Patent ID: 7345553

Claim:
An apparatus comprising: a quantum absorber comprising a material having first and second low energy states coupled to a common high energy state, transitions between said first low energy state and said common high energy state or between said second low energy state being induced by electromagnetic radiation; an electromagnetic radiation source that generates electromagnetic radiation having first and second CPT-generating frequency components, said first CPT-generating frequency component having a frequency ν L −ν, and a first CPT component amplitude and said second CPT-generating frequency component having a frequency ν L +ν and a second CPT component amplitude, said first and second CPT-generating frequency components irradiating said quantum absorber; a detector for generating a detector signal related to the power of electromagnetic radiation that leaves said quantum absorber, said detector signal exhibiting an asymmetry as a function of frequency ν in a frequency range about a frequency ν O ; a CPT servo loop that alters v in response to said detector signal; and an asymmetry servo loop that alters one of ν L , said first CPT component amplitude, and said second CPT component amplitude in a manner that reduces said asymmetry.