Intra-Cavity DWDM Laser with Ring Resonator ITU-Grid Tuning
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Solution Overview
Problem
Existing tunable lasers face challenges in achieving a wide tuning range with narrow linewidth and precise tuning to a predetermined fixed wavelength spacing grid, such as the ITU-grid, due to high optical losses, waveguide bending losses, and difficulties in fabricating gratings with high Q-factors, leading to broadened linewidth and complex control mechanisms.
Innovation Solution
A tunable DWDM intra-cavity laser device with a first and second optical waveguide, an active gain section, a phase section, and an intra-cavity ring resonator between them, where the ring resonator's length is optimized to match the ITU-grid, allowing discrete tuning and narrow linewidth through Lorentzian filtering and DBR sections, eliminating the need for external Fabry-Perot etalon filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external Fabry-Perot etalon filters are used to match the ITU grid, then wavelength tuning precision is improved, but device complexity and packaging cost increase
Solution Approach 1:
The patent integrates the ITU grid matching function directly into the laser cavity by incorporating a ring resonator with a free spectral range matching the ITU grid spacing. This merges the wavelength selection function with the laser oscillation cavity, eliminating the need for external Fabry-Perot etalon filters and reducing device complexity while maintaining wavelength tuning precision.
Solution Approach 2:
The patent extracts the grid matching function from the external filter component and relocates it into the laser cavity itself through the ring resonator. This extraction eliminates the separate external filter module, simplifying the overall device structure while preserving the precise wavelength selection capability.
2Ease of operation
If Coupled Cavity Lasers with long active cavity are used to match the 100 GHz grid, then wavelength tuning is improved, but optical losses increase and linewidth broadens
Solution Approach 1:
The patent uses a tunable ring resonator within the laser cavity that can dynamically adjust its resonance conditions. The ring resonator's free spectral range is designed to match the ITU grid, allowing the laser to automatically lock to grid wavelengths while maintaining a shorter effective cavity length, thus reducing optical losses and preserving narrow linewidth.
Solution Approach 2:
The patent changes the cavity configuration from a long coupled cavity structure to a shorter cavity with an integrated ring resonator. By adjusting the ring resonator parameters (radius, coupling coefficients) to achieve the desired free spectral range matching the ITU grid, the system achieves wavelength tuning without the high optical losses associated with long active cavities.
3Adaptability or versatility
If ring resonators with small radius are used to achieve wide tuning range, then tuning range is improved, but waveguide bending losses increase and linewidth broadens
Solution Approach 1:
The patent optimizes the ring resonator parameters, specifically the radius and coupling coefficients, to achieve the desired free spectral range matching the ITU grid. By carefully selecting these parameters, the system achieves wide tuning range across the C-band while maintaining low waveguide bending losses and narrow linewidth, avoiding the trade-off between tuning range and loss.
4Reliability
If hybrid integration with III-V active sections is used for silicon based ring resonators, then Q factor is improved, but fabrication complexity and cost increase
Solution Approach 1:
The patent employs hybrid integration of silicon-based ring resonators with III-V active sections to achieve high Q factor performance. The silicon provides low-loss waveguiding with high Q factor, while the III-V material provides efficient light emission. This composite structure achieves high reliability while the integration process, though complex, enables monolithic fabrication of the laser device.
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 device provides automatic matching to the ITU-grid with a narrow optical linewidth below 200 kHz, wide tuning range of at least 20 nm, and simplified control, using monolithic InP processing without hybrid integration, thus reducing fabrication costs and maintaining low propagation losses.
Implementation Method 1
narrow linewidth through Lorentzian filtering
Implementation Method 2
intra-cavity ring resonator arranged between two gratings
Implementation Method 3
first optical wave guide having a first optical grating section, a second optical wave guide having a second optical grating section
Data Source
AI summary
The present invention concerns a tunable Dense Wavelength Division Multiplex (DWDM) intra cavity laser device having a first optical wave guide having a first optical grating section, a second optical wave guide having a second optical grating section, an active gain section spatially separated from the second optical grating section and a phase section, and a DWDM-filter having an intra-cavity ring resonator located between the first optical wave guide and the second optical wave guide for coupling optical waves between the first and second optical wave guides. The tunable laser device is tunable in a discrete manner depending on a length of the ring resonator that is selected such that the free spectral range of the ring resonator matches a predetermined fixed wavelength spacing grid.