III-V/SOI Tapered Gain Region for Better Waveguide Coupling
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Solution Overview
Problem
The coupling efficiency between the gain region and the waveguide in semiconductor optical devices is limited due to inadequate shaping of the tapered tip, leading to reduced performance in oscillation threshold current density, power consumption, and optical properties.
Innovation Solution
A method involving the sequential stacking of III-V group compound semiconductors on an SOI substrate, with a first cladding layer, core layer, and second cladding layer, followed by etching to form a tapered portion along the waveguide, enhancing the coupling efficiency by precise shaping of the tapered tip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the gain region is bonded to the waveguide without tapered shaping, then the device structure is simple and easy to manufacture, but the coupling efficiency between gain region and waveguide is limited
Solution Approach 1:
The patent applies curvature by forming a tapered portion at the tip of the gain region that gradually reduces in thickness along the light propagation direction. This curved/tapered structure replaces a straight cylindrical shape, enabling smoother light transition and improved coupling efficiency between the gain region and waveguide by reducing abrupt refractive index changes.
Solution Approach 2:
The patent changes the geometric parameter of the gain region tip by forming a tapered portion with gradually varying thickness. The thickness parameter transitions from the full thickness of the core layer and second cladding layer at the base to a reduced thickness at the tip, creating a continuous gradient that improves optical coupling while maintaining manufacturing feasibility through controlled etching processes.
2Manufacturing precision
If the tapered portion is formed by etching the core layer and second cladding layer, then the light transition becomes smoother and coupling efficiency improves, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies preliminary action by forming the tapered portion through a controlled etching process that removes material in advance to create the desired gradient structure. The etching process is performed with specific parameters (depth, angle, profile) predetermined to achieve optimal light transition, allowing subsequent bonding and operation without requiring additional complex adjustments.
Solution Approach 2:
The patent segments the gain region structure into distinct portions: a base portion with full thickness and a tapered tip portion with gradually reduced thickness. This segmentation allows the etching process to be applied selectively to create the tapered profile, separating the manufacturing of the high-efficiency tapered region from the rest of the device structure.
3Loss of energy
If the second cladding layer is etched partway to form the tapered portion, then the refractive index uniformity increases and optical loss decreases, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by creating a tapered portion with specific etching characteristics only at the tip region of the gain region, while maintaining the full thickness of the core layer and second cladding layer in the base portion. This localized etching approach reduces optical loss at the critical coupling interface without requiring precision control over the entire device structure, as only the tapered tip region needs precise depth and profile control.
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 method significantly improves the coupling efficiency between the gain region and the waveguide, resulting in enhanced optical properties and reduced optical loss, with the tapered portion allowing smoother light transition and increased refractive index uniformity.
Implementation Method 1
etching partway in the thickness direction the second cladding layer exposed from the first insulating film; forming a second insulating film covering from the covered portion with the first insulating layer of the second cladding layer to a part of a remaining portion of the second cladding layer that remains in the region of the second cladding layer etched partway in the thickness direction; and forming a first tapered portion that is disposed on the waveguide and tapered along the extending direction of the waveguide by etching the core layer and the second cladding layer
Data Source
AI summary
A method for producing a semiconductor optical device includes the steps of bonding a semiconductor chip to an SOI substrate having a waveguide, the semiconductor chip having an optical gain and including a first cladding layer, a core layer, and a second cladding layer that contain III-V group compound semiconductors and are sequentially stacked in this order, forming a covered portion with a first insulating layer on the second cladding layer, etching partway in the thickness direction the second cladding layer exposed from the first insulating film, forming a second insulating film covering from the covered portion to a part of a remaining portion of the second cladding layer, and forming a first tapered portion that is disposed on the waveguide and tapered along the extending direction of the waveguide by etching the core layer and the second cladding layer exposed from the second insulating film.