Cs 728 nm excited state Faraday anomalous dispersion optical filter with indirect pump

• A Cs ESFADOF operating at 728 nm is realized using an indirect pump method.
• The ESFADOF can be applied to both laser frequency stabilization and future four-level active optical clocks.
• Multiple wavelength filters exploiting atomic transitions to these states can be realized.
• This method can also be extended to other wavelengths of ESFADOF.

We demonstrate a Cs excited state Faraday anomalous dispersion optical filter (ESFADOF) operating at 728 nm using a novel pump method, by which the pump beam and the probe beam in the ESFADOF realized here have no a common energy level. Using this method, the ESFADOF achieves a transmission of 2.39% with a bandwidth of 22.52 MHz, which can be applied to both laser frequency stabilization and future four-level active optical clocks. Under the 455 nm laser pump, in addition to 52D5/252D5/2, other states such as 72S1/272S1/2, 72P3/272P3/2, 62P3/262P3/2, 62P1/262P1/2 and 52D3/252D3/2 have also been populated effectively. Meanwhile, multiple wavelength filters exploiting atomic transitions to these states can be realized.