A method of detecting Coherent Population Trapping resonance by phase modulation (PM)
was studied to expand the frequency locking range (LR). We calculated error signals by
density matrix analysis using an eigenvector algorithm and verified the calculated result
using an 87 Rb vapor cell and a Rb-D 1 vertical cavity surface-emitting laser. By comparing
the error signal for PM with that for conventional frequency modulation (FM), it was found
that the LR with PM is one order of magnitude wider than that with FM without degrading the …