Super Structure Grating Discretization for Tunable Laser Peak Control
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Solution Overview
Problem
Existing super structure gratings in tunable lasers cannot separately optimize reflectivity and Full Width Half Maximum (FWHM) of reflection peaks, limiting the achievement of both desirable reflectivity and FWHM.
Innovation Solution
The method involves discretizing the modulation function to obtain (N+1) modulation function discrete values, adjusting reflectivity based on the ratio of optical waveguide length to total grating length, and adjusting FWHM based on the total grating length and discrete value ratio, allowing separate optimization of reflectivity and FWHM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If two-level discretization is used to simplify production, then ease of manufacture is improved, but the ability to separately optimize reflectivity and FWHM deteriorates
Solution Approach 1:
The patent divides the continuous modulation function into multiple discrete levels (three-level or higher discretization) instead of simple two-level discretization. This segmentation allows different regions of the grating to have distinct refractive index values, enabling independent control of reflectivity and FWHM while maintaining manufacturing feasibility through discrete fabrication steps.
Solution Approach 2:
The patent introduces an additional design dimension by using multiple discretization levels beyond the conventional two-level approach. This extra degree of freedom in the refractive index distribution enables separate optimization of reflectivity and FWHM parameters that were previously coupled in two-level discretized gratings.
2Length of stationary object
If total grating length is fixed, then device size is reduced, but the ability to independently adjust reflectivity and FWHM deteriorates
Solution Approach 1:
The patent applies local quality by creating non-uniform refractive index distributions within the grating structure through multi-level discretization. Different sections of the grating have different discretization levels, allowing local optimization of reflectivity and FWHM characteristics while maintaining a compact overall grating length.
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 enables both desirable reflectivity and FWHM to be achieved, improving the performance of tunable lasers by enhancing reflectivity and mode selection features.
Implementation Method 1
A super structure grating (Super Structure Grating, SSG) has a comb reflection spectrum, a reflector region of the tunable laser may reflect light by using the SSG
Implementation Method 2
distribution of refractive indices of the SSG is shown in the following formula (1)
Implementation Method 3
a threshold may be usually selected to perform two-level digital discretization processing on the continuous function shown in the formula (3), so that the SSG can be easily produced
Implementation Method 4
the reflectivity of the reflection peak of the super structure grating is adjusted based on the relationship of the ratio of a length of an optical waveguide corresponding to at least one of the (N+1) modulation function discrete values to a total grating length
Data Source
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AI summary
Embodiments of this application disclose a super structure grating and a tunable laser, to meet both a relatively desirable reflectivity and a relatively desirable FWHM. The super structure grating spatially performs amplitude and phase modulation on a uniform grating by using a modulation function, to generate a comb reflection spectrum, (N+1) modulation function discrete values are obtained after discretization processing is performed on the modulation function by using N thresholds, and N is a positive integer greater than or equal to 2. Each of the (N+1) modulation function discrete values corresponds to one section of optical waveguide whose refractive index is uniform or corresponds to one section of uniform grating. A reflectivity of a reflection peak of the super structure grating is adjusted based on a relationship of a ratio of a length of an optical waveguide corresponding to at least one of the (N+1) modulation function discrete values to a total grating length of the super structure grating, and based on the total grating length of the super structure grating. An FWHM of the reflection peak of the super structure grating is adjusted based on the ratio relationship and the total grating length of the super structure grating.