Bragg Grating Laser Beam Combining Wavelength Deviation Detection
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Solution Overview
Problem
Existing beam combining devices for VBG grating external-cavity laser modules struggle to detect and correct deviations in wavelengths, leading to decreased beam quality and power due to the inability to identify which wavelengths are deviated from the theoretical wavelength.
Innovation Solution
A beam combining device with multiple light-emitting modules, a focusing optical element, a beam combining element, a light splitting element, a dispersion element, a conversion optical element, and an image acquisition mechanism, which allows for the detection of wavelength deviations by forming spots on an image acquisition mechanism and adjusting the locked wavelength of Bragg gratings using a temperature control device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Bragg grating feedback method is used to achieve wavelength locking, then spectral line width is narrowed and adaptability is enhanced, but wavelength deviation occurs between actual locked wavelength and preset wavelength, resulting in decreased beam quality and power
Solution Approach 1:
The patent introduces a feedback mechanism by adding a dispersion element that separates wavelengths and an image acquisition device that detects spot positions. The system compares actual spot positions with theoretical positions to identify wavelength deviations, then feeds this information back to adjust the Bragg grating locked wavelengths, forming a closed-loop control system that continuously corrects wavelength accuracy.
Solution Approach 2:
The patent replaces manual wavelength detection and adjustment methods with an automated optical detection system. The dispersion element and image acquisition device create an automated measurement system that identifies wavelength deviations, eliminating the need for manual spectral analysis and enabling precise, rapid wavelength correction.
2Power
If multiple laser chips are placed in the same external cavity for spectral beam combining, then high-power output is achieved, but crosstalk occurs leading to deterioration of beam quality
Solution Approach 1:
The patent segments the wavelength combination process by using a dispersion element to spatially separate different wavelengths from multiple laser chips. Each wavelength forms a distinct spot on the image acquisition device, allowing individual wavelength detection and correction without interference from other wavelengths, thus eliminating crosstalk while maintaining high-power output.
Solution Approach 2:
The patent transforms the wavelength domain problem into a spatial domain problem by using the dispersion element to map different wavelengths to different spatial positions (spots). This dimensional transformation allows independent detection and correction of each wavelength component, resolving the crosstalk issue that occurs when multiple wavelengths coexist in the same spatial cavity.
3Manufacturing precision
If Bragg grating locked wavelength deviates from preset wavelength, then beam combining light quality decreases, but it is difficult to detect or judge which wavelengths are deviated
Solution Approach 1:
The patent introduces a dispersion element as an intermediary that converts wavelength information into spatial position information. The dispersion element separates different wavelengths and focuses them at different positions on the image acquisition device, creating a visual map where wavelength deviations can be easily detected as spot position deviations from theoretical positions.
Solution Approach 2:
The patent creates a spatial copy of the spectral information by using the dispersion element to map wavelengths to positions. The image acquisition device captures this spatial copy, allowing direct visual comparison between actual spot positions and theoretical spot positions, thereby simplifying the detection of wavelength deviations without complex spectral analysis equipment.
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 solution effectively enhances beam quality and power by allowing for quick detection and adjustment of wavelength deviations, ensuring that all wavelengths are locked to the preset values, thereby improving the overall performance of the beam combining device.
Implementation Method 1
a Bragg grating configured to receive laser emitted by the laser unit, and lock lasers of different wavelengths to form parallel light
Implementation Method 2
the parallel light is incident to the Fourier transform lens, is focused on the grating through the Fourier transform lens
Implementation Method 3
is then diffracted by the grating to form beam combining light
Implementation Method 4
a dispersion element, arranged on any one of the output optical paths of the light splitting element, and configured to disperse beam combining light into dispersed light
Data Source
AI summary
A beam combining device and method for a Bragg grating external-cavity laser module has a plurality of side by side light-emitting modules that use a Bragg grating to perform wavelength locking. Output light of the modules is incident to a beam combining element after passing through a focusing optical element for beam combining, and light subjected to beam combining is reflected partially and transmitted partially under the effect of a light splitting element. A part is incident into a dispersion element at a diffraction angle of the element. Parallel light is formed under the effect of a conversion optical element. Spots of the light beams of corresponding wavelengths of the light-emitting modules are formed on an image acquisition mechanism. Whether the wavelengths of the corresponding light-emitting modules are locked is determined by whether there is a deviation between preset spots and spots formed by the module on the acquisition mechanism.