From what I have been able to find, Epitron Technology was dedicated to the manufacturing and selling of GaAs wafers.
http://www.barchart.com/plmodules/?module=secFilings&filingid=10426663&type=CONVPDF&popup=1&override=1&symbol=UMC (page 11)
I guess Wavetek (due to their Merger announced Jan 2015 with Epitron, finalized in April 2015) could be a Wafer Supplier and Manufacturer (as revealed in recent NR) for Poet?