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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.
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