High transparency of thin platelet semiconductor lasers

The high transparency of the passive portions of a thin platelet CdSe or Ga(AsP) semicondutor laser resonator, pumped over only part of its length by a Ga(AsP) junction laser, indicates by direct observation (visible-red) that the output photon energy is less than bandgap. Two possible explanations for this are suggested. This behavior makes possible operation of thin platelet lasers over very long path lengths, e.g., long zig-zag modes and ring modes.