If you want to synt the laser:
If it is a shooting laser:
Get a mettalic, somewhat dissonant soundsource with fm or wavetable synth. Use a pitch envelope the get the piuuu. Then use a filter lp/bp with another decaying envelope. experiemnt with resoanze till you get a pleasant piuuu.
Try to layer it with some textures out of Omnisphere or whatever if it need some more life.
Granulize and autoamte fitlers to let the shot disolve at the end.
To treat the sample you should go for a Doubbler Effect. it can work wonders! Especially the Wave Doubbler has some cool presets as a starting point.
Instead of envelopes you can use Sawtooth alike LFOs. so you can get the effect of a "railgun laser"
then use reverb and shelfing eqs to get the desired distance to position it in the sound field!
If it is a static laser you want to synth a sustained/modulated sound:
Get a synth and build a dissonant metallic soudnsource, double it and slighty hcange the pitch to get some phasing. Get tons of unsynced modulation on pitch, filter and maybe vibrato.
find nice organic textures that have a bright, shining feel to it. and layer them over the sound. treat with doubbler and reverb and remove any heave bass.
i hope this gives you a starting point to get a laser. gl