Taper Waveguide Refractive Index Profile for Planar Light Emission
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Solution Overview
Problem
The emission efficiency of semiconductor light-emitting devices is reduced due to the arc-shaped wave front of light in taper-shaped waveguides, causing light to be dissipated outside the waveguide.
Innovation Solution
A semiconductor light-emitting device with a waveguide where the equivalent refractive index is higher at the center than on the outer sides, aligning the phases of light and preventing dissipation by ensuring equal optical propagation distances and symmetry at the end face.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a taper-shaped waveguide is used to amplify light in fundamental mode, then light amplification is achieved, but the wave front becomes arc-shaped causing light dissipation
Solution Approach 1:
The waveguide structure is designed with spatially varying properties: the width changes along the propagation direction (taper shape) while the refractive index is specifically engineered to be higher at the center than at the edges. This local variation in refractive index creates a gradient that compensates for the arc-shaped wave front, keeping light confined and maintaining planar wave front characteristics despite the taper geometry
Solution Approach 2:
The waveguide employs asymmetric refractive index distribution across its width, with the central region having a different refractive index than the edge regions. This asymmetric design creates optical path differences that counteract the arc-shaped wave front formation, ensuring that light from different parts of the waveguide arrives at the end face with aligned phases, thereby preventing dissipation while maintaining amplification
2Loss of energy
If the wave front is kept planar to prevent light dissipation, then emission efficiency is improved, but light amplification in taper waveguide is reduced
Solution Approach 1:
The refractive index parameter is deliberately changed across the waveguide cross-section, creating a profile where the center has a higher refractive index than the edges. This parameter modification allows the waveguide to maintain planar wave front characteristics while still providing the tapered geometry needed for light amplification, effectively decoupling the two requirements
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
Enhances light emission efficiency by suppressing light dissipation and maintaining a planar wave front, thereby improving the overall performance of the semiconductor light-emitting device.
Implementation Method 1
an equivalent refractive index of the waveguide is, in a predetermined range from an end face of the waveguide, higher at a center in a width direction of the waveguide than on an outer side in the width direction of the waveguide
Data Source
AI summary
A semiconductor light-emitting device includes: a semiconductor light-emitting element; a submount configured to have mounted thereon the semiconductor light-emitting element; and the like. The semiconductor light-emitting element includes a light guide layer, and a taper waveguide configured to cause light generated in the light guide layer to propagate. An equivalent refractive index of the taper waveguide is, in a predetermined range from an end face of the taper waveguide, higher at a center in a width direction of the taper waveguide than on outer sides in the width direction of the taper waveguide.