U-Shaped LN Waveguide for Equalized Optical Path Lengths
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Solution Overview
Problem
The increasing length of LN modulating units in optical modulators leads to an increase in chip size, particularly due to the need for a delay device on the LN optical waveguide with a U-shaped structure, which affects the waveguide length and bias point of Mach-Zehnder interferometers, causing losses and size issues.
Innovation Solution
The optical device employs a U-shaped structure for the LN optical waveguide with adjusted waveguide lengths and curvatures to equalize optical path lengths across Mach-Zehnder interferometers, using silicon optical waveguides to confine light and reduce the area needed for delay adjustments, thereby preventing an increase in chip size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the LN optical waveguide length is increased to achieve proper modulation, then the modulation performance is improved, but the chip size increases
Solution Approach 1:
The patent transitions from a conventional linear waveguide layout to a U-shaped waveguide structure, utilizing two-dimensional spatial arrangement to achieve the required waveguide length without proportionally increasing the chip area. The U-shaped configuration allows the waveguide to fold back on itself, effectively using vertical and horizontal dimensions to achieve the necessary interaction length while compacting the overall footprint.
Solution Approach 2:
The patent employs curved waveguide sections in the U-shaped structure, particularly in the turning portions, to manage the waveguide path efficiently. The curved transitions allow for compact routing while maintaining proper light confinement and reducing the overall area required compared to sharp angular turns would require.
2Area of stationary object
If a U-shaped structure is used for the LN optical waveguide, then the chip size is reduced, but the waveguide length becomes unequal among Mach-Zehnder interferometers
Solution Approach 1:
The patent applies different waveguide length configurations to different branches of the Mach-Zehnder interferometer based on their specific requirements. By adjusting the arm lengths locally in each interferometer branch, the design compensates for the U-shaped waveguide geometry to ensure that all interferometers have equal effective path lengths, maintaining interference performance while using the compact U-shaped layout.
Solution Approach 2:
The patent modifies the waveguide length parameter in specific sections to compensate for the U-shaped geometry. By carefully controlling the lengths of different waveguide segments and adjusting the dimensions of the U-shaped structure, the design achieves equal optical path lengths across all Mach-Zehnder interferometers despite the non-linear layout.
3Reliability
If the waveguide length is adjusted to equalize optical paths, then the interference performance is improved, but the area for delay adjustment increases
Solution Approach 1:
The patent integrates the delay adjustment functionality directly into the existing U-shaped waveguide structure rather than adding separate delay adjustment components. By incorporating length compensation sections within the U-shaped path itself, the design merges the delay adjustment function with the waveguide structure, avoiding the need for additional dedicated area and maintaining compactness.
Solution Approach 2:
The U-shaped waveguide structure serves multiple functions simultaneously: it provides the necessary waveguide length for modulation, enables compact chip packaging, and incorporates delay adjustment capabilities through its geometric configuration. This multi-functional design eliminates the need for separate delay adjustment components, saving area while maintaining interference performance.
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 effectively prevents an increase in chip size by equalizing optical path lengths and reducing the area required for delay adjustments, maintaining efficient light confinement and modulation performance.
Implementation Method 1
The LN optical waveguide is able to confine light more strongly
Implementation Method 2
The refractive index of the optical waveguide varies due to the electric field; therefore, the phase of light propagating in the optical waveguide is changed
Data Source
AI summary
An optical device includes a plurality of first Si waveguides that split and output an optical signal received from an input unit, plurality of LN waveguides that are included in a LN modulator and that transmit the optical signals that are split and output by the first Si waveguides, and a plurality of second Si waveguides that multiplex and output the associated optical signals that are output from the plurality of respective LN waveguides. The device includes an output unit that outputs the optical signal multiplexed by the second Si waveguides, and a plurality of Mach-Zehnder interferometers disposed on each of waveguides connected by the first Si waveguides, the LN waveguides, and the second Si waveguides, respectively. When there are differences among waveguide lengths of the LN waveguides, the device is configured such that the optical path lengths of the waveguides for the respective Mach-Zehnder interferometers are equalized.