Compact External Grating PBS/PBC Coupler Design
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Solution Overview
Problem
Current 2D polarization beam splitters (PBS) and polarization beam combiners (PBC) in silicon photonics suffer from high insertion loss and low polarization extinction ratio, requiring complex sub-micron alignment and being polarization-dependent, which limits their efficiency and versatility in optical coupling with silicon photonics chips.
Innovation Solution
A compact PBS/PBC design utilizing a lens to focus light, a YVO4 crystal to split the light into ordinary and extraordinary rays, and a glass wedge to direct these rays onto a silicon chip, minimizing distortion and achieving better mode matching and polarization extinction ratio, resulting in reduced insertion loss and increased spectral bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lensed fibers are used to enhance coupling efficiency, then coupling efficiency is improved, but alignment complexity and sensitivity increase
Solution Approach 1:
A lens is introduced as an intermediary component between the optical fiber and the silicon photonics chip. The lens focuses the optical beam to improve mode matching and coupling efficiency, while the system design accommodates this additional component to manage alignment requirements
Solution Approach 2:
The patent modifies optical parameters such as beam focusing characteristics and mode field diameter to optimize coupling efficiency. By changing the optical parameters through lens design and positioning, the system achieves better coupling without requiring sub-micron alignment precision
2Adaptability or versatility
If photonic integrated circuits operate independent of polarization, then versatility is improved, but polarization extinction ratio decreases
Solution Approach 1:
The system segments the optical path into distinct polarization-handling sections. By dividing the functionality into separate polarization-maintaining and polarization-independent sections, the system achieves both polarization versatility and high extinction ratio through dedicated components in each segment
3Ease of manufacture
If 2D PBS/PBC are used in silicon photonics, then integration is improved, but insertion loss increases
Solution Approach 1:
The patent employs composite material structures combining silicon photonics waveguides with external optical components. This composite approach allows the integrated circuit to maintain fabrication simplicity while using external lenses and optical elements to reduce insertion loss that would be inherent in purely integrated 2D PBS/PBC designs
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 provides a compact, efficient optical coupling with lower insertion loss and improved polarization extinction ratio, enabling thinner and more versatile designs suitable for both hermetical and non-hermetical applications, while maintaining high coupling efficiency and spectral bandwidth.
Implementation Method 1
a lens that receives an incoming light and produces a focused light
Implementation Method 2
a crystal that receives the focused light from the lens and splits the light into a first ray and a second ray
Implementation Method 3
a wedge that receives the first ray and the second ray and bends the rays in the direction of a surface of a silicon chip
Data Source
AI summary
Approaches to Compact External Grating PBS/PBC Coupling are described according to embodiments of the present invention. In one embodiment, a YVO4 crystal is used to split a beam or combine multiple beams into a single beam. A lens is used to convert a mode of the light to match a mode of a grating port. A glass wedge is designed to bend the light from horizontal to a nearly vertical orientation to match an exit angle of a grating port. When a source or a receiver utilizes an optical fiber, a fiber holder may be used to bond the fiber to the source or receiver. The PBS/PBC described has much less insertion loss compared to existing 2D grating coupler techniques, and has a wider spectral bandwidth due to flexibility in mode matching compared to existing 2D grating couplers. The PBS/PBC described herein also has a better polarization-extinction ratio than the existing 2D grating couplers, and the horizontal coupling configuration enables a design that is thinner and more compact compared to the near vertical coupling in 2D grating coupling.