Development of short‐wavelength far‐infrared lasers and measurement of optical constants

Nakayama, Keiichi I.; Tazawa, H.; Okajima, S.; Kawahata, K.; Tanaka, K.; Tokuzawa, T.; Ito, Y.

doi:10.1002/eej.20082

Cited by 3 publications

(2 citation statements)

References 8 publications

(11 reference statements)

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“…However, the measured absorption coefficient of quartz at 47.6 m is about ten times larger than that at 118.8 m. So we have measured optical constants 13 of several optical materials suitable for the short wavelength FIR regime and found that a silicon etalon with high resistivity is a useful material in this regime. In the figure, an YAG laser ͑wavelength: 1.06 m, power: 100 mW͒ is used for the alignment of the interferometer since the visible He-Ne laser is not transmitted through silicon.…”

Section: F132-2mentioning

confidence: 95%

Two color far infrared laser interferometer

Kawahata

Akiyama

Pavlichenko

et al. 2006

Review of Scientific Instruments

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Two color interferometer using a short wavelength far infrared laser has been developed for high performance plasmas on large helical device and for future fusion devices such as ITER. High power laser lines simultaneously oscillating at 57.2 and 47.6 m were achieved in a CO 2 -laser-pumped CH 3 OD laser. By introducing Ge:Ga photoconductive detectors operating at liquid He temperature, we have successfully detected two color beat signals ͑0.55 and 1.2 MHz͒ with excellent signal-to-noise ratio ͑ϳ40 dB͒. These beat signals were fed into phase comparators for phase measurement after passing through intermediate frequency bandpass filters. Two color far infraned laser interferometer work was successful in the demonstration of mechanical vibration compensation.

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Section: F132-2mentioning

confidence: 95%

Two color far infrared laser interferometer

Kawahata

Akiyama

Pavlichenko

et al. 2006

Review of Scientific Instruments

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“…Another advantage of adapting 50 µm is to reduce the beam bending effect to a quarter of that at 119 µm. Therefore, we have been developing shorter wavelength laser oscillation lines, and achieved a lot of high power oscillation lines between 40 µm and 100 µm [3]. Among them, the most powerful oscillation line is a 57.2 µm CH 3 OD laser line pumped by a continuous wave 9R(8) CO 2 laser, which simultaneously oscillates with a 47.7 µm line [4].…”

Section: Introductionmentioning

confidence: 99%

Progress in development of two color laser diagnostics for the ITER poloidal polarimeter

Kawahata¹,

Akiyama²,

Tanaka³

et al. 2012

J. Inst.

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Two color laser diagnostics using THz laser sources are under development for a high performance operation of the Large Helical Device and for future fusion devices such as ITER. So far, we have achieved high power laser oscillation lines simultaneously oscillating at 57.2 µm (1.6 W) and 47.7 µm (0.8 W) by using a twin optically-pumped CH 3 OD laser. And, we confirmed the usefulness of this two color laser operation for two-color laser interferometry in a test stand. For the measurement of the Faraday rotation angle we have developed a photo-elastic modulator (PEM) operating around 50 µm, and performed bench tests of the polarimeter with dual PEMs and demonstrated the feasibility of the polarimeter. The achieved angular resolution is 0.01 degrees with a time resolution of 1 ms, which satisfies diagnostic requirements for q-profile measurements on ITER (0.05 deg. at 10 ms time resolution). In this symposium, recent hardware developments and simultaneous measurements of a phase shift and a rotation angle will be presented.

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Development of terahertz laser diagnostics for electron density measurements

Kawahata

Akiyama

Tanaka

et al. 2008

Review of Scientific Instruments

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A two color laser interferometer using terahertz laser sources is under development for high performance operation on the large helical device and for future burning plasma experiments such as ITER. Through investigation of terahertz laser sources, we have achieved high power simultaneous oscillations at 57.2 and 47.6 m of a CH 3 OD laser pumped by a cw 9R͑8͒ CO 2 laser line. The laser wavelength around 50 m is the optimum value for future fusion devices from the consideration of the beam refraction effect and signal-to-noise ratio for an expected phase shift due to plasma. In this article, recent progress of the terahertz laser diagnostics, especially in mechanical vibration compensation by using a two color laser operation and terahertz laser beam transmission through a dielectric waveguide, will be presented.

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Development of short‐wavelength far‐infrared lasers and measurement of optical constants

Cited by 3 publications

References 8 publications

Two color far infrared laser interferometer

Two color far infrared laser interferometer

Progress in development of two color laser diagnostics for the ITER poloidal polarimeter

Development of terahertz laser diagnostics for electron density measurements

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