SummaryWe propose a potassium Faraday laser using a potassium atom-based Faraday anomalous dispersion optical filter (FADOF) as the frequency selection element. By adjusting the transmission spectrum of the potassium FADOF, the potassium Faraday laser achieves single-mode operation, with the wavelength automatically covering all the39K D2 transitions. During free-running, the wavelength fluctuation is less than 0.4 pm over 3.5 hours measured by a wavelength meter, with the frequency stability of 5.70 × 10-10at 1 s measured by optical heterodyne between two identical systems. After using modulation transfer spectroscopy (MTS) to stabilize the laser, the frequency stability is 6.22×10-13at 1 s. This potassium Faraday laser system is a desirable option for applications including potassium magnetometers, laser cooling and frequency standards.
SummaryWe propose a potassium Faraday laser using a potassium atom-based Faraday anomalous dispersion optical filter (FADOF) as the frequency selection element. By adjusting the transmission spectrum of the potassium FADOF, the potassium Faraday laser achieves single-mode operation, with the wavelength automatically covering all the39K D2 transitions. During free-running, the wavelength fluctuation is less than 0.4 pm over 3.5 hours measured by a wavelength meter, with the frequency stability of 5.70 × 10-10at 1 s measured by optical heterodyne between two identical systems. After using modulation transfer spectroscopy (MTS) to stabilize the laser, the frequency stability is 6.22×10-13at 1 s. This potassium Faraday laser system is a desirable option for applications including potassium magnetometers, laser cooling and frequency standards.
A laser with a switchable wavelength between 770 nm and 767 nm, corresponding to the potassium D1 and D2 lines, is a promising tool for manipulating potassium atoms. Here, we develop a potassium Faraday laser using a potassium atom-based Faraday anomalous dispersion optical filter (FADOF) as its frequency selection element. By dynamically adjusting the central frequency of the peak transmission across the entire transmitted spectrum of the potassium FADOF, the laser can operate either in single mode at either 770 nm or 767 nm, or emit both simultaneously. In single-mode operation, the laser wavelength remains aligned with the atomic transitions, exhibiting a narrow linewidth of 14.96 kHz at 770 nm and 13.07 kHz at 767 nm. In dual-mode operation, both modes are sustained continuously, with frequency drifts of less than 0.3 GHz for 200 minutes. Furthermore, we perform modulation transfer spectroscopy (MTS) and stabilize the laser to the 39 K 4S 1/2 F = (1, 2) → 4P 1/2 F ′ = 2 and 4S 1/2 F = (1, 2) → 4P 3/2 F ′ transitions. The corresponding frequency stability, measured by the optical heterodyne beat note between two identical systems, is 1.57 × 10 −12 and 8.77 × 10 −13 at 1 s, respectively. This architecture introduces a novel approach to the generation of wide-range wavelength switching within a single laser. In addition, with its narrow linewidth and impressive frequency stability, it serves as a reliable source for ultracold atom physics and quantum precision measurement.
In the development of atomic physics, laser sources with Frequencies corresponding to atomic transition and high stability are essential. The Faraday laser is a special diode laser using the Faraday anomalous dispersion optical filter (FADOF) to realize frequency selection, so the output laser frequency is automatically limited to the atomic Doppler broadening. However, the frequency of a Faraday laser corresponds to the range around only one atomic hyperfine transition. Here, we realize a switchable Faraday laser with two isotopes laser frequencies corresponding to 85Rb 52S1/2 (F=3)→52P3/2 and 87Rb 52S1/2 (F=2)→52P3/2 transitions based on a single isotope 87Rb-FADOF. The laser has good robustness against the fluctuation of diode current and temperature, with wavelength fluctuating within 0.8 pm from 16 to 30 °C of diode temperature, and has a free-running linewidth of 18 kHz. We also lock the laser frequency to the two cycling transitions of 85Rb 52S1/2 (F=3)→52P3/2 (F′=4) and 87Rb 52S1/2 (F=2)→52P3/2 (F′=3) by the modulation transfer spectroscopy technique. The Allan deviation of the residual error signal is 3×10−14/τ, and the frequency stability of the beat detection reaches 2.8×10−12 at 1 s integration time. This 780 nm switchable Faraday laser expands the application scenarios of Faraday lasers, which can be used in laser cooling atoms, optical frequency standards, and other quantum precision measurement fields.
The Faraday laser, with Faraday anomalous dispersion optical filter (FADOF) as frequency-selection element, is a natural narrow-bandwidth light source for laser physic experiments. In this work, a dual-frequency (DF) Faraday laser is demonstrated for the first time on Cs D2 line at 852 nm. The frequencies of the two modes of DF Faraday laser hinge on the peak transition frequencies of 852 nm FADOF transmittance spectrum corresponding to the ground state F=4 and F=3. The frequency difference between the two modes is tunable over a range of 1.4 GHz with the temperature of Cs vapor cell inside the FADOF. The linewidth of each laser mode is less than 33 kHz. Furthermore, the most probable linewidth of the beat-note spectra between the two modes is 902.95 Hz at different vapor-cell temperatures. Such a DF Faraday laser has many potential applications in atomic physics, such as sub-Doppler spectroscopy and coherent population trapping atomic clocks.
The atomic magnetometer exhibits high sensitivity in weak magnetic field detection, with diverse applications in dark matter detection, biomagnetic sensing, wireless communication, etc. However, its performance, especially in environmental robustness and sensitivity, is largely limited by laser characteristics. Here, we realized two potassium Faraday lasers operating at potassium D1 (770 nm) and D2 (767 nm) lines, serving as pump and probe lasers for a potassium atomic magnetometer. Utilizing the Faraday anomalous dispersive effect for frequency selection, the lasers achieve automatic wavelength locking within the atomic Doppler broadening, enabling robust, self-stabilizing operation without tedious adjustments. Furthermore, both lasers exhibit strong immunity to environmental disturbances, such as vibration and temperature variations. By implementing the modulation transfer spectroscopy (MTS) technique, the frequency stability of the pump laser and probe laser reaches approximately 5.1 × 10 − 13 / τ and 6.2 × 10 − 13 / τ , respectively. Notably, the optimized frequency stability is accompanied by better power stability, showing threefold and fivefold improvements over their free-running counterparts, which reaches the 10 − 5 level at 1 s. The enhancements in laser performance directly improved the magnetometer’s performance, yielding a magnetic noise floor of approximately 100 fT / Hz at 10 Hz under a bias field of 1000 nT. Therefore, with hands-off operation, environmental robustness and competitive sensitivity, this achievement holds promising prospects for both laboratory and field-deployable applications.
We demonstrate a dual-frequency (DF) Faraday laser operating on 780 nm using an87Rb Faraday anomalous dispersion optical filter (FADOF) as the frequency selection element. The frequencies of the two modes correspond to the transition of87Rb 52S1/2(F=1) to 52P3/2and 52S1/2(F=2) to 52P3/2, respectively. The output laser wavelength has good robustness to the laser diode’s current and temperature fluctuations. The frequency difference between the two modes is tunable with the temperature of87Rb vapor cell and cavity length. Besides, the two modes share good coherence with the most probable linewidth of the beat-note spectra being 3 kHz. Such a 780 nm DF Faraday laser can be used in precision measurement, such as, laser frequency stabilization, optical microwave generation, and coherent population trapping (CPT) atomic clocks.
The study of atomic physics has been greatly influenced by the development of high-stability diode lasers whose output corresponds to the atomic transition. Recently, an atomic filter laser “Faraday laser” shines on stage, owing to its great robustness to the fluctuation of the diode parameters and potentially higher tolerance to vibration. However, cost reduction and portability require the Faraday laser to have a more compact structure. Here, we report on the development of a promising atomic filter laser—a “Voigt laser”—using a Voigt anomalous dispersion optical filter (VADOF) as the frequency-selective element, which has a structural advantage in miniaturization. The influencing factors toward the VADOF are investigated in detail to produce a parameter set for the best performance of a Voigt laser. In this case, the Voigt laser has great robustness to the fluctuation in the diode current and temperature, where the wavelength fluctuation is ±0.5 pm with the variation of the diode parameters (diode current: 73–150 mA and diode temperature: 12–30 °C). In addition, the wavelength of the Voigt laser fluctuates about ± 0.5 pm for 48-h free-running operation and shows excellent reproducibility without manual adjustment. The laser system developed here provides a stable and reliable laser source for substantially improving existing technologies such as the atomic clock, electromagnetically induced transparency, and laser cooling of atoms.