Coherent Polarization Beam Combination All the papers I have read regarding coherent polarization beam combination split laser beams and then coherently combine the components. But is it possible to coherently combine two different lasers with the same frequency and orthogonal polarizations?
 A: Your comment explains better what you want

By coherently combine, I mean to combine to different laser sources to produce a beam of greater intensity

even if I wouldn't use the word "coherently". You can combine, or superpose, as many beams as you want with any polarization just using beam splitters (better non-polarizing). Contrary to polarizers, they split and recombine any polarization. But check the specs because you'll never have exactly 50-50% for s and p polarization components. 
A: Simply getting higher intensity by combining two beams of orthogonal polarization is easy: a polarizing beamsplitter will do it.  Of course the resulting beam will be unpolarized.
In order to combine beams from two lasers coherently, it is necessary to make the two lasers mutually coherent: to phase-lock them.  This isn't very difficult.  You need a fast photodetector, an amplifier, and a piezo-driven mirror (or other frequency-adjusting method) in one of the lasers.  Small fractions of the two beams are split off and both used to illuminate the fast photodetector.  This produces a "beat frequency" output that goes through the amplifier and is used to drive the piezo mirror to the point where the beat frequency is zero.  That means the lasers are phase-locked -- and they are now mutually coherent.  Rotate the polarization of one of the laser beams so the two polarizations are mutually orthogonal, and then combine them using a polarizing beamsplitter.  If you need to control the polarization of the combined beam, put a phase shifter in one of the beams upstream from the beam splitter and adjust it to get the desired linear or circular polarization, then rotate the polarization downstream as needed.
