Well these two dual beam laser pencils, pointing at each other do fill the space between with what seems to be no energy anywhere as well as one does. Single beam lasers pointing at each other can not do that even if of exactly the same polarization (E field directions) and frequency. When "clashing head on" each beam will feed into the other laser's source. This could make one cease to lase as inside each laser (When lasing.) there is stronger E fields than in the external beams and the entering beam of one can be in principle, be a negative feedback, as if mirror reflected the laser's own beam back inside it. If the stimulated emission is thus killed by the other laser's beam entering, and the non-thermal excitation of the upper state continues, then the intensity of the random direction light produced by that upper to lower state transition will increases (by the energy of the beam being feed back into the laser from the other laser which is still functioning.) With exactly opposite pointed lasers you really only have one laser system. How much laser light part "A" produces, if any, will depend upon part "B" (and conversely). The total energy pumping up the non-thermal population upper states and decaying radiatively to the lower states, will ultimately exit in random directions mainly thru the sides of the laser (This because the laser beams are not sending the energy anywhere out side of the integrated Part "A" / Part "B" single laser. BTW, I would expect that this integrated laser is an oscillator probably with frequency in the audio range. I.e. when one part can not lase because of the negative feed back from the other the non-thermal upper state population will be increasing as the strong E field it has internally (When it is lasing) is not causing stimulated radiative depopulation of the upper state. In the other lasing laser, in contrast, it is as they say "burning a hole" in the Doppler distribution of atoms /molecules which can be stimulated to radiate in phase. I.e. its "lasable" upper state population is decreasing. Soon it will go off and the other laser, now with no negative feed back will begin to lase. - I.e.alternation of which is lasing is very likely. - an (I would guess) audio frequency oscillator.