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Mode-resolved frequency comb interferometry for high-accuracy long distance measurement.

van den Berg SA, van Eldik S, Bhattacharya N - Sci Rep (2015)

Bottom Line: By applying a high-resolution spectrometer based on a virtually imaged phased array, the frequency comb modes are resolved spectrally to the level of an individual mode.From the spectrally resolved output of a Michelson interferometer a distance is derived.Comparison with a fringe counting laser interferometer shows an agreement within <10(-8) for a distance of 50 m.

View Article: PubMed Central - PubMed

Affiliation: VSL, Thijsseweg 11, 2629 JA Delft, The Netherlands.

ABSTRACT
Optical frequency combs have developed into powerful tools for distance metrology. In this paper we demonstrate absolute long distance measurement using a single femtosecond frequency comb laser as a multi-wavelength source. By applying a high-resolution spectrometer based on a virtually imaged phased array, the frequency comb modes are resolved spectrally to the level of an individual mode. Having the frequency comb stabilized against an atomic clock, thousands of accurately known wavelengths are available for interferometry. From the spectrally resolved output of a Michelson interferometer a distance is derived. The presented measurement method combines spectral interferometry, white light interferometry and multi-wavelength interferometry in a single scheme. Comparison with a fringe counting laser interferometer shows an agreement within <10(-8) for a distance of 50 m.

No MeSH data available.


Related in: MedlinePlus

Schematic overview of the measurement setup for comparing distance measurement up to 50 m with a counting helium-neon laser and a frequency comb.The comb light is delivered to the setup with a single mode (SM) fiber, providing a clean mode profile. Both the HeNe laser (orange line) and comb laser (red line) measure the displacement quasi-simultaneously. PBS: polarizing beam splitter, POL: polarizer, λ/2: half-waveplate, CCD: charge-coupled device camera, M: planar mirror, RR: hollow retro reflector, CL: cylindrical lens (100 mm focal length), SL: spherical lens (400 mm focal length).
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f3: Schematic overview of the measurement setup for comparing distance measurement up to 50 m with a counting helium-neon laser and a frequency comb.The comb light is delivered to the setup with a single mode (SM) fiber, providing a clean mode profile. Both the HeNe laser (orange line) and comb laser (red line) measure the displacement quasi-simultaneously. PBS: polarizing beam splitter, POL: polarizer, λ/2: half-waveplate, CCD: charge-coupled device camera, M: planar mirror, RR: hollow retro reflector, CL: cylindrical lens (100 mm focal length), SL: spherical lens (400 mm focal length).

Mentions: We exploit a Ti:Sapphire laser as a frequency comb for the experiment. The laser operates at a repetition frequency of 1 GHz. About 6000 wavelengths in the range from 813.5 nm to 827.5 nm are used for the experiment. This corresponds to Q = 363664, p = 1…6000. The frequency comb is phase-locked to a cesium atomic clock with a stability of 10−11 in 1 second. About 10 mW of optical power is provided to the experiment via a single mode fiber. The light is sent into a Michelson interferometer, which is polarization sensitive by using a polarizing beam splitter for directing the light into the measurement and reference arm. The light is reflected by gold-coated hollow retroreflectors. The polarization of the incoming comb light is controlled with a λ/2 plate. We have chosen for this configuration because it allows for direct comparison to an independent laser interferometer, which is a heterodyne system with orthogonally polarized modes, requiring a polarization sensitive interferometer. By using the same interferometer with both lasers, effects of vibrations and drift on the comparison are minimized. After the Michelson interferometer, interference between the orthogonal components of the frequency comb light is obtained by a polarizer inserted at 45°. The light is subsequently analyzed with a spectrometer based on a Virtually Imaged Phase Array (VIPA) spectrometer, which is inspired on VIPA applications in telecommunications21 and comb spectroscopy22. The VIPA has a free spectral range (FSR) of 50 GHz and coating reflectances of >99.94% and 99.5%, respectively. The VIPA provides angular dispersion along the vertical axis. A grating (blazed, 1200 grooves/mm), provides angular dispersion in the horizontal plane. The light is imaged on charge-coupled device (CCD) camera with a 400 mm lens, resulting in individually resolved comb wavelengths, appearing as dots. An overview of the setup is shown in Fig. 3.


Mode-resolved frequency comb interferometry for high-accuracy long distance measurement.

van den Berg SA, van Eldik S, Bhattacharya N - Sci Rep (2015)

Schematic overview of the measurement setup for comparing distance measurement up to 50 m with a counting helium-neon laser and a frequency comb.The comb light is delivered to the setup with a single mode (SM) fiber, providing a clean mode profile. Both the HeNe laser (orange line) and comb laser (red line) measure the displacement quasi-simultaneously. PBS: polarizing beam splitter, POL: polarizer, λ/2: half-waveplate, CCD: charge-coupled device camera, M: planar mirror, RR: hollow retro reflector, CL: cylindrical lens (100 mm focal length), SL: spherical lens (400 mm focal length).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588503&req=5

f3: Schematic overview of the measurement setup for comparing distance measurement up to 50 m with a counting helium-neon laser and a frequency comb.The comb light is delivered to the setup with a single mode (SM) fiber, providing a clean mode profile. Both the HeNe laser (orange line) and comb laser (red line) measure the displacement quasi-simultaneously. PBS: polarizing beam splitter, POL: polarizer, λ/2: half-waveplate, CCD: charge-coupled device camera, M: planar mirror, RR: hollow retro reflector, CL: cylindrical lens (100 mm focal length), SL: spherical lens (400 mm focal length).
Mentions: We exploit a Ti:Sapphire laser as a frequency comb for the experiment. The laser operates at a repetition frequency of 1 GHz. About 6000 wavelengths in the range from 813.5 nm to 827.5 nm are used for the experiment. This corresponds to Q = 363664, p = 1…6000. The frequency comb is phase-locked to a cesium atomic clock with a stability of 10−11 in 1 second. About 10 mW of optical power is provided to the experiment via a single mode fiber. The light is sent into a Michelson interferometer, which is polarization sensitive by using a polarizing beam splitter for directing the light into the measurement and reference arm. The light is reflected by gold-coated hollow retroreflectors. The polarization of the incoming comb light is controlled with a λ/2 plate. We have chosen for this configuration because it allows for direct comparison to an independent laser interferometer, which is a heterodyne system with orthogonally polarized modes, requiring a polarization sensitive interferometer. By using the same interferometer with both lasers, effects of vibrations and drift on the comparison are minimized. After the Michelson interferometer, interference between the orthogonal components of the frequency comb light is obtained by a polarizer inserted at 45°. The light is subsequently analyzed with a spectrometer based on a Virtually Imaged Phase Array (VIPA) spectrometer, which is inspired on VIPA applications in telecommunications21 and comb spectroscopy22. The VIPA has a free spectral range (FSR) of 50 GHz and coating reflectances of >99.94% and 99.5%, respectively. The VIPA provides angular dispersion along the vertical axis. A grating (blazed, 1200 grooves/mm), provides angular dispersion in the horizontal plane. The light is imaged on charge-coupled device (CCD) camera with a 400 mm lens, resulting in individually resolved comb wavelengths, appearing as dots. An overview of the setup is shown in Fig. 3.

Bottom Line: By applying a high-resolution spectrometer based on a virtually imaged phased array, the frequency comb modes are resolved spectrally to the level of an individual mode.From the spectrally resolved output of a Michelson interferometer a distance is derived.Comparison with a fringe counting laser interferometer shows an agreement within <10(-8) for a distance of 50 m.

View Article: PubMed Central - PubMed

Affiliation: VSL, Thijsseweg 11, 2629 JA Delft, The Netherlands.

ABSTRACT
Optical frequency combs have developed into powerful tools for distance metrology. In this paper we demonstrate absolute long distance measurement using a single femtosecond frequency comb laser as a multi-wavelength source. By applying a high-resolution spectrometer based on a virtually imaged phased array, the frequency comb modes are resolved spectrally to the level of an individual mode. Having the frequency comb stabilized against an atomic clock, thousands of accurately known wavelengths are available for interferometry. From the spectrally resolved output of a Michelson interferometer a distance is derived. The presented measurement method combines spectral interferometry, white light interferometry and multi-wavelength interferometry in a single scheme. Comparison with a fringe counting laser interferometer shows an agreement within <10(-8) for a distance of 50 m.

No MeSH data available.


Related in: MedlinePlus