An inexpensive apparatus for the measurement of the group velocity of light in transparent media using a modified Helium–Neon laser

Barr, R. D.; Armstrong, T.R.

doi:10.1119/1.16271

Cited by 4 publications

(3 citation statements)

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“…It is used a modified He-Ne laser as a light source. Results for the velocity of light in air have been obtained with the aid of an oscilloscope [1].…”

Section: Introductionmentioning

confidence: 99%

Speed of Light Measurement with a Simple Way

Pagiatakis¹

2018

EJENG

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A method for a measurement of the speed of light is described. It is used a combination of simple, low-cost experiments. We will try to measure the wavelength and frequency of light and then we will determine the speed of light using the fundamental equation of wave. The measuring of wavelength based on the phenomenon of light interference or the phenomenon of light diffraction. The measuring of frequency based on the fact that the energy of a photon is proportional to the voltage needed to cause electrons to flow. The experiments are accessible to upper secondary school (or to college) students and particular to non-major science or engineering students. Experimental setup and equipment details are given. Also limitations of the method and experimental results are analyzed.

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“…It is used a modified He-Ne laser as a light source. Results for the velocity of light in air have been obtained with the aid of an oscilloscope [1].…”

Section: Introductionmentioning

confidence: 99%

Speed of Light Measurement with a Simple Way

Pagiatakis¹

2018

EJENG

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“…These obstacles can be overcome by using the laser as a simple light source, amplitude modulated at the intermode beat frequency, and measuring the phase difference between detectors placed at two different locations along the laser path. [13] This modulation technique improves the measurement of the speed of light by an order of magnitude, but at the cost of increasing the conceptual complexity. The introduction of the adjustable-length HeNe laser significantly reduces the consequences of uncertainty in mirror location and the index of refraction, and improves the measurement by a order of magnitude over the modulation technique, while retaining the conceptual simplicity of the original study of Ref.…”

Section: Introductionmentioning

confidence: 99%

Measuring the speed of light using beating longitudinal modes in an open-cavity HeNe laser

D’Orazio

Pearson

Schultz

et al. 2010

American Journal of Physics

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We describe an undergraduate laboratory that combines an accurate measurement of the speed of light, a fundamental investigation of a basic laser system, and a nontrivial use of statistical analysis. Students grapple with the existence of longitudinal modes in a laser cavity as they change the cavity length of an adjustable-cavity HeNe laser and tune the cavity to produce lasing in the TEM00 mode. For appropriate laser cavity lengths, the laser gain curve of a HeNe laser allows simultaneous operation of multiple longitudinal modes. The difference frequency between the modes is measured using a self-heterodyne detection with a diode photodetector and a radio frequency spectrum analyzer. Asymmetric effects due to frequency pushing and frequency pulling, as well as transverse modes, are minimized by simultaneously monitoring and adjusting the mode structure as viewed with a Fabry-Perot interferometer. The frequency spacing of longitudinal modes is proportional to the inverse of the cavity length with a proportionality constant equal to half the speed of light. By changing the length of the cavity, without changing the path length within the HeNe gas, the speed of light in air can be measured to be (2.9972 ± 0.0002) × 10 8 m/s, which is to high enough precision to distinguish between the speed of light in air and that in a vacuum. arXiv:1006.5462v1 [physics.class-ph]

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“…8-12. A few experiments use the laser as a light source and study the underlying physics. [13][14][15] Quite often, physics teachers present complaints about the lack of experiments which would demonstrate features of the physics in these very common devices. In this paper we describe an experiment where the physical phenomenon of frequency pulling of the longitudinal laser modes is studied.…”

Section: Introductionmentioning

confidence: 99%

Mode frequency pulling in He–Ne lasers

Lindberg

1999

American Journal of Physics

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Articles you may be interested inSelf-heterodyne mixing method of two inter-mode beat frequencies for frequency stabilization of a three-mode He-Ne laser AIP Advances 2, 022170 (2012); 10.1063/1.4733344 Design and test of miniaturized glass ceramics HeNe laser with frequency and intensity simultaneously stabilized Rev. Sci. Instrum. 81, 105116 (2010); 10.1063/1.3499247 Study on single-transverse mode output of high-power flat He-Ne laser Rev. Sci. Instrum. 80, 053112 (2009); 10.1063/1.3142460 Frequency stabilization of an internal mirror He-Ne laser by digital control Rev. Sci. Instrum. 73, 221 (2002); 10.1063/1.1419215Distance measurement method using the two intermode beat frequencies of a three-longitudinal mode He-Ne laser Rev.In this experiment, the frequency separation between two longitudinal He-Ne laser modes is studied. A description is given of the physics that causes a change in the frequency separation when the modes are observed at various positions in the gain profile. The frequency separation is measured with a fast photodetector in combination with a counter as a function of the mode intensity ratio. The intensity ratio is monitored with a scanning Fabry-Perot interferometer. For a scan of the two modes through the gain profile, a frequency separation change of ϳ30 kHz was observed.

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An inexpensive apparatus for the measurement of the group velocity of light in transparent media using a modified Helium–Neon laser

Abstract: Articles you may be interested inDistance measurement method using the two intermode beat frequencies of a three-longitudinal mode He-Ne laser Rev.

Cited by 4 publications

References 0 publications

Speed of Light Measurement with a Simple Way

Speed of Light Measurement with a Simple Way

Measuring the speed of light using beating longitudinal modes in an open-cavity HeNe laser

Mode frequency pulling in He–Ne lasers

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