Laser TEM Modes - What Determines Output?

[Goodver]

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.

 

[davenn]

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

 

[Andy Resnick]

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...