Laser Diode Driver Waveform Pre-Compensation for Nonlinear Output

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Solution Overview

Problem

Fiber laser systems face non-linear performance characteristics that result in optical output power waveforms not accurately following commanded shapes, leading to effectiveness degradation and potential damage from overshoot and overheating in high-power applications.

Innovation Solution

A predictive modification of the laser diode driver current waveform is achieved by using a performance model to pre-compensate electrical commands, allowing for precise control of laser output power through a sequence of current steps, optimizing parameters like rise time, fall time, and minimizing overshoot.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a single command is used to control the laser diode driver, then the control system is simple, but the optical output power waveform does not accurately follow the commanded shape

Engineering Contradiction:

Improveoutput waveform accuracyVSAvoidcontrol system complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The single command is segmented into multiple sub-commands that are executed in sequence. The processing device divides the original command into a series of smaller control steps, each adjusting the laser diode current by a specific amount. This segmentation allows the system to achieve more precise control over the output waveform shape while managing complexity through systematic breakdown of the control process.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system performs preliminary analysis of the single command to determine the optimal sequence of sub-commands before execution. The processing device pre-calculates the required current adjustments and timing based on the desired output waveform, allowing the laser diode driver to follow the commanded shape more accurately without requiring real-time complex computations.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If the laser diode driver responds quickly to commands, then productivity is improved, but overshoot and undershoot occur causing damage and overheating

Engineering Contradiction:

Improveresponse speedVSAvoidsystem safety

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The processing device applies preliminary anti-action by calculating compensatory adjustments to the command sequence. Before the laser diode driver responds to each command segment, the system pre-determines the appropriate current adjustment magnitude to prevent overshoot and undershoot. This anticipatory control ensures fast response while maintaining system safety by avoiding excessive current fluctuations that could cause damage or overheating.

Inventive Principle:

Principle #9Preliminary anti-action

3Measurement precision

If the laser system follows the commanded waveform exactly, then measurement precision is improved, but non-linear performance characteristics cause effectiveness degradation

Engineering Contradiction:

Improvecommand following accuracyVSAvoidsystem effectiveness

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system inverts the conventional approach by not directly commanding the desired output waveform, but rather calculating the inverse control sequence needed to achieve it. The processing device analyzes the non-linear performance characteristics and determines the sequence of current adjustments that, when applied through the non-linear system, will produce the exact commanded output waveform. This inversion strategy accounts for non-linearities while maintaining command following accuracy and system effectiveness.

Inventive Principle:

Principle #13The other way round (Inversion)

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 enables laser output power waveforms to closely match commanded shapes, reducing the risk of damage and improving reliability by compensating for non-linear behavior in downstream components, thus enhancing the dynamic performance of fiber laser systems.

Implementation Method 1

a laser diode driver 25 controlling the current into a laser diode 26, which outputs photons of a particular wavelength in response to the electrical current applied to the laser diode 26

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Implementation Method 2

a wavelength conversion optics 27 that output a different wavelength of photons in response to input photons of a certain wavelength

Methodology Applied

Scientific EffectWavelength conversion:

Data Source

PatentUS10074960B2Predictive modification of laser diode drive current waveform in order to optimize optical output waveform in high power laser systems

Publication Date: 2018.09.11 NLIGHT INC

AI summary

In an example, a laser system receives an externally generated single command. The single command may be selected from a set of commands usable to control a laser diode driver of the laser system. The laser system may determine whether to select a group of one or more commands from the set of commands. In response to a determination to select the group of the one or more commands from the set of commands, the laser diode driver may be controlled using the one or more commands of the group.