Tunable Semiconductor Laser Linewidth Reduction

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Solution Overview

Problem

Monolithically integrated semiconductor lasers with tunable distributed Bragg reflectors face challenges in achieving narrow linewidths due to the requirement for short laser cavities, which results in significant optical output linewidths dominated by photon population and round trip time within the cavity.

Innovation Solution

Incorporating a non-driven region with a length of at least 100 μm without electrical contact or reflective Bragg gratings, and a phase control section with a length of less than 80 μm, along with control electrodes on the optical gain and distributed Bragg reflector sections, to reduce linewidth and phase noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If narrow electrical isolation regions are provided between control electrodes to minimize cavity length, then the device complexity is reduced, but electrical interference increases

Engineering Contradiction:

Improveelectrical isolation region structureVSAvoidelectrical interference

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The passive section serves as an intermediary region that electrically isolates adjacent control electrodes while maintaining optical waveguide continuity. This non-driven region with length ≥100 μm without electrical contact blocks electrical interference paths between electrodes, reducing crosstalk and electrical noise without requiring complex isolation structures.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The passive section introduces local variation in the waveguide structure by creating a region with different electrical properties (no electrical contact) while maintaining optical guidance. This local change in electrical isolation quality allows adjacent electrode regions to be electrically separated without affecting the overall device simplicity or requiring additional complex isolation mechanisms.

Inventive Principle:

Principle #3Local quality

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 results in reduced Lorentzian linewidth and improved side mode suppression ratio, maintaining single longitudinal cavity mode operation while enhancing mode selectivity and reducing electrical interference.

Implementation Method 1

at least one of the reflectors is a distributed Bragg reflector section configured to have a tunable reflection spectrum

Methodology Applied

Scientific EffectBragg reflection: Bragg Diffraction

Implementation Method 2

an optical gain section

Methodology Applied

Scientific EffectStimulated emission: Laser

Data Source

PatentUS9209602B2Monolithically integrated tunable semiconductor laser

Publication Date: 2015.12.08 LUMENTUM TECHNOLOGY UK LTD

AI summary

A monolithically integrated, tunable semiconductor laser with an optical waveguide, comprising epitaxial layers on a substrate and having first and second reflectors bounding an optical gain section and a non-driven region, wherein at least one of the reflectors is a distributed Bragg reflector section configured to have a tunable reflection spectrum, wherein control electrodes are provided to at least the optical gain section, and the distributed Bragg reflector section, and wherein the non-driven region has a length of at least 100 μm, is without an electrical contact directly contacting onto the epitaxially grown side of the non-driven region, and the non-driven region is without a reflective Bragg grating within the epitaxial layers of the non-driven region.