Gradient-Index Nonlinear Optical Waveguide for Better End Coupling
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Solution Overview
Problem
Existing nonlinear optical waveguides face challenges in achieving high frequency conversion efficiency due to low coupling efficiency between the end coupling device and the optical waveguide, caused by a mismatch between the large spot size of the output light and the reduced core size of the waveguide, leading to significant light loss.
Innovation Solution
A method for fabricating a nonlinear optical waveguide with a gradient refractive index distribution using heavy ion irradiation to create refractive index dips at specific depths, forming a sandwich-type structure that focuses light within the waveguide core without reducing the core size, achieved by bombarding a nonlinear optical crystal with first and second heavy ion beams of different energies to form distinct optical barriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the core size of the optical waveguide is reduced to improve frequency conversion efficiency, then the transmission cross-sectional area is reduced and power density is increased, but the coupling efficiency with end coupling devices deteriorates due to spot size mismatch
Solution Approach 1:
The patent applies local quality by creating a gradient refractive index distribution within the waveguide core through selective heavy ion irradiation. The refractive index is modified locally at different depth positions to form optical barriers, while the overall core dimensions remain unchanged. This allows the waveguide to maintain both high power density for frequency conversion and proper mode matching for coupling with end devices.
Solution Approach 2:
The patent changes the refractive index parameter through heavy ion irradiation to create the desired optical barriers. By controlling the irradiation dose and ion energy, the refractive index is modified at specific depths to form the sandwich-type structure with high-index core and low-index barriers, resolving the contradiction between core size reduction and coupling efficiency.
2Reliability
If heavy ion irradiation is used to create optical barriers, then light confinement is improved, but the manufacturing complexity increases due to multiple irradiation steps
Solution Approach 1:
The patent segments the irradiation process into multiple steps, each creating a specific optical barrier at different depths. The first irradiation creates the first optical barrier, the second irradiation creates the second optical barrier, forming a sandwich-type structure. This segmentation allows precise control of light confinement while maintaining manufacturing feasibility through standardized irradiation procedures.
Data Source
AI summary
A method for fabricating a nonlinear optical waveguide with gradient refractive index distribution, in which a nonlinear optical crystal is prepared; a type of first heavy ions, a type of second heavy ions and parameters related to an irradiation process are determined; the first heavy ions are accelerated to generate a first ion beam; the nonlinear optical crystal is bombarded with the first ion beam to obtain a primary processed crystal; the second heavy ions are accelerated to generate a second ion beam; the primary processed crystal is bombarded with the second ion beam to obtain a secondary processed crystal; and the secondary processed crystal is segmented to obtain the desired optical waveguide.