Optical Modulator Using Nonlinear Crystal for High-Speed UV Light
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Solution Overview
Problem
Conventional spatial light modulators (SLMs) using liquid crystals have slow response times, limiting their ability for high-speed modulation, and are not suitable for high-energy light applications such as ultraviolet light, which is desirable for laser machining of materials like carbon fiber reinforced plastics (CFRP).
Innovation Solution
A light modulator with a grating structure formed by nonlinear optical crystal refractive index regions, surrounded by regions with lower refractive indices, and equipped with conductive films that apply voltage to change the refractive index via electro-optical effects, enabling high-speed modulation and improved resistance to high-energy light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a liquid crystal-based spatial light modulator is used, then light modulation capability is achieved, but the response time becomes slow
Solution Approach 1:
The patent changes the material parameter from liquid crystal to nonlinear optical crystal, which fundamentally alters the response mechanism. The nonlinear optical crystal enables electro-optical modulation with significantly faster response times by utilizing the Pockels effect, where the refractive index changes linearly with applied electric field, eliminating the slow response inherent in liquid crystal molecules.
Solution Approach 2:
The invention replaces the mechanical reorientation of liquid crystal molecules with an electro-optical effect in a solid crystal. Instead of relying on viscous flow and molecular alignment (mechanical processes), the system uses direct electro-optical modulation where an applied voltage changes the refractive index instantaneously, substituting mechanical response with electrical field control.
2Reliability
If conventional light modulators are used, then light modulation is possible, but resistance to high-energy light such as ultraviolet is insufficient
Solution Approach 1:
The patent employs a composite structure combining nonlinear optical crystal with specific optical layers (high refractive index layer, low refractive index layer, and reflective layer). This composite material system provides both the electro-optical modulation capability and enhanced resistance to high-energy ultraviolet light, enabling the device to handle wavelengths suitable for laser machining applications.
Solution Approach 2:
The invention changes the material composition from liquid crystal to nonlinear optical crystal, which has fundamentally different optical properties. The nonlinear optical crystal exhibits higher damage threshold and better resistance to high-energy ultraviolet radiation, expanding the device's applicability to high-energy light wavelengths while maintaining modulation functionality.
3Productivity
If a grating structure with nonlinear optical crystal is implemented, then high-speed modulation is achieved, but device complexity increases
Solution Approach 1:
The patent segments the optical path into distinct functional layers: nonlinear optical crystal regions forming the grating, high refractive index layers, low refractive index layers, and reflective layers. This segmentation allows each layer to perform its specific function efficiently while maintaining overall device manageability and enabling high-speed modulation through the nonlinear optical crystal's electro-optical properties.
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 light modulator achieves faster response times compared to liquid crystal SLMs, allowing for high-speed modulation and extended usability to high-energy light wavelengths, including ultraviolet, making it suitable for applications like CFRP laser machining.
Implementation Method 1
Non-Patent Document 1 discloses a light modulator that modulates UV light (wavelength of 355 nm) by utilizing the Pockels effect
Implementation Method 2
The plurality of refractive index regions is sequentially arranged on a reference plane at a constant arrangement pitch so as to form a grating
Implementation Method 3
The plurality of refractive index regions is sequentially arranged on a reference plane at a constant arrangement pitch so as to form a grating
Data Source
AI summary
A light modulator of to this embodiment enables high-speed modulation to an SLM using a liquid crystal. The light modulator comprises refractive index regions arranged in a first direction on a reference plane, a region surrounding each refractive index regions and having a refractive index lower than that of each refractive index region, a first conductive film, and a second conductive film. The first conductive film is provided on any one of a pair of side surfaces arranged in the first direction in at least one refractive index region selected from the refractive index regions and belonging to a first group. The second conductive film is provided on any one of the pair of side surfaces so as not to overlap with the first conductive film in at least one refractive index region selected from the refractive index regions and belonging to a second group.