| 摘要 |
A tunable optical filter includes a medium configured to perform polarization rotation on a portion of a linearly polarized signal beam having a frequency within a selected frequency band, wherein the medium is circularly birefringent within the frequency band, and wherein the polarization rotation is achieved based on two-photon-absorption. The medium may include a gaseous substance, a first reference laser beam having a first reference frequency and a right circular polarization state, and a second reference laser beam having a second reference frequency and a left circular polarization state. The medium may also include a gaseous substance, a reference laser beam having a reference frequency and a linear polarization state, and magnetic field.
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