Nitride Laser Diode Ridge Structure for Low Threshold Current
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Solution Overview
Problem
Group-III nitride laser diodes require high threshold currents and voltages for operation, leading to heat generation and potential damage during continuous wave (CW) operation, especially in optical storage devices, which increases cost and complexity with the use of heat sinks for cooling.
Innovation Solution
A nitride-based laser diode epitaxial structure with a separate confinement heterostructure and a ridge formation that reduces threshold current and voltage, achieved through specific layer growth and etching processes, including off-angle substrate growth and low threading dislocation densities, to enhance optical and electrical confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If Group-III nitride laser diodes operate at high threshold currents and voltages, then laser radiation can be achieved, but heat is generated that can damage or destroy the laser diode during continuous wave operation
Solution Approach 1:
The patent changes the structural parameters of the laser diode by introducing a distributed Bragg reflector (DBR) cavity with specific layer structures and optical properties. This modifies the optical feedback mechanism, enabling lasing at lower threshold currents and voltages, thereby reducing heat generation during CW operation while maintaining laser radiation output
Solution Approach 2:
The patent employs composite material structures including multiple semiconductor layers with different bandgaps and optical properties forming the DBR cavity. These composite structures optimize light reflection and confinement, improving optical efficiency and reducing the electrical power required for lasing, which directly addresses the heat generation problem
2Object-affected harmful factors
If heat sinks or cooling methods are employed to reduce operating heat, then heat damage is prevented, but cost and complexity increase and additional space is required
Solution Approach 1:
The patent enables the laser diode to self-regulate its operating conditions by utilizing the DBR cavity's optical feedback mechanism. The cavity provides wavelength-selective feedback that stabilizes lasing operation and reduces threshold requirements, allowing the device to operate efficiently at lower power levels without requiring external cooling systems
Solution Approach 2:
The patent extracts the cooling function from the system by eliminating the need for heat sinks and external cooling mechanisms. Through optimized optical cavity design and material selection, the invention achieves sufficient heat management through improved electrical and optical efficiency, removing the complex cooling subsystem entirely
3Use of energy by moving object
If the ridge is etched deeper to improve optical confinement, then optical efficiency improves, but the laser diode reliability decreases due to increased stress and potential damage
Solution Approach 1:
The patent optimizes the ridge etch depth parameter to a specific range that balances optical confinement and mechanical reliability. By precisely controlling the etch depth and introducing the DBR cavity structure, the invention achieves high optical efficiency without creating excessive stress concentrations that would compromise device reliability
Solution Approach 2:
The patent applies different structural qualities to different regions: the ridge provides mechanical support and electrical contact, while the DBR cavity provides optical feedback. This localized functional differentiation allows the ridge to be optimized for both optical confinement and mechanical strength, rather than requiring deep etching that would compromise 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 solution results in high reliability and efficient operation at reduced temperatures with lower threshold current densities and voltages, enabling reliable CW operation without the need for additional cooling methods, thus reducing costs and complexity.
Implementation Method 1
separate confinement heterostructure with a ridge formation that reduces threshold current and voltage, achieved through specific layer growth and etching processes, including off-angle substrate growth and low threading dislocation densities, to enhance optical and electrical confinement
Implementation Method 2
A laser is a device that produces a beam of coherent light as a result of stimulated emission. Light beams produced by lasers can have high energy because of their single wavelength, frequency, and coherence
Implementation Method 3
Light from the active region is reflected between the edges and within the cavity by the reflective elements, with stimulated emission emitting from the edge with the AR material
Data Source
AI summary
A laser diode comprising a first separate confinement heterostructure and an active region on the first separate confinement heterostructure. A second separate confinement heterostructure is on the active region and one or more epitaxial layers is on the second separate confinement heterostructure. A ridge is formed in the epitaxial layers with a first mesa around the ridge. The first mesa is 0.1 to 0.2 microns above the second confinement heterostructure.