Waveguide Laser Recess for Mode Selection and Power Output

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Solution Overview

Problem

Existing CO2 slab waveguide lasers face limitations in mode quality and output power due to electrode spacing restrictions and manufacturing complexities, particularly in achieving stable beam quality and high power generation.

Innovation Solution

Incorporating a recess on the waveguide surface to allow free space propagation, which simplifies electrode manufacturing and enables mode selection by controlling the length and depth of the recess within the discharge region, allowing for improved beam quality and power output.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If electrodes are spaced more than 2mm apart to increase output power, then power output increases, but mode quality deteriorates

Engineering Contradiction:

Improveoutput powerVSAvoidmode quality

Core Design Contradiction:

PowerVSManufacturing precision

Solution Approach 1:

The waveguide surface is segmented by introducing a recess that divides the propagation path into two regions: a waveguide region and a free space region. This segmentation allows different propagation modes to be supported simultaneously, enabling fundamental mode selection even with larger electrode spacing.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The recess creates a localized region with different optical properties (free space propagation) within the overall waveguide structure. This local quality change allows the fundamental mode to be preferentially selected in the free space region while maintaining stable operation across the entire laser cavity.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If curved electrodes are used to achieve mode selection, then mode quality improves, but manufacturing complexity increases

Engineering Contradiction:

Improvemode qualityVSAvoidelectrode manufacturing

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

Instead of curving the electrodes to achieve mode selection, the invention inverts the approach by maintaining planar electrodes and introducing a recess in the waveguide surface. This reverses the conventional wisdom and achieves mode selection through the recess geometry rather than electrode curvature.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The curvature function is extracted from the electrodes and transferred to the recess structure. The recess, with its specific depth and width dimensions, performs the mode selection function that would otherwise require curved electrodes, simplifying electrode manufacturing while maintaining mode quality.

Inventive Principle:

Principle #2Taking out (Extraction)

3Manufacturing precision

If tight tolerances are applied to electrode arrangement and mirror alignment, then mode quality improves, but device complexity increases

Engineering Contradiction:

Improvemode qualityVSAvoidalignment tolerancing

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The recess dimensions (depth and width) are optimized to provide mode selection with relaxed alignment tolerances. By carefully selecting these parameters, the system achieves robust fundamental mode operation that is less sensitive to variations in electrode spacing and mirror alignment, reducing device complexity.

Inventive Principle:

Principle #35Parameter changes

4Volume of stationary object

If electrode spacing is increased to expand active region volume, then power output increases, but discharge stability deteriorates

Engineering Contradiction:

Improveactive region volumeVSAvoiddischarge stability

Core Design Contradiction:

Volume of stationary objectVSReliability

Solution Approach 1:

The recess acts as an intermediary structure that mediates between the electrodes. It provides a controlled free space propagation region that stabilizes the discharge by allowing proper mode formation, enabling larger electrode spacing while maintaining discharge stability through the recess's geometric constraints.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The recess allows for preferential selection of the fundamental mode, enhancing beam stability and output power while reducing manufacturing complexities and tolerancing issues, achieving improved mode quality and power generation.

Implementation Method 1

a recess is located on a surface of the waveguide to provide a region of free space propagation within the waveguide

Methodology Applied

Scientific EffectFree space propagation:

Implementation Method 2

the radius of curvature of the wavefront of the laser beam in the stable waveguide resonant cavity at the mirror location substantially matches the radius of curvature of the mirrors selected for the unstable resonator

Methodology Applied

Scientific EffectWavefront radius of curvature matching:

Data Source

PatentEP2362502B1Mode selection technique for a waveguide laser

Publication Date: 2014.08.13 ROFIN SINAR UK

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Figure 3a~5b
Figure 6a~6d

AI summary

A mode selection technique in a laser is proposed wherein a recess is formed in a surface of a waveguide in the laser. The recess provides a region of free space propagation within the waveguide which preferentially selects the lowest order mode. A mode selective RF excited CO2 slab laser, having a stable resonator in the waveguide dimension and a negative branch unstable resonator in the non-waveguide dimension, is provided and the position and size of the recess is considered to provide low order mode selection.