PIC Stray Light Collectors and Dampers for Signal Integrity

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Solution Overview

Problem

Photonic integrated circuits (PICs) face issues with stray light generation due to non-guided radiation modes, which can lead to erroneous signals in applications requiring stable output polarization, such as interferometric modulators and coherent communication systems, as the stray light can interfere with the desired signal and degrade system performance.

Innovation Solution

The implementation of a photonic integrated circuit (PIC) with integrated stray light collectors and dampers, where the collectors are waveguides with tapered ends to efficiently collect stray light and direct it to damping areas with absorptive materials, effectively mitigating stray light by converting it into heat, thereby reducing interference and improving signal integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If stray light collectors and dampers are integrated into the PIC, then stray light suppression is improved, but device complexity increases

Engineering Contradiction:

Improvestray light interferenceVSAvoidPIC structure complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The stray light collector waveguides are nested within or adjacent to the main optical circuit waveguides, sharing the same substrate and fabrication process. The dampers are integrated at strategic locations within the device footprint, allowing stray light suppression functionality to be embedded without requiring separate external components.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The stray light collectors and dampers are fabricated using the same materials and processes as the main optical circuit, ensuring uniform refractive indices and compatibility with the existing waveguide structures. This homogeneous approach simplifies manufacturing while maintaining effective stray light suppression.

Inventive Principle:

Principle #33Homogeneity

2Object-affected harmful factors

If absorptive materials are used in dampers, then stray light mitigation is improved, but energy loss increases

Engineering Contradiction:

Improvestray light intensityVSAvoidoptical energy conversion to heat

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The harmful stray light energy is extracted from the optical circuit through dedicated collector waveguides and directed to specialized damper regions. This separates the energy dissipation function from the main signal path, allowing controlled energy conversion to heat in isolated areas without affecting the primary optical signal transmission.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The stray light energy, which would otherwise cause interference and degradation, is converted into thermal energy in the damper regions. This conversion transforms a harmful effect into a manageable form that can be dissipated as heat, effectively eliminating the stray light interference problem.

Inventive Principle:

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

3Productivity

If tapered waveguide ends are used for collection, then collection efficiency is improved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvestray light collection efficiencyVSAvoidtaper geometry control

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The waveguide taper geometry is optimized by adjusting parameters such as taper angle, length, and profile curvature. These parameter changes enable the collector waveguides to efficiently couple stray light while maintaining compatibility with standard fabrication tolerances and processes.

Inventive Principle:

Principle #35Parameter changes

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 solution achieves significant suppression of stray light, with over 20 dB reduction in stray light intensity, enhancing the accuracy and reliability of PIC-based systems by minimizing erroneous signal generation and maintaining stable polarization states.

Implementation Method 1

a light damper configured to receive the non-guided stray light collected by the at least one stray light collector and to mitigate the non-guided stray light

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Data Source

PatentUS12136681B2Method and apparatus for control and suppression of stray light in a photonic integrated circuit

Publication Date: 2024.11.05 EMCORE CORP

AI summary

In a photonic integrate circuit (PIC) architecture, non-guided stray light that is radiated from components, junctions, discontinuous and scattering points in an integrated optic device, may be received by an integrated waveguide structure in the path of the stray radiation. The integrated waveguide structure may comprise a plurality of collectors that are configured to collect the non-guided stray light from the radiating source. Each of the collectors may comprise an integrated waveguide with a front end that is tapered to increase the mode-field size and pointed toward the stray light source, and with a back end that is connected to a secondary waveguide. The collectors are placed in the path of the stray light and aligned in the propagation direction of the stray light. The collected stray light is guided to a light energy damper through the second waveguide for converting light energy into heat.