Insights on Picophotonics and Measurement Techniques

Nov 11, 2024

Notes on Picophotonics Lecture

Introduction

  • Speaker: Works for University of Southampton and NTU Singapore
  • Topic: Picophotonics – seeing and studying picometric scale events optically.

Imaging Technologies Overview

  • Electron and optical microscopy resolutions are limited to several tens of picometers.
  • New imaging and metrology techniques allow entry into the "no man's land" beyond current limitations.
  • Focus on picometer imaging using free electron beams.

Free Electron Beam Imaging

  • Concept:
    • Focus electron beam on nanoscale objects (e.g., cantilevers) in a scanning electron microscope (SEM).
    • Rate of secondary electron production is position-dependent and can detect displacements as small as one picometer.
  • Imaging Technique:
    • Instead of scanning across structures, keep electron beam fixed and detect secondary electrons over time.
    • Calculate modulation spectrum to create hyperspectral images.
  • Example: Observing a flea's setae and their movements using this technique.

Brownian Motion Detection

  • Importance of studying Brownian motion in nanoscale structures.
  • Example of a cantilever and its thermal motion.
  • Brownian motion amplitude can be in the range of picometers to hundreds of picometers.
  • Characteristic trace of cantilever motion shows both thermal and ballistic regimes.
    • Ballistic motion observed in short time frames, transitioning to random motion.

Optical Techniques in Metrology

  • Focus on metamaterials for optical measurements.
  • Metamaterials can have their optical properties changed by mechanical movements.
  • Brownian motion detection in optomechanical metamaterials shows oscillations around 100-200 picometers.
  • Optical detection through changes in reflectivity/transmission of light.

Challenges of Optical Metrology

  • Traditional optical measurement limitations due to diffraction limits (e.g., size of the atom vs. wavelength).
  • Solution: Using structured, topologically structured light to improve resolution.
  • Concepts of singularities and local k-vectors in structured light can lead to resolutions much smaller than the wavelength.

Artificial Intelligence in Optical Measurement

  • AI techniques can enhance optical measurement resolution via deep learning.
  • Training sets based on diffraction patterns can improve the estimation of parameters like the width and position of slits in metallic films.
  • Results show optical measurement resolutions comparable to electron microscopy techniques.

Recent Advances in Nanostructure Measurements

  • Use of topologically structured light to detect scatter from nanowires.
  • Improvement in training sets leads to better accuracy in detecting displacement.
  • Recent results: ability to measure displacements as small as 28 picometers, aiming for under 2 picometers.
  • Potential applications include studying dynamics of Brownian motion in nanostructures.

Conclusions

  • Highly trained AI networks can solve complex measurement problems in picophotonics.
  • Topological illumination and sensitivity are key to achieving high resolutions in optical metrology.
  • Future work includes studying fundamental physics at picometric scales and potential biomedical applications.

Q&A Session Highlights

  • Clarification on collision time related to internal Brownian motion.
  • Discussion on the relation to x-ray interferometry and the complexity of current advanced systems versus new optical methods.