A pulse driver based on inductive storage and discharge is developed for driving short 1-5ns current pulses through laser diodes. This driver overcomes the laser diode impedance matching challenge by coil discharge through the laser diode which produces a high compliance 100V open circuit pulse current source. The pulse driver is demonstrated in a laser ranging experiment which employs linear PD amplifier and time gated receiver. The aim of this laser ranging system is immunity to optical interference and capability of ranging through reflecting objects that are not of interest, like water surface or vegetation.
We show a fast settling digital laser controller with pulse width modulation (PWM) current drive output. By using self learning feed forward and delayed proportional integral and differential (PID) feedback control, the drive current settles faster than the digital control loop execution time. The feed forward model is updated based on parameters learned from stable feedback operation. Pulse modulation settling time and stable high efficient CW operation is made possible with this approach. The laser diode controller is well suited for pulse modulation or electrical gating of high power laser diodes due to its high efficiency and over dampened settling.
In this work we propose a laser diode pulse modulation algorithm suitable for implementation in microcontrollers. This algorithm overcomes the speed limitations in microcontroller based laser pulse drivers. A feed forward signal is added to a proportional integral and differential (PID) feedback signal after a settling time. The initial feed forward control gives a fast rise time (<5 μs) and the PID feedback ensure immunity to drift for large pulse widths. This algorithm enables a settling time 10 times faster than the PID settling time. The controller is self-learning and updates the feed forward estimator based on the settled feedback control output. The use of pulse width modulation (PWM) for digital to analog conversion scales well to high power laser diodes due to its high efficiency.
We are presenting an inversion estimator based controller for master oscillator power amplifier (MOPA) laser systems. The controller is here applied to a Ytterbium doped MOPA fiber laser. The control algorithm regulates the pump power to limit the amplifier gain, so operation is restricted to the boundaries set by damage threshold or nonlinearities. In particular, it allows low pulse repetition frequency operation down to single shot and arbitrary gating.
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