Scanning Probe Microscope Near-Field Light Modulation
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Solution Overview
Problem
The plasmon propagation-type optical scanning probe microscope faces challenges in achieving high-precision and sensitive measurements due to noise interference from control light and background frequencies, which deteriorate the signal-to-noise ratio, especially when measuring optical properties at nanometer spatial resolution.
Innovation Solution
A scanning probe microscope method that modulates near-field light and varies the relative distance between the near-field light and the sample, using a cantilever oscillation frequency to generate an interference signal, and selectively extracts specific frequency components using a photodetector with filtering to enhance measurement precision and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light is radiated to a cantilever to excite plasmon and near-field light is generated at the forefront of the probe for measurement, then optical property measurement at nanometer spatial resolution is achieved, but control light and background light mix with measured light causing noise interference and deteriorating signal-to-noise ratio
Solution Approach 1:
The patent applies periodic modulation to the excitation light source at a specific frequency to periodically excite plasmon in the cantilever. This creates a time-varying near-field light signal that can be distinguished from continuous control light and background light through frequency-selective detection, thereby resolving the noise interference problem while maintaining measurement precision
Solution Approach 2:
The patent introduces a photodetector as an intermediary that selectively detects light at the specific modulation frequency. This intermediary device filters out control light and background light by responding only to the modulated frequency, enabling precise extraction of near-field light signal from the mixed light components
2Measurement precision
If near-field light is used for high spatial resolution measurement, then nanometer-scale optical property measurement is achieved, but detected light is feeble making high-precision and sensitive measurement difficult
Solution Approach 1:
By periodically modulating the excitation light at a specific frequency, the patent creates a time-varying near-field light signal with enhanced detectability. The periodic nature allows synchronization detection that amplifies the weak signal relative to background noise, enabling sensitive measurement despite low light intensity
Solution Approach 2:
The patent employs feedback through frequency-selective detection where the detected signal at the modulation frequency is used to optimize measurement parameters. This feedback mechanism enhances the detection of weak near-field light by continuously adjusting detection sensitivity based on the modulated signal characteristics
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for precise measurement of a sample's shape and optical properties using near-field light without degrading the signal-to-noise ratio, effectively reducing noise interference and improving measurement sensitivity.
Implementation Method 1
a frequency for oscillating the cantilever is selectively extracted
Implementation Method 2
An optical property of a surface of a sample can be measured at spatial resolution of a few tens nm similar to the aperture by holding clearance between the minute aperture and the sample in a range of a few nm to a few tens nm and scanning the aperture
Implementation Method 3
scattered light by the sample of the near-field light and having a characteristic that the near-field light is modulated, relative distance between the near-field light and the sample is periodically varied and an interference signal generated by a frequency of modulation applied to the near-field light and a frequency for varying the relative distance between the near-field light and the sample is selectively extracted
Data Source
AI summary
Disclosed is a measurement method of a scanning probe microscope based upon a measurement method of a scanning probe microscope for observing a shape and an optical property of a sample by exciting near-field light, scanning relative positions of the near-field light and the sample and detecting scattered light by the sample of the near-field light and having a characteristic that the near-field light is modulated to periodically vary the relative positions of the near-field light and the sample and that a frequency of modulation applied to the near-field light and an interference signal generated at a frequency for varying the relative positions of the near-field light and the sample are selectively extracted.