Faraday anomalous dispersion optical filter with a single transmission peak using a buffer-gas-filled rubidium cell

Isotope 87Rb Faraday filter with a single transmission peak resonant with atomic transition at 780 nm

We demonstrate an isotope ⁸⁷Rb Faraday anomalous dispersion optical filter (FADOF) with a single transmission peak resonant with the 5S_1/2, F = 2 → 5P_3/2, F' = 1, 2, 3 transitions at 780 nm with an enriched ⁸⁷Rb isotope at low temperature. The isotope ⁸⁷Rb FADOF achieves a single peak transmission of 74.8% with a bandwidth of 0.96 GHz. Compared with most of FADOFs operated at frequencies far from absorption, the isotope ⁸⁷Rb FADOF that we have achieved can provide a transmission band exactly covering atomic transitions for many practical applications.

A Faraday laser lasing on Rb 1529 nm transition

We present the design and performance characterization of a Faraday laser directly lasing on the Rb 1529 nm transition (Rb, 5P_3/2 − 4D_5/2) with high stability, narrow spectral linewidth and low cost. This system does not need an additional frequency-stabilized pump laser as a prerequisite to preparing Rb atom from 5S to 5P excited state. Just by using a performance-improved electrodeless discharge lamp-based excited-state Faraday anomalous dispersion optical filter (LESFADOF), we realized a heterogeneously Faraday laser with the frequency corresponding to atomic transition, working stably over a range of laser diode (LD) current from 85 mA to 171 mA and the LD temperature from 11 °C to 32 °C, as well as the 24-hour long-term frequency fluctuation range of no more than 600 MHz. Both the laser linewidth and relative intensity noisy (RIN) are measured. The Faraday laser lasing on Rb 1529 nm transition (telecom C-band) can be applied to further research on metrology, microwave photonics and optical communication systems. Besides, since the transitions correspongding to the populated excited-states of alkali atoms within lamp are extraordinarily rich, this scheme can increase the flexibility for choosing proper wavelengths for Faraday laser and greatly expand the coverage of wavelength corresponding to atomic transmission for laser frequency stabilization.

Isotope ⁸⁷Rb Faraday anomalous dispersion optical filter at 420 nm

We demonstrate a Faraday anomalous dispersion optical filter (FADOF) operating on 5S(1/2)-6P(3/2) transition at 420 nm with a 5 cm long cell of 96.5% enriched 87Rb and measure the transmission as a function of the magnetic field and temperature. The isotope 87Rb FADOF achieves a peak transmission of 98% with a bandwidth of 2.5 GHz when the temperature of the isotope 87Rb cell is 280°C and the magnetic field is 500 G. The corresponding equivalent noise bandwidth is 5.9 GHz. The isotope 87Rb FADOF is applied to submarine communications, is used as the laser frequency stabilization for some atomic lines, and is also used as the pump laser in four-level Rb active optical clock.

An all-optical locking of a semiconductor laser to the atomic resonance line with 1 MHz accuracy

An all-optical locking technique without extra electrical feedback control system for a semiconductor laser has been used in stabilizing the laser frequency to a hyperfine crossover transition of 87Rb 5(2)S(1/2), F = 2 → 5(2)P(3/2), F' = 2, 3 with 1 MHz level accuracy. The optical feedback signal is generated from the narrow-band Faraday anomalous dispersion optical filter (FADOF) with nonlinear saturation effect. The peak transmission of the narrow-band FADOF corresponding to 5(2)S(1/2), F = 2 → 5(2)P(3/2), F' = 2, 3 crossover transition is 18.6 %. The bandwidth is as wide as 38.9 MHz as the laser frequency changes. After locking, the laser frequency fluctuation is reduced to 1.7 MHz. The all-optical laser locking technique can be improved to much higher accuracy with increased external cavity length. The laser we have realized can provide light exactly resonant with atomic transitions used for other atom-light interaction experiments.