DFB Semiconductor Laser Mesa Structure for High Output Mode Suppression
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Solution Overview
Problem
Semiconductor lasers face challenges in achieving high light output characteristics while minimizing the occurrence of lateral high-order modes, which can lead to reduced continuity of currents and undesirable kinks in optical communications.
Innovation Solution
A semiconductor laser design featuring a mesa structure with varying widths, including a first region with a narrow mesa width and a second region with a wider mesa width, where the first region has a higher normalized coupling coefficient and includes a diffraction grating region for reflecting Bragg wavelength light, and the second region includes both diffraction and non-diffraction grating regions for transmission, forming a resonator and suppressing high-order modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the mesa width is increased to increase the light output, then the light output is improved, but the lateral high-order mode occurs which reduces current continuity and causes kinks
Solution Approach 1:
The mesa structure is segmented into multiple regions with different widths along the extension direction. The first region has a narrower width that suppresses lateral high-order modes, while the second region has a wider width that increases light output. This segmentation allows simultaneous achievement of high output and mode suppression.
Solution Approach 2:
Different regions of the mesa structure are assigned different local qualities (widths) to perform different functions. The first region has narrow width for mode suppression, the second region has wide width for high output. The diffraction grating structure also varies locally with different normalized coupling coefficients in different regions.
2Productivity
If the mesa width is increased to increase the light output, then the light output is improved, but lateral high-order modes occur which are undesired for optical communications
Solution Approach 1:
The mesa is divided into regions with different widths. The first region with narrower width acts as a mode-suppression zone that prevents lateral high-order modes, while the second region with wider width provides high light output capability.
Solution Approach 2:
The mesa width parameter is changed along the extension direction, transitioning from a narrower width in the first region to a wider width in the second region. This parameter variation allows the structure to simultaneously achieve mode suppression and high output.
3Productivity
If the normalized coupling coefficient is increased to improve light output characteristic, then the light output is improved, but the lateral high-order mode suppression may be affected
Solution Approach 1:
The diffraction grating structure is designed with different local qualities - the first region has a higher normalized coupling coefficient for strong reflection and mode control, while the second region has a lower normalized coupling coefficient for high light output. This local differentiation resolves the contradiction between output and mode suppression.
Solution Approach 2:
The diffraction grating is segmented into regions with different coupling coefficients. The first diffraction grating region has higher coupling for reflection, the second has lower coupling for transmission and high output, allowing both requirements to be met 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
This design enhances light output intensity and maintains single-mode oscillation without lateral high-order modes, achieving excellent light output characteristics and reducing kinks, thereby improving performance for optical communications.
Implementation Method 1
a first diffraction grating region in which a plurality of first refractive index regions and a plurality of second refractive index regions for use in reflecting a light beam having a Bragg wavelength are alternately arranged
Implementation Method 2
a non-diffraction grating region which transmits the light beam having the Bragg wavelength
Implementation Method 3
the first diffraction grating region and the second diffraction grating region form a resonator
Data Source
AI summary
To provide a semiconductor laser with which a high light output characteristic and reduction in occurrence of a lateral high-order mode can be achieved, the semiconductor laser includes a diffraction grating layer including first and second refractive index regions. A mesa structure includes a first region having a first width and a second region having a second width wider than the first width. The first region includes a diffraction grating region in which the first and second refractive index regions for use in reflecting a light beam having a Bragg wavelength are alternately arranged at the same period. The second region includes a diffraction grating region and a non-diffraction grating region. The diffraction grating region of the first region and the diffraction grating region of the second region form a resonator. A normalized coupling coefficient of the first region is larger than a normalized coupling coefficient of the second region.