Hermetic Laser-PIC Photonic Package for Wafer-Level Coupling
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Solution Overview
Problem
The packaging of silicon photonic devices, particularly with semiconductor lasers and optical amplifiers, is challenging due to the small optical mode field of single-mode silicon waveguides, leading to high packaging costs that outweigh wafer fabrication costs, and there is a need for innovative packaging technologies to address compactness and power consumption constraints.
Innovation Solution
A hermetically sealed photonic package design incorporating a laser assembly tier and a photonic integrated circuit (PIC) tier, with a transparent wafer layer between them, using single crystalline silicon and wafer-level packaging techniques, including flip-bonding and micro-optic components like lenses and gratings, to efficiently couple and amplify laser light for applications like LIDAR in autonomous vehicles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hermetically sealed enclosures are used for semiconductor lasers and optical amplifiers, then reliability and performance are improved, but packaging cost and complexity increase significantly
Solution Approach 1:
The patent combines multiple discrete components (semiconductor laser, optical amplifier, waveguides, lenses, and hermetic enclosure) into a single integrated photonic chip. The laser and amplifier are fabricated using standard semiconductor processes on the same substrate, eliminating the need for separate hermetic enclosures for each component while maintaining reliability through monolithic integration.
Solution Approach 2:
The photonic chip serves multiple functions simultaneously: it generates light (laser), amplifies light (optical amplifier), guides light (waveguides), and focuses light (lenses). This multi-functional integration replaces what would traditionally require multiple separate packaged components, reducing overall packaging complexity and cost.
2Ease of manufacture
If traditional packaging methods are used for silicon photonic devices with lasers, then manufacturing is simpler, but packaging cost significantly outweighs wafer fabrication cost
Solution Approach 1:
The patent segments the photonic device into distinct functional regions on a single chip (laser region, amplifier region, waveguide regions, lens regions) that can be fabricated using standard semiconductor processing steps. This segmentation allows for scalable wafer-level fabrication and reduces the need for complex post-fabrication assembly operations.
Solution Approach 2:
The patent replaces mechanical packaging approaches (separate enclosures, manual alignment, physical mounting) with semiconductor fabrication processes (photolithography, etching, deposition, wafer bonding). This substitution enables high-volume, low-cost manufacturing while maintaining precise alignment and integration.
3Reliability
If single mode silicon waveguides are used, then optical performance is improved, but coupling with light sources becomes challenging due to small mode field
Solution Approach 1:
The patent uses lens structures with curved surfaces to focus and expand the optical mode from the single-mode waveguides. These integrated lenses compensate for the small mode field diameter by providing optical expansion and mode matching, enabling efficient coupling with larger-mode-area light sources without sacrificing the advantages of single-mode propagation.
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
This design significantly reduces packaging costs and enhances the efficiency of silicon photonic devices by enabling compact, low-power, and high-transmission silicon photonic packages suitable for LIDAR and other sensing applications, improving the integration of semiconductor lasers and optical amplifiers with PICs.
Implementation Method 1
The laser assembly tier includes a laser configured to emit laser light
Implementation Method 2
The wafer layer includes a lens configured to receive the infrared laser light from the laser assembly tier and the lens is integrated into the wafer layer and configured to focus the infrared laser light to an input grating of the PIC wafer
Implementation Method 3
The PIC wafer includes an input grating and an output grating. The input grating is configured to incouple the laser light reflected from the mirror and direct the laser light to the SOA
Implementation Method 4
The PIC tier includes a semiconductor optical amplifier (SOA) and a PIC wafer configured to incouple the laser light into the PIC wafer and direct the laser light to the SOA
Implementation Method 5
The wafer layer and the PIC wafer are formed of single crystalline silicon. The wafer layer seals the SOA from an environment of the LIDAR device
Data Source
AI summary
A light detection and ranging (LIDAR) device includes a first wafer layer, a laser assembly disposed on the first wafer layer, a capping layer, a second wafer layer, and a photonic integrated circuit (PIC). The capping layer is coupled to the first wafer layer and configured to seal the laser assembly. The second wafer layer is at least partially coupled to the first wafer layer. The PIC is formed on the second wafer layer. The second wafer includes an exit feature configured to outcouple laser light from the laser assembly.