3D Optical Functionalization of Semiconductors via Picosecond Laser Writing
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Solution Overview
Problem
Current methods for optical functionalization of semiconductor materials, such as silicon, are limited by the inability to create three-dimensional structures and require complex, clean environments due to the self-protection effects of silicon during femtosecond laser processing, which restricts the depth and complexity of optical waveguide inscription.
Innovation Solution
A method involving the emission of laser pulses with controlled duration and intensity, focused deep within the semiconductor material to achieve multi-photon absorption and controlled variation of the real part of the refractive index, allowing for the precise creation of optical elements like waveguides and diffraction gratings without damaging the material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If femtosecond laser is used for direct 3D laser writing in semiconductor materials, then optical functionalization can be achieved, but the self-protection effect of silicon limits energy deposition to an insufficient level for material modification
Solution Approach 1:
The patent changes the temporal parameter of the laser pulse from femtosecond to picosecond range (1-100 ps), which fundamentally alters the interaction mechanism with silicon. This parameter change overcomes the self-protection effect that limits energy deposition in femtosecond laser processing, enabling sufficient energy accumulation for reliable material modification and optical functionalization while maintaining controllable energy deposition levels.
2Reliability
If SOI technology is used for optical functionalization, then excellent optical performance is obtained, but waveguides are contained in one plane (2D) which prevents three-dimensional architectures
Solution Approach 1:
The patent transitions from two-dimensional waveguide fabrication (SOI technology) to three-dimensional optical structures by using picosecond laser pulses for direct volumetric writing. The laser can modify refractive index throughout the bulk material volume, enabling true 3D optical architectures including waveguides, resonators, and photonic crystals that extend in multiple dimensions, thereby achieving both excellent optical performance and three-dimensional adaptability.
3Reliability
If SOI technology is used for optical functionalization, then excellent optical performance is obtained, but several steps in a clean and controlled environment are required to overcome problems associated with undesirable external pollution
Solution Approach 1:
The patent extracts the optical functionalization process from the complex multi-step cleanroom fabrication environment of SOI technology. By using picosecond laser direct writing, the entire optical structure fabrication can be performed in a single step without requiring lithography, etching, deposition, and other cleanroom processes, thereby eliminating the complexity of multiple process steps while maintaining excellent optical performance.
4Reliability
If laser intensity is increased to overcome self-protection effect, then material modification can be achieved, but optical defects increase
Solution Approach 1:
The patent uses picosecond pulse duration (1-100 ps) which provides optimal balance between energy deposition efficiency and defect minimization. This temporal parameter enables sufficient energy accumulation for material modification while the longer pulse duration compared to femtosecond allows heat diffusion that prevents excessive localized heating and damage, thereby achieving material modification with minimal optical defects.
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
Enables reliable and reproducible three-dimensional optical functionalization of semiconductor materials, achieving excellent optical performance with minimal optical defects and allowing for the creation of complex optical micro-devices within the material.
Implementation Method 1
the light intensity per pulse in a focusing volume of the laser beam being adapted to generate a multi-photon absorption
Data Source
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AI summary
One aspect of the invention relates to a system (100) for optical functionalisation at different depths of a sample (10) made of semiconductor material, comprising: - a source (20) for emitting a laser beam formed of pulses having effective durations between 1 ps and 100 ns, having a wavelength in the spectral band of transparency of the material; - a microscope lens (40) for focusing of the laser beam at different depths in the sample according to a predetermined pattern, the luminous intensity per pulse in a focal volume of the laser beam being suitable for generating a multi-photonic absorption in the semiconductor material; - a measurement device (30) for measuring the real part of the refractive index of the sample at each point of the pattern; - a control unit (60) for controlling the number of pulses received per point of the pattern depending on said measurement of the real part of the refractive index, in such a way as to obtain, at each point of the pattern, a gradual modification of the real part of the refractive index of the material up to a relative variation of the real part of the refractive index greater than 10-3 in absolute value.