Triangular Pulse Fiber Laser Suppresses SPM Linewidth Broadening

Solution Overview

Problem

High-peak-power nanosecond pulsed fiber lasers face linewidth broadening due to self-phase modulation (SPM), which existing phase compensation methods cannot adequately address, especially at high power levels, limiting the performance of narrow-linewidth laser systems used in applications like LADAR and remote sensing.

Innovation Solution

A high-peak-power single-frequency narrow-linewidth nanosecond fiber laser based on triangular pulses is developed, utilizing a master oscillator power amplifier (MOPA) structure with electro-optic and acousto-optic modulators to generate triangle-shaped pulses, which inherently suppress SPM and maintain narrow linewidths, avoiding the need for complex phase compensation systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If phase compensation methods are used to suppress SPM-induced linewidth broadening, then linewidth can be maintained, but device complexity increases and insertion losses increase

Engineering Contradiction:

ImprovelinewidthVSAvoidsystem structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent converts the harmful SPM effect into a beneficial triangular pulse shape. By intentionally shaping the pulse to have linear rising and falling edges, the SPM-induced phase modulation becomes a controlled quadratic phase distribution that results in a narrower spectral width, transforming the broadening mechanism into a linewidth-narrowing mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the temporal intensity distribution parameter of the laser pulse from a conventional shape to a triangular shape with specific rise and fall times. This parameter change in pulse waveform directly controls the SPM effect to achieve linewidth narrowing without requiring additional phase compensation components.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If phase compensation methods are used to suppress SPM-induced linewidth broadening, then linewidth can be maintained, but insertion losses increase

Engineering Contradiction:

ImprovelinewidthVSAvoidinsertion losses

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The patent converts the harmful SPM effect into a beneficial triangular pulse shape. By intentionally shaping the pulse to have linear rising and falling edges, the SPM-induced phase modulation becomes a controlled quadratic phase distribution that results in a narrower spectral width, transforming the broadening mechanism into a linewidth-narrowing mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Power

If high peak power is increased, then power output is improved, but SPM-induced linewidth broadening increases

Engineering Contradiction:

Improvepeak powerVSAvoidlinewidth

Core Design Contradiction:

PowerVSMeasurement precision

Solution Approach 1:

The patent changes the temporal intensity distribution parameter of the laser pulse from a conventional shape to a triangular shape with specific rise and fall times. This parameter change in pulse waveform directly controls the SPM effect to achieve linewidth narrowing without requiring additional phase compensation components.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs dynamic pulse shaping through electro-optic modulators to create a triangular waveform with controlled rise and fall edges. This dynamic control of the intensity temporal profile allows the SPM effect to be harnessed for linewidth narrowing while maintaining high peak power capability.

Inventive Principle:

Principle #15Dynamics

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 effectively suppresses SPM-induced linewidth broadening, achieving peak powers over 20 kW with stable pulse shapes and narrow linewidths, simplifying the system structure and reducing insertion losses, while facilitating industrial integration and wavelength versatility.

Implementation Method 1

electro-optic intensity and acousto-optic modulator (EOIM and AOM) to modulate continuous wave (CW) single-frequency laser

Methodology Applied

Scientific EffectElectro-optic effect: Electro-Optic Effects

Implementation Method 2

electro-optic intensity and acousto-optic modulator (EOIM and AOM) to modulate continuous wave (CW) single-frequency laser

Methodology Applied

Scientific EffectAcousto-optic effect: Acousto-optic Effect

Implementation Method 3

a first pumping source, a first combiner, a first double-clad active fiber

Methodology Applied

Scientific EffectStimulated emission: Laser

Data Source

PatentUS11670904B2High-peak-power single-frequency narrow-linewidth nanosecond fiber laser based on a triangular pulse

Publication Date: 2023.06.06 TIANJIN UNIV

AI summary

The present invention discloses a high-peak-power single-frequency narrow-linewidth nanosecond fiber laser based on a triangular pulse, wherein the laser includes: pulsed laser generated by the laser seed injecting into a first power pre-amplifier through a first isolator, and then injecting into a second pre-amplifier and then injecting into a power amplifier; wherein triangle-shaped pulsed laser with fast rising edge is obtained by using electro-optic and acousto-optic modulator to modulate continuous wave single-frequency laser or a single-frequency semiconductor laser directly modulated by radio frequency signal; single-frequency triangle-shaped pulsed laser is employed as the laser source according to the characteristics of narrow intrinsic linewidth and suppression of linewidth broadening caused by SPM, and the power of pulsed laser is amplified through the MOPA system.