Laser TEM Modes - What Determines Output?

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SUMMARY

The output mode of a laser, specifically the transverse electromagnetic (TEM) mode, is determined by the construction of the laser and the desired output characteristics. Lasers can be configured to emit in the TEM00 mode by incorporating a pinhole with a diameter equal to that of the lower mode between the mirrors, allowing only this mode to pass while attenuating higher modes. The transverse cavity dimensions also play a crucial role in defining the spatial mode structure, with apertures used to select specific modes within the resonant cavity. This configuration is particularly relevant for unstable cavities often found in high-power, high-gain laser systems.

PREREQUISITES
  • Understanding of transverse electromagnetic (TEM) modes
  • Knowledge of laser cavity construction and design
  • Familiarity with optical apertures and their role in mode selection
  • Basic principles of laser operation and amplification
NEXT STEPS
  • Research the impact of cavity dimensions on laser mode selection
  • Explore the use of pinholes in laser design for achieving TEM00 output
  • Investigate unstable cavity configurations in high-power laser systems
  • Learn about the principles of laser amplification and mode competition
USEFUL FOR

Laser engineers, optical physicists, and anyone involved in laser design and optimization will benefit from this discussion on TEM modes and their implications for laser output.

Goodver
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What determines which TEM mode will the laser output have?

Why some lasers emit in TEM00, while other in a donut mode, and other in a superposition of multiple modes.

Thank you.
 
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typing your first Q into google came up with many good responses

for your second Q

lasers will transmit in various modes depending on how it is constructed and the desired mode required
eg
Lasers can be forced to lase in a single TEM00 mode by simply putting a pinhole with proper diameter between the two mirrors. The pinhole diameter should be equal to the diameter of the lower mode as this would allow only this mode to pass through the pinhole, and all higher modes will be attenuated. Since radiation inside the optical cavity undergoes multiple passes, only the basic mode will be amplified, and appear in the output.cheers
Dave
 
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Goodver said:
What determines which TEM mode will the laser output have?

Why some lasers emit in TEM00, while other in a donut mode, and other in a superposition of multiple modes.

Thank you.

The transverse cavity dimensions dictate the spatial mode structure, and the specific transverse mode for a resonant cavity is typically selected by placing an aperture within the cavity. For unstable cavities, typically associated with high-power high-gain systems, I'm not sure where the mode selection occurs.

Edit- I see davenn already mentioned this...
 

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