Bragg Grating Chip Temperature Stability via Negative Thermal-Optical Cladding

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Solution Overview

Problem

The refractive index changes in lithium niobate crystals with temperature variations cause significant shifts in the central wavelength of the reflection spectrum of Bragg grating-based optical devices, affecting their performance.

Innovation Solution

A Bragg grating chip is designed with a monocrystalline silicon substrate, a silicon dioxide layer, a Bragg grating, and a negative thermal-optical coefficient material like titanium dioxide, which eliminates temperature-induced shifts in the central wavelength by incorporating a cladding layer and metal electrodes for tunability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If lithium niobate crystal is used for Bragg grating, then good electro-optical effect and tunable central wavelength are achieved, but the refractive index changes with temperature causing significant shift in central wavelength

Engineering Contradiction:

Improvetunable central wavelengthVSAvoidcentral wavelength stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent uses a composite structure combining lithium niobate crystal (positive thermal-optical coefficient) with a material having negative thermal-optical coefficient. This composite approach compensates for temperature-induced refractive index changes in the lithium niobate by using the opposite effect from the negative coefficient material, thereby stabilizing the central wavelength while preserving the electro-optical tuning capability.

Inventive Principle:

Principle #40Composite materials

2Measurement precision

If Bragg grating is used for optical filtering, then wavelength selection is achieved, but temperature variations cause drift in reflection spectrum center wavelength

Engineering Contradiction:

Improvewavelength selection precisionVSAvoidtemperature-induced wavelength drift

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful temperature-induced wavelength drift into a beneficial compensation mechanism. By introducing a material with negative thermal-optical coefficient, the temperature changes that originally caused harmful drift now produce a compensating effect that offsets the refractive index changes in lithium niobate, thereby eliminating the wavelength drift while maintaining the optical filtering function.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 ensures that the central wavelength of the Bragg grating chip remains insensitive to ambient temperature changes, enhancing the stability and performance of optical filters and lasers by eliminating temperature-induced spectral drift.

Implementation Method 1

the refractive index of lithium niobate material changes with the change of ambient temperature, and the thermal-optical coefficient thereof reaches around 3.5×10−5

Methodology Applied

Scientific EffectThermal-optical effect: Thermal Expansion

Implementation Method 2

a negative thermal-optical coefficient material arranged on the Bragg grating

Methodology Applied

Scientific EffectNegative thermal-optical coefficient effect: Negative Thermal Expansion

Implementation Method 3

The Bragg grating structure has the property of reflecting light signals with specific wavelength

Methodology Applied

Scientific EffectBragg diffraction: Bragg Diffraction

Data Source

PatentUS11796842B2Bragg grating chip

Publication Date: 2023.10.24 SHENZHEN IRPLUS TECHNOLOGY CO LTD

AI summary

The present invention relates to a Bragg grating chip, which comprises a monocrystalline silicon substrate, a silicon dioxide layer arranged on the monocrystalline silicon substrate, a Bragg grating arranged on the silicon dioxide layer and a negative thermal-optical coefficient material arranged on the Bragg grating, so that the sensitivity of the Bragg grating based on lithium niobate crystals to temperature is eliminated, the drift amount of the reflection spectrum center wavelength of the Bragg grating chip in the environment temperature change of 1 k is basically zero, and the insensitivity of the spectral response of photoelectric devices such as optical filter, laser and the like formed by the lithium niobate Bragg grating to the temperature change can be realized.