Transparent Oxide Glass for Submicron Refractive Index Modulation
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Solution Overview
Problem
Current glasses are not suitable for high-energy optical applications due to limited spectral transmission beyond 3 microns and inability to achieve submicron refractive index modulation in three-dimensional structures, especially in the infrared range up to 8 microns.
Innovation Solution
Development of transparent oxide glasses containing photosensitive silver ions, specifically formulated with silicon, phosphate, or germanium oxides, which can be inscribed with femtosecond laser beams to create high refractive index modulation structures with submicron spatial resolution and repeatability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional photothermoreactive glass is used to produce bulk Bragg grating, then the glass can be transparent in the visible range, but the spectral transmission beyond 3 microns is limited and losses prevent realistic applications in laser sources beyond 2 μm
Solution Approach 1:
The patent modifies the chemical composition parameters of the glass by incorporating specific oxide ratios (silica 30-80%, phosphate 10-40%, germanium oxide 5-20%, plus metal oxides) to achieve both visible and infrared transparency up to 8 microns, resolving the contradiction between visible transparency and infrared transmission capability
Solution Approach 2:
The invention creates a composite glass system combining multiple oxide components (silica, phosphate, germanium oxide) with metal ion dopants (silver, gold, copper) to achieve simultaneous visible and infrared transparency, overcoming the limitations of single-component or conventional composite glasses
2Manufacturing precision
If conventional UV lighting with interference pattern is used to modulate refractive index, then the grating can be stabilized by curing techniques, but the amplitude of refractive index variation is limited to about 10^-5
Solution Approach 1:
The patent replaces conventional UV lighting and curing processes with direct femtosecond laser writing, using multiphoton absorption to induce permanent refractive index modulation without thermal curing, achieving Δn > 10^-3 while simplifying the manufacturing process
Solution Approach 2:
The invention uses periodic femtosecond laser pulses to write three-dimensional refractive index modulation structures, enabling precise control of grating formation through controlled pulse sequences and spatial scanning patterns
3Manufacturing precision
If femtosecond laser beam is used for direct 3D writing in transparent materials, then submicron spatial resolution can be achieved, but no satisfactory technique has been demonstrated for inscription of optical refractive index modulation structures beyond 3 microns
Solution Approach 1:
The patent changes the material parameters by developing a specific glass composition formula with controlled oxide ratios and metal ion content, enabling the material to be inscribed with femtosecond lasers while maintaining transparency beyond 3 microns up to 8 microns
Solution Approach 2:
The invention creates a composite glass system combining silica, phosphate, and germanium oxide with metal ion dopants to achieve both submicron inscription capability and extended spectral transmission, resolving the contradiction between writing precision and spectral range
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 glasses enable the production of bulk Bragg gratings with refractive index variations greater than 10^-3 and submicron spatial resolution, suitable for high-energy optical applications across a wide spectral band, including the visible and infrared ranges up to 8 microns.
Implementation Method 1
The emergence of femtosecond laser sources has made it possible to develop direct 3D laser writing technologies in transparent materials such as glass
Implementation Method 2
The method is suitable for producing three-dimensional structures of modulation of refractive index to form a Bragg grating
Implementation Method 3
transparent glasses based on oxides of silica, of phosphate or of germanium containing photosensitive silver ions suitable for bulk inscription of a structure by a femtosecond laser beam
Data Source
AI summary
The invention relates to a process for inscribing a three-dimensional structure formed from variations in refractive index in the bulk of a transparent oxide glass comprising silver ions by femtosecond-laser-beam irradiation, the method comprising: generating a laser beam made up of a series of ultra-brief light pulses of pulse duration shorter than the characteristic time of thermalization of the glass so as to achieve an excitation at the point of irradiation via multi-photon interaction; focusing said beam at a desired depth in the glass; irradiating point by point the glass with said beam so as to form the structure in the glass along a predetermined path, the number of pulses, the repetition rate of the pulses and the irradiance at each irradiation point being controlled to induce an accumulation of silver aggregates localised in an annular peripheral region around an irradiation point, said accumulation of aggregates generating a variation in refractive index in the annular peripheral region around the irradiation point, and to erase a variation in refractive index in a segment of an annular peripheral region generated around another irradiation point when said segment of the peripheral region coincides with a region of the laser beam.