Frequency Stabilization System Research Articles

Synchronous achievement of laser frequency stabilization and tunability via modulation transfer spectroscopy on the rubidium D1 line

In the Spin Exchange Relaxation Free (SERF) magnetometer, the laser frequency must be stabilized at the alkali D1 line and tunable within a range of several gigahertz (GHz). We theoretically and experimentally analyzed the modulated sideband and resonant frequencies on the D1 transition line of rubidium (Rb) atoms using a modulation transfer spectroscopy (MTS) frequency stabilization system. The laser's self-estimated frequency stability shows the Allan deviation of 1.5 × 10−12/τ for resonance peak stabilization and 1.4 × 10−12/τ for sideband stabilization. The spectrum of the modulated laser interacting with the rubidium D1 line exhibits several absorption peaks and MTS signals across a 6 GHz scanning frequency range, which can be used to lock and tune the laser. This method enhances the application of distributed feedback semiconductor lasers in Rb atom-based magnetometers.

Measuring Transverse Relaxation with a Single-Beam 894 nm VCSEL for Cs-Xe NMR Gyroscope Miniaturization.

The spin-exchange-pumped nuclear magnetic resonance gyroscope (NMRG) is a pivotal tool in quantum navigation. The transverse relaxation of atoms critically impacts the NMRG's performance parameters and is essential for judging normal operation. Conventional methods for measuring transverse relaxation typically use dual beams, which involves complex optical path and frequency stabilization systems, thereby complicating miniaturization and integration. This paper proposes a method to construct a 133Cs parametric resonance magnetometer using a single-beam vertical-cavity surface-emitting laser (VCSEL) to measure the transverse relaxation of 129Xe and 131Xe. Based on this method, the volume of the gyroscope probe is significantly reduced to 50 cm3. Experimental results demonstrate that the constructed Cs-Xe NMRG can achieve a transverse relaxation time (T2) of 8.1 s under static conditions. Within the cell temperature range of 70 °C to 110 °C, T2 decreases with increasing temperature, while the signal amplitude inversely increases. The research lays the foundation for continuous measurement operations of miniaturized NMRGs.

Design of voltage and frequency stabilization system for fishing vessel shaft generator based on UPS backup power supply

Abstract A fishing boat shaft generator is a kind of power supply device driven by the main diesel engine, which has the advantage of saving energy compared with a diesel generator and eliminating the need to be equipped with an additional diesel engine, witnessing wide applications in the use of power supply equipment for fishing boats. However, because the shaft generator is mounted on the main diesel engine, the fishing boat encounters bad sea conditions at sea, and the speed of the diesel engine fluctuates, resulting in the instability of the power frequency and voltage sent by the shaft generator, which will endanger the electrical equipment of the fishing vessel in serious cases. In this paper, a design of a voltage and frequency stabilization system for a fishing vessel shaft generator based on a UPS backup power supply was proposed. The system consists of a three-phase shaft generator, inverter, battery, and electrical equipment. The inverter control strategy is introduced, and the battery charge/discharge and DC boost are designed.

Design of a real-time frequency stabilization system for dual laser-based interferometer on EAST.

This study addresses the challenge of intermediate frequency (IF) instability in the far-infrared polarimeter/interferometer (POINT) of the Experimental Advanced Superconducting Tokamak (EAST) to ensure the accuracy and stability of electron density measurements. Sudden and extensive IF shifts of the lasers can cause instability and even measurement errors of the diagnostic system. This paper introduces a comprehensive solution for stabilizing IF fluctuations. First, analog IF is converted into digital form using an analog-to-digital converter, and the digitalized signal is processed by a digital signal system based on a ZYNQ processor. The exact value of the IF is obtained by acquiring the point of maximum amplitude through the fast Fourier transform method, while the ZYNQ processor loaded with a fuzzy control algorithm will precisely adjust the laser cavity length via piezoelectric ceramics, achieving frequency stabilization within a target range. Comparative analyses confirm the method's efficacy in managing sudden frequency shifts, maintaining stability within 850 ± 100kHz (a central frequency of 850kHz, fluctuating within a range of ±100kHz), with a control speed of 0.5s per action and robust against variations up to 270kHz. This efficient and rapid control mechanism fulfills the critical need for IF stabilization, ensuring the stability and precision of the POINT system in the EAST discharge experiments.

Simplified 1.5 μm Distributed Feedback Semiconductor Laser (DFB-LD) Frequency Stabilization System Based on Gas Absorption Chamber

The classical 1.5 μm band frequency-stabilized laser using acetylene gas saturated absorption can achieve high frequency stability and reproducibility, but its system design is complex and bulky. For some practical applications, a simple, compact system containing anti-interference abilities is preferred. In this study, a low-cost and simple-structured 1.5 μm frequency-stabilized laser is constructed using digital control methods, wavelength modulation technology, and acetylene gas absorption. The fiber input and output optical devices of the system significantly simplify the optical path and reduce the volume of the system. The error signal is obtained by the first-order differential method, and a combination of the high-speed comparator circuit and the microcontroller unit (MCU) is used to detect the error signal. Through the feedback control method of coarse temperature adjustment and fine current adjustment, the second-level frequency stability of the laser is stabilized within 100 kHz, that is, the frequency stability reaches 10​−10. The designed system achieved continuous and stable operation for more than 6 h, and the long-term frequency stability reached 10​−9.

Adaptive frequency-stabilization of MEMS oscillators using mode coupling

Microelectromechanical systems (MEMS) oscillators with high frequency stability hold significant potential for a myriad of applications across diverse fields. This letter delves into an adaptive frequency stabilization system designed to significantly improve the performance of MEMS oscillators. Our approach leverages the concept of mode coupling to dynamically adjust the oscillator’s frequency based on phase control, ensuring optimal stability under varying operating conditions. The MEMS oscillator comprises a nonlinear low-frequency resonator and a linear high-frequency resonator. Through mode coupling and phase control, the nonlinear resonator is harnessed to regulate the oscillation frequency of the linear resonator. Experimental results prove that by applying the proposed approach, the frequency stability of the MEMS oscillator is enhanced by nearly 700 times for long-term stability at 1000 s. Additionally, in the scenario with varying temperature, the system also effectively improves the frequency stability by over 1000 times at 802 s.

Near-infrared dual-gas sensor for simultaneous detection of CO and CH4 using a double spot-ring plane-concave multipass cell and a digital laser frequency stabilization system

A novel double spot-ring plane-concave multipass cell (DSPC-MPC) gas sensor was proposed for simultaneous detection of trace gases, which has lower cost and higher mirror utilization than the traditional multipass cell with 129 m, 107 m, 85 m, 63 m and 40 m effective optical path lengths adjustable. The performance of the DSPC-MPC gas sensor was evaluated by measuring CO and CH4 using two narrow linewidth distributed feedback lasers with center wavelengths of 1567 nm and 1653 nm, respectively. An adjustable digital PID laser frequency stabilization system based on LabVIEW platform was developed to continuously stabilize the laser frequency within ∼±30.3 MHz. The Allan deviation results showed that the minimum detection limits for CO and CH4 were 0.07 ppmv and 0.008 ppmv at integration times of 711 s and 245 s, respectively. The proposed concept of DSPC-MPC provides more ideas for the realization of gas detection under different absorption path lengths and the development of multi-component gas sensing systems.

Research on the Frequency Stabilization System of an External Cavity Diode Laser Based on Rubidium Atomic Modulation Transfer Spectroscopy Technology

To achieve high-frequency stability on the external cavity diode laser (ECDL), a 780 nm ECDL serves as the seed light source, and its frequency is precisely locked to the saturated absorption peak of rubidium (Rb) atoms using modulation transfer spectroscopy (MTS) technology. For improving the performance of frequency locking, the scheme is designed to find the optimal operating conditions. Correlations between the frequency discrimination signal (FDS) and critical parameters, such as the temperature of the Rb cell, the power ratio of the probe and pump light, and the frequency and amplitude of the modulation and demodulation signals, are observed to attain the optimal conditions for frequency locking. To evaluate the performance of the frequency-stabilized 780 nm ECDL, a dual-beam heterodyne setup was constructed. Through this arrangement, the laser linewidth, approximately 65.4 kHz, is measured. Then, the frequency stability of the laser, quantified as low as 4.886 × 10−12 @32 s, is determined by measuring the beat-frequency signal with a frequency counter and calculating the Allan variance. Furthermore, using the realized frequency locking technology, the 780 nm ECDL can achieve long-term stabilization even after 25 h. The test results show the exceptional performance of the implemented frequency stabilization system for the 780 nm ECDL.

Modulation-free laser stabilization technique using integrated cavity-coupled Mach-Zehnder interferometer

Stable lasers play a significant role in precision optical systems where an electro-optic laser frequency stabilization system, such as the Pound-Drever-Hall technique, measures laser frequency and actively stabilizes it by comparing it to a frequency reference. Despite their excellent performance, there has been a trade-off between complexity, scalability, and noise measurement sensitivity. Here, we propose and experimentally demonstrate a modulation-free laser stabilization method using an integrated cavity-coupled Mach-Zehnder interferometer as a frequency noise discriminator. The proposed architecture maintains the sensitivity of the Pound-Drever-Hall architecture without the need for any modulation. This significantly simplifies the architecture and makes miniaturization into an integrated photonic platform easier. The implemented chip suppresses the frequency noise of a semiconductor laser by 4 orders-of-magnitude using an on-chip silicon microresonator with a quality factor of 2.5 × 106. The implemented passive photonic chip occupies an area of 0.456 mm2 and is integrated on AIM Photonics 100 nm silicon-on-insulator process.

An upgrade of the primary length standard of Republic of Serbia where digital stabilization is performed by Arduino Due board.

An upgrade of the electronic system for frequency stabilization of the HeNe laser, primary length standard of Republic of Serbia, based on digital electronics, is described. Arduino microcontrollers have been used for stabilization, and laptop computer has been used only to communicate with the user. In addition, an analog electronics has been developed in order to boost the performance of the setup. The setup is simple and inexpensive, made of off-the-shelf electronics components. Despite this, good performances have been achieved.

Towards space-deployable laser stabilization systems based on vibration-insensitive cubic cavities with crystalline coatings.

We present the development of a transportable laser frequency stabilization system with application to both optical clocks and a next-generation gravity mission (NGGM) in space. This effort leverages a 5-cm long cubic cavity with crystalline coatings operating at room temperature and with a center wavelength of 1064 nm. The cavity is integrated in a custom vacuum chamber with dedicated low-noise locking electronics. Our vacuum-mounted cavity and control system are well suited for space applications, exhibiting state-of-the-art noise performance while being resilient to radiation exposure, vibration, shock, and temperature variations. Furthermore, we demonstrate a robust means of automatically (re)locking the laser to the cavity when resonance is lost. We show that the mounted cavity is capable of reaching technology readiness level (TRL) 6, paving the way for high-performance ultrastable laser systems and eventually optical atomic clocks amenable to future satellite platforms.

Integration of a proton exchange membrane fuel cell system for voltage and frequency stabilization in a micro hydro system

This work discusses the frequency and voltage stabilization in a stand-alone self-excited induction generator system (SEIGs) using a fuel cell (FC)-based generation unit. The proposed SEIG acts as the power generator in a microhydro system. Variations in load create fluctuations in voltage and frequency, which have to be stabilized. In this work, authors have proposed integrating a FC-based generation unit with the existing SEIGs to improve its voltage and frequency profiles. For this work, a proton exchange membrane fuel cell (PEMFC) has been considered. Modeling of a 36 kW PEMFC is taken for the proposed work, which has to be integrated with the 22 kW self-excited induction generator. The design of the system and converter parameters have also been included in the work. Authors have proposed an orthogonal current component-based controlstructure that provides independent control of active and reactive power in the system. Considering the FC system working conditions, this article aims to assure optimum power transfer capability between the self-excited induction generator, fuel cell system, and the time-varying loads. The system is exposed to time-varying RL loads dynamic load switching, and the performance is evaluated in real-time. OP 4510 real-time simulator verifies the proposed system's dynamic model created using Matlab/Simulink.

Improved islanded microgrid performance with sliding mode controller based electric spring

In this research manuscript, an innovative solution is proposed to address intermittency challenges in self-excited induction generator-based islanded microgrids. The approach makes the use of an electric spring to maintain a constant voltage across critical loads. For simplifying the design and reduce the need for additional storage devices, and lower costs, a novel voltage source-based electric spring concept is introduced, complete with a comprehensive modelling approach specifically tailored for microgrid applications. Furthermore, a first-order sliding mode controller is suggested to enhance voltage and frequency regulation, stability, and overall system efficiency. This control strategy is designed to linearize voltage errors and provide swift responses under varying steady-state and transient conditions. To validate the effectiveness of the proposed scheme, the model is compared against the widely used quadrature voltage injection scheme under different load and torque conditions. Moreover, the system exhibits a rapid settling time, typically requiring only one to two cycles to stabilize. This underscores the robustness and stability of the controller. The validation of this work is carried out in real-time using an OPAL-RT 4510 and MATLAB/Simulink platform.

Designing an Automatic Frequency Stabilization System for an External Cavity Diode Laser Using a Data Acquisition Card in the LabVIEW Platform

The frequency stability of free-running lasers is susceptible to the influence of environmental factors, which cannot meet the long-term frequency stabilization requirements for atom interferometry precision measurements. To obtain a frequency-stabilized 780 nm laser beam, an automatic frequency stabilization system for an external cavity diode laser (ECDL) based on rubidium (Rb) atomic saturated absorption spectrum was designed using a commercial data acquisition (DAQ) card. The signals acquired by the A/D terminal are processed and analyzed by LabVIEW, which can automatically identify all the locking points and output the piezoelectric ceramic transducer (PZT) scan and digital feedback through the D/A terminal. The experimental results show that the system can lock to six different frequencies separately and realize automatic relocking within 3.5 s after unlocking. The system has a stability of 1.68 × 10−10@1 s and 4.77 × 10−12@1000 s, which meets the laboratory’s requirements for atomic interference experiments.

The Application of Pound–Drever–Hall Technology in High-Resolution Sensing—A Review

Pound–Drever–Hall (PDH) technology is a frequency stabilization technology, which is widely used in laser frequency stabilization systems. The high-frequency stability in this technology has attracted the attention of sensor researchers. In this article, we review the basic principle of PDH technology and introduce the related improved PDH technology. In view of the wide application of PDH technology in high-resolution sensors in recent years, we will introduce the sensors involved in this technology in detail according to the core optical sensing components and their main features. Furthermore, we summarize the physical quantities suitable for high-resolution sensing using PDH technology. The problems and prospects of PDH in high-resolution sensors are presented at the conclusion to assist researchers in clarifying their research directions. This article presents an in-depth analysis of the current state of research regarding PDH-related high-resolution sensor technologies and makes a prognosis regarding the future direction of the high-resolution sensor, which can improve the sensing performance in many areas.

Frequency-Multiplexed Storage and Distribution of Narrowband Telecom Photon Pairs over a 10-km Fiber Link with Long-Term System Stability

The ability to transmit quantum states over long distances is a fundamental requirement of the quantum internet and is reliant upon quantum repeaters. Quantum repeaters involve entangled photon sources that emit and deliver photonic entangled states at high rates and quantum memories that can temporarily store quantum states. Improvement of the entanglement distribution rate is essential for quantum repeaters, and multiplexing is expected to be a breakthrough. However, limited studies exist on multiplexed photon sources and their coupling with a multiplexed quantum memory. Here, we demonstrate the storing of a frequency-multiplexed two-photon source at telecommunication wavelengths in a quantum memory accepting visible wavelengths via wavelength conversion after 10-km distribution. To achieve this, quantum systems are connected via wavelength conversion with a frequency stabilization system and a noise reduction system. The developed system was stably operated for more than 42 h. Therefore, it can be applied to quantum repeater systems comprising various physical systems requiring long-term system stability.

Multi-channel optical radiation frequency stabilization system in geoplositioning systems of mine surveying and geodetic equipment

Multi-channel optical radiation frequency stabilization system in geoplositioning systems of mine surveying and geodetic equipment

Experimental Investigation of an Optical Resonator Gyroscope with a Mach–Zehnder Modulator and Its Sensitive Elements

Today, the task of developing microoptical gyroscopes is topical. Usually, tunable lasers with a built-in frequency stabilization system are used in such gyroscopes. They are comparatively bulky, which hinders the real miniaturization of optical gyroscopes. We propose a new approach implemented by using a Mach–Zehnder modulator with a passive ring resonator connected to one of its arms. This makes it possible to obtain a mutual configuration and makes the use of a tunable laser optional. Two ring resonators made of the polarization-maintaining fiber, suitable for use as sensitive elements of a gyroscope, were realized and investigated. Their Q-factor is equal to 14.5 × 106 and 28.9 × 106. The maximum sensitivity of the proposed method when using the described resonators is 3.2 and 1.8 °/h, respectively. The first experimental setup of a resonator gyroscope implementing this approach has been manufactured and analyzed. When measuring the rotation speed by the quasi-harmonic signal span and its phase, the measurement accuracy was approximately 11 and 0.4 °/s, respectively.

Input optics systems of the KAGRA detector during O3GK

Abstract KAGRA, the underground and cryogenic gravitational-wave detector, was operated for its solo observation from February 25 to March 10, 2020, and its first joint observation with the GEO 600 detector from April 7 to April 21, 2020 (O3GK). This study presents an overview of the input optics systems of the KAGRA detector, which consist of various optical systems, such as a laser source, its intensity and frequency stabilization systems, modulators, a Faraday isolator, mode-matching telescopes, and a high-power beam dump. These optics were successfully delivered to the KAGRA interferometer and operated stably during the observations. The laser frequency noise was observed to limit the detector sensitivity above a few kilohertz, whereas the laser intensity did not significantly limit the detector sensitivity.

Multi-channel laser interferometer based on automatic frequency stabilization system for improving coordinate measurement accuracy

Multi-channel laser interferometer based on automatic frequency stabilization system for improving coordinate measurement accuracy