I need a list of suppliers for laser diodes (poloroid etc)....500mw,
635nm and with the ablility to be pulsed up to 50 watts...for medical
use in the treatment of cancer.  If a laser such as this exists I
would also like to know the supplier.

Polaroid?  They sold off their laser business years ago.  I forgot who
bought it.  But the trade magazines are a good place to start.  If
this link doesn't work, just browse the buyers guide:
http://laserfocusworld.365media.com/laserfocusworld/searchResult.asp?cat=489032&d=453&st=1

other place to look would be http://www.optics.org

There are a number of laser diode suppliers out there. Two common ones
are Spectra Physics (http://www.spectraphysics.com/products/spsl_products/spsl_product_ov.html)
and Coherent (http://www.cohr.com/Products/index.cfm?fuseaction=Interfaces.ProductLine&PCID=23&PLID=40),
both of which make a number of diode products.

Other places to check include resellers such as Thorlabs
(www.thorlabs.com), which has a LD buyer's guide:
http://www.thorlabs.com/DiodesGroup.cfm?CATID=91&ObjectGroup_ID=7&ReQuery=0

You should be aware that 50W pulsed output would probably only be
achievable with bars and stacks of smaller diodes, and a system for
medical use would probably need to be fibre-coupled.