Optical Device Passive Window HR-COMD Mitigation
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Solution Overview
Problem
High-performance optical devices like EMLs are prone to catastrophic optical mirror damage (HR-COMD) due to cleaving damage, high current injection, and optical intensity, which affects their reliability and manufacturing quality.
Innovation Solution
Incorporating a passive window structure with an inactive region between the active region and the rear face, and a wider waveguide adjacent to the emissive face, which prevents current injection and reduces optical intensity, thereby minimizing HR-COMD risk and improving cleave quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the rear face is formed by cleaving to provide HR coating, then the manufacturing process is simple, but the facet is damaged and prone to catastrophic optical mirror damage (HR-COMD)
Solution Approach 1:
The optical cavity is divided into an active region and a passive window region. The passive window region is positioned adjacent to the rear face where the HR coating is applied, separating the high-stress cleaved facet area from the high optical intensity active region, thereby preventing HR-COMD while maintaining simple cleaving fabrication.
Solution Approach 2:
The passive window region acts as an intermediary between the HR-coated rear face and the active region. It provides a transition zone that reduces optical intensity and prevents direct interaction between the cleaved facet damage and the high-intensity optical field, eliminating HR-COMD risk.
2Power
If current injection is applied to the active region, then light emission is stimulated, but cleave damage and optical intensity cause catastrophic optical mirror damage (HR-COMD)
Solution Approach 1:
The device separates the current injection function (active region) from the HR-coated facet function (passive window region adjacent to rear face). This segmentation allows high power light emission from the active region while the passive window region protects the cleaved facet from both optical intensity and current injection effects.
Solution Approach 2:
The harmful combination of high current injection and high optical intensity at the rear face is eliminated by extracting these functions to separate regions. The active region handles current injection and light generation, while the passive window region adjacent to the rear face handles only low-intensity light transmission without current injection.
3Device complexity
If the waveguide width is constant throughout the cavity, then the device structure is simple, but the cleave quality and damage tolerance are reduced
Solution Approach 1:
The waveguide width is varied locally: it is wider in the passive window region adjacent to the rear face and narrower in the active region. This local quality change improves cleave quality at the rear face by providing a larger area that is less sensitive to cleaving variations, while maintaining the necessary confinement in the active region for efficient light emission.
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 reduces the likelihood of HR-COMD, enhances cleave quality, and maintains device performance without requiring additional fabrication steps, resulting in a more reliable and tolerant optical device to cleaving damage.
Implementation Method 1
a waveguide extending with the optical cavity for inducing light in the cavity to travel along the length of the cavity
Implementation Method 2
by ion-implantation
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3(a)~3(b)
AI summary
An optical device having a first face, a second face and an optical cavity, the optical cavity being defined by a semiconductor substrate and having a length extending between the first face and the second face, the device comprising: a waveguide extending with the optical cavity for inducing light in the cavity to travel along the length of the cavity; an active region configured for injection of charge into the cavity, the active region being spaced from the first face; and an inactive region, the inactive region being located between the active region and the first face. This passive window structure results in a device which may have better cleave quality and which is less prone to cleave damage, has lower optical intensity and reduced heating at the first face. This may help to prevent HR-COMD from occurring in the device.