Semiconductor Laser Asymmetric Waveguide Trailing Pulse Suppression
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Solution Overview
Problem
Existing semiconductor lasers face challenges in generating high-power single optical pulses without producing undesirable trailing pulses, which occurs when increasing the amplitude of electric current pulses or the dimensions of the active layer, making it difficult to achieve high output pulse energy with low-cost, compact power sources.
Innovation Solution
A semiconductor laser with a large active layer volume and a radially asymmetric structure, where the active layer is positioned near the p-doped cladding layer and far from the n-doped cladding layer, reducing the optical confinement factor and preventing the generation of trailing pulses, even with high-amplitude current pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the amplitude of the electric current pulse is increased to increase optical power, then the power of the optical pulse increases, but a second trailing optical pulse appears which is highly undesirable
Solution Approach 1:
The patent applies asymmetry by positioning the active layer radially asymmetrically within the waveguide structure, specifically placing it closer to the p-doped cladding layer than to the n-doped cladding layer. This asymmetric positioning creates an uneven optical confinement distribution that suppresses the generation of trailing pulses while allowing high-amplitude current pulses to generate high-power main optical pulses without producing unwanted secondary pulses
2Power
If the volume or dimensions of the active layer are increased to increase optical power, then the power of the optical pulse increases, but at least one trailing optical pulse appears
Solution Approach 1:
The patent employs radial asymmetry in the waveguide structure where the active layer is positioned at an asymmetric distance from the p-doped and n-doped cladding layers. This asymmetric configuration allows the optical mode to be confined differently in radial directions, suppressing trailing pulse formation even when the active layer volume is increased to achieve higher optical power output
3Object-generated harmful factors
If a very sharp trailing end electric current pulse is formed to reduce trailing pulse probability, then the probability of trailing pulse is reduced, but it is beyond reach of or nontrivial to achieve with high-power electronics
Solution Approach 1:
The patent converts the potentially harmful effect of simple electric current pulse shapes (which normally cause trailing pulses) into a beneficial outcome by using the asymmetric waveguide structure. The asymmetric optical confinement compensates for the lack of sharp trailing edges in the current pulse, allowing standard electronics to generate clean single pulses without requiring complex pulse shaping circuits
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
Enables high-power single optical pulses without trailing pulses by maintaining a small optical confinement factor, allowing for higher injection current amplitudes and increased pulse energy while preventing secondary pulse emission.
Implementation Method 1
An active layer, where free electrons and holes exist and recombine by stimulated emission during the operation
Implementation Method 2
a complex narrow gap waveguide layered structure 116, which is an optical cavity for stimulated emission
Data Source
Figure 1A~1B
Figure 2
Figure 3~4
AI summary
A single pulse semiconductor laser operating in the gain- switching regime comprises a plane asymmetric waveguide and an active layer in the waveguide, the ratio of a thickness of the active layer to an optical confinement factor of the laser being extremely large, larger than about 5μm, for example.