Timing Jitter Research Articles

Reduction of arrival time jitter or energy spread with arclike variable bunch compressors

Synchronizing free-electron laser pulses for time-resolved experiments is necessary as an unsynchronized system reduces the effective repetition rate of the experiment. Additionally, free-electron laser longitudinal coherence and spectral brightness are limited by electron beam energy spread. In this paper, a variable bunch compressor design and compression schemes were developed to: reduce klystron-induced arrival time jitter by 85% while preserving peak current and transverse emittance and to minimize electron beam correlated energy spread for potential self-seeding or HB-SASE modes. Published by the American Physical Society 2024

Research on Phase Stabilization Algorithm of Femtosecond Timing System

This paper presents the design, implementation, and validation of a femtosecond timing system aimed at achieving precise time control and phase synchronization for large particle accelerators. A prototype system utilizing a continuous wave laser was developed, focusing on minimizing timing jitter and long-term phase drift. Key components include an optical delay line for coarse adjustments and a fiber stretcher for fine-tuning, achieving an adjustment precision of 1 femtosecond. The system incorporates a phase detection module with a non-In-phase/Quadrature downconversion approach, enabling high-accuracy phase measurements. A collaborative algorithm was designed to optimize the interplay between the optical delay line and the fiber stretcher, utilizing a proportional-integral-derivative (PID) control algorithm to enhance adjustment precision. A Field Programmable Gate Array (FPGA) served as the core interface converter, facilitating data communication and real-time phase information acquisition. Experimental results demonstrated significant improvements in phase stability, with average phase deviation reduced from 1374.104 fs to 15.782 fs, showcasing the effectiveness of the proposed system in achieving high precision and stability in phase control. This research provides a solid foundation for future advancements in timing systems for high-frequency reference signals.

Attosecond-precision timing jitter measurement based on temporal sampling method

We propose a timing jitter measurement scheme based on the temporal sampling method. This scheme offers a wide dynamic range and high measurement accuracy for measuring timing jitter between pulses, allowing for attosecond precision in measuring timing jitter of ultrashort pulses with short and long pulse duration. By utilizing a balanced measuring configuration, this scheme is naturally immune to the environmental and laser amplitude noises, and has been successfully used to measure timing jitter of two femtosecond pulses. This scheme can be utilized to measure and control timing jitter in the beam combining systems for generation of ultrafast laser, with high average and peak powers.

1.8-µm pitch, 47-ps jitter SPAD array in a 130 nm SiGe BiCMOS process

We introduce the world’s first SPAD family design in 130 nm SiGe BiCMOS process. At 1.8 µm, we achieved the smallest pitch on record thanks to guard-ring sharing techniques, while keeping a relatively high fill factor of 24.2%. 4×4 SPAD arrays with two parallel selective readout circuits were designed to explore crosstalk and scalability. The SPAD family has a minimum breakdown voltage of 11 V, a maximum PDP of 40.6%, and a typical timing jitter of 47 ps FWHM. The development of silicon SPADs in SiGe process paves the way to Ge-on-Si SPADs for SWIR applications, and to cryogenic optical interfaces for quantum applications.

Amplitude and time response characterization of avalanche signals in InGaAs single-photon avalanche diode

Photon and dark avalanche signals of InGaAs single-photon avalanche diodes (SPAD) are detected and counted indiscriminately, while their specific characteristics are not well understood, which hinders further performance optimization of InGaAs SPAD. Here, we investigate back-incidence InGaAs SPAD operating at room temperature by designing a dual-threshold discriminator and tuning the threshold voltage. The photon count rate and dark count rates (DCR) exhibit different abrupt-voltage variations with the threshold voltage, and the amplitude distribution of dark avalanche signals is more concentrated and slightly larger than that of photon avalanche signals. The smaller photon avalanche signals have a faster time response. It can be inferred that the above characteristics are related to the photon absorption position and carrier transport, depending on physical structure and operating mode, and dark counts are mainly caused by holes drifting from N-type material. We use a dual-threshold discriminator to reduce the time jitter and DCR caused by thermally excited carriers. The experimental results are in good agreement with theoretical analysis, indicating that the insertion of an i-InP layer or the use of a front-incidence technique can further optimize the overall performance and enable InGaAs SPAD with high performance operation at room temperature.

Talbot laser for Airy pulse generation

Abstract We report a C-band fiber Talbot laser—an injection-seeded frequency-shifting active ring cavity operated above threshold—emitting trains of far-field Airy pulses characterized by a dominant cubic spectral phase. Pulses are created by the coherent addition of the recirculating seed wavelength under a large roundtrip first-order dispersion. Single-sided Airy pulse trains with sub-ns pulse widths, 80 MHz repetition rate, and bandwidth exceeding 10 GHz are generated at both integer and fractional Talbot conditions. At detuned Talbot conditions pulses are shown to be tailorable by recirculation-induced first-order dispersion. The far-field character of the resulting waveforms is demonstrated, and the performance in terms of amplitude noise and timing jitter, in this last case after the introduction of active loop stabilization, is evaluated.

PICOSEC-Micromegas Detector, an innovative solution for Lepton Time Tagging

The PICOSEC-Micromegas (PICOSEC-MM) detector is a novel gaseous detector designed for precise timing resolution in experimental measurements. It eliminates time jitter from charged particles in ionization gaps by using extreme UV Cherenkov light emitted in a crystal, detected by a Micromegas photodetector with an appropriate photocathode. The first single-channel prototype tested in 150 GeV/c muon beams achieved a timing resolution below 25 ps, a significant improvement compared to standard Micropattern Gaseous Detectors (MPGDs). This work explores the specifications for applying these detectors in monitored neutrino beams for the ENUBET Project. Key aspects include exploring resistive technologies, resilient photocathodes, and scalable electronics. New 7-pad resistive detectors are designed to handle the particle flux. In this paper, two potential scenarios are briefly considered: tagging electromagnetic showers with a timing resolution below 30ps in an electromagnetic calorimeter as well as individual particles (mainly muons) with about 20ps respectively.

Controllable lasing characteristics in Brillouin random fiber lasers by tailoring gain and random feedback fibers

Brillouin random fiber lasers (BRFLs), the combination of stimulated Brillouin scattering (SBS) gain and random distributed feedback, offer narrow linewidth lasing with simplicity and flexibility. However, BRFLs may not gain broad acceptance unless the fundamental lasing mechanisms governing their operation are fully understood and the lasing properties are effectively manipulated. Here, we demonstrate the control of lasing characteristics in BRFLs by tailoring the SBS gain fiber and the scattering pattern of the random feedback fiber. Experimental results show that BRFLs with 5 cm random fiber gratings (RFGs) feedback exhibit lower intensity fluctuation, longer coherence time, and more stable frequency compared to those with 6 km Rayleigh scattering fiber (RSF) feedback thanks to more correlated phase, lower mode density, and weaker dependence on external variations of RFGs. The low-randomness RFG feedback further improves the coherence time and intensity fluctuation attributed to the small period variation of sub-gratings. Moreover, the BRFL based on the high gain fiber and the strong scattering RFG feedback with low loss achieves high lasing efficiency and low threshold. The frequency jitter, intensity noise, and coherence time are also improved by reducing the gain fiber from 20 km to 1 km due to decreased mode hopping from mode competition. These results clarify the impact of gain and random feedback fibers on BRFL performance, offering insights for optimizing complex laser design for applications requiring high frequency stability and long coherence time.

Dynamic counterpropagating all-normal dispersion (DCANDi) fiber laser

The fiber single-cavity dual-comb laser (SCDCL) is an emerging light-source architecture that opens up the possibility for low-complexity dual-comb pump-probe measurements. However, the fundamental trade-off between measurement speed and time resolution remains a hurdle for the widespread use of fiber SCDCLs in dual-comb pump-probe measurements. In this paper, we break this fundamental trade-off by devising an all-optical dynamic repetition rate difference (Δf rep ) modulation technique. We demonstrate the dynamic Δf rep modulation in a modified version of the recently developed counterpropagating all-normal dispersion (CANDi) fiber laser. We verify that our all-optical dynamic Δf rep modulation technique does not introduce excessive relative timing jitter. In addition, the dynamic modulation mechanism is studied and validated both theoretically and experimentally. As a proof-of-principle experiment, we apply this so-called dynamic CANDi (DCANDi) fiber laser to measure the relaxation time of a semiconductor saturable absorber mirror, achieving a measurement speed and duty cycle enhancement factor of 143. DCANDi fiber laser is a promising light source for low-complexity, high-speed, high-sensitivity ultrafast dual-comb pump-probe measurements.

Self-Suppressed Quantum-Limited Timing Jitter and Fundamental Noise Limit of Soliton Microcombs.

Quantum-limited timing jitter of soliton microcombs has long been recognized as their fundamental noise limit. Here, we surpass such limit by utilizing dispersive wave dynamics in multimode microresonators. Through the viscous force provided by these dispersive waves, the quantum-limited timing jitter can be suppressed to a much lower level that forms the ultimate fundamental noise limit of soliton microcombs. Our findings enable coherence engineering of soliton microcombs in the quantum regime, providing critical guidelines for using soliton microcombs to synthesize ultralow-noise microwave and optical signals.

Relative timing jitter compression in a Fabry–Pérot cavity-assisted free-running dual-comb interferometry

Relative timing jitter compression in a Fabry–Pérot cavity-assisted free-running dual-comb interferometry

Scatter estimation and correction using time-of-flight and deconvolution in x-ray medical imaging.

Objective Time-of-flight (TOF) scatter rejection requires a total timing jitter,
including the detector timing jitter and the X-ray source's pulses width, of 50 ps or less
to mitigate most of the effects of scattered photons in radiography and CT imaging.
However, since the total contribution of the source and detector to the timing jitter
can be retrieved during an acquisition with nothing between the source and detector,
it can be demonstrated that this contribution may be partially removed to improve
the image quality.
Approach A scatter correction method using iterative deconvolution of the measured
time point-spread function estimates the number of scattered photons detected in each
pixel. To evaluate the quality of the estimation, GATE was used to simulate the
radiography of a water cylinder with bone inserts, and a head and torso in a system
with total timing jitters from 100 ps up to 500 ps full-width-at-half-maximum.
Main results With a total timing jitter of 200 ps, 89% of the contrast degradation
caused by scattered photons was recovered in a head and torso radiography, compared
to 28% with a simple time threshold method. Corrected images using the estimation
have a percent root-mean square error between 2 and 14% in both phantoms with
timing jitters from 100 to 500 ps which is lower than the error achieved with scatter
rejection alone at 100 ps.
Significance TOF X-ray imaging has the potential to mitigate the effects of the
scattering contribution and offers an alternative to anti-scatter grids that avoids loss
of primary photons. Compare to simple TOF scatter rejection using only a threshold,
the deconvolution estimation approach has lower requirements on both the source and
detector. These requirements are now within reach of state-of-the-art systems.

Improved echo signal detection for pseudo-random single-photon counting laser ranging

In this paper, a new echo signal detection method, to the best of our knowledge, for pseudo-random single-photon counting ranging (PSPCR) LiDAR systems is proposed, which is applied for long distances, low repetition rates, and system cost reduction. First, in order to achieve a comparable temporal resolution as that in time-correlated single-photon counting (TCSPC) systems, we extend the pseudo-random code to discriminate the minimal time slot in time correlation. Second, we use the full width at half maxima (FWHM) in the duration of each pseudo-random code for correlation to reduce the impact of pulse width variation and timing jitters on ranging accuracy. Third, we study the bias and errors caused by using synchronous signals as the “START” signal, and propose to use the time of flight (ToF) at half energy to reduce the walk error. Simulation results show that, compared with existing PSPCR methods, the proposed method improves ranging accuracy with a lower repetition rate and lower peak and average power—centimeter-level ranging accuracy over tens of kilometers can be achieved using a laser with a repetition rate of 400 kHz, peak power of up to 1 kW, and average power of up to 1 W.

Direct-modulation optoelectronic oscillator for optical pulse and frequency comb generation

We report the generation of an optical pulse train with a 10 GHz repetition rate in a dual loop direct-modulation optoelectronic oscillator (OEO). Pulse generation is achieved using nonlinear compression in the OEO 5-km-long optical delay line. 3 ps pulses with a timing jitter of 13 fs are reported, while the OEO maintains a phase noise of −133dBc/Hz at 10 kHz from the carrier. Two architectures are compared experimentally and theoretically. A frequency comb with a 1.2 THz linewidth at −30dB is generated.

Adaptive feedback control for intelligent phase noise suppression in a figure-9 fiber laser.

Phase noise characteristics of ultrafast fiber lasers are critical to practical applications, such as high-resolution photonics sampling. Herein, we investigated the impact of pump power and linear phase shift difference of counter-propagating light in the nonlinear amplifying loop mirror on phase noise suppression in a figure-9 fiber laser. Based on these results, we proposed a method for intelligent suppression of phase noise through real-time feedback control. By adaptively controlling the linear phase shift difference and pump power, the phase noise can be effectively suppressed in the high offset frequency region even in variable environments. In particular, a reduction of ∼21.40% of integrated timing jitter in the offset frequency region from 10 kHz to 1 MHz was achieved. Our approach was proved to be effective and automatic to obtain ultrafast lasers with low phase noise and may also facilitate the related applications.

Advection-based multiframe iterative correction on PIV fields for improved pressure estimation

A novel method to improve the accuracy of pressure field estimation for advection-dominated flows from time-resolved Particle Image Velocimetry (PIV) data is proposed. Leveraging an advection model we can propagate in time velocity fields from each snapshot. The multiple time-series obtained from time propagation are used to smooth the nonphysical features in the original time-series. This correction is done iteratively. The technique reduces spatial noise by leveraging temporal information while simultaneously correcting temporal jitters using spatial data. Two validation methods are proposed to evaluate the method without knowing the true value of the pressure field. In this paper we provide a proof of the concept using a 3D synthetic dataset based on channel flow and a 2D PIV data set on the wake of a wing foil. Various noise models are tested by superimposing them onto the synthetic dataset, including Gaussian white noise and errors with spatial coherence. The results demonstrate that the proposed method outperforms conventional filters in improving the velocity and pressure fields from noisy velocity data, and in suppressing time jittering of the estimated pressure fields.

Modifying the Kalman Filter for Random Jitter in Sampling Time

Modifying the Kalman Filter for Random Jitter in Sampling Time

Characterization of noise spectra in low-jitter GHz mode-locked fs-laser-inscribed waveguide lasers

We demonstrate low-noise, continuous-wave mode-locking of a diode-pumped Yb:KLuW waveguide laser operating at fundamental repetition rates in the GHz range. Utilizing a femtosecond-laser-inscribed Yb:KLuW channel waveguide laser with a tunable cavity length of a few centimeters, we successfully generate femtosecond pulses near 1030 nm, employing either single-walled carbon nanotubes or semiconductor saturable absorbers. Although timing noise is one of the most critical factors in the implementation of high-repetition-rate laser sources for various applications, investigations into timing noise characteristics in waveguide lasers remain limited. This study fills this gap by presenting timing jitter measurements for GHz mode-locked waveguide lasers with diverse cavity parameters. To quantitatively analyze noise spectral characteristics, including relaxation oscillation processes induced by intensity noise features, we introduce a theoretical modeling approach. The present investigation directly enables the provision of strategies for further suppression of timing jitter and designing high-performance, low-noise mode-locked lasers.

A Prospective Comparative Analysis to Study the Impact on Voice Changes Following Endoscopic Thyroidectomy.

Endoscopic approach has come up as a safe and feasible procedure for thyroidectomy with better cosmetic outcomes. However, concerns over its safety in terms of nerve injury and postoperative voice changes remain. This prospective study evaluated the role of vocal cord function assessment using laryngeal examination and voice analysis in patients who underwent endoscopic hemithyroidectomy either by the trans-oral endoscopic thyroidectomy vestibular approach (TOETVA) or the bilateral axillobreast approach (BABA). Thirty-nine consecutive patients were randomly allocated to either of the 2 groups of endoscopic hemithyroidectomy; 19 in TOETVA and 20 in the BABA groups. Vocal cord function was assessed subjectively using the GRBAS scale and objectively by acoustic analysis of parameters such as jitter, shimmer, mean frequency (F 0 ), noise-to-harmonic ratio (NHR), and maximum phonatory time (MPT) at baseline, postoperative day 10, and 3 months after surgery. There were no significant differences in mean GRBAS scores and values of mean frequency, jitter and shimmer between the 2 groups and on postoperative day 10 and at 3 months compared with baseline. The mean NHR and MPT showed no differences between the 2 procedures. However, there was a significant decrease in their values on day 10 postsurgery, compared with baseline. These values returned to their baseline at 3 months. The other operative parameters were comparable between the 2 groups, except for the shorter mean operative time in the TOETVA group. Perioperative quantitative voice parameters were comparable with no statistically significant difference between the 2 techniques of endoscopic thyroidectomy.

A multi-mass and multi-hit two-camera 3D ion momentum imaging system.

We demonstrate an improved two-camera system for multi-mass and multi-hit three-dimensional (3D) momentum imaging of ions. The imaging system employs two conventional complementary metal-oxide-semiconductor cameras. We have shown previously that the system can time slice ion Newton spheres with a time resolution of 8.8ns, limited by camera timing jitter [J. Chem. Phys., 158, 191104 (2023)]. In this work, a jitter correction method was developed to suppress the camera jitter and improve the time resolution to better than 2ns. With this resolution, full 3D momentum distributions of ions can be obtained. We further show that this method can detect two ions with different masses when utilizing both the rising and falling edges of the cameras.