Monolithic Semiconductor Laser Current Constriction Layers
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Solution Overview
Problem
Conventional monolithic semiconductor lasers face challenges in achieving high temperature and high output operation due to light absorption by current constriction layers and refractive index differences, leading to manufacturing complexity and yield issues when trying to combine AlGaAs and InGaAlP based semiconductor laser elements.
Innovation Solution
The use of AlzGa1-zAs (0.5≦z≦0.8) and In0.5(Ga1-xAlx)0.5P (0.6≦x≦1) materials for current constriction layers, which have larger band gap energy than the active layers, and refractive indices differing by 0.1 or less, allows for the same material to be used for both infrared and red elements, enabling high temperature and high output operation without increasing crystal growing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If different materials are used for current constriction layers of AlGaAs and InGaAlP based semiconductor laser elements, then high output operation is achieved, but manufacturing complexity increases and yield decreases
Solution Approach 1:
The patent applies homogeneity by using the same material (n-type GaAs) for current constriction layers of both AlGaAs-based and InGaAlP-based semiconductor laser elements. This uniform material selection simplifies the manufacturing process, allowing both types of elements to be produced using identical fabrication steps, thereby reducing manufacturing complexity and improving yield while maintaining high output capability.
2Ease of manufacture
If GaAs is used for current constriction layers with smaller band gap energy than active layers, then manufacturing is simplified, but light absorption occurs and high output operation becomes impossible
Solution Approach 1:
The patent applies parameter changes by carefully selecting the band gap energy parameter of the current constriction layer material. By using n-type GaAs with a band gap energy larger than that of the InGaAlP-based active layer (which emits red light), the patent ensures that the current constriction layer does not absorb the emitted light, thereby enabling high output operation while maintaining manufacturing simplicity through the use of a single material system.
3Power
If real refractive index structure is employed with materials having large band gap energy, then high output operation is enabled, but different materials are required for different elements increasing manufacturing steps
Solution Approach 1:
The patent applies universality by making the current constriction layer material (n-type GaAs) serve multiple functions for both AlGaAs-based and InGaAlP-based semiconductor laser elements. This single material provides both the necessary electrical current constriction function and the optical transparency function for high output operation across different laser element types, eliminating the need for separate material systems and thereby improving manufacturing yield.
4Shape
If current constriction layers absorb light from active layers, then waveguide structure is formed, but waveguide loss increases and threshold current becomes large
Solution Approach 1:
The patent applies parameter changes by adjusting the band gap energy parameter of the current constriction layer material to be larger than that of the active layer. This parameter selection ensures that the current constriction layer remains transparent to the emitted light wavelength, preventing light absorption while still maintaining the necessary waveguide structure for optical confinement, thereby reducing waveguide loss and threshold current.
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 approach allows for stable high output characteristics and inhibits kink occurrence, maintaining manufacturing yield by using the same material for current constriction layers, ensuring single mode oscillation and high temperature operation.
Implementation Method 1
materials forming the current constriction layers for the first and second wavelength semiconductor laser elements are the same material and the material has larger band gap energy than that of the active layer of the second wavelength semiconductor laser element
Implementation Method 2
refractive indices differing by 0.1 or less
Data Source
AI summary
There is disclosed a monolithic semiconductor laser which is provided with an AlGaAs based semiconductor laser element (10a) and an InGaAlP based semiconductor laser element (10b) formed on a semiconductor substrate (1). The AlGaAs based semiconductor laser element (10a) is composed of an infrared light emitting layer forming portion (9a), which has an n-type cladding layer (2a), an active layer (3a) and a p-type cladding layer (4a) formed so as to have a ridge portion, and a current constriction layer (5a) provided on sides of the ridge portion, while the InGaP based semiconductor laser element (10b) is composed of a red light emitting layer forming portion (9a), which has an n-type cladding layer (2b), an active layer (3b) and a p-type cladding layer (4b) formed so as to have a ridge portion, and a current constriction layer (5b) provided on sides of the ridge portion. The current constriction layers of the both elements are made of the same material having a larger band gap than that of the active layer (3b) of the red light emitting layer forming portion. Consequently, there can be obtained a monolithic semiconductor laser capable of high temperature and high output operation without increasing the number of processes of the growth.