Long-term Frequency Stabilization Research Articles

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.

Enhancing long-term frequency stability of a single-mode optoelectronic oscillator based on phase conjugation.

We propose and experimentally demonstrate what we believe to be a novel single-mode optoelectronic oscillator (OEO) with low frequency drift based on phase conjugation. The long-term frequency stabilization of the OEO is achieved by using photonic microwave phase-conjugate passive compensation. Besides, since there happens to be a nonlinear coupled double loop structure in the OEO, single-mode oscillation can be achieved. The experimental results show that the side mode suppression ratio (SMSR) of the radio frequency (RF) signal from the OEO at 9.93 GHz is enhanced from 5 dB to 68 dB after side mode suppression, and the maximum frequency drift within 600 s reduced from 1.51 ppm to 0.04 ppm, optimized by a factor of about 40. The OEO has a simple structure, no external injection, and the phase noise is not limited by the injected signal.

Digital long-term laser frequency stabilization with an optical frequency comb.

Laser frequency stabilization plays an important role in high-precision spectroscopic measurements. Since high-accuracy commercial wavemeters became available, wavemeter-based frequency stabilization has found a broad application due to its convenience, flexibility, and wide applicability. However, such stabilization schemes frequently suffer from long-term drift, since the accuracy of the wavelength measurement of a wavemeter is affected by ambient temperature fluctuation. In this work, we demonstrate that such long-term drift can be suppressed by regularly calibrating the frequency of a wavemeter-locked laser utilizing an optical frequency comb, which has much better long-term stability. Under this dual-referenced locking scheme, the Allan deviation is reduced to 3.5 E-12 at 4000 s for a fiber laser operated at 548 nm, which when used in the optical Ramsey spectroscopic measurement of 7Li+, reduces the standard deviation by as much as 40%, compared to the case when only wavemeter locking is applied.

A Frequency-Stable Optoelectronic Oscillator Based on Passive Phase Compensation

A novel passive phase compensated optoelectronic oscillator (PPC-OEO) with low frequency drift is proposed and experimentally demonstrated. It consists of a main oscillation loop and a compensation path. A passive phase compensation technique (PPCT) is adopted for the long-term frequency stabilization of the OEO. Once the optoelectronic oscillation is established, the OEO output frequency is stably locked to twice the frequency of an external signal injected into the compensation path. The experimental results show that the frequency drift of the generated radio frequency (RF) signal at 10 GHz is about 5 Hz over 6 hours. The simple structure of the proposed OEO, without any temperature control or active servo control, makes it highly reliable.

Solid-state generator of EHF range with increased long-term frequency stability

A method for long-term frequency stabilization of a solid-state generator of the EHF range by maintaining a constant temperature of the resonant system is described. An open resonator with resonant frequency mainly determined by its length is used. The resonator temperature was controlled by a semiconductor sensor and the temperature stabilization was carried out using Peltier elements connected between the fuel element (Gunn diode) and the radiator. The multi-link matching of the active element and the open resonator, which rarefy the spectrum of the output signal in both transverse and longitudinal types of oscillations, was used to match a high-Q open resonator with a low-impedance source of electrical oscillations. The generation frequency with the Gunn diode was 36 GHz, the modulation characteristic of the generator S = Δfг /ΔUД = 6 MHz / V, output power was not less than 50 mW, accuracy of temperature control t = ± 1 0C in the range of external temperature changes -20 - + 30 0C, operating temperature was 35 0C. As a result, the open resonator generator had a frequency drift of less than 0.5 MHz for 7 hours. For comparison, the frequency drift of a similar generator with a waveguide resonator for the same time was about 20 MHz. In addition, the generator with an open resonator and thermal stabilization entered the frequency stabilization mode earlier. Frequency stability, estimated by the labels of the spectrum analyzer, is not worse than 1 ∙ 10-7 min-1. Long-term temperature stability (Δf/f)/ΔТ = ±1·10-6/0C. It should be noted that the resonator is excited on a quasi-basic type of oscillation, which allows additional frequency tuning by changing the length L of the resonator ~ 0.25 GHz with a decrease in the output power by 3 dB. A similar method could be used to create a solid-state sources with long-term stability in the 150-300 GHz frequency range.

Microcontroller based scanning transfer cavity lock for long-term laser frequency stabilization.

We present a compact all-digital implementation of a scanning transfer cavity lock (STCL) for long-term laser frequency stabilization. An interrupt-driven state machine is employed to realize the STCL with the capability to correct for frequency drifts in the slave laser frequency due to measured changes in the lab environmental conditions. We demonstrate an accuracy of 0.9 MHz for master laser and slave laser wavelengths of 556 nm and 798 nm as an example. The slave laser is also demonstrated to dynamically scan over a wide frequency range while retaining its lock, allowing us to accurately interrogate atomic transitions.

基于波长计实现多路激光的长稳锁定

基于波长计实现多路激光的长稳锁定

532 nm测风激光雷达长时间稳频系统

532 nm测风激光雷达长时间稳频系统

Long-Term Frequency Stabilization of 10-GHz Quantum-Dash Passively Mode-Locked Lasers

This paper reports on the repetition frequency stability of InAs/InP quantum-dash-based mode locked lasers emitting in the 1.55-μm telecom window and of a long-term frequency stabilization schemes. We discuss the main noise sources that affect the frequency stability. In free running operation, quantum-dash-based mode locked lasers demonstrate an initial long-term stability of $\sim 10^{-7}$ . In order to improve it, we developed different approaches based on electrical feedback and optical feedback loops. The stabilization systems exploit the bias-dependent frequency drift and the optical feedback sensitivity to keep repetition frequency in lock for an extensive period of time with a stability of $1.5 \times 10^{-9}$ .

Long-term laser frequency stabilization using fiber interferometers.

We report long-term laser frequency stabilization using only the target laser and a pair of 5 m fiber interferometers, one as a frequency reference and the second as a sensitive thermometer to stabilize the frequency reference. When used to stabilize a distributed feedback laser at 795 nm, the frequency Allan deviation at 1000 s drops from 5.6 × 10(-8) to 6.9 × 10(-10). The performance equals that of an offset lock employing a second, atom-stabilized laser in the temperature control.

Simple digital system for tuning and long-term frequency stabilization of a CW Ti:Sapphire laser

We have implemented a simple digital system for long-term frequency stabilization and locking to an arbitrary wavelength of the single-frequency ring CW Ti:Sapphire laser. This system is built using two confocal Fabry-Pérot cavities, one of which is used to narrow the short-term linewidth of the laser and the other to improve the long-term stability of the laser frequency. The length of the second cavity is stabilized using the radiation from an external-cavity diode laser locked to an atomic transition. Our system is an improvement of a commercial Tekhnoscan laser lock. This system has been successfully used in our experiments on high-resolution laser spectroscopy of ultracold rubidium Rydberg atoms.

A Feedback Control Loop for Frequency Stabilization in an Opto-Electronic Oscillator

A new method for the long-term frequency stabilization of an opto-electronic oscillator (OEO) is proposed. All existing methods are based on the precise temperature stabilization of specific components of an OEO, for example, the optical fiber and the microwave band-pass filter. We propose a new method based on a feedback control loop that detects the oscillator frequency using a frequency discriminator and modifies the laser wavelength to keep the oscillator frequency constant using the fiber chromatic dispersion. With the proposed method we achieved a frequency-temperature coefficient of 0.2 ppm/K. Unlike previous methods, our method also compensates the effects of other unstabilized OEO components on the OEO's frequency. Other benefits are that there is no need for an accurate temperature stabilization of the optical fiber and mode hopping is prevented.

Long-Term Frequency Stabilization of an Optoelectronic Oscillator Using Phase-Locked Loop

We demonstrate an approach of long-term frequency stabilization of a single-loop optoelectronic oscillator (OEO) with a phase-locked loop (PLL). The OEO is frequency locked to a highly stable microwave reference via a PLL circuit with a PID regulator. With this approach, we obtained a highly stable 3.035-GHz microwave signal with phase noise of −65 dBC/Hz at 10-Hz offset frequency, and the frequency stability has reached 6.98 × 10−14 at average time of 1000 s. These experimental results show that the PLL-locked OEO is greatly improved in both long-term frequency stability and phase noise performance at low offset frequencies. Therefore, the PLL-locked OEO can be a strong candidate of highly stable, low phase noise microwave generators for microwave photonics applications.

A long-term frequency stabilized deep ultraviolet laser for Mg+ ions trapping experiments

As many precision laser spectroscopy experiments require frequency stabilized lasers, development of long-term stabilized lasers is of great interest. In this work, we report long-term frequency stabilization of a 280 nm deep ultraviolet laser to a high precision wavemeter with digital servo control such that the long-term drift of the laser frequency was greatly reduced. Long-term laser frequency drift was measured with a fiber frequency comb system over 8 h. After locking, the maximum drift rate of the 280 nm laser was lowered from 576 MHz/h to 6.4 MHz/h. With proper environment control of the wavemeter, the maximum drift rate of the 280 nm laser was further lowered to less than 480 kHz/h. The locked laser system was successfully used in a Mg(+) ions trapping experiment, which was also discussed in this work.

Long-Term Repetition Frequency Stabilization of Passively Mode-Locked Fiber Lasers Using High-Frequency Harmonic Synchronization

Long-term repetition frequency stabilization of passively mode-locked (ML) fiber lasers using high-frequency harmonic synchronization is investigated. First, the standard cavity length controlling-based stabilization scheme is studied mathematically, and its disadvantages in high-frequency harmonic synchronization are analyzed. Theoretical studies are then carried out to prove that by modulating the pump power of lasers, the disadvantages can be overcome, and high-stability stabilization with low noises can thus be achieved. Based on the studies, an improved frequency stabilization scheme for passively ML fiber lasers is proposed. Its performances are evaluated by synchronizing a high-frequency harmonic of an ML laser with a 3.035-GHz reference microwave signal. Results show that the residual phase noise for the stabilization (synchronization) reaches around ${-}{100}~{\rm dBc}/{\rm Hz}~({-}{\rm 120}~{\rm dBc}/{\rm Hz})$ at 3-Hz (10 KHz) offset frequency, which results in 14.9 fs (21.2 fs) timing jitter integrated from 1 Hz to 0.1 MHz (1 MHz). The long-term (2 h) phase drift is less than 12 fs for in-loop measurement. For out-of-loop measurement, the drift is ${\sim}{\rm 74}~{\rm fs}$ , while the measurement setup itself brings a drift of ${\sim}{\rm 55}~{\rm fs}$ . The research provides deep studies for frequency stabilization of passively ML fiber lasers and can benefit their applications in various areas.

Long-term frequency stabilization of a 16 m^2ring laser gyroscope

A 16 m(2) helium-neon-based ring laser gyroscope has been frequency stabilized to within 60 kHz over a period of three months. This is achieved using the beat frequency of the ring laser and an iodine-stabilized reference laser as a feedback signal on a pressure vessel enclosing the entire laser, under servo control. We demonstrate that we can compensate for, and thereby negate the influence of, atmospheric pressure variations, which are considerable sources of long-term instability.

Long-term frequency stabilization system for external cavity diode laser based on mode boundary detection

We have realized a long-term frequency stabilization system for external cavity diode laser (ECDL) based on mode boundary detection method. In this system, the saturated absorption spectroscopy was used. The current and the grating of the ECDL were controlled by a computer-based feedback control system. By checking if there are mode boundaries in the spectrum, the control system determined how to adjust current to avoid mode hopping. This procedure was executed periodically to ensure the long-term stabilization of ECDL in the absence of mode hops. This diode laser system with non-antireflection coating had operated in the condition of long-term mode-hop-free stabilization for almost 400 h, which is a significant improvement of ECDL frequency stabilization system.

Fast scanning cavity offset lock for laser frequency drift stabilization

We have implemented a compact setup for long-term laser frequency stabilization. Light from a stable reference laser and several slave lasers is coupled into a confocal Fabry-Perot resonator. By stabilizing the position of the transmission peaks of the slave lasers relative to successive peaks of the master laser as the length of the cavity is scanned over one free spectral range, the long-term stability of the master laser is transferred to the slave lasers. By using fast analog peak detection and low-latency microcontroller-based digital feedback, with a scanning frequency of 3 kHz, we obtain a feedback bandwidth of 380 Hz and a relative stability of better than 10 kHz at timescales longer than 1 s, a significant improvement on previous scanning-cavity stabilization systems.

数字伺服系统实现激光器频率长期锁定

数字伺服系统实现激光器频率长期锁定

Long-term frequency stabilization of a continuous-wave tunable laser with the help of a precision wavelengthmeter

For the first time to our knowledge we experimentally demonstrate an efficient method for the reduction of long-term radiation line drift in single-frequency cw Ti:sapphire and dye lasers that relies on a fast and precise wavelengthmeter together with a digital-analog feedback system. Generation line drift of lasers is reduced approximately by an order of magnitude down to 40 MHz/h, which corresponds to the residual drift in readings of the wavelengthmeter itself. The implemented automatic frequency control system allows us to lock the laser generation frequency to a specified absolute value. This approach may be used in single-frequency lasers of different types (solid-state, fiber, diode, dye lasers, etc.) and allows reduction by an order of magnitude or more of the long-term generation line drift in lasers that are not equipped with other systems for long-term stabilization of output radiation frequency.