Mobile Charge Poling for Periodic Domain Gratings
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Solution Overview
Problem
Existing methods for creating short period domain inversion gratings in MgO:CLN struggle with achieving reliable and repeatable results at room temperature, due to issues like current flow through the substrate disrupting domain seeding uniformity and domain wall misalignment, which affects the efficiency and quality of nonlinear optical interactions.
Innovation Solution
A high voltage electric field poling process that generates mobile charges within the substrate, combined with patterned current flow and optical illumination, to create a tapered domain grating structure with a 50/50 duty cycle region within the bulk of the crystal, ensuring efficient nonlinear interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high voltage electric field poling is applied at room temperature to create short period domain inversion gratings, then domain inversion can be achieved without thermal processes, but current flow through the substrate disrupts domain seeding uniformity and reduces manufacturing precision
Solution Approach 1:
The patent introduces mobile charges as an intermediary mechanism to mediate between the applied electric field and the domain inversion process. These mobile charges, generated through optical illumination, serve as a controllable intermediate step that enables domain seeding without relying on current flow through the substrate, thus resolving the contradiction between room temperature poling and domain seeding uniformity
Solution Approach 2:
The patent changes the poling process parameters by combining optical illumination with electric field application. This parameter change generates mobile charges that facilitate domain inversion at room temperature while maintaining uniformity, overcoming the limitations of conventional high voltage poling alone
2Reliability
If conventional electric field poling methods are used, then domain inversion can be achieved, but domain wall misalignment occurs which affects nonlinear optical interaction efficiency
Solution Approach 1:
The patent employs a feedback mechanism where the distribution of mobile charges, generated through optical illumination, provides real-time control over the domain inversion process. This feedback ensures proper domain wall alignment by modulating the electric field distribution according to the mobile charge density, thereby maintaining both reliability of domain inversion and efficiency of nonlinear optical interactions
Solution Approach 2:
The patent applies local quality by creating spatially varying mobile charge distributions through patterned optical illumination. This results in locally optimized electric field conditions that ensure proper domain wall alignment in different regions of the substrate, maintaining high nonlinear optical interaction efficiency across the entire device
3Ease of manufacture
If impurity diffusion methods are used to create domain inversion, then domain structures can be formed, but the diffusion depth is shallow and domains are triangular or semicircular rather than extending through the bulk
Solution Approach 1:
The patent replaces the thermal diffusion mechanism with an electric field-driven mobile charge mechanism. This substitution eliminates the shallow diffusion depth limitation by using electric field poling that can penetrate through the entire bulk of the substrate, creating domains that extend from surface to surface rather than being confined to shallow triangular or semicircular regions
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 approach results in high efficiency and resistance to photorefractive effects, allowing for the fabrication of high-quality short period domain inversion gratings that maintain lateral dimensions and efficiency, even when domain inversion is not precisely controlled at the surface, with a peak conversion efficiency of greater than 98% of the theoretical maximum.
Implementation Method 1
Optical illumination is used to generate mobile charges and patterned current flows
Implementation Method 2
A high voltage electric field poling process that generates mobile charges within the substrate
Data Source
AI summary
Devices and methods are disclosed for realizing a high quality bulk domain grating structure utilizing mobile charges that are generated by means of photo-excitation in a substrate. An effect of light exposure (UV, visible, or a combination of wavelengths) is to generate photo-induced charges. The application of a voltage across the substrate combined with the application of light exposure causes a photo-induced current to flow through the substrate. The photo-induced charges (behaving like virtual electrode inside the material) and the photo-induced current result in both reduction of the coercive field required for domain inversion in the material and improve realization of the domain inversion pattern, which previously has not been possible at room temperature.