Extraction of spectra and thresholds from full-wave lasing eigenvalue problems

In this paper, thresholdless laser is not more realistic than a perpetual motion machine. No crystal is infinite, therefore the threshold can be only made small. In fact, zero threshold is completely equivalent to zero output light. Therefore it appears that analysis of lasing in infinite photonic crystals are either erroneous, if done approximately or with coarse numerical methods like FDTD, or has so sense at all, if done with accurate methods, which correctly account for the radiation conditions. Instead, one must simply formulate the lasing eigen value problem with a finite-size photonic crystal encasing a laser resonator and study the reduction of the thresholds as a function of elementary cell size, topology, filling, and number.