Lithium Niobate Optical Modulator for Visible Light
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Solution Overview
Problem
Conventional optical modulators for visible light suffer from significant optical loss, which hampers the efficient use of light emitted from light sources in applications like XR glasses and small projectors.
Innovation Solution
A Mach-Zehnder-type optical modulator with an optical waveguide layer featuring lithium niobate film and ridge portions, where the lengths of the first and second multimode interference waveguides are optimized based on the wavelength of input light to minimize optical loss, with visible light beams of different wavelengths being input to these ridge portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the length of multimode interference waveguide is increased, then the optical loss is reduced for shorter wavelengths, but the device length increases and optical loss increases for longer wavelengths
Solution Approach 1:
The patent applies local quality by setting different waveguide lengths for different wavelength channels. Specifically, the first waveguide having a first length and the second waveguide having a second length that is different from the first length, optimized according to the respective wavelengths of the first and second light. This allows each wavelength to experience optimal coupling conditions without being constrained by a single uniform length, thereby reducing overall optical loss while maintaining compact device dimensions.
2Loss of energy
If the waveguide length is optimized for longer wavelengths, then optical loss is reduced for longer wavelengths, but optical loss increases for shorter wavelengths
Solution Approach 1:
The patent implements universality by designing a multi-functional waveguide system that simultaneously handles multiple wavelength channels with different optimal lengths. The first waveguide and second waveguide are both part of the same optical modulator device, allowing it to universally process different wavelengths (e.g., red and green light) with各自 optimized parameters. This enables the device to maintain high efficiency across multiple wavelength bands without requiring separate dedicated structures for each wavelength.
3Device complexity
If a single waveguide length is used for all wavelengths, then the device structure is simplified, but optical loss increases for at least one wavelength channel
Solution Approach 1:
The patent applies segmentation by dividing the waveguide system into multiple independent waveguide paths with different lengths. Instead of using a single uniform waveguide for all wavelengths, the invention segments the optical path into a first waveguide for the first wavelength and a second waveguide for the second wavelength, each with independently optimized lengths. This segmentation allows each wavelength to be optimized separately while maintaining overall device integration, effectively reducing optical loss without excessive complexity increase.
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 significantly reduces optical loss by adjusting the lengths of the multimode interference waveguides according to the wavelength of the input light, enhancing the efficiency of light transmission and utilization in optical engines and XR glasses.
Implementation Method 1
an optical waveguide layer including a plurality of flat portions and n ridge portions arranged between the flat portions to be adjacent, where n is an integer of two or more, each of the n ridge portions including a main waveguide to which visible light is input
Implementation Method 2
an in-depth study has been made by the present inventors as shown below in consideration of relationships between lengths of a multimode interference waveguide through which a waveguide of each ridge portion is branched into two waveguides and a multimode interference waveguide to which the two branch waveguides are coupled
Data Source
AI summary
An optical modulator is a Mach-Zehnder-type optical modulator having a substrate and an optical waveguide layer including a lithium niobate film formed on the substrate. The optical waveguide layer includes a plurality of flat portions and n ridge portions arranged between the flat portions to be adjacent, where n is two or more. Each of the n ridge portions includes a main waveguide to which visible light is input, a first multimode interference waveguide through which the main waveguide is branched into a first and a second optical branch waveguide, and a second multimode interference waveguide through which the first and the second optical branch waveguide are coupled to form a coupling waveguide. Visible light beams having different wavelengths are input to the n ridge portions. The first multimode interference waveguide and the second multimode interference waveguide have shorter lengths when input light having a longer wavelength is transmitted.