Apertureless near-field optical microscopy via local second-harmonic generation
Anatoly V. Zayats,
Vahid Sandoghdar
Journal of Microscopy-Oxford
202
94-99
(2001)
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We describe an apertureless scanning near-field optical microscope (SNOM) based on the local second-harmonic generation enhancement resulting from an electromagnetic interaction between a probe tip and a surface. The imaging mechanisms of such apertureless second-harmonic SNOM are numerically studied. The technique allows one to achieve strongly confined sources of second-harmonic light at the probe tip apex and/or surface area under the tip. First experimental realization of this technique has been carried out using a silver-coated fibre tip as a probe. The experiments reveal a strong influence of the tip-surface interaction as well as polarization of the excitation light on images obtained with apertureless second-harmonic SNOM. The technique can be useful for studying the localized electromagnetic excitations on surfaces as well as for visualization of lateral variations of linear and nonlinear optical properties of surfaces.
Results and thoughts on optical microscopy using a single-molecule probe
Vahid Sandoghdar,
J. Michaelis,
C. Hettich,
C. Schmitt,
J. Zitzmann,
S. Kuhn
We discuss our recent results as well as planned experiments for obtaining molecular resolution in optical microscopy. By combining single molecule spectroscopy and scanning probe microscopy we have demonstrated optical microscopy with a single-molecule light source. We also sketch a method for the use of an inhomogeneous static electric field for determining the position of a molecule in all three dimensions.
The optical microscope is probably the only scientific instrument that children are familiar with, and possibly the only one that can be bought in toy shops. At school, most of us looked into such microscopes with great expectations, hoping to see unimaginable details of a leaf or dead fly. Often we were disappointed that we could not see more. Where were all those atoms and molecules that everything is supposed to be made of? If we complained to the teacher, we were usually told that one cannot see things that are too small in an optical microscope. Until recently the teacher was right, but not any more.
Diamond colour centres as a nanoscopic light source for scanning near-field optical microscopy
S. Kuhn,
C. Hettich,
C. Schmitt,
J-PH. Poizat,
Vahid Sandoghdar
Journal of Microscopy-Oxford
202
2-6
(2001)
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Recently it was shown that a single molecule at cryogenic temperatures could be used as a local light source for illumination of a sample in the near field. Conventional light-emitting systems such as dye molecules and semiconductor quantum dots could also be used for this purpose, but they suffer from lack of photostability. However, colour centres in diamond have been found to be remarkably stable against bleaching and blinking effects. Here we present the fist SNOM images taken with nanoscopic diamond crystals as a light source.
Direct spectroscopy of a deep two-dimensional photonic crystal microresonator
P. Kramper,
A. Birner,
Mario Agio,
C.M. Soukoulis,
F. Muller,
U. Gosele,
Jürgen Mlynek,
Vahid Sandoghdar
Photonic crystals based on macroporous silicon with fundamental band gaps in the middle infrared region 3.4-5.8 mum were fabricated. Scanning probe optical microscopy and laser spectroscopy were combined to examine a deep two-dimensional photonic crystal microresonator based on a single point defect. Two sharp resonances were recorded in the band gap, in excellent agreement with the results of numerical simulations. Such a microresonator with high-quality factors and a subwavelength mode extension could be used for a range of applications including integrated optical gas sensors.
Towards controlled coupling between a high-Q whispering-gallery mode and a single nanoparticle
We discuss our recent experiments that aim at the realization of coupling between a nano-emitter that is placed at the extremity of a sharp glass-fiber tip and a high-Q whispering-gallery mode. We quantify the influence of the tip using different probes and modes of a microsphere with different quality factors and mode extensions. Our measurements show that a micron-sized tip results in a substantial perturbation of the modes. On the contrary, by using a tip of diameter about 100 nm it should be possible to couple a nanoparticle to the most-confined modes of a microsphere without spoiling quality factors even as high as 10(8).
Mapping and manipulating whispering gallery modes of a microsphere resonator with a near-field probe
Stephan Götzinger,
S. Demmerer,
O. Benson,
Vahid Sandoghdar
Journal of Microscopy-Oxford
202
117-121
(2001)
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We report high spatial resolution mapping of high-Q whispering gallery modes in microsphere resonators with a near-field probe. We present experimental results on the effect of Q-factor degradation when the probe interacts with the evanescent field and discuss future applications of our experimental set-up for realization of novel nanolasers and nano light-emitting-diodes.
A single gold particle as a probe for apertureless scanning near-field optical microscopy
Thomas Kalkbrenner,
M. Ramstein,
Jürgen Mlynek,
Vahid Sandoghdar
Journal of Microscopy-Oxford
202
72-76
(2001)
| Journal
We report on the fabrication, characterization and application of a probe consisting of a single gold nanoparticle for apertureless scanning near-field optical microscopy. Particles with diameters of 100 nm have been successfully and reproducibly mounted at the end of sharp glass fibre tips. We present the first optical images taken with such a probe. We have also recorded plasmon resonances of gold particles and discuss schemes for exploiting the wavelength dependence of their scattering cross-section for a novel form of apertureless scanning near-field optical microscopy.
A model system for two-dimensional and three-dimensional photonic crystals: macroporous silicon
J. Schilling,
R.B. Wehrspohn,
A. Birner,
F. Muller,
R. Hillebrand,
U. Goesele,
S.W. Leonard,
J.P. Mondia,
F. Genereux, et al.
Journal of Optics A-Pure and Applied Optics
3
S121-S132
(2001)
| Journal
A review of the optical properties of two-dimensional and three-dimensional photonic crystals based on macroporous silicon is given. As macroporous silicon provides structures with aspect ratios exceeding 100, it can be considered to be an ideal two-dimensional photonic crystal. Most of the features of the photonic dispersion relation have been experimentally determined and were compared to theoretical calculations. This includes transmission and reflection of finite and bulk photonic crystals and their variation with the pore radius to determine the gap map. All measurements have been carried out for both polarizations separately since they decouple in two-dimensional photonic crystals. Moreover, by inhibiting the growth of selected pores, point and line defects were realized and the corresponding high-Q microcavity resonances as well as waveguiding properties were studied via transmission. The tunability of the bandgap was demonstrated by changing the refractive index inside the pores caused by an infiltrated liquid crystal undergoing a temperature-induced phase transition. Finally different realizations of three-dimensional photonic crystals using macroporous silicon are discussed. In all cases an excellent agreement between experimental results and theory is observed.
Kontakt
Abteilung Nanooptik Prof. Vahid Sandoghdar
Max-Planck-Institut für die Physik des Lichts Staudtstr. 2 91058 Erlangen
