Vertically Emitting Semiconductor Laser Gain Modulation for Spectral Tuning
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Solution Overview
Problem
Vertically emitting semiconductor lasers exhibit a wide spectral bandwidth and require complex, costly spectral filters like etalons or birefringent filters, which impose optical losses and are difficult to adjust mechanically for rapid wavelength tuning.
Innovation Solution
A semiconductor laser design with an asymmetric periodic gain structure inside the resonant cavity, allowing adjustable optical path lengths between the gain structure and reflectors, enabling precise phase matching and spectral filtering without mechanical filters, using actuators or refractive index variations for rapid spectral tuning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectral filters like etalons or birefringent filters are used to restrict spectral bandwidth, then spectral control is improved, but optical losses increase and device complexity increases
Solution Approach 1:
The patent extracts and eliminates the need for separate spectral filter components (etalons, birefringent filters) by integrating spectral control functionality directly into the periodic gain structure itself. The periodic modulation of the gain medium provides inherent spectral selectivity without requiring additional optical filter elements in the cavity.
Solution Approach 2:
The patent merges the spectral filtering function with the gain structure by periodically modulating the gain medium's properties. This combines what were previously separate functions (gain provision and spectral filtering) into a single integrated component, reducing overall device complexity and optical losses.
2Measurement precision
If mechanical filters are used for wavelength tuning, then spectral control is improved, but device complexity increases and adjustment speed decreases
Solution Approach 1:
The patent replaces mechanical filter adjustment mechanisms with direct electrical or optical control of the periodic gain structure's properties. By modulating the gain medium's periodic structure through non-mechanical means (such as electrical fields, temperature control, or optical pumping), the system achieves wavelength tuning without moving parts, thereby reducing complexity and enabling faster response times.
Solution Approach 2:
The patent introduces dynamic control of the periodic gain structure parameters, allowing real-time adjustment of spectral characteristics. The periodic modulation depth, frequency, or phase can be dynamically changed to tune the laser wavelength, providing fast and flexible spectral control without mechanical intervention.
3Manufacturing precision
If periodic gain structure is monolithically integrated with reflectors, then manufacturing precision is improved, but spectral bandwidth becomes too wide for many applications
Solution Approach 1:
The patent applies local quality modification by periodically modulating specific regions of the gain structure while maintaining overall monolithic integration. The periodic variation in gain properties at specific locations within the active medium provides spectral selectivity without compromising the benefits of monolithic construction. This localized periodic modulation creates wavelength-specific gain regions that narrow the spectral bandwidth while preserving manufacturing simplicity.
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
Achieves precise spectral control and tunability with reduced optical losses, allowing fast and efficient adjustment of laser emission characteristics.
Implementation Method 1
the quantum wells and hence the periodic gain structure provides optical gain
Implementation Method 2
a first reflector and a second reflector. The second reflector is separated from the first reflector along a longitudinal direction
Implementation Method 3
the standing wave pattern of the resonator or resonant cavity
Implementation Method 4
Matching of the periodic gain structure with the standing wave pattern of the intracavity laser radiation may be assured by monolithic construction
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
The present disclosure relates to a semiconductor laser comprising: - a first reflector (12), - a second reflector (14) separated from the first reflector (12) along a longitudinal direction (z), - a resonant cavity (8) confined by the first reflector (12) and by the second reflector (14), - a periodic gain structure (16) inside the resonant cavity (8), the periodic gain structure (16) is separated from the first reflector (12) by a first optical path length (L1) and is separated from the second reflector (14) by a second optical path length (L2), wherein the first optical path length (L1) is shorter than the second optical path length (L2), characterized in that - the first optical path length (L1) between the periodic gain structure (16) and the first reflector (12) is adjustable.