The ST: Prodigy Relay Station has a "Rectangular Slit" emitter that looks kind of like "Cyclops VISOR" from X-men.
It's even Red Jeweled colored and fires a rectangular beam.
That opens up the door to end users designing beam emitting columns of any shape they want.
It doesn't always have to be circular.
Does anybody want funky beam patterns emitting out of their weapons?
Hmm yeah, it isn't the first time we see the phaser slit emitter.