Beam profiling by vibrating knife edge: Implications for near-field optical scanning microscopy
✍ Scribed by A. Korpel; D. J. Mehrl; S. Samson
- Publisher
- John Wiley and Sons
- Year
- 1990
- Tongue
- English
- Weight
- 490 KB
- Volume
- 2
- Category
- Article
- ISSN
- 0899-9457
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✦ Synopsis
We show theoretically and experimentally that beam profiling with a vibrating knife exhibits spatial resolution equal to the knife-edge excursion. We discuss the implications of this for near-field optical scanning microscopy, propose an extension of the method to two dimensions, and calculate impulse response, step response, and spatial frequency response.
[ 181, and the near-field scanning acoustical microscope (NSAM) [19]. This communication deals with a proposed implementation of a NSOM which may have advantages in ease of construction and possibly in signal-to-noise ratio.
In Ref. 13 the authors call their technique "optical stethoscopy''-a seemingly obvious reference to a doctor's stethoscope, which allows localization of the patient's heart within one-thousandth of the wavelength emitted. However, this analogy fails in a very important aspect. As pointed out by the authors of Ref. 19, a cylindrical acoustical waveguide, such as an aperture in a thick rigid screen, supports at least one propagation mode no matter how narrow the constriction. Hence attenuation of the signal within the aperture is small compared to the optical case where such a guide would be cut off. This is indeed the difficulty with every proposed NSOM: if the aperture-whose diameter sets a lower limit to resolvable detail-is too thick, if acts as a cut-off waveguide; if it is too thin, the leakage of the electromagnetic field through the metal destroys the expected resolution. An excellent description of these difficulties may be found in Refs. 20 and 21. Detectors other than simple holes in a screen have been tried, such as tapered aluminum coated pipettes carrying an aper-