Inverse synchronization in semiconductor laser diodes

A compact three-laser source for optical sensing is presented. It is based on a low-noise implementation of the Pound-Drever-Hall method and comprises high-bandwidth optical phase-locked loops. The outputs from three semiconductor distributed feedback lasers, mounted on thermo-electric coolers (TEC), are coupled with micro-lenses into a silicon photonics (SiP) chip that performs beat note detection and several other functions. The chip comprises phase modulators, variable optical attenuators, multi-mode-interference couplers, variable ratio tap couplers, integrated photodiodes and optical fiber butt-couplers. Electrical connections between a metallized ceramic and the TECs, lasers and SiP chip are achieved by wirebonds. All these components stand within a 35 mm by 35 mm package which is interfaced with 90 electrical pins and two fiber pigtails. One pigtail carries the signals from a master and slave lasers, while another carries that from a second slave laser. The pins are soldered to a printed circuit board featuring a micro-processor that controls and monitors the system to ensure stable operation over fluctuating environmental conditions. This highly adaptable multi-laser source can address various sensing applications requiring the tracking of up to three narrow spectral features with a high bandwidth. It is used to sense a fiber-based ring resonator emulating a resonant fiber optics gyroscope. The master laser is locked to the resonator with a loop bandwidth greater than 1 MHz. The slave lasers are offset frequency locked to the master laser with loop bandwidths greater than 100 MHz. This high performance source is compact, automated, robust, and remains locked for days.

We perform numerical simulations of the dynamics of two VCSELs optically coupled in a master-slave configuration. We show that the interplay of nonlinearity and spontaneous emission noise can yield logic behavior, and the emergent outcome of such system is a reliable logic gate. Specifically in our case represents an all-optical logic gate, with the logic input encoded in the strength of the light injected in the slave laser by the master laser, and the fast and robust response decoded from the polarization state of the light emitted by the slave laser.

Synchronized mode-locking of monolithic mode-locked diode lasers has been demonstrated by injecting the light output from a master monolithic mode-locked diode laser. The master diode laser is a 10 GHZ hybridly mode-locked two section InGaASP quantum well laser. The slave lasers are a 10 GHz two section laser which is similar to the master laser, and a 20 GHz three section colliding pulse mode-locking laser. Both the slave lasers were greatly stabilized at 10 GHz frequency by a synchronous mode-locking mechanism under the injection of master laser pulses.

This work concerns the synchronization of chaotic dynamical systems by using the program Mathematica and follows up a previous one (also included in this volume) devoted to the same topic [2]. In particular, this second paper classifies and illustrates the wide range of chaotic synchronization phenomena. Some examples of each kind are briefly analyzed in this paper with the help of a Mathematica package already introduced in the previous paper.KeywordsLyapunov ExponentTemporal SeriesLorenz SystemSlave SystemChaotic SignalThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

We study the nonlinear dynamics of a vertical-cavity surface-emitting laser (VCSEL) subject to a repetitive optical pulse injection numerically using the SFM model. In our study, a linearly polarized slave laser is optically injected by a train of optical pulses from a master laser, where the polarization of the master laser is orthogonal to the polarization of the solitary slave laser (x-polarized). By varying the strength and the repetition frequency of the injected pulses, different dynamical states, including regular pulsations, period-doubled pulsations, chaotic pulsations, periodic oscillations, quasi-periodic oscillations, and chaotic oscillations, are found. Instead of having only one polarization mode at the slave laser output, both the y- and x-polarized modes are observed for the pulsation and oscillation states. While the pulsation states with y-polarization follow a period-doubling route to chaotic pulsations, the oscillation states with the x-polarization undergo a quasi-periodic route to chaos oscillations. Then, with adequate strength of the injection, the x-polarized mode will be suppressed (i.e. polarization switching) and eventually the slave laser will lock to the master laser with higher injection strength. Also, the switching points, the boundary of the injection-locked, and the regions of the chaotic states are found to be strongly influenced by the repetition frequency of the injection pulses and the detuning frequency between the two lasers.

A method of coherently summing the outputs of two diode-pumped ring lasers has been tested. The output of one such Nd:YAG laser (the master laser) at 1064 nm was mode-matched into a similar laser (the slave laser). The frequency of the slave laser was tuned toward that of the master laser by adjusting the crystal temperature (and thus the optical path length). The difference frequency was detected until the locking range was reached, when the free-running oscillation of the slave laser was completely injection-locked by the injected signal. With the master laser power of 15 mW and the slave laser power of 5 mW, the locking frequency occurred at ~23 MHz. The combined output power during locking ranged from ~20 to 21 mW with the maximum representing a 5% increase over the summation of the unlocked free-running lasers. Locking was held for periods >15 min. These results indicate the possibility of chaining together this type of laser to obtain coherent single-mode outputs with higher powers than currently possible.

Photonic generation of wideband chaotic signals with time delay signature elimination is investigated experimentally and numerically based on a semiconductor laser (slave laser) with chaotic optical injection from a master laser. The master laser is subject to moderate optical feedback where the feedback strength and external-cavity length are fixed, while the slave laser stands alone. The experimental results show that wideband chaotic signals with successful time delay concealment can be generated in the slave laser by simply adjusting the coupling strength and frequency detuning between the two lasers. Furthermore, the numerical results are in accordance with the experimental observations. Finally, we propose a simple method for simultaneously generating multiple streams of high-quality chaotic signals using multichaotic lasers, where the time delay is effectively concealed in the autocorrelation function and delayed mutual information calculated from the chaotic time series.

The instability of optical phase chaos synchronization between semiconductor lasers under master-slave open-loop configuration is investigated. The phase difference between the master and slave lasers is obtained and analyzed in experiment by heterodyne detection and Hilbert transform, and in simulation by solving the rate equations. The results show that the phase difference only maintains in a short duration time and then jumps to another value. A statistical analysis shows that both duration time and jumping values are random, proving that the phase chaos synchronization is unstable. A theoretical analysis shows that the instability of phase synchronization is caused by the jumping of the external cavity mode in the master laser.

Extreme events (EEs) are rare and unexpected events that emerge in many natural systems and are the object of intensive studies. Here, we experimentally investigate the evolution of deterministic optical EEs in a slave laser (SL) subject to chaotic optical injection from a master laser (ML) with optical feedback. Although the ML operates in the long-cavity regime, we observe occasional pulses that are high enough to be considered EEs, and the appearance probability of EEs can be significantly enhanced in the SL for certain injection parameters outside the injection-locking regions of the master-slave configuration. Additionally, the evolution of EEs can be readily identified from the two-dimensional maps. The numerical results show good qualitative agreement with the experiment. These results reveal the importance of injection parameters for the appearance of EEs in chaotic lasers and can be easily extended to other coupled systems.

A novel method to reduce optical beat noise (OBN) which is critical in subcarrier multiplexed-based optical access link is suggested. The chirped optical signal was generated by using dual current modulation through master and slave lasers. The sidelobes of the slave laser decreased up to -90 dBm close to the noise floor. The OBN was reduced by 20 dB because of the spectral broadening of the slave laser resulted from the increased chirp.

Ultra-wideband signal generator based on cross gain modulation effect in a distributed feedback laser

We propose a novel, high-performance, and practical laser source system for optical clocks. The laser linewidth of a fiber-based frequency comb is reduced by phase locking a comb mode to an ultrastable master laser at 1064 nm with a broad servo bandwidth. A slave laser at 578 nm is successively phase locked to a comb mode at 578 nm with a broad servo bandwidth without any pre-stabilization. Laser frequency characteristics such as spectral linewidth and frequency stability are transferred to the 578-nm slave laser from the 1064-nm master laser. Using the slave laser, we have succeeded in observing the clock transition of (171)Yb atoms confined in an optical lattice with a 20-Hz spectral linewidth.

A primary frequency standard based on cold Cs atoms is under development at the Time and Frequency Division of the Centre Nacional de Metrologia, CENAM. A Cs magneto-optical trap has been developed using the standard sigma+sigma$4-horizontal 2-vertical laser beams of 1.9 cm in diameter, with 5 mW each. We use 852 nm, 5 mW, DBR laser as a master laser which is stabilized by saturation spectroscopy. Linewidth of the master laser is 1 MHz. A 50 mW, 852 nm, semiconductor laser is used as slave laser in order to amplify the light of the master laser. The slave laser is stabilized by injection light technique. 12 MHz red shift of the light is performed by double pass through two AOM's. In this paper we present some preliminary results of our MOT characterization as function of MOT's parameters such as intensity of laser beams and gradient of the magnetic field.

The nonlinear dynamics of a semiconductor laser (slave laser) injected by optical pulses with high repetition rate are investigated experimentally. The pulses for injection are generated from a laser (master laser) subjected to either an optoelectronic feedback or an optical feedback. The repetition rates of the pulses are controlled by varying the delay time and the feedback strength of the feedback loop. By injecting the repetitive optical pulses of different intensities and repetition frequencies into another laser (slave laser), rich dynamical states including regular pulsations, frequency beatings, and chaotic pulsations are observed. Moreover, frequency-locked states with different winding number, the ratio of the main pulsation frequency of the slave laser and the repetition frequency of the injected pulses, are also found. Compared to a laser subject to a sine modulated optical injection, the linewidths of the high-order microwave components in the output spectrum of the slave laser are substantially narrower for the laser under repetitive optical pulse injection.

The combined spectral linewidth of master and slave laser and loop propagation delay are the trade-offs for suppressing residual loop noise in optical phase-locked loop systems. To reduce the slave laser’s linewidth and shorten the loop delay, a heterodyne hybrid optical phase-locked loop system that packages self-injection locked semiconductor laser, photodiode, the electronic circuit is proposed. By employing a DFB laser diode coupled to a microring resonator based on Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> integrated waveguide platform, the slave laser realizes a narrow spectral linewidth of 2.8 kHz. Due to the full use of the external microring cavity, the optical path delay is shortened to 30 ps. In this way, the residual loop noise has been reduced to −70 dBc/Hz at as low as 10 Hz offset from the carrier frequency, and phase noise variance is 0.0018 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$rad^{2}$</tex-math></inline-formula> at 600 MHz carrier frequency for offset between 10 Hz and 10 MHz.