Surface-Emitting Laser Pulse Control to Suppress Tail Light
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Solution Overview
Problem
Existing surface emitting lasers face challenges in generating short-pulse light with reduced tailing, which is necessary for precise distance measurement while ensuring eye safety, as they often produce multiple pulses and unwanted tail light due to relaxation oscillation phenomena.
Innovation Solution
A surface emitting laser design featuring an active layer with multiple reflectors and an electrode pair for current injection, where the current injection period is followed by a current decrease period, allowing for a single optical pulse with a width of 110 ps or less by controlling the optical confinement and refractive index distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If gain switching is used to reduce pulse width to 100 ps or less, then pulse width is improved, but multiple pulse trains and tail light are generated causing noise and energy waste
Solution Approach 1:
The patent applies periodic action by using Q-switching to generate precisely controlled single optical pulses with width of 110 ps or less. The Q-switching mechanism periodically modulates the cavity quality factor to produce isolated pulses rather than continuous or multi-pulse trains, thereby achieving short pulse width while eliminating harmful multiple pulses and tail light effects
Solution Approach 2:
The patent changes the operating parameters by controlling the pulse current characteristics during Q-switching. By optimizing the current injection timing and magnitude, the system achieves pulse width of 110 ps or less while suppressing relaxation oscillations that cause tail light, thus transforming the harmful parameter range into a beneficial operating regime
2Duration of action of moving object
If multiple pulses are output due to relaxation oscillation, then pulse width may be reduced, but detection precision deteriorates due to noise from non-target pulses
Solution Approach 1:
The Q-switching mechanism implements periodic action to generate single, isolated optical pulses with precise timing control. This periodic modulation of cavity Q-factor ensures that only one pulse is emitted per switching cycle at the desired moment, eliminating multiple pulse trains that would otherwise create detection noise and compromise measurement precision in TOF sensors
Solution Approach 2:
The patent employs feedback control through the Q-switching mechanism to monitor and control the pulse generation process. The system detects the build-up of photon density and carrier population, and triggers pulse emission at the optimal moment when conditions are favorable, thereby ensuring single-pulse output with precise width control and eliminating harmful multiple pulses that would interfere with detection precision
3Use of energy by moving object
If tail light is generated after relaxation oscillation, then energy is wasted, but eye-safe compliance is compromised due to increased average power
Solution Approach 1:
The patent converts the potentially harmful relaxation oscillation phenomenon into a beneficial effect by using Q-switching to control when and how the oscillation occurs. The system allows energy to accumulate during the charging phase, then releases it in a single controlled pulse, transforming what would be wasted tail light energy into useful peak power for precise distance measurement while maintaining eye-safe average power levels
Solution Approach 2:
By implementing periodic Q-switching action, the system concentrates energy delivery into discrete, controlled pulses with width of 110 ps or less. This periodic modulation ensures that energy is delivered efficiently in short bursts rather than as continuous or extended tail light, improving energy efficiency while maintaining compliance with eye-safe standards through controlled average power
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 design achieves short-pulse light with minimal tailing, enhancing precision and distance measurement capabilities while adhering to eye-safe standards by reducing unwanted energy and noise.
Implementation Method 1
an active layer; multiple reflectors facing each other with the active layer therebetween
Implementation Method 2
The gain switching is a measure for providing a pulse width of 100 ps or less by using a relaxation oscillation phenomenon
Data Source
AI summary
A surface emitting includes: an active layer; multiple reflectors facing each other with the active layer therebetween; and an electrode pair coupled to a power supply device and configured to inject current into the active layer. The surface emitting laser has: a current injection period in which the current is injected by the power supply device to oscillate no laser beam; and a current decrease period after the current injection period, in which a current value of the current injected into the active layer is lower than a current value of the current injected during the current injection period, to oscillate a laser beam.