Reflection Cancellation Circuit for Stable Silicon Photonic Lasers

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional methods for stabilizing laser light sources in photonics applications, such as data transfer and telecommunication systems, are hindered by parasitic reflections, which cause instability and require costly magneto-optical isolators or RF modulators that are not readily integrated into silicon photonic platforms, leading to high optical losses and form factor issues.

Innovation Solution

An electronic-photonic integrated circuit-based reflection cancellation method that taps a portion of the laser output, phase-shifts it to be out-of-phase with parasitic reflections, and superimposes it to destructively interfere with the reflections, thereby reducing their magnitude, using a tunable tap and phase shifter controlled by a photodetector feedback loop.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If magneto-optical isolators are used to block parasitic reflections, then laser stability is improved, but device complexity and cost increase due to integration difficulties on silicon photonic platforms

Engineering Contradiction:

Improvelaser stabilityVSAvoidintegration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces magneto-optical isolators (mechanical/optical system) with an electronic feedback system using phase shifters and modulators. The feedback signal is generated by detecting parasitic reflections and actively canceling them through phase manipulation, eliminating the need for complex magneto-optical materials and their associated integration challenges on silicon photonic platforms

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements a feedback mechanism where parasitic reflections are detected by photodetectors, converted to electrical signals, processed through phase shifters and modulators, and then re-injected to cancel the original reflections. This closed-loop feedback system continuously monitors and corrects parasitic reflections, providing laser stability without requiring complex passive isolators

Inventive Principle:

Principle #23Feedback

2Reliability

If RF modulators are used to reduce parasitic reflections, then laser stability is improved, but optical losses increase and integration becomes difficult

Engineering Contradiction:

Improvelaser stabilityVSAvoidoptical losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent replaces RF modulators with an all-optical feedback approach using phase shifters and direct optical modulation. The feedback signal is generated optically by manipulating the phase of the reflected light itself rather than using electrical RF signals, reducing conversion losses and improving overall optical efficiency

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent converts the harmful parasitic reflections into a useful feedback signal. Instead of attempting to block or absorb the reflections, the system detects them and uses them to generate a counter-phase signal that actively cancels the harmful effects, transforming the problem into a solution

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach effectively cancels parasitic reflections, stabilizes the laser, and reduces optical losses, allowing for the omission of traditional optical isolators, with demonstrated cancellation of up to 40 dB, and can be integrated into silicon photonic platforms without the need for costly magneto-optical materials.

Implementation Method 1

generating a feedback signal by phase shifting a tapped portion of the laser output, wherein the feedback signal is out-of-phase with a parasitic reflection of the laser output

Methodology Applied

Scientific EffectPhase shifting:

Implementation Method 2

superimposes it to destructively interfere with the reflections, thereby reducing their magnitude

Methodology Applied

Scientific EffectDestructive interference: Interference

Implementation Method 3

using a tunable tap and phase shifter controlled by a photodetector feedback loop

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS12199398B2Method and circuit for reflection cancellation

Publication Date: 2025.01.14 THE UNIV OF BRITISH COLUMBIA

AI summary

Methods, circuits, and techniques for reflection cancellation. Laser output is tapped. A tapped portion of the laser output is phase shifted to generate a feedback signal, with the feedback signal being out-of-phase with a parasitic reflection of the laser output. The feedback signal is directed towards the laser such that the parasitic reflection and feedback signal are superpositioned before entering the laser. A magnitude and a phase of the feedback signal are such that superposition of the feedback signal and the parasitic reflection results in a resulting signal of lower magnitude than the parasitic reflection alone. During laser operation, a magnitude of the resulting signal is monitored and, as the parasitic reflection varies, the magnitude of the resulting signal is adjusted by adjusting at least one of the magnitude and the phase of the feedback signal in response to the monitoring of the resulting signal.