DFB Laser with Tunable Bragg Reflector for Stable Single-Mode Output
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Solution Overview
Problem
The production yield of single mode DFB lasers with high side mode suppression ratios (SMSRs) is limited due to manufacturing process uncertainties, particularly in wafer cleaving, which affect the precise alignment between the reflective back facet and the diffraction grating.
Innovation Solution
A distributed feedback (DFB) laser design that includes a phase control section between the back reflector and the diffraction grating, allowing for control of the laser light spectrum independent of the back facet alignment. This design decouples the spectral performance from the alignment uncertainties, enhancing the production yield of single mode DFB lasers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diffraction grating is used to provide distributed optical feedback in a DFB laser, then single mode laser oscillation can be achieved, but the alignment precision between the back facet and the diffraction grating becomes critical and difficult to maintain due to manufacturing uncertainties
Solution Approach 1:
The device is segmented into three main functional sections: a gain section for light amplification, a distributed feedback (DFB) section with diffraction grating for single mode selection, and a wavelength selective reflector (WSR) section for spectral control. This segmentation allows each section to be optimized independently, reducing the impact of alignment uncertainties on overall performance
Solution Approach 2:
A wavelength selective reflector (WSR) is introduced as an intermediary element between the gain section and the DFB section. This WSR acts as a mediator that provides wavelength-selective feedback to the gain medium, enabling spectral control without requiring precise alignment between the back facet and the diffraction grating in the DFB section
2Reliability
If precise alignment between the back facet and diffraction grating is maintained to achieve high side mode suppression ratio, then single mode performance is improved, but production yield decreases due to manufacturing process uncertainties
Solution Approach 1:
The wavelength selective reflector serves as an intermediary that decouples the spectral performance from the mechanical alignment between the back facet and the diffraction grating. By providing wavelength-selective feedback through this intermediate element, high side mode suppression ratios can be achieved without requiring sub-micron alignment precision, thereby improving production yield
Solution Approach 2:
The invention changes the control parameter for spectral performance from mechanical alignment position to optical feedback wavelength selection. By using the WSR to select wavelengths optically rather than relying on mechanical positioning, the system achieves high SMSR through parameter change rather than precise geometric alignment
3Stability of the object's composition
If the back facet position is fixed relative to the diffraction grating to ensure consistent spectral performance, then laser spectrum stability is improved, but device complexity increases due to additional alignment and positioning requirements
Solution Approach 1:
The wavelength selective reflector acts as an intermediary that stabilizes the laser spectrum through optical feedback rather than mechanical positioning. This mediator provides wavelength-selective reinforcement that inherently stabilizes the spectrum without requiring complex alignment mechanisms or precise positioning systems
Solution Approach 2:
The wavelength selective reflector provides self-stabilizing optical feedback that automatically reinforces the desired wavelength without requiring external alignment control systems. The system self-regulates its spectral output through the optical properties of the WSR, eliminating the need for complex positioning mechanisms
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 proposed design improves the production yield of single mode DFB lasers with high SMSRs by effectively controlling the laser spectrum, thereby reducing the impact of manufacturing alignment uncertainties.
Implementation Method 1
an optical gain medium configured to amplify light having wavelength within an operational wavelength range of the DFB
Implementation Method 2
a first diffraction grating providing distributed optical feedback to the light amplified by the pumped gain region
Implementation Method 3
a back reflector configured to retroreflect laser light received from the back end of the first diffraction grating back to the first diffraction grating
Implementation Method 4
the phase control section configured to control the spectrum of the laser light by controlling a phase of light transmitted through the phase control section
Implementation Method 5
The reflection band of the wavelength selective reflector can be tunable via electro-optic, thermo-optic effects, or by current injection
Implementation Method 6
The reflection band of the wavelength selective reflector can be tunable via electro-optic, thermo-optic effects, or by current injection
Data Source
AI summary
A modified distributed feedback (DFB) laser comprises a gain region with a distributed feedback grating and a back reflector that receives a portion of laser light generated by the gain region and the distributed feedback. The back reflector is a wavelength-selective reflector that retroreflects the portion of the received laser light back to the gain region, thereby stimulating single mode laser oscillation and/or improving a side mode suppression ratio (SMSR) of the laser light generated by the modified DFB laser. The spectral properties of the laser output by the modified DFB laser can be independent of position of a cleaved facet of the laser chip near a back end of the modified DFB laser and/or the performance of the modified DFB laser can be maintained over a large number of laser chips separated from a wafer.