Objectives

• Scanning near-field optical microscopy of metal films modified by spatially modulated laser radiation
• Interactions of the surface plasmon/polaritons and localized surface plasmons
• Scanning Near-field optical microscopy of biological objects (erythrocytes etc.)
• Fluorescence near-field optical microscopy
• Spatially resolved spectroscopy
• Optical nanolithography
• Creation of aperturless SNOM and heterodyne aperture SNOM
• Creation of fiber probes for SNOM

Principle

Near-field optical microscopy is based upon the detection of non-propagating evanescent waves in the near-field region. The near-field region is defined as the region away from the sample that is less than the wavelength of the incident light. In near-field scanning optical microscopy this distance is typically on the order of a nanometer. In order to achieve an optical resolution better than the diffraction limit, a probe has to be brought within the near-field region. The probe can either detect in the near-field directly, by means of a sub-wavelength size aperture (collection mode), or by using the probe as a waveguide with a sub-wavelength scattering source and detecting the evanescent waves as they propagate into the far-field (transmission mode).

The configuration of the tip in these applications is of utmost importance to the performance of the system. The tip, which is coated with a metal of small skin depth, works as a probe, as well as a light waveguide.

Advantages

• Scanning near-field optical microscopy is, until today, the only technique that combines sub diffraction limit optical resolution ( 100 nm) with nanometer topographical information.
• Opportunity to receive optical spectra with the nanometer spatial resolution
• Opportunity to investigate fast optical kinetic processes with nanometer spatial resolution

Configuration

We use SNOM developed and made in Institute of Spectroscopy of the Russian Academy of Science. Technical specifications may be found at http://www.isan.troitsk.ru/win/exhib/isan.htm#b6_reg

Scanner: Sample position - horizontal, X,Y scan range - 20 µm x 20 µm, Z scan range - 5 µm, Initial Z approach - slip-and-stick motion upward or downward, automatically controlled. Coarse slip-and-stick motion in x, y plane - step 1 µm, the full range - 10 mm.

Probes: Standard optical fiber probes for SNOM glued onto a tuning fork (standard watch quartz resonator for 32 kHz)

Controller electronics: Electronic unit specially designed to work with the 32 kHz resonance frequency tuning fork with an attached probe. The performance of such a detector is really close to the theoretical noise and resolution limit.

Frequency range - 31 - 33 kHz,
Frequency accuracy - < 0.01 Hz,
Frequency stability f/f - < 10-8
Force sensitivity - 1 pN/Hz
Response time - 2 ms.

Photon detection: Electronics provides the possibility to count the photons in a time gating mode with an external synchronization (the shortest time interval available is 100 ns). Both direct output of PMT (negative single-photon pulses with an amplitude of 10 mV and duration of a few ns) or TTL - pulses from other counters can be used.

Light Sources:
CW He-Ne laser (632 nm)
CW He-Cd laser (441 nm, 325nm)
CW YAG laser (second harmonic - 532 nm)

Applications

• Study of physical characteristics of metal and semiconductor nanoparticles.
• Study of physical characteristics of biological objects
• Nondestructive testing of various materials at micro- and nano-level.
• Nanolithography
• Nanophotonics
• Metal plasmon waveguides

Contact

Dr. Valerii Yasinskii LOD, IP NASB
e-mail: Diese E-Mail Adresse ist gegen Spam Bots geschützt, Sie müssen Javascript aktivieren, damit Sie es sehen können
tel.: +375(0)17 284 14 20

SNOM imaging of evanescent standing light wave