Injection Seeded Q-Switched Laser Peak Power Stability

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Solution Overview

Problem

Q-switched lasers experience reduced efficiency and peak power at high repetition rates, making them less effective for applications like precision micro-machining, where high repetition rates are desired for precise material removal.

Innovation Solution

The technique of injection seeding, where short pulses from a seed laser are introduced into the cavity of a Q-switched laser to enhance peak power and frequency conversion efficiency, reducing damage to non-linear frequency conversion materials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If Q-switched lasers operate at high repetition rates, then productivity is improved, but frequency conversion efficiency deteriorates

Engineering Contradiction:

Improverepetition rateVSAvoidfrequency conversion efficiency

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent applies preliminary action by pre-seeding the laser cavity with short pulses from a mode-locked laser before the Q-switched laser operates. This pre-seeding establishes a controlled temporal mode structure that maintains high peak power even at high repetition rates, thereby preserving frequency conversion efficiency while enabling high productivity operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the temporal parameters of the laser output by using injection seeding to control the pulse duration and peak power characteristics. By adjusting the seed laser parameters and coupling conditions, the system maintains optimal peak power for frequency conversion across a wide range of repetition rates, resolving the trade-off between productivity and conversion efficiency.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If Q-switched lasers operate at high repetition rates, then productivity is improved, but peak power deteriorates

Engineering Contradiction:

Improverepetition rateVSAvoidpeak power

Core Design Contradiction:

ProductivityVSPower

Solution Approach 1:

The mode-locked laser provides preliminary action by seeding the cavity with short, high-peak-power pulses before the Q-switched laser amplification. This pre-established temporal structure ensures that even at high repetition rates, the amplified output maintains high peak power, enabling both high productivity and sufficient peak power for material processing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary system (mode-locked laser) that mediates between the Q-switched laser and the frequency conversion process. The seed laser acts as an intermediary that imposes a controlled temporal mode structure, ensuring high peak power is maintained throughout the amplification process even at high repetition rates.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Power

If optical amplification is used to enhance peak power, then peak power is improved, but damage to non-linear materials increases

Engineering Contradiction:

Improvepeak powerVSAvoiddamage to non-linear materials

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by using a mode-locked laser to pre-establish the temporal pulse structure before Q-switched amplification. This results in shorter pulse durations with higher peak power, which reduces the total energy exposure to the non-linear frequency conversion materials, thereby minimizing damage while maintaining high peak power for efficient conversion.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The mode-locked laser produces periodic short pulses that serve as seeds for the Q-switched laser. This periodic action with controlled duty cycle allows high peak power to be achieved during the pulse while keeping the average power and total energy exposure to the non-linear materials at acceptable levels, reducing damage risk.

Inventive Principle:

Principle #19Periodic action

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

Injection seeding maintains high peak power and frequency conversion efficiency across a wider range of repetition rates, improving pulse-to-pulse stability and reducing damage to non-linear frequency conversion media.

Implementation Method 1

Frequency converting crystals, e.g. Lithium Triborate (LBO) convert the 1064-nm fundamental radiation from the Nd:YAG to the higher harmonics

Methodology Applied

Scientific EffectNon-linear frequency conversion: Second Harmonic Generation

Implementation Method 2

A Q-switched laser is 'injection seeded' with short pulses from another laser, called a seed laser

Methodology Applied

Scientific EffectStimulated emission: Laser

Data Source

PatentUS7391794B2Injection seeding of frequency-converted Q-switched laser

Publication Date: 2008.06.24 WELLS FARGO BANK NA

AI summary

A non-linearly frequency-converted Q-switched laser is “injection seeded” with short pulses from another laser, called a seed laser. Radiation produced by the Q-switched laser is frequency converted in a non-linear process. The injection seeding can enhance peak power and frequency conversion efficiency while reducing damage to a non-linear medium used to frequency convert radiation generated by the Q-switched laser.