Rough example:

As you will notice, this takes up roughly the same space, put puts out a laser a few hundred degrees hotter.

Overall though, your laser is looking pretty good.

EDIT: for the people suggesting superheated ARAY as a heat source:

ARAY is rather difficult to use effectively in a laser, to make it work, your going to need to:

Shield your ARAY from heat and general damage, as they are backed with metal and battery, they are easily destroyed, especially in lasers with high heat.

Even the fastest type (PSCN backed, it shoots rapid shots, in my opinion, it beats regular metl backed due to not leaving a bunch of useless ray behind for a few seconds before shooting another shot) is still less space efficient then a normal GOL generator...you have to leave a row in between each ARAY, lest they melt eachother.

Plus, unlike a GOL generator, an ARAY heat generator has the additional effect of being weak to EMP.

Basically, what im trying to say, is that while an ARAY heat generator can be effective enough, its generally more trouble then its worth unless you specifically want to build a ARAY heated laser.