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arXiv:2609.27447

A 75-mL intrinsically stable atom-filtered laser enabling deployable quantum devices

Zijie Liu, Zheng Xiao, Zhiyang Wang, Xiaolei Guan, Xiaomin Qin, Suyang Wei, Hongtian Song, Baoshuai Wang, Jia Zhang, Xiaopeng Xie, Tiantian Shi, Anhong Dang, Jingbiao Chen

quant-phphysics.atom-phphysics.opticsSubmitted Sep 23, 2026• Announced Sep 24, 2026• 0 citations
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Abstract

Numerous quantum devices require lasers strictly locked to atomic transitions. Atom-filtered lasers (AFLs) are considered a leading candidate for quantum device laser sources due to their ability to self-align to atomic transitions. However, the sub-GHz sharp transmission spectra of conventional atomic filters impose constraints on both laser miniaturization and output stability. Herein, we demonstrate a micro Faraday anomalous dispersion optical filter (μFADOF) operating within the extreme hyperfine Paschen-Back regime, generating a 7.5 GHz flat-top transmission window. By integrating this filter, the miniaturization bottleneck of the AFLs is overcome, achieving a 30-fold volume reduction to a compact package volume of 75 mL. Simultaneously, investigations into the optical self-feedback characteristics of the μFADOF reveal a stable operating regime, where the optical self-feedback of the atomic filter acts as a stabilizing mechanism, enabling the laser to achieve a power instability of 9 x 10^-6 at 1 s and 3.2 x 10^-5 at 8400 s. The optical frequency standard based on this 75-mL AFL achieves a further improvement in long-term frequency stability to 3 x 10^-13 at 10000 s and maintains turn-key operation under environmental shocks, highlighting the critical role of this laser in the development of deployable quantum devices.

AI Summary

Atom-filtered lasers use intracavity atomic filters to keep emission near an atomic transition, but conventional narrow transmission windows constrain cavity miniaturization and contribute to power fluctuations. This paper develops a compact rubidium laser using a broadband, flat-top Faraday anomalous dispersion optical filter operated in the hyperfine Paschen–Back regime. A 10-mm $^{85}$Rb cell in an inhomogeneous 1000–3550 G magnetic field produces a 7.5 GHz transmission window. Transmission measurements versus optical intensity, supported by susceptibility-based calculations, identify saturable-absorption, intensity-insensitive, and reverse-saturable-absorption regimes. Saturation removes transmission distortions associated with magnetic-field inhomogeneity; the measured stable regime spans approximately $5\times10^3$–$3\times10^4\,\mathrm{mW/cm^2}$. Integrating this filter yields a 3.3-cm cavity in a 75-mL package, a reported 30-fold volume reduction, with a 24-kHz linewidth. Free-running wavelength drift stays below 1.5 pm over 42 days without observed mode hops. With optimized diode current, multistage temperature control, and MTS frequency locking, power Allan deviation reaches $9\times10^{-6}$ at 1 s and $3.2\times10^{-5}$ at 8400 s. An MTS-locked optical frequency standard, evaluated against another standard and a hydrogen-maser-referenced frequency comb, reaches fractional instability $3\times10^{-13}$ at 10,000 s. A 9°C temperature excursion preserves locking; 0.8–2.5 g shocks cause unlocking followed by automatic relocking within 3 s. The measured stable-intensity range is narrower than predicted. Frequency-standard performance remains limited by locking-loop noise and system temperature drift; residual amplitude noise and locking electronics require improvement for better short-term stability.

Little sign of AI-generated textOverclaimsMissing comparison

Central claim may not hold: The abstract attributes the headline power stability to intrinsic optical self-feedback, whereas the Methods establish those exact values only with active temperature control, operating-point optimization, and external MTS frequency locking. The filter's stable regime has approximately intensity-independent transmission rather than negative intensity feedback; the demonstrated power stabilization instead relies on operating-point-dependent compensation between diode gain and frequency-dependent filter loss.

Written by gpt-6.1-sol from the paper's full text. Automated: it can be wrong.

Comments
14 pages, 8 figures

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Numerous quantum devices require lasers strictly locked to atomic transitions. Atom-filtered lasers (AFLs) are considered a leading candidate for quantum device laser sources due to their ability to self-align to atomic transitions. However, the sub-GHz sharp transmission spectra of conventional atomic filters impose constraints on both laser miniaturization and output stability. Herein, we demonstrate a micro Faraday anomalous dispersion optical filter (μFADOF) operating within the extreme hyperfine Paschen-Back regime, generating a 7.5 GHz flat-top transmission window. By integrating this filter, the miniaturization bottleneck of the AFLs is overcome, achieving a 30-fold volume reduction to a compact package volume of 75 mL. Simultaneously, investigations into the optical self-feedback characteristics of the μFADOF reveal a stable operating regime, where the optical self-feedback of the atomic filter acts as a stabilizing mechanism, enabling the laser to achieve a power instability of 9 x 10^-6 at 1 s and 3.2 x 10^-5 at 8400 s. The optical frequency standard based on this 75-mL AFL achieves a further improvement in long-term frequency stability to 3 x 10^-13 at 10000 s and maintains turn-key operation under environmental shocks, highlighting the critical role of this laser in the development of deployable quantum devices.
Atom-filtered lasers use intracavity atomic filters to keep emission near an atomic transition, but conventional narrow transmission windows constrain cavity miniaturization and contribute to power fluctuations. This paper develops a compact rubidium laser using a broadband, flat-top Faraday anomalous dispersion optical filter operated in the hyperfine Paschen–Back regime.
A 10-mm 85^{85}85Rb cell in an inhomogeneous 1000–3550 G magnetic field produces a 7.5 GHz transmission window. Transmission measurements versus optical intensity, supported by susceptibility-based calculations, identify saturable-absorption, intensity-insensitive, and reverse-saturable-absorption regimes. Saturation removes transmission distortions associated with magnetic-field inhomogeneity; the measured stable regime spans approximately 5×1035\times10^35×103–3×104 mW/cm23\times10^4\,\mathrm{mW/cm^2}3×104mW/cm2. Integrating this filter yields a 3.3-cm cavity in a 75-mL package, a reported 30-fold volume reduction, with a 24-kHz linewidth. Free-running wavelength drift stays below 1.5 pm over 42 days without observed mode hops.
With optimized diode current, multistage temperature control, and MTS frequency locking, power Allan deviation reaches 9×10−69\times10^{-6}9×10−6 at 1 s and 3.2×10−53.2\times10^{-5}3.2×10−5 at 8400 s. An MTS-locked optical frequency standard, evaluated against another standard and a hydrogen-maser-referenced frequency comb, reaches fractional instability 3×10−133\times10^{-13}3×10−13 at 10,000 s. A 9°C temperature excursion preserves locking; 0.8–2.5 g shocks cause unlocking followed by automatic relocking within 3 s.
The measured stable-intensity range is narrower than predicted. Frequency-standard performance remains limited by locking-loop noise and system temperature drift; residual amplitude noise and locking electronics require improvement for better short-term stability.
Using laser cooling technology, we demonstrate an ultranarrow-bandwidth Faraday anomalous dispersion optical filter (FADOF) which operates on the52S1/25^{2}\text{S}_{1/2}52S1/2​(F=2F = 2F=2) to62P3/26^{2}\text{P}_{3/2}62P3/2​(F′=3F' = 3F′=3) transition at 420 nm based on cold 87Rb atoms. The filter achieves a single 2.7(2) MHz passband at a peak transmission of 3.2%. It is the narrowest bandwidth FADOF known at present, as the influence of Doppler broadening on the bandwidth narrowing of FADOF is effectively overcome by cold atoms. This ultranarrow-bandwidth FADOF has a figure of merit (FOM) value of 11.85 GHz−1, which is seven times larger than the largest FOM achieved by thermal vapor atomic optical filter published to date. Furthermore, the scheme can be extended to almost all kinds of atomic optical filters and may find applications in active Faraday optical frequency standard and self-stabilizing laser.
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.
An excited state Faraday anomalous dispersion optical filter (ES-FADOF) working at the optical communication wavelength (1.5 μm) is realized. Unlike the usual ES-FADOF schemes using an external frequency stabilization, an internal frequency stabilization scheme is proposed and the working atoms inside the filter are adopted as the reference. A particular cross line of multiple transitions is used for the frequency stabilization for the pump laser and thus, a higher pump efficiency is achieved. For example, compared with previous ES-FADOF schemes, this method can increase the transmittance from 10% to 60% at 100 °C. Moreover, in this scheme, the external frequency stabilization is not necessary and the volume of the atomic filter can be reduced. This simplifies the whole structure and a compact ES-FADOF can thus be realized.
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.
We demonstrate an extended cavity Faraday laser system using an antireflection-coated laser diode as the gain medium and the isotope (87)Rb Faraday anomalous dispersion optical filter (FADOF) as the frequency selective device. Using this method, the laser wavelength works stably at the highest transmission peak of the isotope (87)Rb FADOF over the laser diode current from 55 to 140 mA and the temperature from 15°C to 35°C. Neither the current nor the temperature of the laser diode has significant influence on the output frequency. Compared with previous extended cavity laser systems operating at frequencies irrelevant to spectacular atomic transition lines, the laser system realized here provides a stable laser source with the frequency operating on atomic transitions for many practical applications.
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.