Hey Everyone!
It's been a while since I've made a thread here.
As i've been delving deeper and deeper into the technical side of lasers: questions kept growing.
As I've been doing more and more laser experiments out of my own the interest in a ion sputter coater build has grown.. they are not easy builds but they are do-able.. the information is out there and build files have started to spring up on the internet more and more.
However that brings me to a big question: The sputtering targets.
I know dielectric mirrors are made using sputtering and also output couplers which is a semi-transparent dielectric mirror (and I also believe dichroic filters too)
I keep hearing the formulas of these coatings are secrets held closely within optics companies and while I can understand this for optics with really exotic narrow band coatings.. I find it quite hard to believe that general formulas aren't more publicised.
For example I've been reading papers of optical cavities made where the lab sputter coated their mirrors in house.. meaning: They used some kind of target aquired from somewhere.
Can anyone shed more light on the compositions that are used and how its determined in advance what target is useful for what wavelength range?
and last not at least: how do they achieve certain transmittance percentages with sputtering?? are they slightly contaminating the argon enviroment with oxygen resulting in a semi transparent dielectric mirror because of oxidization?? or is it coating thickness??
So why would one go through this effort over just ordering them?: Testing different focal lengths or different reflectance/pass through properties of output couplers or recoating third party purchased non linear crystals that are bought uncoated.
Maybe these labs have enormous budgets and have a seperate facility they collaborate with and the papers do not shed light on these things: but I'd be interested to know!!