Pulsed Laser Electro-Optic Modulator Driving Circuit
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Solution Overview
Problem
Pulsed laser devices of the MOPA type face challenges in achieving high output power at low duty ratios, leading to reduced ON/OFF extinction ratios due to the inefficiency of driving circuits when the duty ratio is extremely low, necessitating a solution to enhance the driving circuit's ability to maintain optimal voltage amplitude.
Innovation Solution
The implementation of a pulsed laser device with a control unit that adjusts the pulse modulation of the laser light source and electro-optic modulator to ensure the electro-optic modulator transitions to an ON state during the laser light source's ON state and at least once during its OFF state, thereby increasing the duty ratio of the pulse modulation for the electro-optic modulator relative to the laser light source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the duty ratio is reduced to achieve short pulse width and low repetition frequency, then the pulse width can be reduced to 1 ns or smaller, but the driving circuit cannot output sufficient voltage amplitude, causing reduced ON/OFF extinction ratios
Solution Approach 1:
The patent segments the driving waveform into multiple pulses within one period, where at least one pulse is positioned during the ON state of the modulator and another pulse during the OFF state. This segmentation allows the driving circuit to deliver sufficient voltage amplitude during each pulse while maintaining an overall low duty ratio, thereby resolving the contradiction between short pulse width and adequate voltage output for maintaining extinction ratio.
Solution Approach 2:
The patent employs periodic multi-pulse driving waveforms where multiple voltage pulses are applied periodically to the modulator within each driving period. This periodic action with multiple pulses per period enables the driving circuit to maintain high voltage amplitude during critical ON and OFF states while keeping the average duty ratio low, thus achieving both short effective pulse width and high ON/OFF extinction ratio.
2Reliability
If the duty ratio is increased to improve voltage amplitude output from the driving circuit, then the ON/OFF extinction ratio improves, but the size of the driving circuit increases
Solution Approach 1:
The patent segments the driving period into multiple discrete voltage pulses rather than using a continuous high-duty-ratio waveform. This segmentation allows the driving circuit to be optimized for pulsed operation at lower duty ratios, reducing the required circuit size while still delivering sufficient peak voltage amplitude during each pulse to maintain high ON/OFF extinction ratios.
Solution Approach 2:
The patent changes the temporal distribution parameters of the driving waveform, specifically using multiple pulses with optimized widths and spacing within each period. This parameter optimization allows the driving circuit to operate efficiently at lower duty ratios without sacrificing voltage amplitude during critical states, thereby reducing circuit size while maintaining extinction ratio performance.
3Productivity
If the duty ratio is reduced to achieve low repetition frequency operation, then the laser processing conditions are optimized, but the driving circuit output voltage amplitude is reduced
Solution Approach 1:
The patent uses periodic multi-pulse driving waveforms where multiple voltage pulses are delivered within each driving period at the low repetition frequency. This periodic multi-pulse approach ensures that during each period, sufficient voltage amplitude is delivered during the ON and OFF states of the modulator, maintaining effective power delivery even at low repetition frequencies with low overall duty ratio.
Solution Approach 2:
The patent segments the low-duty-ratio driving period into multiple concentrated voltage pulses, ensuring that each pulse delivers sufficient voltage amplitude for proper modulator operation. This segmentation allows the system to operate at low repetition frequencies with low average power consumption while maintaining high peak voltage amplitude during each pulse for effective laser processing.
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 approach allows for improved ON/OFF extinction ratios and increased output power even at low duty ratios, optimizing the performance of the pulsed laser device by ensuring the electro-optic modulator receives the necessary voltage amplitude for efficient operation.
Implementation Method 1
an electro-optic modulator that outputs pulsed laser light obtained by pulse-modulating the pulsed laser light
Data Source
AI summary
A pulsed laser device includes a laser light source, an electro-optic modulator, a laser light source driver, an electro-optic modulator driver, and a controller to control the laser light source driver and the electro-optic modulator driver. The laser light source outputs pulsed laser light pulse-modulated by the laser light source driver. The electro-optic modulator outputs pulsed laser light obtained by causing the electro-optic modulator driver to pulse-modulate the pulsed laser light from the laser light source. The control unit controls the laser light source driver and the electro-optic modulator driver such that the electro-optic modulator turns on at least while the laser light source is on and the electro-optic modulator turns on at least once while the laser light source is off, thereby increasing a duty ratio of the pulse modulation for the electro-optic modulator relative to a duty ratio of the pulse modulation for the laser light source.