DFB Laser Grating and Output Facet Alignment for Higher SMSR

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Solution Overview

Problem

Conventional chip bonding processes for integrating III-V semiconductor devices with silicon-on-insulator (SOI) platforms are costly and have low yield due to metal bumping requirements and alignment challenges, particularly affecting the side mode suppress ratio (SMSR) of Distributed Feedback (DFB) lasers.

Innovation Solution

A method of preparing DFB lasers by etching a grating into the active waveguide and an output facet, ensuring the grating is located between the reflective and output facets, allowing for precise alignment and reducing phase changes near the facet, thereby improving SMSR and yield.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional chip bonding processes use flip-chip bonding to integrate III-V semiconductor devices with SOI platforms, then device integration is achieved, but manufacturing cost increases and yield decreases due to metal bumping requirements and alignment difficulties

Engineering Contradiction:

Improveintegration yieldVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent extracts and eliminates the metal bumping step from the integration process by using direct wafer bonding. The III-V semiconductor device is bonded directly to the SOI platform without requiring metal bumps, thereby reducing manufacturing complexity and cost while improving alignment precision and yield

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical alignment system (metal bumps and complex alignment mechanisms) with a direct bonding approach. The alignment is achieved through precise positioning during the bonding process itself, eliminating the need for mechanical bumping structures and associated alignment complexities

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If the grating extends over the output facet in conventional DFB lasers, then the laser structure is simplified, but the side mode suppress ratio decreases due to phase uncertainty from imprecise facet cleaving

Engineering Contradiction:

Improvegrating alignment precisionVSAvoidfabrication process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by defining the grating position relative to the output facet before the actual fabrication step. The grating is designed to extend a specific distance (5-50 μm) from the output facet, and this position is predetermined in the design stage, allowing for precise control of the phase reference point without requiring post-fabrication adjustments

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the critical parameter from facet cleavage position (which has ± few microns uncertainty) to grating-to-facet distance (controlled to within ±100 nm). By controlling the distance between the grating and the output facet rather than relying on precise facet cleaving, the phase uncertainty is dramatically reduced and SMSR is improved

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20240170919A1Device coupon

Publication Date: 2024.05.23 ROCKLEY PHOTONICS LTD

AI summary

A method of preparing a distributed feedback laser. The distributed feedback laser comprises an active waveguide with a reflective facet. The method comprises: etching a grating into the distributed feedback laser; and etching an output facet into the active waveguide.