User:Andy Maloney/Notebook/Lab Notebook of Andy Maloney/2009/02/22/Optical tweezers/Spatial filtering

To get rid of higher order modes in a laser beam, one needs to filter the higher orders out of the beam. To do this, we can use either a single mode fiber that only allows the TEM00 mode to propagate through it, or we can use a spatial filter. I have a design for a spatial filter and the parts list can be found below.

I am a fan of spatial filters because they are cheaper than single mode fiber launches and because the optomechanics you use for them can be harvested for other uses if you don't need it anymore. As Alton Brown would say, a single mode fiber launch is a uni-tasker and the only uni-tasker I want in my kitchen is the fire extinguisher.

Unfortunately both a spatial filter and a fiber launch have advantages and disadvantages over each other. If anyone reading this is on the fence about purchasing one, then I'd suggest a pro/con list for your setup.

Spatial Filter

Component	Model Number	Cost	# Needed	CAD Drawing	Sketchup
Mounting Base, 1" x 2.3" x 3/8"	BA1S	$5.13	1	Yes	Yes
Translating TR Post 2" to 2 1/4"	TRT2	$49.50	1	Yes	Yes
Post Holder with Spring-Loaded Thumbscrew, L=3"	PH3-ST	$8.27	1	Yes	Yes
SM1 Series Z Translator	SM1Z	$175.40	1	Yes	Yes
SM1 to 9mm Lens Cell Adapter	S1TM09	$20.10	1	Yes	Yes
Asphere	C220TME-A	$89.00	1	Yes	No
30 mm Cage Plate Adapter	CP02B	$13.70	1	Yes	Yes
30 mm Cage Assembly, XY Translating Lens Mount	HPT1	$161.00	1	Yes	Yes
Ø10 µm Mounted Pinhole	P10S	$59.30	1	Yes	Yes
SM1 Threaded 30 mm Cage Plate	CP02	$15.63	1	Yes	Yes
SM1 Lens Tube, 0.5" Long	SM1L05	$12.59	1	Yes	Yes
Achromat	AC254-075-A1	$71.25	1	Yes	No