Grating Coupler Inverse Taper III-V Silicon Optical Loss
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Solution Overview
Problem
Current optical interconnects in high-performance computing systems face inefficiencies due to low wall-plug efficiency and wavelength stability issues in laser sources, with excessive power consumption by thermal-electric cooling and high optical coupling loss between III-V semiconductor and silicon optical waveguides.
Innovation Solution
A photonic integrated circuit (PIC) design featuring a substrate with a bottom cladding layer, an active layer with a bandgap wavelength exceeding silicon, and a top cladding layer, including a grating coupler that couples the optical signal out of the active layer plane, with an inverse taper and diffraction grating for improved manufacturability and reduced absorption, and a reflecting layer for constructive interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If thermal-electric cooling (TEC) is used to maintain stable wavelength and good slope efficiency, then wavelength stability is improved, but power consumption increases significantly
Solution Approach 1:
The patent extracts and removes the thermal-electric cooling (TEC) component from the laser source design. By eliminating the TEC, the system achieves uncooled operation, dramatically reducing power consumption while maintaining acceptable wavelength stability through alternative design approaches in the laser cavity and grating coupler.
Solution Approach 2:
The laser source is designed to self-regulate its operating temperature and wavelength stability without external active cooling. The device uses its own structural design elements (such as the laser cavity configuration and grating coupler geometry) to maintain stable operation, making the system self-sufficient and eliminating the need for power-hungry cooling mechanisms.
2Ease of operation
If grating coupler is used to couple optical signal between chips, then alignment tolerance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes key parameters of the grating coupler including the grating period, depth, and fill factor to achieve a balance between alignment tolerance and manufacturing feasibility. By carefully selecting these parameters, the design achieves sufficient coupling efficiency and alignment tolerance while remaining compatible with standard semiconductor fabrication processes.
Solution Approach 2:
The grating coupler is integrated into a composite structure combining III-V semiconductor laser material with silicon photonic waveguide. This composite design allows the grating to serve dual functions: providing mode transformation for improved alignment tolerance while being fabricated using compatible processes for both material systems.
3Power
If III-V semiconductor laser source is used, then output power is sufficient, but optical coupling loss to silicon waveguide increases
Solution Approach 1:
The grating coupler acts as an intermediary device that mediates the optical coupling between the III-V semiconductor laser source and the silicon photonic waveguide. It transforms the optical mode from the laser source into a form that matches the silicon waveguide mode, thereby reducing coupling loss while preserving the high output power capability of the III-V laser.
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 PIC achieves high wall-plug efficiency and narrow lasing linewidth, facilitating low-power, high-performance optical interconnects with reduced optical loss and improved alignment tolerance, enabling efficient coupling between III-V and silicon photonic chips.
Implementation Method 1
The optical coupler may include a diffraction grating that couples the optical signal out of the plane of the active layer
Implementation Method 2
the laser light reflected by the reflector layer, which propagates towards the surface of the PIC, interferes constructively with the laser light diffracted by the optical coupler towards a surface of the PIC
Data Source
AI summary
A photonic integrated circuit (PIC) that includes an optical source that provides an optical signal having a wavelength is described. This optical source includes a reflecting layer, a bottom cladding layer, an active layer (such as a III-V semiconductor) having a bandgap wavelength that exceeds that of silicon, and a top cladding layer. Moreover, an optical coupler (such as a grating coupler) that couples the optical signal out of a plane of the active layer is included in a region of the active layer. In this region, the top cladding layer is absent. Furthermore, in an adjacent region, the top cladding layer includes an inverse taper so that the top cladding layer is tapered down from a width distal from the region. In conjunction with the optical coupler, the inverse taper may facilitate low-loss optical coupling of the optical signal between the PIC and another PIC.