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

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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