Integrated Semiconductor Laser Element Narrowing Spectral Linewidth
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Solution Overview
Problem
Integrated semiconductor laser elements face challenges in achieving desired spectral linewidth and optical intensity due to limitations in current-to-light conversion efficiency and spectral linewidth broadening caused by increased cavity lengths and amplification factors, which affect their performance in high-speed optical communication systems.
Innovation Solution
The integrated semiconductor laser element incorporates a plurality of distributed feedback lasers with an optical coupler and a semiconductor optical amplifier, where the amplifier length and cavity length are optimized to satisfy the relation LsoaLdfb ≤ (R-1)·N·1.44·A-0.74, ensuring the spectral linewidth of the amplified laser light is within desired limits, thereby maintaining narrow linewidth and high optical power intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the cavity length Ldfb of DFB lasers is increased to narrow the spectral linewidth, then the spectral linewidth is narrowed, but the current-to-light conversion efficiency decreases
Solution Approach 1:
The patent applies parameter changes by establishing a specific mathematical relationship between the cavity length Ldfb and amplifier length Lsoa (Lsoa/Ldfb ≤ (R-1)·N·1.44·A-0.74) to optimize both spectral linewidth and current-to-light conversion efficiency simultaneously, rather than simply increasing Ldfb to narrow linewidth
2Power
If the amplification factor A of the semiconductor optical amplifier is increased to compensate for lowered conversion efficiency, then the optical power intensity is maintained, but the spectral linewidth broadens
Solution Approach 1:
The patent resolves this contradiction by establishing an optimized relationship between amplification factor A and other parameters (Lsoa/Ldfb ≤ (R-1)·N·1.44·A-0.74), determining the appropriate amplification factor that maintains optical power intensity while minimizing spectral linewidth broadening
3Power
If the driving current of DFB lasers is increased to compensate for lowered conversion efficiency, then the optical power intensity is maintained, but spatial hole-burning occurs and spectral linewidth widens
Solution Approach 1:
The patent avoids increasing driving current by optimizing the relationship between cavity length and amplifier length, thereby maintaining optical power intensity through efficient amplification rather than increased pump current, preventing spatial hole-burning and spectral linewidth widening
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 configuration allows for the realization of a wavelength variable laser capable of outputting high-intensity laser light with a narrow spectral linewidth, suitable for applications in digital coherent transmission systems, while maintaining efficient current-to-light conversion and suppressing spectral linewidth widening.
Implementation Method 1
a plurality of semiconductor lasers of distributed feedback type that oscillate in single mode at emission wavelengths different from each other
Implementation Method 2
an optical coupler that has as many input ports as the plurality of semiconductor lasers, the input ports to which output light from the plurality of semiconductor lasers are input
Implementation Method 3
a semiconductor optical amplifier that amplifies the output light from the optical coupler
Data Source
AI summary
Integrated are: semiconductor lasers of distributed feedback type that oscillate in single mode at emission wavelengths different from one another; a coupler that has as many input ports as the semiconductor lasers, the input ports to which output light from the semiconductor lasers are input, the coupler guiding and outputting the output light; and an amplifier that amplifies the output light from the coupler, and a predetermined relation holds true, where “N” is the number of the semiconductor lasers, “Ldfb” is a cavity length of each of the semiconductor lasers, “Δν0” is a spectral linewidth of laser light output therefrom, “Lsoa” is an amplifier length of the amplifier, “A” is an amplification factor of the amplifier, “Δν” is a spectral linewidth of amplified laser light output therefrom, and “R” is Δν/Δν0.