Semiconductor Laser Structure for Pulse Tail Reduction in ToF Ranging
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Solution Overview
Problem
Conventional semiconductor lasers used in time-of-flight measurement methods suffer from significant pulse tails, which complicate distance measurement accuracy and require precise control of pulse currents, leading to system complexity.
Innovation Solution
A semiconductor laser with alternately formed gain and absorption regions on a substrate, emitting orthogonal polarized laser pulses, and a light separation unit to minimize pulse tail influence, allowing for improved distance measurement precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional semiconductor lasers are used for time-of-flight measurement, then distance measurement can be performed, but pulse tail interference occurs which reduces measurement accuracy
Solution Approach 1:
The active layer is segmented into multiple gain regions and absorption regions that are alternately arranged along the light propagation direction. This segmentation allows different regions to perform different functions: gain regions amplify light while absorption regions suppress pulse tails, thereby resolving the contradiction between achieving distance measurement and eliminating pulse tail interference
Solution Approach 2:
Different regions of the active layer are given different local properties: gain regions have high gain characteristics for light amplification, while absorption regions have high absorption characteristics for suppressing pulse tails. This local differentiation enables each region to optimize its function, reducing overall pulse tail interference while maintaining measurement capability
2Measurement precision
If pulse current control is used to minimize pulse tail, then measurement accuracy improves, but system complexity increases
Solution Approach 1:
The absorption regions are designed to automatically suppress pulse tails through their inherent absorption characteristics when carriers are depleted, eliminating the need for complex real-time pulse current control systems. The structure itself provides the pulse tail suppression function, reducing system complexity while maintaining measurement accuracy
3Object-generated harmful factors
If orthogonal polarized pulses are emitted, then pulse tail influence is minimized, but device structure becomes more complex
Solution Approach 1:
The alternating gain and absorption regions create an asymmetric structure along the light propagation direction, which generates orthogonal polarized pulses. This asymmetric design naturally produces the desired orthogonal polarization states that minimize pulse tail influence, achieving the goal while the structural complexity is managed through the regular alternating pattern
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
The solution effectively reduces pulse tail interference, enhancing distance measurement accuracy and simplifying system control by emitting orthogonal laser pulses, thereby improving the precision and reliability of distance measurements.
Implementation Method 1
a first laser pulse having a first polarized light is emitted and a second laser pulse having a second polarized light is subsequently emitted
Implementation Method 2
the first polarized light and the second polarized light are orthogonal to each other
Implementation Method 3
a light separation unit, in which the first laser pulse and the second laser pulse are separated by the light separation unit
Data Source
AI summary
For example, an influence of a tail in a laser pulse is reduced. A semiconductor laser includes at least two or more gain regions and at least two or more absorption regions formed on a semiconductor substrate, in which the gain regions and the absorption regions include a continuous active layer, and the gain regions and the absorption regions are alternately formed via a separation region, and from a front end surface, a first laser pulse having a first polarized light is emitted and a second laser pulse having a second polarized light is subsequently emitted, and the first polarized light and the second polarized light are orthogonal to each other.