THz Scanning Near-field Microscopy (SNOM)

Applications: scanning near-field optical microscopy (SNOM, NSOM), THz spectroscopy (THz-SNOM), scattering SNOM, apertureless SNOM (aSNOM), transient force microscopy (TFM), dual-modulated SNOM.

SNOM microscopes remarkably improve the resolution of optical microscopes by going way beyond the limit imposed by the wavelength of light (called far-field). The imaging resolution of SNOMs depends on the size of the optical aperture, and for apertureless detection on the radius of the scanning tip, and can therefore be as low as 10 nm.

Apertureless SNOMs use an oscillating tip driven at resonance in order to modulate the incident light or THz radiation. Keeping the tip in resonance provides maximum sensor sensitivity and is conveniently achieved with a phase-locked loop (PLL). The THz radiation is modulated by the tip and detected with a lock-in amplifier. Even better signal-to-noise can be achieved by double modulation approaches, for instance by modulating the incident THz beam.

Objectives: perform high resolution detection with optical microscopy with very high signal-to-noise ratio
Benefits: all in one box measurement solution for scattering SNOM and apertureless SNOM with considerable reduction of number of instruments compared to existing setups, top performance provided by the best digital lock-in amplifier in the market with 120 dB dynamic range, fast scanning with the worlds fastest digital PLL, best-in-class software programming support
Relevant products: HF2PLL Phase-locked Loop, HF2LI-PID Quad-PID Controller, HF2LI-MF Multi-frequency, HF2LI-MOD AM/FM Modulation

HF2PLL THz Scanning Near-field Microscopy (SNOM) Setups

Key Features of the HF2PLL Phase-locked Loop for this Application

  • Integrated solution for the demodulation of 2 independent signals up to 50 MHz
  • 2 independent phase-locked loops with operation up to 50 MHz
  • Integrated quadruple PID controller for configurable Z-feedback behavior
  • Demodulator dynamic reserve at 120 dB
  • Best-in-class programming support for LabVIEW, MATLAB, Python, and C++

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