Stepped Graded Index SCH Laser Device
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Solution Overview
Problem
Existing multiple quantum well (MQW) lasers face inefficiencies due to the 'notch' in the valence band caused by discontinuity between the MQW region and the separate confinement heterostructure (SCH), leading to increased resistance and reduced injection efficiency, which affects the wall-plug efficiency and power consumption.
Innovation Solution
A stepped graded index SCH design is implemented, with a steeply graded first portion and a shallowly graded second portion, avoiding the 'notch' while providing high confinement and efficient hot carrier recovery, using a compositionally graded SCH layer to manage conduction band energy increases from the MQW to the p-side of the laser device junction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional separate confinement heterostructure (SCH) with discontinuous composition is used, then optical confinement is provided, but a 'notch' is formed in the valence band causing increased resistance and reduced injection efficiency
Solution Approach 1:
The patent applies parameter changes by transitioning from a conventional discontinuous SCH to a stepped graded index SCH where the composition is gradually changed through multiple steps. The AlGaAs layers have progressively increasing aluminum composition (x=0.25, 0.35, 0.45, 0.55) which continuously modifies the band structure parameters, eliminating the valence band notch and reducing resistance while maintaining optical confinement.
Solution Approach 2:
The stepped graded index SCH implements local quality by creating different composition regions with specific aluminum concentrations at different positions within the heterostructure. Each step has a distinct local composition tailored to provide optimal confinement and band alignment at that specific location, rather than using a uniform composition throughout.
2Reliability
If the SCH provides strong optical confinement, then laser performance is improved, but power consumption increases at high bias currents
Solution Approach 1:
The stepped graded index structure continuously changes the refractive index and bandgap parameters through progressive composition grading. This provides strong optical confinement comparable to conventional SCH designs while reducing carrier leakage and improving injection efficiency, thereby lowering power consumption at high bias currents through more efficient electrical-to-optical conversion.
Solution Approach 2:
The SCH is constructed as a composite structure with multiple AlGaAs layers having different aluminum compositions (x=0.25, 0.35, 0.45, 0.55). This composite approach combines the benefits of strong confinement from high-index-contrast interfaces with the advantages of continuous band alignment from graded composition, achieving both high confinement efficiency and low power consumption.
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 stepped graded index SCH design enhances injection efficiency, confinement, and reduces resistance, resulting in higher wall-plug efficiency and lower power consumption, even at high bias currents and optical powers.
Implementation Method 1
A composition of the first portion is graded to provide a first conduction band energy increase over a distance from multiple quantum wells (MQW) to a p-side of a laser device junction. A composition of the second portion is graded to provide a second conduction band energy increase over the distance from the MQW to the p-side of the laser device junction.
Implementation Method 2
semiconductor lasers may be used as components in optical transceivers for digital communications products
Data Source
AI summary
Embodiments of the present disclosure are directed towards a laser device with a stepped graded index separate confinement heterostructure (SCH), in accordance with some embodiments. One embodiment includes a substrate area, and an active region adjacent to the substrate area. The active region includes an SCH layer, which comprises a first portion and a second portion adjacent to the first portion. A composition of the first portion is graded to provide a first conduction band energy increase over a distance from multiple quantum wells (MQW) to a p-side of a laser device junction. A composition of the second portion is graded to provide a second conduction band energy increase over the MQW to the p-side distance. The first conduction band energy increase is different than the second conduction band energy increase. Other embodiments may be described and/or claimed.