Optical Module Surface Grating Back-Reflection Prevention
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Solution Overview
Problem
Existing optical modules face instability due to light intensity fluctuations and potential damage to the emitter, leading to sub-optimal operation and eventual failure of the photonic integrated circuit.
Innovation Solution
A diffraction grating is positioned on the surface of the semiconductor device facing the emitter, with the same pitch as the coupling grating within the device, to reduce or prevent back-reflection of light, thereby stabilizing the emitter's operation and preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the emitter is attached to the semiconductor device, then the optical module can function as a photonic integrated circuit, but back-reflection of light into the emitter causes instability and potential damage
Solution Approach 1:
A surface grating is introduced as an intermediary element between the emitter and the coupling grating. This surface grating acts as a mediator that diffracts back-reflected light away from the emitter, preventing the harmful feedback while maintaining the necessary optical coupling function. The surface grating is formed by depositing semiconductor material onto the coupling grating, creating a projection that extends toward the emitter without direct contact.
2Reliability
If the emitter is spaced apart from the semiconductor device by a gap, then back-reflection is reduced, but coupling efficiency into the waveguide decreases
Solution Approach 1:
The solution moves from a one-dimensional spacing problem to a three-dimensional grating structure. Instead of simply increasing the gap distance, a surface grating is formed that projects into the gap region. This adds a new dimensional element (the grating projection height) that enables light manipulation in the vertical dimension while maintaining horizontal coupling efficiency. The grating structure creates multiple diffraction orders that can guide light into the waveguide effectively.
3Reliability
If a surface grating is added to the semiconductor device, then back-reflection is prevented, but device complexity increases
Solution Approach 1:
The surface grating and coupling grating are merged into a single integrated structure. The surface grating is formed by depositing semiconductor material directly onto the coupling grating, combining two functional elements into one monolithic structure. This integration reduces the number of separate fabrication steps and components, simplifying the overall device architecture while maintaining the back-reflection prevention function.
Solution Approach 2:
The coupled grating structure serves multiple functions simultaneously: it acts as both the coupling grating for guiding light into the waveguide and as the template for forming the surface grating that prevents back-reflection. This multi-functionality reduces the need for separate components and simplifies the device design.
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 surface grating effectively diffracts reflected light away from the emitter, maintaining the optical performance and extending the lifespan of the photonic integrated circuit by preventing back-reflection and associated damage.
Implementation Method 1
The diffraction grating on the surface of the semiconductor device reduces or prevents back-reflection of light into the emitter
Implementation Method 2
the diffraction grating being a coupling diffraction grating configured to couple light emitted from the emitter into the waveguide
Data Source
AI summary
An optical module includes an emitter and a semiconductor device. The emitter is attached to the semiconductor device and is separated from the semiconductor device by a gap. The semiconductor device includes a waveguide and a diffraction grating located within semiconductor of the semiconductor device. The diffraction grating is a coupling diffraction grating configured to couple light emitted from the emitter into the waveguide. The semiconductor device further includes an additional diffraction grating which is provided on a surface of the semiconductor device which faces the emitter.