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Optics Letters

Optics Letters


  • Vol. 25, Iss. 9 — May. 1, 2000
  • pp: 628–630

Resolution enhancement in a reflection mode near-field optical microscope by second-harmonic modulation signals

June-Hyoung Park, Myong R. Kim, and Wonho Jhe  »View Author Affiliations

Optics Letters, Vol. 25, Issue 9, pp. 628-630 (2000)

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The motion of the probe tip in a near-field scanning optical microscope, dithered by vibration of a tuning fork, can modulate the reflection signal from the sample surface not only at the fundamental dithering frequency but also at its second harmonic. By lock-in amplification of these modulated signals, enhanced optical images are obtained, even with an uncoated fiber probe. In particular, accurate optical images with higher resolution are obtained when the second-harmonic signal is detected, which results from the parametric modulation of the tip–sample separation at the double frequency of the horizontal dithering motion of the tip. Using a DVD ROM with a track pitch of 0.74 μm as a test sample, we observed that the sharp edges around the pits are clearly resolved with the second-harmonic signals and obtained enhanced resolution of ∼70 nm full width at half-maximum.

© 2000 Optical Society of America

OCIS Codes
(120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
(180.5810) Microscopy : Scanning microscopy

June-Hyoung Park, Myong R. Kim, and Wonho Jhe, "Resolution enhancement in a reflection mode near-field optical microscope by second-harmonic modulation signals," Opt. Lett. 25, 628-630 (2000)

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