Mesa-Width DFB Semiconductor Laser for Stable Single-Mode Output
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Solution Overview
Problem
Semiconductor lasers face challenges in achieving high output power and stable single-mode oscillation due to variations in grating structure and effective refractive index, leading to reflection and scattering issues at the boundary of grating regions, which deteriorate output characteristics and single-mode oscillation.
Innovation Solution
A semiconductor laser design with a mesa structure that includes regions with varying mesa widths and grating structures, where the normalized coupling coefficients and effective refractive indices are adjusted to ensure consistent Bragg wavelengths and minimize scattering, enhancing single-mode oscillation and output intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a grating structure is removed at a constant period to increase light output intensity, then output power is improved, but reflection and scattering at the boundary between grating regions occurs, deteriorating single mode oscillation
Solution Approach 1:
The patent applies local quality by creating different mesa widths in different regions of the semiconductor laser. Specifically, the first region has a first mesa width while the second region has a second mesa width that is different from the first. This local variation in geometric properties allows different regions to have different effective refractive indices, enabling independent optimization of each region's optical characteristics while maintaining overall device performance.
Solution Approach 2:
The patent implements parameter changes by varying the mesa width parameter across different regions of the device. The first mesa width in the first region and the second mesa width in the second region are deliberately set to different values, which changes the effective refractive index in each region. This parameter variation allows the grating structures in different regions to have matching Bragg wavelengths despite having different numbers of stages, thereby eliminating boundary reflection and scattering issues.
2Reliability
If the effective refractive index is varied in different regions to optimize Bragg wavelength, then single mode oscillation is improved, but the Bragg wavelength varies across regions, deteriorating single mode oscillation
Solution Approach 1:
The patent applies local quality by creating different mesa widths in different regions of the semiconductor laser. Specifically, the first region has a first mesa width while the second region has a second mesa width that is different from the first. This local variation in geometric properties allows different regions to have different effective refractive indices, enabling independent optimization of each region's optical characteristics while maintaining overall device performance.
Solution Approach 2:
The patent implements parameter changes by varying the mesa width parameter across different regions of the device. The first mesa width in the first region and the second mesa width in the second region are deliberately set to different values, which changes the effective refractive index in each region. This parameter variation allows the grating structures in different regions to have matching Bragg wavelengths despite having different numbers of stages, thereby eliminating boundary reflection and scattering issues.
3Reliability
If a phase shift region is included in the grating to improve characteristics, then single wavelength operation is improved, but the reflectance distribution becomes complex, making it difficult to achieve high output power
Solution Approach 1:
The patent applies local quality by creating different mesa widths in different regions of the semiconductor laser. Specifically, the first region has a first mesa width while the second region has a second mesa width that is different from the first. This local variation in geometric properties allows different regions to have different effective refractive indices, enabling independent optimization of each region's optical characteristics while maintaining overall device performance.
Solution Approach 2:
The patent applies another dimension by introducing a vertical dimension variation through different mesa widths in different regions. Instead of only varying grating parameters in the horizontal plane, the invention uses the vertical dimension (mesa height/width) to control the effective refractive index. This dimensional approach provides an additional degree of freedom for optimizing both single wavelength operation and output power simultaneously.
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 design achieves high output power and stable single-mode oscillation by optimizing the grating structure and mesa width, resulting in increased light output intensity and suppressed scattering, thereby improving the semiconductor laser's performance.
Implementation Method 1
A reflectance with respect to a Bragg-reflected light beam can be changed between the front and the rear of the phase shift region so that output from one facet is increased
Implementation Method 2
a semiconductor laser can have a mesa structure formed in an optical waveguide structure for the purpose of partially concentrating a current injected for drive
Implementation Method 3
an optical waveguide structure can be changed
Data Source
AI summary
To provide a semiconductor laser excellent in high output characteristic and single mode oscillation, the semiconductor laser includes a substrate, an active layer, a cladding layer including a first grating layer having a first grating structure and a second grating layer having a second grating structure, and an electrode. The active layer and the cladding layer form a mesa structure, and the mesa structure includes first and second reflection regions forming a resonator in a direction in which the mesa structure extends. The second grating structure is formed in the first reflection region, and any one of the first grating structure or the second grating structure is formed in the second reflection region. A normalized coupling coefficient of the first reflection region is larger than that of the second reflection region. Mesa widths in the first reflection region and the second reflection region are different from each other.