Transmission Grating Structure for Low-Loss WBC Lasers
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Solution Overview
Problem
Current wavelength beam combining (WBC) laser devices face limitations in increasing optical output due to reflection loss and heat generation issues with reflection gratings, and the production of diffraction gratings is costly and inefficient, especially for high-quality transmission gratings with low optical loss.
Innovation Solution
A transmission grating with alternating light-transmissive regions of different refractive indices, designed to minimize reflection loss and heat generation, is produced using a method involving glass plates with elongated reverse trapezoidal grooves and protrusions, allowing for high diffraction efficiency and mass production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a reflection grating is used to achieve high diffraction efficiency, then diffraction efficiency is improved, but heat generation increases due to light absorption by metal film
Solution Approach 1:
The patent changes the fundamental operating principle from reflection-based diffraction to transmission-based diffraction. By using a transmission grating with alternating refractive index regions instead of a reflection grating with metal film, the system achieves high diffraction efficiency while eliminating heat generation from metal absorption, thus resolving the contradiction between energy efficiency and temperature control
Solution Approach 2:
The patent substitutes the mechanical/optical system of reflection gratings with metal films for a transmission grating system using dielectric materials with alternating refractive indices. This replacement eliminates the need for metal film absorption mechanisms, thereby preventing heat generation while maintaining diffraction functionality
2Temperature
If a transmission grating is used to reduce heat generation, then heat generation is reduced, but diffraction efficiency decreases due to mirror surface reflection loss
Solution Approach 1:
The patent optimizes the refractive index parameters of the alternating regions to maximize transmission efficiency. By carefully selecting the refractive indices and dimensions of the alternating high and low index regions, the system achieves high diffraction efficiency through constructive interference while minimizing reflection losses, thus resolving the contradiction between heat reduction and efficiency maintenance
Solution Approach 2:
The patent employs a composite structure with alternating regions of different refractive indices (dielectric materials) to create a transmission grating. This composite approach enables the system to achieve both low heat generation (through dielectric transmission) and high diffraction efficiency (through optimized refractive index contrast and periodic structure), resolving the contradiction between thermal management and optical performance
3Reliability
If conventional methods are used to produce diffraction gratings with microscopic blazes, then diffraction functionality is achieved, but production cost increases and mass production becomes difficult
Solution Approach 1:
The patent segments the grating structure into alternating regions of different refractive indices that can be formed through standard photolithography and etching processes. This segmentation approach replaces the need for complex microscopic blaze formation, enabling cost-effective mass production while maintaining diffraction functionality through the periodic refractive index modulation
Solution Approach 2:
The patent uses photolithography to create periodic patterns of alternating refractive index regions by copying the desired grating pattern onto the substrate. This copying method enables precise, repeatable fabrication of diffraction gratings at low cost, replacing expensive and difficult-to-scale conventional blaze formation techniques
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 diffraction efficiency and cost-effective mass production of transmission gratings, reducing heat generation and reflection loss, thereby enhancing the performance and reliability of WBC laser devices.
Implementation Method 1
diffracted light is transmitted therethrough
Implementation Method 2
a plurality of first light-transmissive regions (10) each having a refractive index of n1 and a plurality of second light-transmissive regions (20) each having a refractive index of n2 that is smaller than n1
Data Source
AI summary
A method of producing a transmission grating includes: providing first and second glass plates, each having a first main surface defining a plurality of elongated reverse trapezoidal grooves, each having a reverse trapezoidal shape in a vertical cross-section and being defined by a first wall, a second wall, and a bottom surface, wherein the elongated reverse trapezoidal grooves are formed at an uniform interval, thus defining a plurality of elongated trapezoidal protrusions, each having a first wall, a second wall, and an upper surface; engaging the elongated trapezoidal protrusions of the first glass plate with the elongated reverse trapezoidal grooves of the second glass plate; and fitting the first walls of the protrusions with the first walls of the grooves and closely fitting the upper surfaces of the protrusions with the bottom surfaces of the grooves, and bonding the first glass plate to the second glass plate.