Double Waveguide Edge-Emitting Laser for Stable Facet Coupling
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Solution Overview
Problem
High power edge-emitting semiconductor lasers face issues with facet degradation and thermally-induced waveguides that degrade beam quality and increase the risk of catastrophic optical damage, while existing non-absorbing mirror structures often compromise coupling efficiency and absorption levels.
Innovation Solution
A double waveguide structure is introduced, featuring a second waveguiding and cladding layer sequence over an original cladding layer, with a regrowth interface between the first cladding layer and the second waveguiding layer, which increases vertical separation and controls refractive index changes to minimize absorption and enhance coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a non-absorbing mirror structure is created by etching and epitaxial regrowth, then facet stability is improved, but coupling efficiency between active and passive regions deteriorates
Solution Approach 1:
The patent introduces a vertical separation dimension by positioning the regrowth interface between the first cladding layer and the second waveguiding layer. This vertical arrangement allows the optical mode to propagate away from the regrowth interface while maintaining horizontal coupling between active and passive regions, thus improving facet stability without compromising coupling efficiency.
Solution Approach 2:
The second waveguiding layer acts as an intermediary between the active region and the non-absorbing mirror structure. It provides a transition zone that maintains optical coupling while separating the propagating mode from the regrowth interface, resolving the contradiction between stability and coupling efficiency.
2Power
If injection current is increased to achieve desired output power, then power output is improved, but beam quality deteriorates due to thermally-induced waveguides
Solution Approach 1:
The double waveguide structure with vertical separation preemptively counteracts the formation of unwanted lateral modes by controlling the refractive index profile. The second waveguiding layer's composition and thickness are designed to maintain single-mode operation even when high injection currents create thermal effects, thus preserving beam quality at high power levels.
Solution Approach 2:
The patent modifies the refractive index parameters by introducing the second waveguiding layer with specific composition and thickness. This parameter change creates a refractive index profile that suppresses thermally-induced lateral modes, allowing high power output without beam quality degradation.
3Ease of manufacture
If the regrowth interface is located close to the active region to improve coupling, then coupling efficiency is improved, but absorption increases leading to potential catastrophic optical damage
Solution Approach 1:
The patent resolves this contradiction by moving the separation to the vertical dimension rather than horizontal. The regrowth interface is positioned vertically between layers, allowing horizontal coupling to remain efficient while the vertical separation prevents the optical mode from interacting with absorbing defects at the interface.
Solution Approach 2:
The first cladding layer serves as an intermediary between the active region and the regrowth interface. It provides optical confinement that maintains coupling efficiency while protecting the interface from direct interaction with the propagating mode, thus reducing absorption and preventing catastrophic optical damage.
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 double waveguide structure improves facet stability, maintains optical coupling efficiency, and reduces the excitation of unwanted lateral modes, resulting in enhanced beam quality and power output.
Implementation Method 1
compensate for the thermally-induced localized changes in refractive index and control the number of excited lateral modes
Implementation Method 2
The presence of the injected current is known to elevate the temperature in the localized area along the injection stripe, increasing the relative refractive index in the area of current injection by an amount sufficient to create a thermally-induced waveguide
Data Source
AI summary
An edge-emitting semiconductor laser and fabrication method is disclosed that includes a second, passive waveguide and cladding layer disposed above the multi-layer arrangement of a first waveguiding layer and a first cladding layer. The active region of the laser is contained within or along a lower surface of the first waveguiding layer, as in standard devices. The regrowth interface is located along a top surface of the first cladding layer, as compared to the prior art where this interface is located within the first waveguiding layer. The resulting configuration exhibits an improved coupling efficiency by maintaining the propagating optical mode within the active waveguiding layer and away from the regrowth interface.