Terahertz Time-Domain Spectroscopy Delay Line
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Solution Overview
Problem
Current time-domain spectroscopy methods using terahertz radiation face challenges in achieving fast and precise measurements due to limited precision in continuously moving optical elements, leading to longer measurement times and reduced accuracy.
Innovation Solution
A method involving a periodically moving optical delay line with an optical element, where the position is determined using a position sensor and smoothed data to enhance precision, allowing for continuous and precise time-domain measurements by eliminating jerks in the position sensor data through low-pass filtering, enabling faster and more accurate terahertz spectroscopic measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the optical element is moved continuously to enable fast measurements, then the measurement speed increases, but the measurement precision deteriorates due to limited precision in continuously moving optical elements
Solution Approach 1:
The patent implements feedback by continuously monitoring the position of the optical element using a position sensor and using this feedback information to correct and determine the actual delay time. The system measures the actual position of the continuously moving optical element and uses this feedback to compensate for motion imperfections, thereby maintaining high measurement precision while enabling fast continuous measurements.
Solution Approach 2:
The patent replaces reliance on purely mechanical positioning precision with a combined system that uses position sensing and electronic signal processing. Instead of depending solely on the mechanical precision of the optical element's continuous movement, the system substitutes mechanical precision requirements with electronic measurement and correction mechanisms, including position sensors and delay time calculation algorithms.
2Measurement precision
If the optical element is stopped at discrete positions for measurement, then the measurement precision improves, but the measurement time increases
Solution Approach 1:
The patent maintains continuous movement of the optical element throughout the measurement process, eliminating the need to stop at discrete positions. The optical element moves continuously while the position sensor continuously monitors its position, and the delay time is determined continuously based on the measured position. This continuous operation eliminates measurement time losses associated with stopping and starting the optical element.
Solution Approach 2:
The system performs preliminary continuous movement and position monitoring to establish the relationship between optical element position and delay time. The position sensor continuously tracks the optical element's position during movement, and this preliminary position information is used to determine the actual delay time without requiring the optical element to stop for measurement.
3Productivity
If the position sensor data is used directly from continuous movement, then the measurement speed is fast, but the data precision deteriorates due to jerks in position sensor data
Solution Approach 1:
The patent converts the harmful effect of jerks and noise in position sensor data into a benefit by using signal filtering and averaging techniques. The system deliberately allows continuous movement that produces some data variability, then applies filtering algorithms to extract the true delay time information from the noisy data. This approach transforms the raw, jerky position data into precise delay time measurements through electronic processing.
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 approach enables faster and more accurate time-domain measurements with improved precision and dynamic range, reducing the impact of environmental factors like temperature, and achieving femtosecond accuracy in delay time measurement.
Implementation Method 1
a transmitter which generates electro-magnetic pulses (pulsed electro-magnetic radiation, e.g. terahertz pulses) upon receipt of pulses of the optical pulse source... The optical pulses of the optical pulse source are radiated onto the photoconductive antenna, wherein the antenna emits terahertz pulses when hit by the optical pulses
Implementation Method 2
a coherent detector for detecting the electro-magnetic pulses and/or an electro-magnetic signal (electro-magnetic radiation, e.g. in the form of a terahertz signal) evoked by the electro-magnetic pulses... the coherent detector may comprise a photoconductor and a terahertz antenna, wherein the detector becomes active (i.e. ready to produce a photocurrent upon receipt of terahertz radiation) when hit by a pulse of the optical pulse source
Implementation Method 3
a delay line periodically changing the optical path length between the optical pulse source and the coherent detector and/or between the optical pulse source and the transmitter by periodically moving an optical element of the delay line
Data Source
AI summary
Time-domain measurements are carried out using arrangements and methods. A transmitter generates electro-magnetic pulses upon receipt of pulses of an optical pulse source. A coherent detector detects the electro-magnetic pulses or an evoked electro-magnetic signal. A delay line periodically changes the optical path length between the optical pulse source and the coherent detector and/or the electro-magnetic transmitter by periodically moving an optical element of the delay line. A position sensor determines the position of the optical element and smoothes the data generated by the position sensor. The coherent detector detects the electro-magnetic signal evoked by the electro-magnetic pulses. Pulses of the optical pulse source trigger the coherent detector. The time-dependency of the electro-magnetic pulses and/or of the electro-magnetic signal evoked by the electro-magnetic pulses are determined using signals of the coherent detector upon receipt of the electro-magnetic pulses and/or of the electro-magnetic signal and the smoothed position sensor data.