Tunable Laser Locked to Whispering Gallery Mode Resonator

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Solution Overview

Problem

Laser stability is compromised by environmental perturbations such as temperature fluctuations and vibrations, leading to wavelength and phase fluctuations, which existing stabilization techniques struggle to fully address.

Innovation Solution

A laser device is optically coupled to a whispering gallery mode optical resonator, which supports a circulating whispering gallery mode and provides optical feedback to stabilize the laser frequency and reduce linewidth, using an electro-optic material that can be tuned via electrical control signals or RF fields to maintain stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a laser is used without stabilization, then the device complexity is low, but the laser frequency stability and linewidth are poor due to environmental perturbations

Engineering Contradiction:

Improvelaser frequency stabilityVSAvoidstabilization system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements optical feedback by coupling the laser output to a high-Q resonator and feeding back a portion of the resonator output to the laser input. This feedback mechanism locks the laser frequency to the resonator's resonant frequency, stabilizing the laser against environmental perturbations such as temperature fluctuations and vibrations.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent uses a high-Q resonator to create an optical potential well that traps and stabilizes the laser frequency. The resonator's high quality factor creates a deep potential well that strongly attracts and holds the laser frequency at the resonant frequency, making the system insensitive to small environmental variations.

Inventive Principle:

Principle #12Equipotentiality

2Reliability

If a Fabry-Perot cavity is used for laser stabilization, then the laser frequency can be stabilized, but the system complexity and alignment sensitivity increase

Engineering Contradiction:

Improvelaser frequency stabilityVSAvoidoptical cavity system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the key parameter from the low Q-factor of Fabry-Perot cavities to the high Q-factor of the whispering gallery mode resonator. This parameter change fundamentally improves the stabilization performance while reducing the feedback power requirements and relaxation oscillation issues associated with low-Q systems.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical alignment-sensitive Fabry-Perot cavity with an optical resonator based on whispering gallery modes. This substitution eliminates the need for precise mechanical alignment of multiple mirrors, replacing it with a robust optical coupling scheme that is much less sensitive to mechanical perturbations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If optical feedback is used to stabilize the laser, then the linewidth is reduced, but the feedback power requirements and relaxation oscillations increase system complexity

Engineering Contradiction:

Improvelaser linewidthVSAvoidfeedback control complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The high-Q resonator creates a deep optical potential well that strongly attracts the laser frequency, enabling effective linewidth reduction with minimal feedback power. The strong confinement effect of the high-Q resonator makes the laser frequency highly sensitive to the resonator's resonant frequency, achieving narrow linewidth without excessive feedback power.

Inventive Principle:

Principle #12Equipotentiality

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 effectively locks the laser frequency to the whispering gallery mode resonator, reducing linewidth and enabling modulation while maintaining stability against environmental perturbations, thereby achieving a tunable and narrow linewidth laser output.

Implementation Method 1

an optical resonator structured to support a whispering gallery mode circulating in the optical resonator

Methodology Applied

Scientific EffectWhispering gallery mode: Resonance

Implementation Method 2

the optical resonator being optically coupled to the laser to receive a portion of the laser beam into the optical resonator in the whispering gallery mode and to feed laser light in the whispering gallery mode in the optical resonator back to the laser

Methodology Applied

Scientific EffectOptical feedback: Feedback