected in an amount that agrees with general relativity to better than half a percent using the Hulse-Taylor binary pulsar, and a growing family of other binary pulsar systems is yielding new tests, especially of strong-field effects. Current and future tests of relativity will center on strong gravity and gravitational waves.
3,394 citations