Laser Drive Current Waveform for Suppressing Relaxation Oscillations
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Solution Overview
Problem
Existing laser power control algorithms fail to effectively suppress relaxation oscillations, leading to potential damage in optical components due to short-duration high-peak-power pulses, and require excessive calibration efforts for varying frequencies and duty cycles, making them unsuitable for mass production of medical devices.
Innovation Solution
A laser current control method using a small-step current waveform with a first step below a safety threshold and a second step adjusted based on average laser output power and drive current relationships, suppressing relaxation oscillations and reducing waveform distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional single-step current waveform is used to control laser output power, then the control algorithm is simple, but relaxation oscillations occur causing high-peak-power pulses that can damage optical components
Solution Approach 1:
The current waveform is segmented into multiple steps (first step and second step) instead of using a single-step waveform. The first step with smaller amplitude suppresses relaxation oscillations while the second step achieves the required peak power, thereby protecting optical components without significantly increasing control algorithm complexity
Solution Approach 2:
The first step of the current waveform is applied before the second step to preliminarily suppress relaxation oscillations. By pre-conditioning the laser diode with a smaller current step that keeps relaxation oscillations below the safety threshold, the subsequent high-power second step can be applied safely without causing damage to optical components
2Adaptability or versatility
If multiple linear equations are defined to cover a frequency range from 1 to 2400 Hz, then the laser can operate across the full frequency range, but the calibration workload becomes excessive making it unsuitable for mass production
Solution Approach 1:
The multi-step current waveform control method serves multiple functions simultaneously: it suppresses relaxation oscillations, enables accurate power control, and reduces calibration requirements. By using a standardized multi-step waveform approach that works across the entire frequency range from 1 to 2400 Hz, the system achieves universal applicability without requiring frequency-specific calibration equations
Solution Approach 2:
The invention changes the waveform parameters (amplitude, duration, timing) of the multi-step current signal to adapt to different operating conditions. By dynamically adjusting the parameters of the first and second steps based on the desired output power and frequency, the system maintains accurate control across the full frequency range without requiring separate calibration equations for each frequency point
3Power
If the drive current is increased to achieve higher peak power, then the laser output power increases, but relaxation oscillations are triggered causing short-duration high-peak-power pulses that may damage optical components
Solution Approach 1:
The drive current is segmented into two distinct steps: the first step with smaller amplitude that suppresses relaxation oscillations to remain below the safety threshold, and the second step with larger amplitude that delivers the required peak power. This segmentation allows the system to achieve high peak power while preventing damage-causing relaxation oscillations
Solution Approach 2:
The first current step is applied as a preliminary action before the main power-delivering second step. This preliminary step conditions the laser diode by suppressing relaxation oscillations, ensuring that when the high-power second step is applied, no damaging pulses are generated. The timing and amplitude of the first step are optimized to provide this protective pre-conditioning
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 method effectively suppresses damage to optical components by maintaining relaxation oscillations within tolerance limits, achieving accurate and precise control of laser output power without the need for extensive calibration across different frequencies and duty cycles.
Implementation Method 1
the current signal of the second step is processed by the laser drive circuit to obtain the drive current
Data Source
AI summary
The present disclosure provides a laser current control method for suppressing laser relaxation oscillations, relating to the field of laser control technologies. The method comprising: controlling a current signal with a preset waveform to be input into a laser drive circuit; the preset waveform includes a first step and a second step, where the amplitude of the first step is less than that of the second step, and the current signal of the first step triggers a laser relaxation oscillation waveform whose amplitude is less than a safety threshold; and adjusting the amplitude of the second step based on a relationship between the average laser output power and the drive current. According to the embodiments of the present disclosure, a small-step current waveform is designed to effectively suppress damage to optical components in the optical path caused by laser relaxation oscillations. The reduced pulse distortion ensures that the threshold current corresponding to different pulse frequencies exhibits linearity under the same duty cycle, eliminating the need to record threshold currents and corresponding linear equations for each duty cycle. This allows the output current to be more precisely and accurately adjusted to achieve a desired terminal average power.