Diffractive Optical Element Pair for Ultrashort Pulse Beam Combination

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Solution Overview

Problem

Fiber lasers are limited in peak power due to nonlinear and damage effects, and existing beam combination techniques for ultrashort pulses, such as diffractive optical beam splitters, suffer from angular dispersion and pulse front tilt, making it inefficient to combine multiple ultrafast laser beams effectively.

Innovation Solution

An optical system using a pair of diffractive optical elements, including a grating array and a beam splitter, which diffracts and combines multiple pulsed beams to cancel pulse front tilt and angular dispersion, allowing for the coherent combination of tens or hundreds of beams while maintaining high efficiency and power handling capability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If diffractive optical beam splitters are used to combine ultrashort pulses, then beam combination is achieved, but angular dispersion and pulse front tilt occur causing inefficiency

Engineering Contradiction:

Improvebeam combination efficiencyVSAvoidenergy loss due to angular dispersion and pulse front tilt

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The system segments the beam combination process into two distinct diffractive stages: first diffractive optical element for spatial separation and second diffractive optical element for recombination. This segmentation allows each element to be optimized for its specific function, eliminating the angular dispersion and pulse front tilt that plague single-element systems.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first diffractive optical element acts as an intermediary that temporarily separates the ultrashort pulses spatially without causing harmful angular dispersion. This intermediate step allows the second diffractive element to recombine the pulses coherently, mediating between the input beams and final combined output to preserve pulse integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If polarizing or non-polarizing beam splitters are used to combine laser beams, then beam combination is achieved, but the system becomes cumbersome requiring trees of beam splitters to combine many beams

Engineering Contradiction:

Improvenumber of beams combinedVSAvoidsystem complexity with trees of beam splitters

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The diffractive optical element pair serves multiple functions simultaneously: it spatially separates beams, maintains pulse front orientation, enables coherent recombination, and handles multiple beams in parallel. This multi-functionality replaces the need for complex trees of specialized beam splitters, achieving high beam combination capacity with a unified compact system.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the functions of multiple beam splitters into a single diffractive optical element pair that can handle tens or hundreds of beams simultaneously. By combining spatial separation, pulse front management, and coherent recombination into one integrated diffractive system, the complexity of traditional beam splitter trees is eliminated.

Inventive Principle:

Principle #5Merging (Combining)

3Power

If fiber lasers are used to produce high energy output, then efficiency and average power capability are improved, but peak power is limited due to nonlinear and damage effects

Engineering Contradiction:

Improveaverage power capabilityVSAvoidnonlinear and damage effects limiting peak power

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary spatial separation and pulse front alignment using the first diffractive optical element before the beams are recombined. This preliminary action ensures that when beams are combined, their pulse fronts are properly aligned to constructively interfere, maximizing peak power without causing nonlinear effects or damage that would occur with misaligned high-power combining.

Inventive Principle:

Principle #10Preliminary 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

This solution enables the efficient combination of ultrafast laser beams, reducing losses to less than 1% and preserving the pulse width, thus overcoming the limitations of existing technologies in scaling energy output from fiber lasers.

Implementation Method 1

The first diffractive optical element receives and diffracts the plurality of pulsed beams. The second diffractive optical element receives the diffracted plurality of pulsed beams and generates a combined pulsed beam.

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

Methodology Applied

Scientific EffectPulse front tilt cancellation:

Data Source

PatentUS10444526B2Optical pulse combiner comprising diffractive optical elements

Publication Date: 2019.10.15 RGT UNIV OF CALIFORNIA

AI summary

This disclosure provides systems, methods, and apparatus related to optical systems. In one aspect, an optical system includes a plurality of optical sources, a first diffractive optical element, and a second diffractive optical element. The plurality of optical sources generates a plurality of pulsed beams that is less than about 1 picosecond in duration. The first diffractive optical element receives and diffracts the plurality of pulsed beams. The second diffractive optical element receives the diffracted plurality of pulsed beams and generates a combined pulsed beam.