A high signal-to-noise ratio passive near-field microscope equipped with a helium-free cryostat

We have developed a passive long-wavelength infrared (LWIR) scattering-type scanning near-field optical microscope (s-SNOM) installed in a helium-free mechanically cooled cryostat, which facilitates cooling of an LWIR detector and optical elements to 4.5 K. To reduce mechanical vibration propagation...

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Bibliographic Details
Published in:Review of scientific instruments 2017-01, Vol.88 (1), p.013706-013706
Main Authors: Lin, Kuan-Ting, Komiyama, Susumu, Kim, Sunmi, Kawamura, Ken-ichi, Kajihara, Yusuke
Format: Article
Language:English
Subjects:
Bellows
Evanescent waves
Helium
Noise
Scientific apparatus & instruments
Signal to noise ratio
Silicon dioxide
Submerging
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Summary:We have developed a passive long-wavelength infrared (LWIR) scattering-type scanning near-field optical microscope (s-SNOM) installed in a helium-free mechanically cooled cryostat, which facilitates cooling of an LWIR detector and optical elements to 4.5 K. To reduce mechanical vibration propagation from a compressor unit, we have introduced a metal bellows damper and a helium gas damper. These dampers ensure the performance of the s-SNOM to be free from mechanical vibration. Furthermore, we have introduced a solid immersion lens to improve the confocal microscope performance. To demonstrate the passive s-SNOM capability, we measured thermally excited surface evanescent waves on Au/SiO2 gratings. A near-field signal-to-noise ratio is 4.5 times the improvement with an acquisition time of 1 s/pixel. These improvements have made the passive s-SNOM a more convenient and higher-performance experimental tool with a higher signal-to-noise ratio for a shorter acquisition time of 0.1 s.
ISSN:0034-6748
1089-7623
DOI:10.1063/1.4973985