ANH novelisation page 178:
"Theoretically, no weapon could penetrate the exceptionally dense stone of the ancient temple, but Luke had seen the shattered remnants of Alderaan and knew that for those in the incredible battle station that the entire moon would present simply another abstract problem in mass-energy conversion."
So, right from novelization we have statement that "superlaser" is not pure DEW.
(unfinished)
Links:
http://www.st-v-sw.net/STSWsuperl-main.html
http://www.starfleetjedi.net/forum/viewtopic.php?f=8&t=1583&sid=ed2fb46a7720b5a5d21e36be36226988
