Crossed-Slit Waveguide Depolarizer for Compact Optical Integration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing depolarizers, particularly Lyot type fiber depolarizers, face challenges in achieving precise 45-degree fusion splices, are fragile, and require long lengths of high-birefringence fibers, making them difficult to integrate and prone to stress, limiting their miniaturization and reliability.
Innovation Solution
An electronically controlled depolarizer based on a crossed-slit waveguide with a horizontal-slit waveguide, 45-degree polarization rotation waveguide, and modulation electrodes, integrated on a silicon substrate with lithium niobate single crystal thin films, where the 45-degree polarization rotation waveguide adjusts the energy balance of TE and TM polarized light to achieve depolarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Lyot type fiber depolarizer is used, then depolarization function is achieved, but device length becomes long and integration becomes difficult
Solution Approach 1:
The patent replaces the mechanical fiber-based Lyot depolarizer with an integrated photonic circuit implementation. The depolarization function is achieved through waveguide structures and phase shifters fabricated on a chip, eliminating the need for long fiber splices and mechanical assembly, thereby achieving both compact size and reliable depolarization performance.
Solution Approach 2:
The patent transitions from one-dimensional fiber splicing to two-dimensional integrated circuit layout. The depolarization paths are arranged in parallel on a chip plane, allowing multiple optical paths to coexist in a compact area, thus reducing the overall device length while maintaining the required optical path difference for depolarization.
2Ease of manufacture
If fiber fusion splice is used, then connection is achieved, but device becomes fragile and stress-prone
Solution Approach 1:
The patent merges the connection functions into a single integrated photonic chip where all waveguides are fabricated as continuous structures. This eliminates multiple fiber fusion splice points, reducing fragility and stress susceptibility while maintaining manufacturing feasibility through standard photonic fabrication processes.
Solution Approach 2:
The patent uses thin film waveguide structures fabricated on a chip substrate, which provide mechanical robustness compared to bare fiber splices. The waveguides are embedded in protective cladding layers, making the device less susceptible to stress and environmental damage while maintaining optical performance.
3Reliability
If precise 45-degree fusion splice is required, then depolarization performance is improved, but manufacturing precision requirement increases
Solution Approach 1:
The patent incorporates 45-degree polarization rotation waveguides during the initial chip fabrication process, eliminating the need for precise post-fabrication alignment and splicing. The 45-degree orientation is built into the waveguide geometry itself, ensuring consistent depolarization performance without requiring high-precision manual alignment operations.
Solution Approach 2:
The patent replaces the mechanical fiber splicing process with integrated photonic circuit fabrication. The polarization rotation and beam splitting functions are achieved through designed waveguide geometries and refractive index profiles, eliminating the need for precise mechanical alignment and reducing manufacturing precision requirements.
4Reliability
If long fiber length is used, then depolarization effectiveness is achieved, but device size increases
Solution Approach 1:
The patent achieves the required optical path difference for depolarization in a two-dimensional planar configuration rather than extending the device length. Multiple optical paths are arranged in parallel on the chip, allowing the optical path difference to be achieved through vertical layering and horizontal routing within a compact footprint.
Solution Approach 2:
The patent changes the refractive index parameters of the waveguide materials and structures to achieve the required phase delay in a compact length. By adjusting waveguide dimensions, material composition, and operating wavelength, the optical path difference is optimized to achieve effective depolarization in a miniaturized device.
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 solution provides a compact, high-integrity depolarizer with reduced transmission loss, enabling equal energy output of TE and TM polarized light, suitable for miniaturization and mass production, and easy integration with other optical chips.
Implementation Method 1
the optical field is strongly confined to a slit with low refractive index therebetween. According to different polarization directions, the slit waveguide is divided into vertical-slit waveguide and horizontal-slit waveguide.
Implementation Method 2
The Lyot type fiber depolarizer includes two high-birefringence polarization maintaining fibers with a length ratio of 1:2 and a birefringent main axis angle of 45°
Implementation Method 3
electronically controlled depolarizer based on a crossed-slit waveguide comprises a horizontal-slit waveguide, a 45-degree polarization rotation waveguide, a crossed-slit waveguide and a pair of modulation electrodes
Data Source
AI summary
An electrically controlled depolarizer based on a crossed-slit waveguide (3) includes a horizontal-slit waveguide (1), a 45-degree polarization rotation waveguide (2), a pair of modulation electrodes (4) and the crossed-slit waveguide (3). Broad-spectrum TM (transverse magnetic) polarized light is inputted from one end of the horizontal-slit waveguide (1), and then a part of the broad-spectrum TM polarized light is converted into broad-spectrum TE (transverse electric) polarized light through the 45-degree polarization rotation waveguide (2), and then the broad-spectrum TE polarized light and the remaining broad-spectrum TM polarized light enter an input end of the crossed-slit waveguide (3); the board-spectrum TE polarized light is transmitted in a vertical slit of the crossed-slit waveguide (3); the remaining broad-spectrum TM polarized light is transmitted in a horizontal slit of the crossed-slit waveguide (3); and the broad-spectrum TE polarized light and the remaining broad-spectrum TM polarized light form depolarized light at an output end of the crossed-slit waveguide (3). The pair of modulation electrodes (4) realize the precise adjustment of the rotation angle of the 45-degree polarization rotation waveguide (2) by electronic control, such that the TE polarized light and the TM polarized light at the output end of the crossed-slit waveguide (3) have equal energy, thereby overcoming uneven light splitting caused by loss of the polarization rotation waveguide and TE and TM waveguide transmission loss.