Vernier Ring Laser Cavity for Stable Wide Wavelength Tuning
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Solution Overview
Problem
Existing tunable semiconductor lasers face limitations in tunability beyond 90 nm, leading to unstable selection of emission frequency due to increased losses and parasitic reflections, while techniques to mitigate these issues result in reduced free spectral range and degraded Side Mode Suppression Ratio (SMSR).
Innovation Solution
A wavelength-tunable laser emission device is designed with a cavity delimited by first and second Sagnac mirrors, incorporating an amplifying medium and a tunable spectral filter using the Vernier effect. This filter comprises at least three resonant rings arranged in cascade, each with a loop mirror having wavelength tunable reflectivity, and a phase control section to adjust the resonant modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the tunability of semiconductor lasers is increased beyond 90 nm using Vernier effect with two ring resonators, then the wavelength tuning range is extended, but the emission frequency selection becomes unstable due to increased losses and parasitic reflections
Solution Approach 1:
The patent divides the filtering function into multiple independent ring resonators (at least three rings) arranged in cascade, each contributing to the overall Vernier effect. This segmentation allows better control over parasitic reflections and losses by distributing the filtering function across multiple stages, thereby maintaining stable single-frequency emission over extended tuning ranges beyond 90 nm
Solution Approach 2:
The patent integrates a Sagnac loop mirror within each ring resonator structure, creating a nested configuration where the Sagnac loop is embedded inside the ring. This nesting allows the Sagnac loop to suppress parasitic reflections from the ring while maintaining the ring's resonant filtering function, thus improving emission stability without compromising tuning range
2Reliability
If a Sagnac loop mirror is added to each ring resonator to suppress parasitic reflections, then the emission stability is improved, but the optical path length is dramatically increased reducing the free spectral range
Solution Approach 1:
The patent employs thermally-tunable ring resonators where the resonant wavelengths can be dynamically adjusted by changing the temperature. This dynamic tuning capability allows the system to maintain optimal free spectral range while compensating for the optical path length increase, ensuring both stability and adequate FSR are achieved across the tuning range
Solution Approach 2:
The patent changes physical parameters (temperature, ring dimensions, Sagnac loop characteristics) to optimize the balance between parasitic reflection suppression and free spectral range maintenance. By carefully designing the Sagnac loop reflectivity and ring resonator dimensions, the system achieves stable emission without excessive FSR reduction
3Adaptability or versatility
If multiple ring resonators are used to achieve wide tunability, then the Vernier effect enhances the free spectral range, but increased losses in some spectral bands occur
Solution Approach 1:
The Sagnac loop mirror provides optical feedback within each ring resonator, enabling controlled enhancement of desired resonant modes while suppressing unwanted ones. This feedback mechanism compensates for losses in specific spectral bands by reinforcing the dominant resonant mode, thus maintaining wide tunability without significant energy loss
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 achieves extended tunability of semiconductor lasers without degrading the SMSR, ensuring stable single-frequency laser emission over a wide range, thereby overcoming the limitations of previous technologies.
Implementation Method 1
a tunable spectral filter using the Vernier effect. This filter comprises at least three resonant rings arranged in cascade, each resonant ring integrating a loop mirror with wavelength tunable reflectivity
Implementation Method 2
a cavity delimited by the first and second Sagnac mirror. The cavity comprises an amplifying medium
Implementation Method 3
each resonant ring integrating a loop mirror with wavelength tunable reflectivity by means of a phase control section
Implementation Method 4
the cavity comprises an amplifying medium
Data Source
AI summary
A wavelength-tunable laser emission device includes a cavity delimited by a first and a second Sagnac mirror. The cavity has an amplifying medium and a tunable spectral filter using the Vernier effect. The filter includes at least three resonant rings arranged in cascade, each resonant ring integrating a loop mirror with wavelength tunable reflectivity.