Laboratory Measurement of the Velocity of Light

Alford, W.P.; Gold, Albert

doi:10.1119/1.1934646

Cited by 43 publications

(37 citation statements)

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“…For longer temporal delays, interference manifest as spectral interference for a given temporal delay. The observation of spectral interference was denoted by Mandel [1,2] as the Alford-Gold effect [3] and it is well-known in optics [4].…”

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confidence: 99%

Observation of spectral interference for any path difference in an interferometer

Salazar-Serrano¹,

Valencia²,

Torres³

2014

Opt. Lett.

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We report the experimental observation of spectral interference in a Michelson interferometer, regardless of the relationship between the temporal path difference introduced between the arms of the interferometer and the spectral width of the input pulse. This observation is possible by introducing the polarization degree of freedom into a Michelson interferometer using a typical weak value amplification scenario. c 2018 Optical Society of America OCIS codes: 260.0260, 260.3160,260.5430, 320.5550,120.3180 Interference is a fundamental concept in any theory based on waves, such as classical electromagnetism or quantum theory. The specific experimental arrangement required for the observation of interference depends on the characteristics of the light source, i.e., its spatiotemporal profile and its degree of coherence. For example, for first-order coherent light in a Michelson interferometer, for temporal delays shorter than the pulse width, interference manifests as a delay-dependent change of the intensity at the output port of the interferometer. For longer temporal delays, interference manifest as spectral interference for a given temporal delay. The observation of spectral interference was denoted by Mandel [1, 2] as the Alford-Gold effect [3] and it is well-known in optics [4].Here we report the observation of spectral interference independently of the temporal regime under consideration. The interference is revealed as a reshaping of the input spectrum that is accomplished by introducing the polarization degree of freedom into a Michelson interferometer. This scenario corresponds precisely to the conditions of a typical weak value amplification configuration [5][6][7][8] that although was originally conceived in the framework of a quantum formalism, it is essentially based on the phenomena of interference and can thus be applied to any scenario with waves [9][10][11][12][13].For the sake of clarity, let us start by describing temporal and spectral interference in a typical Michelson interferometer, without considering polarization. Later on, we will describe the effects that the introduction of the polarization degree of freedom has on spectral interference. Consider the situation depicted in Fig. 1(a). A first-order coherent input pulse with amplitude E 0 , central frequency ν 0 , input polarization e in , and temporal duration τ (full width at half maximum) described by follows a different path and after reflection in a mirror the two pulses recombine at the BS. By changing the position of one of the mirrors, a temporal delay (T ) is generated between the two pulses. The intensity measured by a slow detector at the output port of the interferometer as a function of T can be written aswhere I 0 = |E 0 | 2 . Two interesting cases can be distinguished: i) when T ≪ τ , and therefore, the two pulses traveling the different paths overlap in time and ii) when T ≫ τ and the two pulses do not overlap. In the first case, the output intensity as a function of T reduces to1

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confidence: 99%

Observation of spectral interference for any path difference in an interferometer

Salazar-Serrano¹,

Valencia²,

Torres³

2014

Opt. Lett.

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“…However, when a source straddles a caustic, where the angular separation and time delay between adjacent light rays goes to zero, transient interference effects may be measurable, although signals might be swamped when integrating the decoherence over the entire source (Mandzhos 1991a,b;Zabel & Peterson 2003). We also note claims, expanded over a series of papers, that different path lengths in gravitational lens systems might carry time separated correlations as an application of the Alford & Gold (1958) effect (see Borra 2008Borra , 2011Borra , 2013. However identical reasoning to that already presented here for the scheme of Saha (2019) removes the chance of such correlated signals, regardless of the configuration of the detection apparatus.…”

Section: Discussionmentioning

confidence: 79%

Microlensing and photon bunching: the impact of decoherence

Lewis

Tuthill

2019

Monthly Notices of the Royal Astronomical Society

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Gravitational microlensing within the Galaxy offers the prospect of probing the details of distant stellar sources, as well as revealing the distribution of compact (and potentially non-luminous) masses along the line-of-sight. Recently, it has been suggested that additional constraints on the lensing properties can be determined through the measurement of the time delay between images through the correlation of the bunching of photon arrival times; an application of the Hanbury-Brown Twiss effect. In this paper, we revisit this analysis, examining the impact of decoherence of the radiation from a spatially extended source along the multiple paths to an observer. The result is that, for physically reasonable situations, such decoherence completely erases any correlation that could otherwise be used to measure the gravitational lensing time delay. Indeed, the divergent light paths traverse extremely long effective baselines at the lens plane, corresponding to extremes of angular resolving power well beyond those attainable with any terrestrial technologies; the drawback being that few conceivable celestial objects would be sufficiently compact with high enough surface brightness to yield usable signals.

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“…In an ultra-rapidly pulsating source, the constancy of τ would ensure phase synchronization. Givens (1961) provides a theoretical analysis of the Alford & Gold (1958) experiment.…”

Section: Discussion Of the Applicability Of The Spectral Modulation Tmentioning

confidence: 99%

Spectral signatures of ultra-rapidly varying objects in spectroscopic surveys

Borra¹

2010

A&A

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Context. Astronomy is an observationally-led subject where chance discoveries play an important role. The time domain is the least explored in astronomy. Aims. We alert spectroscopists, particularly those involved in surveys, that rapidly varying sources can induce periodic patterns in spectra. Methods. The analytical treatment is based on standard Fourier theory. It is used to predict the shapes of features introduced by intensity pulses in spectra. These are the shapes that one must look for in spectral surveys. The theoretical analysis is supported by published experiments that measured the spectral modulation, in the visible wavelength region, caused by pairs of 150 femtosecond laser pulses separated by time periods varying between 5 × 10 −13 s and 3 × 10 −11 s. Results. Detection of spectral signatures would allow the detection of new classes of objects that emit bursts of pulses separated by time intervals that are too short to be detected with conventional techniques. The principal advantage of the technique is that there is no need for specialized instruments or surveys: one must only incorporate algorithms capable of searching for periodic spectroscopic signals, such as those shown in a figure in this article, into existing data analyzis software and use it with standard spectroscopic surveys (including existing ones).

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Laboratory Measurement of the Velocity of Light

Cited by 43 publications

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Observation of spectral interference for any path difference in an interferometer

Observation of spectral interference for any path difference in an interferometer

Microlensing and photon bunching: the impact of decoherence

Spectral signatures of ultra-rapidly varying objects in spectroscopic surveys

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