We report a miniaturized photonic-atomic laser, comprising a monolithic ultra-high-Q Fabry-Perot cavity integrated with a micromachined rubidium vapor cell. Leveraging the frequency-stability of the cavity and the atoms, we realize an atomic stable ultranarrow-linewidth laser.
Abstract Lasers with high spectral purity can enable a diverse application space, including precision spectroscopy, coherent high‐speed communications, physical sensing, and manipulation of quantum systems. Already, meticulous design and construction of bench Fabry–Perot cavities has made possible dramatic achievements in active laser‐linewidth reduction, predominantly for optical‐atomic clocks. Yet, there is increasing demand for miniaturized laser systems operating with high performance in ambient environments. Here, a compact and robust photonic‐atomic laser comprising a 2.5 centimeter long, 20 000 finesse, monolithic Fabry–Perot cavity integrated with a micromachined rubidium vapor cell is presented. By leveraging the short‐time frequency stability of the cavity and the long‐time frequency stability of atoms, an ultranarrow‐linewidth laser that enables integration for extended measurements is realized. Specifically, the laser supports a fractional‐frequency stability of at an averaging time of 20 millisecond, at 300 second, an integrated linewidth of 25 Hz that results from thermal noise, frequency noise floor as low as 0.06 Hz2 Hz−1, and a passive vibration immunity as low as 10−10 g−1. The present work explores hybrid laser systems with monolithic photonic and atomic packages based on physical design.
Precision atomic and quantum experiments rely on ultra-stable narrow linewidth lasers constructed using table-top ultra-low expansion reference cavities. These experiments often require multiple lasers, operating at different wavelengths, to perform key steps used in state preparation and measurement required in quantum sensing and computing. This is traditionally achieved by disciplining a cavity-stabilized laser to a key atomic transition and then transferring the transition linewidth and stability to other lasers using the same reference cavity in combination with bulk-optic frequency shifting such as acousto-optic modulators. Transitioning such capabilities to a future potentially low-cost photonic-integrated platform will enable a wide range of portable, low power, scalable quantum experiments and applications. Yet, today’s bulk optic approaches pose challenges related to lack of cavity tunability, large free spectral range, and limited photonic integration potential. Here, we address these challenges with demonstration of an agile photonic-integrated 780 nm ultra-high-Q tunable silicon nitride reference cavity that performs multiple critical experimental steps including laser linewidth narrowing, high resolution rubidium spectroscopy, dual-stage stabilization to a rubidium transition, and stability transfer to other lasers. We achieve up to 20 dB of frequency noise reduction at 10 kHz offset, precision spectroscopy over a 250 MHz range, and dual-stage locking to rubidium with an Allan deviation of 8.5 × 10 −12 at 1 s and up to 40 dB frequency noise reduction at 100 Hz frequency offset. We further use the rubidium-disciplined cavity to provide atomic-referenced frequency stability to a second laser and demonstrate multi-wavelength Rydberg electrometry quantum sensing. These results pave the path for integrated, compact, and scalable solutions for quantum sensing, computing, and other atomic and trapped ion applications.
This work introduces an innovative optical frequency standard that leverages MEMS vapor cells to achieve exceptional stability. To attain these objectives, we have integrated the modulation transfer spectroscopy (MTS) technique, which not only ensures high stability but also contributes to minimal power consumption in a compact form factor. Employing MTS with a high signal-to-noise ratio and utilizing a full bandwidth, high-speed servo feedback, we have successfully stabilized the laser frequency at the hyperfine transitions of rubidium atomic lines within the MEMS vapor cell. Furthermore, after the laser is locked, there is a significant narrowing effect on the laser linewidth. The current specifications of our compact optical frequency standard include a frequency Allan deviation of 4.8E-13@1s and the laser linewidth of only 18 kHz.
High precision portable and deployable frequency standards are required for modern navigation and communication technologies. Optical frequency standards are attractive for their improved stability over their microwave counterparts; however, increased complexities have anchored them in the laboratory. Sacrificing sensitivity of the most stable optical clocks has led to the recent development of deployable and portable optical frequency standards, leveraging hot atomic or molecular vapor. The short term limit for a majority of previous reports on two-photon rubidium standards is either the shot-noise or intermodulation limit hindering the one second fractional frequency stability to around 1×10−13/τ. The answer for the shot-noise limit is to increase optical power and collected fluorescence, while the intermodulation limit solution requires improvements in laser linewidth, stimulated Brillouin scattering (SBS) lasers are known to reduce frequency noise, suppressing noise of the pump laser at high offset frequencies. We investigate an optical frequency standard based on the two-photon transition in 87Rb probed with a narrow linewidth photonic integrated circuit SBS laser with a quality factor over 130 million and instantaneous linewidth < 10 Hz. The use of a narrow linewidth clock laser coupled with operating at higher optical intensities yields clock instabilities of 2×10−14 at one second, currently the best reported short-term stability for a two-photon rubidium optical frequency standard.
We report on the atomic spectroscopy and laser frequency stabilization using a new type of a miniaturized glass vapor cell with a scalable thickness varying from 500 nm up to 8 μm. The cell is fabricated by lithography and etching techniques in a Pyrex glass substrate, followed by anodic bonding. It is filled with rubidium vapor using a distillation procedure. This simple and cost-effective fabrication method provides an attractive and compact solution for atomic cells, with applications in quantum metrology, sensing, communication, and light-vapor manipulations at the subwavelength scale. Using the fabricated cell, we have performed fluorescence and transmission spectroscopy of the Rubidium D2 line and observed sub-Doppler broadened lines. As an example, for a potential application, we have used the fabricated cell to demonstrate the stabilization of a 780 nm diode laser to the level about 10−10 in fractional frequency.