Broadband Pulsed Light Source With Dispersion Stretching
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Solution Overview
Problem
Current spectroscopic measurement techniques using broadband pulsed light face challenges in maintaining the uniqueness of time and wavelength correspondence, especially at high output levels, and struggle with high-speed measurement due to limitations in SN ratio and the need for repeated scanning, which affects measurement accuracy and efficiency.
Innovation Solution
A broadband pulsed light source apparatus that includes a stretching module with two fibers having different dispersion characteristics to spatially divide and stretch the pulsed light, ensuring a one-to-one correspondence between elapsed time and wavelength, and a spectroscopic measurement apparatus that utilizes this light to perform high-speed measurements without losing wavelength-time uniqueness, even at high output levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the output of broadband pulsed light is increased to radiate stronger light, then the illumination intensity is improved, but unintended nonlinear optical effects occur and uniqueness of time and wavelength correspondence is lost
Solution Approach 1:
The broadband pulsed light is divided into multiple wavelength bands using a diffraction grating, and each band is independently detected by separate photodetectors. This segmentation allows the system to handle high output light while maintaining wavelength-time correspondence by processing each wavelength range separately without nonlinear optical interference.
Solution Approach 2:
A diffraction grating is introduced as an intermediary element to disperse the broadband pulsed light into different wavelength components before detection. This intermediary device enables the system to maintain wavelength information while handling high intensity light, preventing direct nonlinear optical effects between different wavelength components.
2Measurement precision
If spectroscopic measurement is performed using diffraction grating scanning, then wavelength resolution is improved, but measurement speed deteriorates due to sequential scanning
Solution Approach 1:
The spectrum is divided into multiple wavelength bands that are simultaneously detected by separate photodetectors. This eliminates the need for sequential scanning while maintaining wavelength resolution, as each photodetector captures a specific wavelength range at the same time.
Solution Approach 2:
The system transitions from temporal scanning (one wavelength at a time over time) to spatial parallel detection (multiple wavelengths detected simultaneously across different photodetectors). This dimensional change from sequential to parallel processing achieves both high resolution and fast measurement.
3Measurement precision
If light is limited in the incident slit for spectroscopic measurement, then measurement precision is maintained, but the SN ratio deteriorates due to reduced light amount
Solution Approach 1:
By dividing the spectrum into multiple wavelength bands and detecting them simultaneously with multiple photodetectors, the system can collect more total light information without requiring tight spatial confinement at a single slit, thereby improving the signal-to-noise ratio while maintaining measurement precision.
Solution Approach 2:
The system continuously detects all wavelength bands simultaneously without interruption or scanning, maximizing the utilization of available light and improving the signal-to-noise ratio by collecting all spectral information in one continuous measurement event.
4Loss of information
If repeated scanning is performed to increase total light amount, then the SN ratio is improved, but measurement time increases and high speed measurement cannot be achieved
Solution Approach 1:
Multiple photodetectors detect different wavelength bands simultaneously, collecting sufficient light information for high SN ratio in a single measurement event rather than requiring repeated scans, thereby achieving fast measurement.
Solution Approach 2:
The system uses pulsed broadband light illumination with simultaneous detection, replacing the need for repeated scanning actions. Each pulse provides complete spectral information across all wavelength bands at once, enabling high-speed measurement without time-consuming repeated scans.
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
The solution enables high-speed and accurate spectroscopic measurements over a wide wavelength band by maintaining the uniqueness of wavelength to time correspondence, suppressing unintended nonlinear optical effects and optimizing wavelength resolution, thus improving the SN ratio and measurement efficiency.
Implementation Method 1
stretching module structured to stretch a pulse width of broadband pulsed light from the broadband pulsed light source such that an elapsed time and a wavelength of light in a pulse correspond to each other on a one-to-one basis
Implementation Method 2
generation of super continuum light (hereinafter, referred to as SC light) using a nonlinear optical effect. The SC light is light obtained by passing light from a pulse laser source through a nonlinear element such as a fiber and broadening the wavelength by a nonlinear optical effect such as self-phase modulation
Implementation Method 3
broadening the wavelength by a nonlinear optical effect such as self-phase modulation or optical soliton
Implementation Method 4
A light receiver is disposed at the condensed position and the light is detected
Data Source
AI summary
Broadband pulsed light from a broadband pulsed light source is pulse-stretched such that an elapsed time and a wavelength in a pulse correspond to each other on a one-to-one basis, and is radiated to an object. The light transmitted through the object is received by a light receiver and converted into a spectrum by a calculator. The broadband pulsed light is divided according to a wavelength by dividing elements, and is pulse-stretched by two fibers having different dispersion characteristics or received by two light receivers having different characteristics.