Squeezed Light at visible wavelength for eye-safe high-spatial-resolution surface microscopy

This research was funded as part of the DFG project " Gequetschtes Licht bei sichtbarer Wellenlänge für augensichere Oberflächenmikroskopie mit hoher räumlicher Auflösung " (project number 431078650).

1. State of the Art

  • Conventional LDV (Laser Doppler Vibrometry) technology employs homodyne and heterodyne interferometry methods to measure mechanical vibrations with high precision.
  • When combined with confocal microscopy—which provides excellent lateral resolution through a tightly focused laser spot—even minor surface topographies and vibrations can be analyzed.
  • Higher laser power for focusing is not feasible due to safety concerns and thermal effects. Lower power, however, results in poor signal-to-noise ratio (SNR).
  • Squeezed light represents a groundbreaking advancement in this regard. By leveraging quantum effects, it reduces statistical fluctuations in photon shot noise. The use of squeezed light in a vacuum state does not increase light intensity and thus does not raise laser power.

2. Objective

  • The goal is to develop a system that utilizes squeezed light and confocal scanning microscopy to measure surface topographies with outstanding lateral resolution—while operating at visible wavelengths that remain eye-safe.

3. Methods

  • Development of a high-precision green LDV combined with confocal microscopy to enhance resolution.
  • Due to the properties of squeezed light, the entire optical setup should exhibit minimal light loss.
  • Optimization of the detector using clipping and demodulation techniques [1] to overcome conventional signal-to-noise limitations.
  • Utilization of nonlinear optical resonators to generate squeezed light. The development of the squeezed light source is led by Prof. Schnabel's team at the University of Hamburg.
  • Combination of confocal scanning microscopy with squeezed light to improve resolution and reduce shot noise.

Lei Xiong, M.Sc.

Scientific Assistant

Tel.: +49 5323 72-4964
E-Mail: lei.xiong@tu-clausthal.de