Combination of differently structured pump beams for selective mode excitation

Area of Science:

• Optics and Photonics
• Laser Physics
• Materials Science

Background:

• Digital Micromirror Devices (DMDs) offer precise spatial control over light.
• Excitation of transverse resonator modes is crucial for laser performance.
• DMD damage thresholds limit output power in spatial gain shaping applications.

Purpose of the Study:

• To investigate pump beam combining to increase laser output power beyond DMD damage thresholds.
• To explore strategies for enhancing output power by optimizing spatial gain distribution.
• To analyze the modal properties resulting from different pump distribution patterns.

Main Methods:

• Utilizing a DMD for spatial gain shaping to target specific transverse resonator modes.
• Implementing a pump beam combining approach with a mode-specific DMD beam and a mode-unspecific beam.
• Performing modal analysis of multi-mode lasing to characterize pump distribution effects.

Main Results:

• Reducing power on the DMD by a factor of three to five using a second pump beam was feasible.
• Output power scaling was achieved by adapting the mode-like pattern on the DMD.
• Center-heavy pump distributions favored target and low-order modes, while eccentric distributions lowered thresholds but reduced mode distinction.

Conclusions:

• Spatial gain shaping with DMDs is a viable method for controlling transverse laser modes.
• Optimizing the DMD pattern offers an alternative to increasing incident power for output scaling.
• The spatial characteristics of the pump distribution significantly influence mode selection and laser threshold.