External Optical Resonator Frequency Tuning Without Mode Hopping

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Solution Overview

Problem

Existing radiation sources struggle to reliably tune electromagnetic radiation frequencies over large ranges without causing mode hopping, which leads to discontinuities and inaccuracies in measurement systems.

Innovation Solution

A method involving the generation of pump radiation, coupling it into an external optical resonator with a tunable resonance frequency, changing the resonance frequency independently of the pump frequency, and decoupling the resonator radiation as useful radiation, preventing feedback and mode jumps.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the gain profile of the laser medium is shifted to tune the frequency over a large range, then the frequency tuning range is improved, but mode hopping occurs causing discontinuities in frequency tuning

Engineering Contradiction:

Improvefrequency tuning rangeVSAvoidfrequency tuning continuity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system separates the frequency tuning function from the gain medium by introducing an external optical resonator. The laser medium maintains a fixed gain profile while the external resonator handles the frequency selection and tuning, eliminating mode hopping caused by gain profile shifting.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An external optical resonator is introduced as an intermediary component between the laser medium and the output. This resonator with tunable resonance frequency acts as a mediator that selects and filters frequencies from the broadband laser emission without requiring changes to the gain medium itself.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the resonator is tuned to extend the frequency range, then the frequency tuning range is improved, but the bandwidth is limited by the gain profile width

Engineering Contradiction:

Improvefrequency tuning rangeVSAvoidsystem configuration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The external optical resonator serves as an intermediary that decouples the frequency tuning function from the gain medium constraints. By placing the resonator outside the laser cavity, it can be tuned over a broader range limited only by the resonator's design rather than the gain profile width.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If feedback from an external resonator is used to stabilize the laser frequency, then the frequency stability is improved, but the tuning range is limited

Engineering Contradiction:

Improvefrequency stabilityVSAvoidfrequency tuning range

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The system separates frequency stabilization and frequency tuning into independent functions. The external resonator provides stabilization through its high Q-factor while allowing manual or automated tuning of the resonator's resonance frequency to extend the overall tuning range beyond what a fixed resonator could provide.

Inventive Principle:

Principle #1Segmentation

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

Enables reproducible and stable generation of electromagnetic radiation with a useful frequency that differs from the pump frequency, allowing tuning over a large range without mode hopping, thus improving the accuracy of measurement systems.

Implementation Method 1

coupling the pump radiation into an external optical resonator with a tunable resonance frequency, the resonance frequency initially being essentially equal to the pump frequency, so that electromagnetic resonator radiation oscillates in the resonator with the resonance frequency

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 2

The resonant frequency is changed after the electromagnetic pump radiation has been coupled in. However, while the resonant frequency of the external optical resonator is changed, electromagnetic pump radiation continues to be coupled into the external optical resonator

Methodology Applied

Scientific EffectElectro-optic effect: Electro-Optic Effects

Data Source

PatentEP3890124A1Method and device for generating electromagnetic useful beam

Publication Date: 2021.10.06 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

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AI summary

The present invention relates to a method for generating useful electromagnetic radiation with a useful frequency, comprising the steps of: a) generating and emitting electromagnetic pump radiation (11) with a pump frequency, b) coupling the pump radiation (11) into an external optical resonator (20) with a tunable resonant frequency, wherein the resonant frequency is essentially initially equal to the pump frequency, so that electromagnetic resonator radiation (21) oscillates in the resonator (20) at the resonant frequency, c) changing the resonant frequency of the resonator (20) so that the resonant frequency of the electromagnetic resonator radiation (21) oscillating in the resonator (20) is changed over a tuning bandwidth, wherein the pump frequency does not follow the change in the resonant frequency.and d) coupling out the electromagnetic resonator radiation (21) oscillating in the resonator (20) as useful radiation (22) with a useful frequency different from the pump frequency, wherein step c) follows step b) in time.