Surface emitting laser

Claim 1

Apparatus comprising at least one electrically pumped vertical cavity laser consisting essentially of an active region containing a semiconductor active material layer for generating photons to result in laser emission, said active region comprising p-type and n-type conductivity portions and including a semiconductor junction, said active region being sandwiched between Distributed Bragg Reflectors each comprising a plurality of layers of relatively low and high refractive index for the said laser emission, together with circuit means for electrically pumping said active region to lasing threshold, lasing entailing presence of a standing wave defining a cavity here described as including the said electrode and as bounded by a cavity between the said Distributed Bragg Reflectors characterized in that said circuit means includes an electrode layer at least part of which is outside said active region, whereby at least a major portion of one DBR is excluded from the circuit means, said electrode layer having a conductivity sufficient to result in total conduction of said circuit greater than that of a circuit including the entire DBR as conductivity-doped to an average carrier concentration of 10 19 carriers/cm 3 , and in that absorption for laser emission is reduced in part due to reduction in conductivity-doping of the excluded portion of the DBR to result in a numerical value of equal to or less than 0.25 for the product r·A p in which r is circuit resistance in ohms of that portion of the circuit consisting of p-type material and the associated electrode layer and A p is per-pass photon absorption for that circuit portion expressed as a fraction.