Standing-Wave Laser Assembly for Stable Frequency Comb Locking

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Solution Overview

Problem

Current semiconductor laser frequency combs face challenges in miniaturization and stability due to optical feedback, requiring bulky optical isolators and limiting their application in mid-infrared spectroscopy, as they often operate in high phase-noise regimes and lack robustness against noise and fluctuations.

Innovation Solution

A laser assembly with a standing wave cavity and an AC injection device that generates a spatially dependent electrical laser beat-note, allowing for injection locking that stabilizes optical frequency combs, reducing the need for optical isolators and enhancing robustness against noise and feedback, enabling compact, cost-effective, and scalable devices for mid-infrared spectroscopy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If optical isolators are used to mitigate optical feedback in semiconductor laser frequency combs, then stability against optical feedback is improved, but device size and complexity increase due to bulky components

Engineering Contradiction:

Improvestability against optical feedbackVSAvoiddevice size

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical/optical system of bulky optical isolators with an electrical injection locking mechanism. By injecting an electrical AC signal at the round-trip frequency into the laser cavity, the system achieves stabilization against optical feedback through electrical control rather than optical isolation components, thereby reducing device size and complexity while maintaining reliability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameters of the laser by applying electrical injection locking at specific frequencies (round-trip frequency and its harmonics). This parameter change allows the laser to operate stably in high phase-noise regimes without requiring traditional optical isolators, thus resolving the contradiction between stability and device size

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If semiconductor laser frequency combs operate in high phase-noise regimes, then miniaturization is enabled, but robustness against noise and fluctuations deteriorates

Engineering Contradiction:

Improvedevice sizeVSAvoidrobustness against noise

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent implements electrical feedback by injecting an AC signal that is locked to the round-trip frequency of the laser cavity. This feedback mechanism actively compensates for noise and fluctuations, enabling the laser to operate robustly in high phase-noise regimes while maintaining miniaturization, thus resolving the contradiction between device size and robustness

Inventive Principle:

Principle #23Feedback

3Reliability

If bulky optical isolators are used to ensure stable comb operation, then reliability is improved, but ease of manufacture and scalability worsen

Engineering Contradiction:

Improvestable comb operationVSAvoidscalability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces bulky optical isolators with an electrical injection locking system that can be integrated into the laser chip itself. This substitution enables stable comb operation while significantly improving ease of manufacture and scalability, as electrical components are easier to miniaturize and integrate than optical isolators

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 allows for the generation and stabilization of optical frequency combs with fast gain media, providing a compact, cost-effective, and robust source for mid-infrared spectroscopy, capable of operating in high phase-noise regimes without bulky optical isolators, thus enabling miniaturized and scalable sensing devices.

Implementation Method 1

Methodology Applied

Scientific EffectInjection locking:

Implementation Method 2

generating standing optical waves in a standing wave cavity of the laser, wherein an electrical laser beat-note with a spatially dependent amplitude is generated

Methodology Applied

Scientific EffectStanding wave:

Implementation Method 3

four-wave mixing can couple the modes in a Fabry-Perot laser with a low cavity dispersion

Methodology Applied

Scientific EffectFour-wave mixing:

Implementation Method 4

a laser with a fast gain medium, in particular a quantum cascade laser (QCL) or an interband cascade laser (ICL)

Methodology Applied

Scientific EffectStimulated emission:

Data Source

PatentUS11916354B2Laser assembly, spectrometer and method for operating a laser

Publication Date: 2024.02.27 VIENNA UNIVERSITY OF TECHNOLOGY

AI summary

A laser assembly comprising: a semiconductor laser with a fast gain medium, wherein the gain relaxation time of the gain medium is smaller than the round-trip time in a standing wave cavity; a DC source coupled to the standing wave cavity; and an AC injection device for injecting an electrical AC signal within a range and/or within an integer multiple of the range into the standing wave cavity, the range within ±1% of the natural round-trip frequency in the standing wave cavity, comprising at least a first and second electric contact section extending along a first longitudinal side of the longitudinal extension of the standing wave cavity, the AC injection device coupled to the first and/or second electric contact section such that the complex amplitude of the electrical AC signal differs for the first and second longitudinal electric contact section.