DFB Laser Diode Thick Waveguide Reduces Optical Damage
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Solution Overview
Problem
DFB laser diodes with lateral coupling face limitations in achieving large light outputs due to catastrophic optical damage (COD) at high optical power densities, which restricts their application in high-power requirements, and existing manufacturing processes can impair crystal quality and yield.
Innovation Solution
The DFB laser diode design features a thick lower waveguide layer (1 µm to 5 µm) and a thin upper waveguide layer (15 nm to 100 nm) with a periodic surface structure, reducing optical intensity density and beam divergence, allowing for increased light output without degrading the laser mirror, and incorporating a high refractive index layer in the waveguide ridge to adjust coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DFB laser diodes with lateral coupling are used to achieve single-mode emission, then emission spectrum purity is improved, but output power is limited due to catastrophic optical damage at high power densities
Solution Approach 1:
The waveguide structure is segmented into multiple layers with different thicknesses: a thick lower waveguide layer (1-5 µm) and a thin upper waveguide layer (15-100 nm). This segmentation allows the optical intensity to be distributed vertically, reducing peak power density at the mirror while maintaining single-mode emission through the upper layer's confinement effect
Solution Approach 2:
The problem of power density concentration in the lateral plane is solved by extending the optical mode distribution into the vertical dimension. The asymmetric waveguide structure creates a vertically extended mode profile that spreads optical intensity across multiple layers, effectively reducing peak power density while maintaining lateral single-mode confinement
2Reliability
If conventional DFB laser diodes are manufactured with interrupted epitaxy and structuring processes, then distributed feedback is achieved, but crystal quality is impaired and yield decreases
Solution Approach 1:
The periodic surface structure is formed in the thick lower waveguide layer before the upper waveguide layer is deposited. This preliminary action allows the feedback structure to be established while maintaining continuous epitaxial growth, avoiding crystal quality degradation from interrupted growth and subsequent structuring processes
Solution Approach 2:
The thick lower waveguide layer serves as an intermediary layer that hosts the periodic surface structure. This intermediary structure provides distributed feedback while being physically separated from the active region by the thin upper waveguide layer, allowing feedback functionality without compromising the quality of the active layer through structuring processes
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
This design enhances light output capabilities while minimizing the risk of catastrophic optical damage, maintaining crystal quality, and improving production yield by distributing optical intensity and reducing beam divergence, facilitating efficient coupling into optical elements.
Implementation Method 1
at least one waveguide layer arranged below and above the active layer, the lower waveguide layer having a thickness in the range from 1 µm to 5 µm, preferably 1.5 µm to 3 µm and particularly preferably from 2.0 µm to 2.5 µm and the upper waveguide layer has a thickness in the range from 15 nm to 100 nm and preferably from 20 nm to 50 nm
Implementation Method 2
at least one periodic surface structure arranged next to the waveguide ridge above the active layer
Implementation Method 3
incorporating a high refractive index layer in the waveguide ridge to adjust coupling efficiency
Data Source
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AI summary
The invention relates to a DFB (distributed feedback) laser diode having a lateral coupling, comprising at least one semiconductor substrate (10), at least one active layer (40) arranged on the semiconductor substrate, at least one wave guide membrane (70) arranged above the active layer (40), at least one periodic surface structure (110) arranged next to the wave guide bride (70) above the active layer (40), and at least one wave guide layer (30, 50) having a thickness of > 1 µm arranged below and/or above the active layer.