TechViking
macrumors regular
To me the fact that he left there in January means lots of things could have changed since then.
Paul Matthews are still listed on Linkedin as being a member of the sapphire team.
And where did he leave? He left to work at Applied Materials. A company apparently heavily involved in the making of Apple's products:
http://mashable.com/2012/04/02/applied-materials-ipad/
Applied Materials are, among other things, also making tools to construct solar panels.