Measurement of the timing jitter and pulse energy fluctuation of aPLL regeneratively mode-locked fiber laser

We measured the timing jitter and pulse energy fluctuation from the noise RF power spectra of a 10-GHz regeneratively mode-locked erbium-doped fiber laser in both free-running and phase-locked-loop (PLL) operation. The measured timing jitter was 90 and 120 fs for free-running and PLL operation, respectively. These values are to our knowledge the smallest timing jitter reported in actively mode-locked fiber lasers. The pulse energy fluctuation was 0.24% for both operation     

Noise of the stretched pulse fiber laser. I. Theory

A perturbation formalism is developed for the passively mode-locked stretched pulse fiber ring laser analogous to that of the fiber ring soliton laser. It is applied to determine the amplitude fluctuations, carrier frequency noise, and the pulse to pulse jitter due to the amplifier spontaneous emission noise     

锁模Cr4+:YAG固体激光器脉冲的时间抖动理论性分析

固体激光器的脉冲稳定性限制了激光器在很多方面的应用.从被动锁模Cr4 :YAG激光器腔内脉冲的传播方程出发,得到了带噪声的非线性Schr(o)dinger方程,进一步分析了脉冲在激光器腔内的时间传播形式,建立了锁模Cr4 :YAG固体激光器振荡脉冲参数的线性扰动方程,推导出了脉冲参数波动的动力学方程以及时间和相位的均方根波动关系式.提出了一个减少锁模Cr4 :YAG固体激光器脉冲时间抖动的实验方案,旨为锁模Cr4 :YAG固体激光器能够用作光纤通信和量子通信中的光源提供理论上的帮助.     

Optical Pulse Characterization in a Regeneratively Mode-Locked Fiber Ring Laser

We characterize optical pulses generated using a regeneratively mode-locked fiber ring laser (RML-FRL) in terms of pulsewidth and pulse noise. These results are then compared with pulses obtained from a conventional active harmonically mode-locked fiber ring laser (ML-FRL). We establish that under the same operating conditions, optical pulses from the RML-FRL are shorter by more than 8% and exhibit a 15-dB improvement in phase noise compared to those obtained from ML-FRL. In addition, over a frequency range 100 Hz–100 kHz, a reduced amplitude noise of 0.3% and rms timing jitter of 0.26 ps have been estimated for the RML-FRL pulses compared to 0.6% and 0.38 ps, respectively, for the pulses in the ML-FRL. Relaxation oscillations are also completely eliminated in the RML-FRL.     

High-quality photonic sampling streams from a semiconductor diodering laser

We report on the development of an ultralow-noise, external-cavity, actively mode-locked semiconductor diode laser for application in next-generation photonic sampling systems. A summary of harmonically mode-locked noise characteristics in a 65-MHz ring cavity is presented through the range of pulse repetition frequencies between 130 MHz and 8.3 GHz (2nd-128th harmonic). Important implications regarding the use of gain-versus-loss modulation as the active modelocking mechanisms are discussed. We also report what are, to our knowledge, the lowest noise characteristics achieved to date for a semiconductor diode laser operating at 10 GHz. Individually optimized results of 0.12% rms amplitude noise (10 Hz-10 MHz), and 43 fs rms residual phase jitter (10 Hz-10 MHz) provide a theoretical resolution of 8.6 bits in a 10-GSPS optical analog-to-digital converter. We have also achieved dispersion-compensated pulsewidths; as short as 1.2 ps, and shown successful operation of a novel phase-locked-loop capable of reducing the rms; residual phase noise by as much as 91% within its response bandwidth. Finally, the first measurements of residual phase noise out to the Nyquist frequency (5 GHz) are presented, providing an upper bound on the rms residual phase jitter of 121 fs (10 Hz-5 GHz)     

Noise characterization of mode-locked color-center laser sources

By using an ultrahigh-speed photodetector and wide bandwidth spectrum analyzer combinations, a noise characterization of the pulse train from a mode-locked KCl:Tl color-center laser has been performed. Amplitude and phase (timing jitter) noise content are quantified and compared when the laser is operated in both synchronously mode-locked and coupled-cavity mode-locked configurations. By deliberately mismatching the color-center laser cavity frequency with respect to that of the Nd:YAG pump-laser and examining resultant noise burst power spectra, it has been confirmed that the coupled-cavity mode-locking process exhibits passive characteristics     

Noise of the stretched pulse fiber laser. II. Experiments

For pt.I see ibid., p.649, 1997. The noise characteristics of the stretched pulse fiber ring laser are determined from the power spectrum of the current of a detector illuminated by the output pulse train. Amplitude fluctuations as low as 0.05% of the pulse energy and jitter <80 fs (measurement time=0.09 s) are obtained with no external stabilization. These are the lowest noise levels reported to date for a passively mode-locked laser. The experimental results are compared with the noise theory of the companion paper. Good agreement is obtained between theory and experiment. Comparison with theory also shows that the jitter at frequencies higher than 60 Hz is due to amplified spontaneous emission (quantum) fluctuations when the measurement time is on the order of 0.1 s     

Low-noise operation modes of a passively mode-locked fiber laser

Optimum low-noise operation modes of a passively mode-locked fiber laser are described and characterized. The laser produces 60 fs bandwidth limited pulses with root mean square amplitude fluctuations of 0.4% in a frequency-band from 30 Hz to 100 kHz. It is shown that low-noise operation up to 5 dB below the amplitude noise of the pump laser is possible with overall negative cavity group-velocity dispersion and a large difference between the intracavity loss under free-running and mode-locked laser operation. Additional frequency stabilization reduces the timing jitter to 4 fs in a frequency band from 1 kHz to 100 kHz and 110 fs in the 30 Hz to 100 kHz band     

Noise characterization of a regeneratively mode-locked fiber ringlaser

A regeneratively mode-locked fiber ring laser (RML-FRL) and an active harmonically mode-locked fiber ring laser (ML-FRL) have been characterized for both amplitude and phase noise by investigating the detected RF spectra of the optical pulse trains. Quantification of noise in the optical pulses reveals that the stability of the RML-FRL in terms of noise performance is superior to its ML-FRL counterpart. The optical pulse noise was measured over a frequency band of 100 Hz to 100 kHz and it was found that the pulse amplitude noise reduced from 0.6% in the ML-FRL to 0.3% in the RML-PRL. The total rms noise in the detected optical pulses from the RML-FRL improved by more than 30% compared to that measured for the ML-FRL, with a phase noise improvement of 15 dB at 100 kHz offset frequency from the carrier. An rms timing jitter of 0.38 ps was estimated in the optical pulse train from the ML-FRL, which reduced to 0.26 ps in the RML-FRL. In addition, complete elimination of the relaxation oscillations noise spikes in the detected RF spectrum of the optical pulses from the RML-FRL has been observed     

Low Noise Performance of Passively Mode-Locked 10-GHz Quantum-Dot Laser Diode

We present a detailed investigation of the radio-frequency (RF) linewidth and noise performance of a 10-GHz packaged monolithic two-section quantum-dot mode-locked laser diode. Record low 500-Hz RF linewidths are reported under passive mode-locking operation, and the single sideband phase noise spectra and associated timing jitter performance under both passive and hybrid mode-locking is investigated.      

Theory of timing jitter in actively mode-locked lasers

An analysis of the pulse-to-pulse timing jitter in an actively mode-locked laser is presented. The model includes spontaneous emission noise, mode-locker driver phase noise, and cavity length detuning. Analytical expressions for the laser pulse train phase noise spectrum, the intensity power spectrum, and the RMS timing jitter are given. The timing fluctuations are characterized by a time constant proportional to the cavity round-trip time times the number of locked modes squared divided by the modulation depth. The contribution from the mode-locker driver phase noise will dominate unless high-stability RF sources are used. The residual timing jitter due to spontaneous emission noise is very sensitive to cavity detuning     

Pulse repetition frequency multiplication via intracavity opticalfiltering in AM mode-locked fiber ring lasers

We demonstrate pulse repetition frequency multiplication in AM mode-locked fiber ring lasers using optical filtering realized via an intracavity fiber Fabry-Perot filter (FFP) and show that the generated optical pulses are highly stable in amplitude noise and timing jitter. A 3.477-GHz optical pulse train is generated using a modulation signal of 869.284 MHz, a fourth subharmonic multiple of the 3.48-GHz free spectral range of FFP. The generated optical pulses exhibit a high degree of pulse stability in terms of a large suppression of supermode noise, a low amplitude noise of 0.93 %, and a timing jitter of 1.2 ps     

Universality of mode-locked jitter performance

It is shown experimentally that the jitter of actively mode-locked laser pulses is determined by two factors: first, by spontaneous noise associated with cavity loss, and second, by round-trip propagation time. As the round-trip time is increased, a characteristic frequency which defines the high-frequency limit of phase noise decreases. For a comparable round-trip time and cavity loss, the jitter of mode-locked lasers based on diverse gain media, whether semiconductor or erbium ion is universal and independent of the upper-state transition lifetime.     

Self-Stabilization of an Actively Mode-Locked Semiconductor-Based Fiber-Ring Laser for Ultralow Jitter

Noise characteristics are studied for a self-stabilized laser utilizing the interplay between the intracavity dispersion and the optical frequency shift. The noise suppression bandwidth of this scheme is from 0 to ~100 KHz and showed the reduction of residual timing jitter (integrated from 0.9 Hz to 1 MHz) from 2.2fs to 660 attosecond which represents, to our knowledge, the lowest timing jitter reported for an actively mode-locked laser     

High-repetition-rate optical pulse generation using a rationalharmonic mode-locked fiber laser

Rational harmonic mode locking takes place in an actively mode-locked fiber laser when the modulation frequency f_m=(n+1/p)f_c, where n and p are both integers and f_c is the inverse of the cavity round-trip time, the 22nd order of rational harmonic mode locking has been observed when f_m ≈1 GHz. An optical pulse train with a repetition rate of 40 GHz has been obtained using a modulation frequency f_m=10 GHz. The theory of rational harmonic mode locking has also been developed. The stability of the mode-locked pulses is improved considerably when a semiconductor optical amplifier is incorporated into the fiber laser cavity. The supermode noise in the RF spectrum of a mode-locked laser is removed for a certain range of current in the semiconductor optical amplifier     

Inter-resonance soliton generation and trapping

We show a new type of actively mode-locked fiber laser that, despite the 2.5-km-long cavity and the average group-velocity dispersion of -20 ps²/km, generates solitons with duration of 2÷4 ps, 1-GHz repetition rate and timing jitter of 0.7 ps. Such short solitons are generated in an inter-resonance condition that favors a highly stable propagation regime. Soliton duration and timing jitter are both controlled by the self-frequency-modulation due to the background radiation emitted by the solitons themselves     

Novel method to simultaneously compress pulses and suppresssupermode noise in actively mode-locked fiber ring laser

Nonlinear polarization rotation is used to compress pulses or suppress supermode noise in mode-locked fiber lasers at different situations. In this letter, we propose a novel method to simultaneously realize the above two effects by exploiting nonlinear polarization rotation in actively mode-locked fiber ring laser at a special state. A simple model derived by theoretical analysis is given to explain this phenomenon. We have also investigated the different transmission situations of nonlinear polarization rotation in the 10-GHz actively mode-locked fiber ring laser. Experimental observations agree well with theoretical predictions     

Greater Than 20-dB Supermode Noise Suppression and Timing Jitter Reduction Via CW Injection of a Harmonically Mode-Locked Laser

Characterization of the timing and amplitude (AM) noise have shown a greater than 20-dB reduction of the supermode noise spurs from a harmonically mode-locked laser by continuous-wave optical injection. A reduction of the timing jitter and AM noise from 127 to 25 fs and 0.85% to 0.12% (10 Hz-100 MHz), respectively, is demonstrated. A reduction of the optical linewidth, implied by the reduction in the close-in phase noise, is also shown.     

Noise characteristics in repetitively pulsed semiconductor lasers

Timing jitter (phase noise) and power fluctuations (intensity noise) in a semiconductor laser driven with a periodic current waveform, in the large signal regime are investigated theoretically. The temporal behavior of the laser output power is calculated numerically from the modified rate equation with Monte Carlo simulation of the random processes, both free-running and active mode-locked configurations are treated. The temporal width and root-mean-square (rms) timing jitter and energy fluctuation of the pulses are calculated, as are the correlation and spectral properties of the noise     

Characterization of the jitter in a mode-locked Er-fiber laser and its application in photonic sampling for analog-to-digital conversion at 10 gsample/s

This paper compares two approaches for evaluating the amplitude and timing jitters of an Er-fiber laser mode-locked at 10 GHz. Using a low-noise oscillator as the clock drive for the mode-locking, relative amplitude jitter was measured as low as 0.0384% and timing jitter as low as 0.0153% (/spl Delta/f=100 Hz-40 MHz). Applying the mode-locked pulse train in a photonic sampling experiment at 10 Gsample/s, a spurious free dynamic range (SFDR) of /spl sim/48.5 dB (over the Nyquist bandwidth of 5 GHz) for multiple analog inputs at L band (1-2.6 GHz). These results correspond to an analog-to-digital conversion resolution of /spl sim/8 SFDR bits at 10 Gsample/s. Finally, the use of "instantaneous companding" is demonstrated to correct for third-order distortions generated by a Mach-Zehnder modulator used in the photonic sampling link.