Distributed Feedback Laser Diode Phase-Shift Region Design
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Solution Overview
Problem
Conventional distributed feedback-laser diodes (DFB-LDs) have limited single mode yield due to random phase in high reflection coatings, high production costs associated with phase-shift gratings, and difficulty in controlling operation wavelengths in complex-coupled DFB-LDs.
Innovation Solution
A distributed feedback-laser diode design incorporating a phase-shift region and ridge waveguide layer with varying effective refractive indices, achieved through specific layer structures and etch stop layers, to enhance single mode generation and control operation wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a high reflection coating is used in conventional DFB-LD, then the device structure is simplified, but the single mode yield decreases to about 20% or less due to random phase
Solution Approach 1:
The patent introduces a phase-shift region with different effective refractive index characteristics within the grating structure. This local variation in optical properties creates a predetermined phase shift that suppresses multi-mode oscillation while maintaining overall structural simplicity, thereby resolving the contradiction between device complexity and single mode yield
Solution Approach 2:
The patent modifies the effective refractive index parameter by introducing a phase-shift region with distinct optical characteristics. This parameter change creates a controlled phase shift that enhances single mode operation without significantly complicating the device structure, addressing both the simplicity and reliability requirements
2Reliability
If a phase-shift grating is used to improve single mode yield, then the single mode performance is enhanced, but the production cost increases due to requiring electron-beam lithography apparatus
Solution Approach 1:
The patent achieves phase shifting through material composition and effective refractive index differences rather than requiring precise sub-wavelength geometric patterns. This approach allows conventional lithography to be used instead of expensive electron-beam lithography, reducing production costs while maintaining enhanced single mode performance
Solution Approach 2:
The patent replaces expensive electron-beam lithography processes with conventional, more cost-effective lithography methods. By achieving the same functional effect through material properties rather than ultra-precise patterning, the invention enables lower-cost manufacturing while preserving the single mode enhancement benefits
3Device complexity
If a gain/complex-coupled grating is used to change optical loss or gain, then the grating structure is enhanced, but the operation wavelength becomes difficult to control
Solution Approach 1:
The patent introduces a phase-shift region with distinct effective refractive index properties within the grating structure. This localized modification provides predetermined phase control that stabilizes the oscillation wavelength, enabling better wavelength control while maintaining a relatively simple grating structure without complex gain/loss variations
Solution Approach 2:
Instead of controlling wavelength through complex gain and loss variations in the grating, the patent inverts the approach by using a phase-shift region with different effective refractive index characteristics. This inverted strategy achieves wavelength control through phase management rather than gain/loss modulation, simplifying the grating structure while improving wavelength stability
4Adaptability or versatility
If the coupling coefficient, reflective index, or operation current is changed to adjust wavelength, then the wavelength can be freely changed, but the oscillation properties are limited and single mode yield decreases
Solution Approach 1:
The patent introduces a phase-shift region with distinct effective refractive index properties that creates a predetermined phase shift. This local modification suppresses multi-mode oscillation and stabilizes wavelength, allowing for controlled wavelength adjustment while maintaining excellent oscillation properties and high single mode yield, thus resolving the contradiction between adaptability and reliability
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 design significantly increases the yield of single mode operation and improves control over operation wavelengths, reducing production costs and enhancing laser diode performance.
Implementation Method 1
A laser light may be oscillated with a wavelength satisfying Bragg condition in a effective refractive index change structure (i.e., index-coupled grating) of a waveguide in the DFB-LD. The grating may oscillate the laser light by satisfying a phase-condition at two wavelengths within a stop band.
Implementation Method 2
the phase-shift region may have a second effective refractive index different from the first effective refractive index. The phase-shift region may change a phase of the laser light transmitted along the ridge waveguide layer by a predetermined amount.
Implementation Method 3
A ridge waveguide layer extending in a second direction crossed the first direction on the phase-shift region
Data Source
AI summary
Distributed feedback-laser diodes are provided. The distributed feedback-laser diode may include a substrate, a lower cladding layer having a grating on the substrate, an active layer disposed on the lower cladding layer, a first upper cladding layer disposed on the active layer, a phase-shift region extending in a first direction on the first upper cladding layer, and a ridge waveguide layer extending in a second direction crossing the first direction on the phase-shift region.