Optical Modulator Mounting Arrangement for Stress Isolation
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Solution Overview
Problem
Optical modulators experience deterioration in transmission properties due to housing deformation, which causes stress-induced refractive index changes and instability in light wave branching ratios, particularly in substrates with piezoelectric effects like lithium niobate.
Innovation Solution
The optical modulator is designed with a mounting arrangement where the fixed end between the substrate and the mounting portion is positioned outside the mode conversion branching portion, preventing external forces from affecting the mode conversion region, and incorporating concave portions to create a cavity that reduces stress distribution within the mode conversion branching portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the fixed end between the substrate and the mounting portion is positioned within the mode conversion branching portion, then the workability for optical fiber connection is improved, but the transmission properties deteriorate due to stress-induced refractive index changes
Solution Approach 1:
The substrate is divided into distinct functional regions: the mode conversion branching portion for optical function and the fixed end region for mechanical mounting. This spatial segmentation allows the fixed end to be positioned outside the mode conversion branching portion, preventing stress-induced refractive index changes while maintaining workability for optical fiber connection.
Solution Approach 2:
The mounting portion acts as an intermediary element between the substrate and the housing. By positioning the fixed end on the mounting portion rather than directly within the mode conversion branching portion, the design isolates the sensitive optical region from mechanical stresses while still providing secure mounting and fiber connection capabilities.
2Reliability
If the housing is airtightly sealed, then the protection and stability are improved, but deformation occurs due to thermal history and manufacturing processes
Solution Approach 1:
The sensitive mode conversion branching portion is extracted from the region affected by housing deformation. By positioning the fixed end outside this portion and creating a cavity beneath it, the design removes the critical optical functionality from the zone subject to thermal and mechanical stresses during sealing and operation.
Solution Approach 2:
A cavity is created beneath the mode conversion branching portion before final housing assembly and sealing. This pre-formed cavity acts as a cushioning space that accommodates housing deformation from thermal history and manufacturing processes, preventing stress transmission to the optical waveguide while maintaining the airtight seal.
3Device complexity
If the fixed end is positioned within the mode conversion branching portion, then the structural compactness is improved, but stress distribution causes refractive index changes and branching ratio instability
Solution Approach 1:
The substrate layout is segmented to separate the fixed end mounting region from the mode conversion branching portion. This spatial division, while slightly increasing footprint, ensures that stress from mounting does not affect the branching ratio, thereby stabilizing the optical performance.
Solution Approach 2:
Different regions of the substrate are assigned different qualities: the mode conversion branching portion is designed with optical precision and stress avoidance, while the fixed end region on the mounting portion is designed for mechanical stability. This local differentiation allows each region to optimize its function without compromising the other.
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
This configuration stabilizes the branching ratio of light waves, reduces loss differences between Mach-Zehnder waveguide arms, and minimizes deterioration of transmission properties, effectively addressing the issues of stress-induced refractive index changes and instability in optical modulators.
Implementation Method 1
an optical waveguide element configured such that an optical waveguide 20 including a Mach-Zehnder waveguide for performing optical modulation is formed on a substrate 10 having an electro-optical effect
Implementation Method 2
a mode conversion portion 22 for converting a light wave mode before branching light waves is disposed on an upstream side of the Y branched waveguide portions 21 in a light wave moving direction
Implementation Method 3
a plurality of Y branched waveguide portions 21 that distribute light waves propagated through an optical waveguide at a uniform power ratio
Implementation Method 4
since a substrate such as an LN substrate (lithium niobate substrate) used for an optical modulator has an excellent piezoelectric effect, a polarization proportional to pressure also occurs at the same time when an external force is applied, a refractive index of a portion having received pressure changing more prominently
Data Source
AI summary
An optical modulator capable of curbing deterioration of transmission properties due to deformation of a housing is provided. Provided is an optical modulator including a substrate (10) on which an optical waveguide (20) is formed and a housing (30) that accommodates the substrate, in which the optical waveguide includes mode conversion branching portions (21, 22) which convert a mode of light waves propagating through the optical waveguide and branch the light waves, a mounting portion (32) protruding from a surface (31) inside the housing and holding the substrate is formed, and the substrate is fixed to the mounting portion in an arrangement in which a fixed end (33) between the substrate and the mounting portion is positioned outside a region including the mode conversion branching portions when the substrate is seen in a plan view.