Surface-Emitting Laser Driving Apparatus Mode Control
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Solution Overview
Problem
Conventional surface-emitting laser elements experience deterioration in signal light quality when driven by modulation currents, leading to poor modulation characteristics due to changes in the number of lateral modes of laser oscillation.
Innovation Solution
A surface-emitting laser apparatus is designed with a driving apparatus that supplies a modulation-driving current intensity-modulated across a bias current, ensuring the first changing current for mode transition from one to two is not between the bias and maximum modulation current values, thereby maintaining signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a modulation-driving current is supplied to the surface-emitting laser element, then the laser can operate and emit signal light, but the number of lateral modes changes causing deterioration in signal light quality
Solution Approach 1:
The patent applies parameter changes by carefully selecting and controlling the bias current value to be greater than the first changing current. This parameter selection ensures that during intensity modulation, the operating current remains in a range where the laser oscillates in a single lateral mode, thereby maintaining signal light quality while enabling proper modulation operation.
Solution Approach 2:
The patent implements preliminary action by pre-determining the relationship between the bias current and the first changing current before actual signal transmission begins. By setting the bias current greater than the first changing current in advance, the system ensures that mode transitions are prevented during operation, eliminating signal quality deterioration before it can occur.
2Reliability
If the bias current is increased to prevent mode transitions, then signal light quality is maintained, but the modulation range is reduced
Solution Approach 1:
The patent resolves this contradiction by optimizing the bias current parameter to be just above the first changing current threshold. This precise parameter selection maintains signal light quality by preventing mode transitions while maximizing the available modulation range, allowing the laser to operate effectively across the full modulation signal amplitude without entering multi-mode regions.
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 effectively restrains signal light quality deterioration and achieves excellent modulation characteristics by controlling the number of lateral modes, particularly when the bias current is set greater than the switching current for mode transitions.
Implementation Method 1
a surface-emitting laser element oscillates laser in a plurality of lateral modes at a wavelength of 850 nm
Implementation Method 2
The modulation-driving current is intensity-modulated to vary across a value of a bias current
Data Source
AI summary
A surface-emitting laser apparatus includes: a surface-emitting laser element; and a driving apparatus supplying a modulation-driving current to the surface-emitting laser element. The modulation-driving current is intensity-modulated to vary across a value of a bias current. The number of lateral modes of laser oscillation of the surface-emitting laser element changes from one to three at maximum in accordance with a value of the modulation-driving current. Among changing currents at which number of the lateral modes of the laser oscillation of the surface-emitting laser element changes, if a first changing current is defined at which the number of the lateral mode of the laser oscillation changes from one to two, the driving apparatus supplies the modulation-driving current to the surface-emitting laser element. The modulation-driving current is set so that a value of the first changing current is not between the bias current and a maximum value of the modulation-driving current.