Thin Plate Optical Modulator Stray Light Removal
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Solution Overview
Problem
Optical modulators with thin substrates face challenges in maintaining mechanical strength and suffer from increased stray light density, which degrades the signal-to-noise (S/N) ratio due to the confinement of stray light within the substrate, especially when the substrate thickness approaches the depth of the optical waveguide.
Innovation Solution
An optical modulator design incorporating a thin plate with an electrooptic effect, where an optical waveguide and modulation electrode are formed, and a stray light removing member such as a light absorbing, high refractive index, or concave portion is strategically placed within or near the thin plate to effectively remove stray light, preventing it from mixing with the output light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the substrate thickness is reduced to achieve velocity matching and lower driving voltage, then the modulation performance is improved, but the mechanical strength of the substrate deteriorates
Solution Approach 1:
The patent uses a composite structure consisting of a thin LN substrate (30 μm or less) combined with a dielectric layer having lower dielectric constant. This composite structure enables velocity matching between optical and microwave while maintaining mechanical strength through the combined properties of the two materials.
2Power
If the substrate thickness is reduced to achieve velocity matching, then the modulation performance is improved, but stray light is confined within the substrate causing S/N ratio deterioration
Solution Approach 1:
The patent extracts stray light from the substrate by introducing a dielectric layer with lower dielectric constant than the LN substrate. This dielectric layer acts as a barrier that prevents stray light confinement, allowing the thin substrate to maintain both velocity matching performance and low stray light influence.
3Strength
If a dielectric layer is added to maintain mechanical strength, then the substrate strength is improved, but the device structure becomes more complex
Solution Approach 1:
The dielectric layer serves multiple functions simultaneously: it provides mechanical strength support, enables velocity matching between optical and microwave, and prevents stray light confinement. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.
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 implementation of a stray light removing member improves the S/N ratio by confining and removing stray light, thereby enhancing the optical modulator's performance and mechanical strength, even at reduced substrate thicknesses.
Implementation Method 1
a thin plate having an electrooptic effect and having a thickness of 20 μm or less, an optical waveguide formed on a top or bottom surface of the thin plate, and a modulation electrode formed on the top surface of the thin plate to modulate light passing through the optical waveguide
Data Source
AI summary
An optical modulator using a thin plate capable of improving an S/N ratio of an output light is provided. The optical modulator including a thin plate 1 having an electrooptic effect and having a thickness of 20 μm or less, an optical waveguide 4 formed on a top or bottom surface of the thin plate, and a modulation electrode formed on the top surface of the thin plate to modulate light passing through the optical waveguide, wherein a stray light removing member 10 is disposed within the thin plate or in a vicinity of the thin plate.