Tilted Truncated Waveguide Reduces Facet Reflections
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Solution Overview
Problem
Conventional semiconductor optical sources face limitations in achieving high output power with extended bandwidth and low spectral modulation due to facet reflections, which restrict their application in high-power and broadband optical systems.
Innovation Solution
A semiconductor waveguide structure with a tilted and truncated design, combined with antireflective coatings, is employed to reduce facet reflectivity significantly, allowing for high gain operation with a broad spectral profile and minimal spectral modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the waveguide is operated at high gain to achieve high output power, then the output power is improved, but the bandwidth is reduced and spectral modulation increases
Solution Approach 1:
The patent extracts and eliminates the harmful facet reflections from the system by implementing anti-reflection coatings on the waveguide facets. This removes the source of spectral modulation and bandwidth limitation, allowing the device to operate at high gain without the traditional trade-off between power and bandwidth
Solution Approach 2:
The patent changes the physical parameters of the waveguide structure, specifically tilting the waveguide at an angle (e.g., 7-15 degrees) relative to the facets and optimizing the anti-reflection coating parameters. These parameter changes enable high gain operation with extended bandwidth by suppressing facet reflections that cause spectral modulation
2Power
If the waveguide is operated at high gain to achieve high output power, then the output power is improved, but spectral modulation increases
Solution Approach 1:
The patent extracts and eliminates the harmful facet reflections from the system by implementing anti-reflection coatings on the waveguide facets. This removes the source of spectral modulation, allowing the device to operate at high gain without introducing spectral instability
Solution Approach 2:
The patent converts the potentially harmful facet reflections into a beneficial configuration by tilting the waveguide and applying anti-reflection coatings. This transforms the reflection issue into an opportunity to achieve high power with low spectral modulation by controlling and directing residual reflections away from the optical path
3Device complexity
If conventional waveguide designs are used, then the device structure is simple, but facet reflections cause spectral modulation and limit bandwidth
Solution Approach 1:
The patent changes the geometric parameters of the waveguide by tilting it at a specific angle relative to the facets and optimizing the anti-reflection coating thickness and material properties. These parameter changes achieve low spectral modulation and extended bandwidth while maintaining practical device complexity
Solution Approach 2:
The patent employs composite material structures by combining the waveguide material with anti-reflection coating materials. This composite approach suppresses facet reflections and enables extended bandwidth operation without significantly increasing device complexity
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 solution enables semiconductor optical sources to achieve higher output power and extended bandwidth while minimizing spectral modulation, making them suitable for applications requiring high optical power and broad spectral coverage.
Implementation Method 1
A tilted waveguide design for this device allows operation at a high gain level without lasing by reducing reflectivity at the end facets of the waveguide
Implementation Method 2
Different waveguide designs have been explored for achieving higher output power from a waveguide light source... a light source having a tilted waveguide structure is disclosed to exhibit higher output power
Implementation Method 3
Most semiconductor optical sources comprise a waveguide structure extending between two parallel end facets... Light from such an edge emitting device propagates at one or both end facets depending upon the reflectivities of the two end facets
Implementation Method 4
A conventional broadband semiconductor light emitting device for example, a Light Emitting Diode (LED) provides very low output power... Alternative edge emitting semiconductor light-generating and amplifying devices, such as Super Luminescent Diodes (SLD) provide higher power output
Data Source
AI summary
A new class of optical source having a truncated waveguide is provided, where a guided section of a light generating medium is terminated at an angle at a predetermined distance away from one end facet of the waveguide, thereby leaving a section for unguided light propagation. A truncated waveguide when implemented in combination with waveguide tilt, effective front facet reflectivity is reduced significantly to eliminate unwanted facet reflections. By extending electrical pumping in the unguided propagation section, the light in the unguided path propagates to a corresponding end facet without attenuation. The reflected light propagates freely without being intercepted by the waveguide. The principles are incorporated in different types of light generating and amplifying medium including a “double-pass” gain medium for designing optical sources having significantly high output power and negligibly small spectral modulation arising from unwanted facet reflections.