Low Timing Jitter Research Articles

Below 100-fs Timing Jitter Seamless Operations in 10-GSample/s 3-bit Photonic Analog-to-Digital Conversion

We experimentally realize seamless operations with below 100-fs timing jitter in a 10-GSample/s 3-bit photonic analog-to-digital converter (ADC) with an input 2.5-GHz sinusoidal electrical signal. To address the energy efficiency, it is necessary to explore some serial approaches to get most operations in a photonic ADC done before serial-to-parallel conversion to save the number of devices. To press forward with the work on subsequent operations after optical sampling in a photonic ADC, we have investigated optical quantization and coding and demonstrated their performances. The experimental results successfully demonstrated seamless operations in a photonic ADC, i.e., sampling, quantization, and coding, while keeping its parallel-configuration-free characteristics and low timing jitter below 100 fs. This demonstration could address the energy efficiency by reduction of the number of devices, including electrical ADCs for subsequent operations after optical sampling in existing high-performance photonic ADCs.

InGaAs/InP Single-Photon Detector Gated at 1.3 GHz With 1.5% Afterpulsing

We demonstrate a single-photon detector based on InGaAs/InP single-photon avalanche diodes (SPADs) sinusoidal-gated at 1.3 GHz with very low afterpulsing (about 1.5%), high dynamic range (maximum count rate is 650 Mcount/s), high photon detection efficiency (>30% at 1550 nm), low noise (per-gate dark count rate is 2.2 × 10−5), and low timing jitter (<70 ps full-width at half-maximum). The SPAD is paired with a “dummy” structure that is biased in antiphase. The sinusoidal gating signals are cancelled by means of a common-cathode configuration and by adjusting the relative amplitude and phase of the signals biasing the two arms. This configuration allows us to adjust the gating frequency from 1 to 1.4 GHz and can be operated also in the so-called gate-free mode, with the gate sine-wave unlocked with respect to the light stimulus, resulting in a free-running equivalent operation of the InGaAs/InP SPAD with about 4% average photon detection efficiency at 1550 nm.

Timing-Jitter Reduction by Use of a Spectral Filter in a Broadband Femtosecond Fiber Laser

We demonstrate an experimental reduction of timing jitter in a nonlinear-polarization-evolution-based passively mode-locked fiber laser. This laser operates on the stretched pulse regime at 201 MHz repetition rate. By incorporating a proper bandpass filter (BPF) into the cavity, the effect of the BPF on pulse output characteristics is investigated. The timing jitter of the output pulse is reduced significantly from 29.9 to 17.4 fs (both integrated within 1 kHz-10 MHz) and the full-width at half-maximum is >60 nm. This high repetition rate, low timing jitter, broadband fiber laser could be an excellent candidate for high-speed, and high-resolution photonic analog-to-digital conversion system.

Stable subpicosecond soliton fiber laser passively mode-locked by gigahertz acoustic resonance in photonic crystal fiber core

Ultrafast lasers with high repetition rates are of considerable interest in applications such as optical fiber telecommunications, frequency metrology, high-speed optical sampling, and arbitrary waveform generation. For fiber lasers mode-locked at the cavity round-trip frequency, the pulse repetition rate is limited to tens or hundreds of megahertz by the meter-order cavity lengths. Here we report a soliton fiber laser passively mode-locked at a high harmonic (∼2 GHz) of its fundamental frequency by means of optoacoustic interactions in the small solid glass core of a short length (60 cm) of photonic crystal fiber. Due to tight confinement of both light and vibrations, the optomechanical interaction is strongly enhanced. The long-lived acoustic vibration provides strong modulation of the refractive index in the photonic crystal fiber core, fixing the soliton spacing in the laser cavity and allowing stable mode-locking, with low pulse timing jitter, at gigahertz repetition rates.

Impact of Damping on High-Speed Large Signal VCSEL Dynamics

An investigation of the optimal relaxation oscillation damping for high-speed 850-nm vertical-cavity surface-emitting laser (VCSEL) under large signal operation is presented, using devices with K -factors ranging from 0.1 to 0.4 ns. Time-domain measurements of turn-on transients are used to quantify damping dependent rise times, overshoots, and signal amplitudes. Optical eye diagrams together with timing jitter and bit error rate measurements reveal a tradeoff between the rise time and the duration of the relaxation oscillations. To produce a high-quality eye at a specific data rate, a proper amount of damping is needed to simultaneously obtain sufficiently high bandwidth and low timing jitter. We found that for error-free transmission, a VCSEL with a 0.3 ns K-factor achieved the best receiver sensitivity at 10 and 25 Gb/s, whereas a less damped VCSEL with a 0.2 ns K-factor achieved the best sensitivity at 40 Gb/s.

Research of optical short pulse source with tunable repetition rate and ultra-low timing jitter

The highly stable optical short-pulse generator with high repetition rate is widely applied in many fields of optical communications, such as optical packet switching systems, high-speed analog-to-digital converter systems, wavelength division multiplexing networks, high-speed optical sampling systems and optical time division multiplexing networks. The optical short-pulse generator which is adopted in such systems mentioned above should possess high stability, low timing jitter, the tunability of the repetition-rate, and narrow pulse width. So far, most of the optical short pulses have been generated from the actively mode-locked lasers and the phase-modulated continuous wave lasers. However, both of the two methods require an additional microwave signal source. Consequently, the stability of such an optical short-pulse generator is strictly limited by the phase noise and stability of the additional microwave signal source. Since the concept of an optoelectronic oscillator which includes the generation of low noise optical pulses together with an ultra-low phase noise microwave signal was proposed by Yao in 1996, the optical short-pulse generator based on the optoelectronic oscillator has attracted much attention in recent years. According to this approach, Lasri demonstrated a novel, self-starting optoelectronic oscillator based on an electro-absorption modulator in a fiber-extended cavity for generating an optical pulse stream with high-rate and ultra-low jitter capabilities in 2003. In the scheme, the repetition rate of the generated optical pulses is 10 GHz, and the phase noise is-115 dBc/Hz at 10 kHz. Devgan demonstrated an optoelectronic oscillator by using a gain-switched vertical-cavity surface-emitting laser in a fiber-feedback configuration in 2006. The structure can generate a 2-GHz optical pulse stream with 750-fs timing jitter (over 100 Hz-10 MHz range). In the present paper, a novel optical short-pulse generator with tunable repetition rate and ultra-low timing jitter based on optoelectronic oscillator is demonstrated. The optoelectronic oscillator system can generate the microwave signal with ultra-low phase noise. The continuous wave light directly modulated by this microwave signal is phase modulated twice, and then the optical pulses with remarkable chirping rate are achieved. By optimizing the length of the dispersion compensating fiber, the optical pulses are further compressed. In this experiment, by utilizing a YIG tunable filter, the high-quality and tunable microwave signal within 8-12 GHz is achieved, which demonstrates the tunability of the repetition rate of the optical pulses. When the frequency of the microwave signal (i.e., the repetition rate of the optical pulses) is 9.6 GHz, the measured pulse width and the phase noise are 3.7 ps and-130.1 dBc/Hz at 10 kHz, respectively. Therefore, the timing jitter of the short optical pulse is calculated to be 60.1 fs (over 100 Hz to 1 MHz).

Investigation of GaAs PCSS Triggered by Laser Pulses With Different Parameters

Photoconductive semiconductor switch (PCSS) has many advantages, such as low time jitter, fast response, high repetition rate, compact size, easy integration, and so on. It has extensive applications in the field of pulse power. The laser pulse adopted to trigger the PCSS exerts significant influences to its output characteristics. The parameters to characterize a laser pulse include rise time, pulsewidth, laser energy, wavelength, and so on. In this paper, a new concept of laser power is proposed and the influences that laser pulse exerts to the PCSSs output characteristics are studied. A laser diode that emits laser pulse with a dominant wavelength of 905 ns is employed to trigger a semi-insulating GaAs PCSS, which is vertical structure. Laser energy is fixed to 6.4 μJ by synchronous adjustment of both laser pulsewidth and laser power. Thus, the influences of triggering laser power to the PCSS are studied. The rise times of triggering laser pulses include 10 and 80 ns. The experiment results show that the influences that laser power exerts to the PCSS vary when the rise time of laser pulses differs.

Low timing-jitter and high precise delay generation with coupled ring oscillators

A novel design of delay generator based on a coupled ring oscillators is investigated; it attains a delay resolution near a fully differential buffer delay divided by the number of rings. A three-input fully differential buffer constructed with shunting three N-type metal-oxide-semiconductor field-effect transistors is employed for the coupled ring oscillators. The coupling structure forces the outputs of a linear array of ring oscillators oscillating at the same frequency to be uniformly offset in phase by a precise fraction of a fully differential buffer delay. Experimental results with Taiwan Semiconductor Manufacturing Company 0.35 μm-process technology demonstrate that the delay generator can achieve an output delay resolution of 163 ps at the operating frequency of 245 MHz with low timing-jitter of 75 ps.

Theoretical Considerations in Designing Ultra-High Speed All-Optical Clock Recovery Using Fiber Optical Parametric Amplifiers

In this paper, a new all-optical phase-locked loop (OPLL) in a TDM system is proposed and analyzed. The scheme relies on using fiber optical parametric amplifier (FOPA) device models and theories. In the proposed OPLL, the local clock pulse stream and the received data signal pulses are fed into the FOPA as its pump and amplified signals, respectively. The power of the resulting, relatively, strong idler signal depends on the phase difference between the local clock and the received data signal pulses, and it is used to reveal the OPLL's error signal. We characterize the mathematical structure of the proposed OPLL and identify its three intrinsic sources of phase noises namely, randomness of received data pulses, detector's shot noise, and the FOPA noises such as amplified spontaneous emission (ASE). The ASE noise is reflected in the FOPA's noise figure parametrically. However, the effects of the other two noise sources on the proposed OPLL performance are investigated, using the power spectral densities (PSDs) of the signals involved in the OPLL. Finally, the PSDs are used to obtain a mathematical expression for the OPLL's timing jitter. From the analytical results, our proposed OPLL benefits from the FOPA's inherent large bandwidth and exhibits a very low timing jitter, which is in the order of femtosecond, for an OTDM system with 80 Gbps data rate.

High-precision distribution of highly stable optical pulse trains with 8.8 × 10⁻¹⁹ instability.

The high-precision distribution of optical pulse trains via fibre links has had a considerable impact in many fields. In most published work, the accuracy is still fundamentally limited by unavoidable noise sources, such as thermal and shot noise from conventional photodiodes and thermal noise from mixers. Here, we demonstrate a new high-precision timing distribution system that uses a highly precise phase detector to obviously reduce the effect of these limitations. Instead of using photodiodes and microwave mixers, we use several fibre Sagnac-loop-based optical-microwave phase detectors (OM-PDs) to achieve optical-electrical conversion and phase measurements, thereby suppressing the sources of noise and achieving ultra-high accuracy. The results of a distribution experiment using a 10-km fibre link indicate that our system exhibits a residual instability of 2.0 × 10−15 at1 s and8.8 × 10−19 at 40,000 s and an integrated timing jitter as low as 3.8 fs in a bandwidth of 1 Hz to 100 kHz. This low instability and timing jitter make it possible for our system to be used in the distribution of optical-clock signals or in applications that require extremely accurate frequency/time synchronisation.

Photon-counting laser ranging with InGaAs/InP avalanche photodiode in the passively quenched and 1-GHz sinusoidally gated

We experimentally studied photon-counting laser ranging at 1550nm using InGaAs/InP avalanche photodiode based single-photon detectors (SPDs). The SPDs operated in the passive quenching and 1-GHz sinusoidal gating Geiger modes, corresponding to continuous and quasi-continuous photon-counting ranging, respectively. Despite that the passively quenched SPD provided relatively high effective detection efficiency, quasi-continuous photon-counting ranging excelled the continuous one with fast acquisition speed and improved depth resolution due to the short deadtime and low timing jitter of the SPD in 1-GHz sinusoidally gated mode.

Stability of Optical Frequency Comb Generated With InAs/InP Quantum-Dash-Based Passive Mode-Locked Lasers

In this paper, we present a systematic investigation of passive mode-locked InAs/InP quantum-dash lasers in terms of frequency and timing stability. Mode-locking features are analyzed using the frequency domain approach based on the concept of supermodes. It is shown that the phase of adjacent longitudinal modes is correlated over 1.3-THz frequency span. The observed strong coherence between modes enables low timing jitter and a long-term stability of the repetition rate frequency within 5×10-8 over 100 s.

超导纳米线单光子探测技术进展

Since the first report on superconducting nanowire single photon detector (SNSPD) in 2001, it has turned to be a‘hotspot’in superconducting electronics. As a novel single photon detector (SPD), SNSPD outperforms the traditional semiconducting SPDs in near infrared wavelength with high detection efficiency, low dark count rate, low timing jitter, high counting rate, wide response waveband and simple circuit etc. In this review we give a brief introduction of materials, fabrication process, properties, system integration and frontier applications of SNSPD from the point of view of application, and also discuss the challenge and future development trend of this field.

Sub-20-Attosecond Timing Jitter Mode-Locked Fiber Lasers

We demonstrate 14.3-attosecond timing jitter [integrated from 10 kHz to 94 MHz offset frequency] optical pulse trains from 188-MHz repetition-rate mode-locked Yb-fiber lasers. In order to minimize the timing jitter, we shorten the non-gain fiber length to shorten the pulsewidth and reduce excessive higher-order nonlinearity and nonlinear chirp in the fiber laser. The measured jitter spectrum is limited by the amplified spontaneous emission limited quantum noise in the 100 kHz - 1 MHz offset frequency range, while it was limited by the relative intensity noise-converted jitter in the lower offset frequency range. This intrinsically low timing jitter enables sub-100-attosecond synchronization between the two mode-locked Yb-fiber lasers over the full Nyquist frequency with a modest 10-kHz locking bandwidth. The demonstrated performance is the lowest timing jitter measured from any free-running mode-locked fiber lasers, comparable to the performance of the lowest-jitter Ti:sapphire solid-state lasers.

Energy-time entanglement generation in optical fibers under CW pumping

In this paper, the energy-time entangled photon-pairs at 1.5 μm are generated by the spontaneous four wave mixing (SFWM) in optical fibers under continuous wave (CW) pumping. The energy-time entanglement property is demonstrated experimentally through an experiment of Franson-type interference. Although the generation rates of the noise photons are one order of magnitude higher than that of the photon-pairs under CW pumping, the impact of noise photons can be highly suppressed in the measurement by a narrow time domain filter supported by superconducting nanowire single photon detectors with low timing jitters and time correlated single photon counting (TCSPC) module with high time resolution. The experiment results show that the SFWM in optical fibers under CW pumping provides a simple and practical way to generate energy-time entanglement at 1.5 μm, which has great potential for long-distance quantum information applications over optical fibers.

23 and 39 GHz low phase noise monosection InAs/InP (113)B quantum dots mode-locked lasers

Here we report for the first time a passive mode-locking of single section Fabry-Perot (FP) lasers based on InAs quantum dots(QDs) grown on (113)B InP substrate. Devices under study are a 1 and 2 mm long laser diodes emitting around 1.58 µm. Self-starting pulses with repetition rates around 23 and 39 GHz and pulse widths down to 1.5 ps are observed after propagation through a suitable length of single-mode fiber for intracavity dispersion compensation. A RF spectral width as low as 20 kHz has been obtained leading to a low timing jitter RMS.

An all solid-state high-voltage ns trigger generator based on magnetic pulse compression and transmission line transformer

Innovative design of an all solid-state high-voltage ns trigger generator, based on magnetic pulse compression and transmission line transformer, is presented. The repetitive trigger pulse generator was developed to trigger a 700 kV trigatron, which has been used to pulse a repetitive intense electron beam accelerator with Tesla transformer charged double pulse forming lines (PFLs). Experimental results show that the trigger pulse generator could produce 180 kV 65 ns duration pulses with a rise time of 20 ns. The repetitive trigger pulses have nice uniform in the voltage waveform. The control time jitter is less then 3 ns. Owing to its good stability and low time jitter, the high-voltage trigger generator is an excellent candidate to trigger the repetitive accelerator.

40-GHz $S$-and $L$-Band Dual-Wavelength Pulse Source Using Fiber Optical Parametric Oscillator

We demonstrate a 40-GHz dual-wavelength pulse source in S-and L-band on the basis of harmonically mode-locked fiber optical parametric oscillator. Through leveraging, a 150-m highly-nonlinear dispersion-shifted fiber with a positive β(4), good quality, and low timing jitter pulse trains in both S- and L-band can be generated simultaneously. Its tuning range is as wide as 71 nm, from 1507 to 1542 nm and from 1570 to 1606 nm, with a wavelength span of ~100 nm. The proposed scheme has the potential to become an efficient high repetition rate pulse source for optical communication beyond conventional wavelength band.

Fabrication and Testing of Metal Foil Planar Switch

Abstract A metal foil spark gap switch is fabricated by using the magnetron sputtering deposition technology and the standard microelectronic technology. The switch consists of two main electrodes and a trigger electrode. Stylus profiler is used to measure the distance between the main electrode and the trigger electrode. The discharge characteristics of the metal foil spark gap switch are discussed. The switch has short delay time and low time jitter. When it is fired by a conventional capacitive discharge unit (CDU), the firing circuit has low inductance and resistance. Because of its low profile structure, it can be easily integrated with the bridge foil used in a conventional exploding foil initiator system (EFIS).

Waveguide integrated low noise NbTiN nanowire single-photon detectors with milli-Hz dark count rate

Superconducting nanowire single-photon detectors are an ideal match for integrated quantum photonic circuits due to their high detection efficiency for telecom wavelength photons. Quantum optical technology also requires single-photon detection with low dark count rate and high timing accuracy. Here we present very low noise superconducting nanowire single-photon detectors based on NbTiN thin films patterned directly on top of Si3N4 waveguides. We systematically investigate a large variety of detector designs and characterize their detection noise performance. Milli-Hz dark count rates are demonstrated over the entire operating range of the nanowire detectors which also feature low timing jitter. The ultra-low dark count rate, in combination with the high detection efficiency inherent to our travelling wave detector geometry, gives rise to a measured noise equivalent power at the 10−20 W/Hz1/2 level.