Sub-terahertz scanning near-field optical microscope using a quartz tuning fork based probe.
Opt Express
; 31(12): 19754-19765, 2023 Jun 05.
Article
en En
| MEDLINE
| ID: mdl-37381384
ABSTRACT
We report a sub-terahertz scattering-type scanning near-field microscope (sub-THz s-SNOM) which uses a 6 mm long metallic tip driven by a quartz tuning fork as the near-field probe. Under continuous-wave illumination by a 94â
GHz Gunn diode oscillator, terahertz near-field images are obtained by demodulating the scattered wave at both the fundamental and the second harmonic of the tuning fork oscillation frequency together with the atomic-force-microscope (AFM) image. The terahertz near-field image of a gold grating with a period of 2.3â
µm obtained at the fundamental modulation frequency agrees well with the AFM image. The experimental relationship between the signal demodulated at the fundamental frequency and the tip-sample distance is well fitted with the coupled dipole model indicating that the scattered signal from the long probe is mainly contributed by the near-field interaction between the tip and the sample. This near-filed probe scheme using quartz tuning fork can adjust the tip length flexibly to match the wavelength over the entire terahertz frequency range and allows for operation in cryogenic environment.
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MEDLINE
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En
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Opt Express
Asunto de la revista:
OFTALMOLOGIA
Año:
2023
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Article