Semiconductor Ring Laser Research Articles

Ultrafast mode switching based on a micro-ring laser

Injection locking and multi-mode switching characteristics of a semiconductor ring laser with the radius of 10μm are investigated based on a nonlinear time domain multimode rate-equation model. The stable injection locking regions for different target modes are studied as the function of detuning frequency and injection power ratio. The results show that ultra-wide detuning range of ∼100GHz wide at 5dB injection power ratio and ultra-low switching power ratio of −27dB can be realized for this micro-ring laser device. Optimal detuning value and high injection power lead to the minimal switching time. An ultrafast response time of 10ps indicates that a 10μm-radius SRL can be utilized for ultrafast all-optical scenarios and high-speed tunable lasers.

Dependence of Modulation Bandwidth on Size of Optical Injection Locked Semiconductor Ring Laser

It has been successfully investigated for the rst time that strength of optical injection locking also depends on the size of semiconductor ring laser. Theoretical study for frequency response of optical injection locking semiconductor ring laser in the master slave con guration using direct, amplitude and phase modulation of master laser is discussed. In the unidirectional regime the locking range of semiconductor ring laser becomes wider when semiconductor ring laser with smaller size is used. Simulation results predict an incredible enhancement in the modulation bandwidth (> 500 GHz) of the slave semiconductor ring laser when used with smaller laser cavity length (50 μm) in the stable unidirectional regime.

Noise Response and Stability in Injection Locked Semiconductor Ring Laser

Stability and e ects of optical injection locking in semiconductor ring laser is modeled in detail. It is veri ed that the injection locking in slave semiconductor ring laser depends on detuning frequency and external optical injection ratio between the master laser and the slave semiconductor ring laser. The stability of injection was locked using the resonance frequency and damping factor. The parasitic phase modulation response due to amplitude modulation (chirp response) is derived and simulated. Similarly parasitic amplitude modulation due to phase modulation response is also investigated.

All-Optical Toggle Flip-Flop Based on Monolithic Semiconductor Ring Laser

A novel monolithic all-optical flip-flop of the toggle type with two complementary outputs is demonstrated based on a semiconductor ring laser (SRL), where the intrinsic directional bistability of the SRL device is combined with the saturable absorption effect that takes place in the reverse-biased input waveguides. Toggle flip-flop (TFF) operation is experimentally demonstrated using optical trigger toggle pulses of 500 ps duration. The achieved bit-rate of 500 Mb/s is the highest reported so far for all-optical TFFs. The operational speed is limited by the carrier recovery time of the saturable absorbers; however, the proposed technology has potential for multi-gigabits per second operation.

Investigation on the intensity noise characteristics of the semiconductor ring laser

Based on the frequency-domain multimode theoretical model, detailed investigations on the noise characteristic of the semiconductor ring laser (SRL) are first performed in this paper. The comprehensive nonlinear terms related to the third order nonlinear susceptibility χ3 are included in this model; the Langevin noise sources for electric field and carrier density fluctuations are also taken into account. As the injection current increases, the SRL may present several operation regimes. Remarkable and unusual low frequency noise enhancement in the form of a broad low frequency tail extending all the way to the relaxation oscillation peak is observed in any of the operation regimes of SRLs. The influences of the backscattering coefficient on the relative intensity noise (RIN) spectrum in typical operation regimes are investigated in detail.

Theoretical Analysis of Unidirectional Operation and Reflection Sensitivity of Semiconductor Ring or Disk Lasers

We theoretically and numerically analyze the unidirectional behavior of ring or disk lasers coupled to a bus waveguide with a relatively strong reflector on one side and find analytical expressions for the ratio of the powers in clockwise and counter clockwise modes. At low bias levels, this ratio depends on the coupling coefficients that determine the coupling between clockwise and counterclockwise modes, whereas at high bias levels it also depends strongly on the gain suppression. We also theoretically and numerically investigate the feedback sensitivity of such lasers and come to the conclusion that ring or disk lasers are generally much more sensitive to external reflections than traditional Fabry-Perot, DFB, or DBR lasers. At high bias levels, the feedback sensitivity also depends strongly on the gain suppression, and at high enough power levels, it can be better than that of traditional edge-emitting lasers.

Monolithic All-Optical Set-Reset Flip-Flop Operating at 10 Gb/s

A monolithic semiconductor ring laser is operated as an all-optical set-reset flip-flop triggered by external optical pulses. Bit-error-rate measurements of set-reset switchings under the injection of a pseudo-random-bit-sequence have been performed, showing reliable operation up to 10 Gb/s.

Enhanced chaos synchronization and communication in cascade-coupled semiconductor ring lasers

We numerically investigate the properties of chaos synchronization in a master–slave configuration consisting of a master semiconductor ring laser (SRL) with self-feedback or cross-feedback and a solitary SRL (slave). Different coupling schemes related to global injection and mode-selective injection are proposed and explored in our simulations. The numerical results demonstrate that among the studied coupling motifs the synchronization performance between the modes of the two chaotic SRLs is better when global injection scheme is employed. Furthermore, enhanced chaos synchronization and communication in three cascade-coupled SRLs via global injection are reported, where the time delay signature cannot be identified from the outputs of the three SRLs due to the proper selection of cross-feedback parameters of the master SRL.

A Numerical Study of Cavity Enhanced Inter-Modal Four Wave Mixing in Injection-Locked Semiconductor Ring Lasers

Mode beating via third order nonlinearity in semiconductor ring lasers has been analyzed using a frequency-domain multimode rate equation model. Compared with Fabry-Perot lasers, semiconductor ring lasers are 1.33, 2, and 4 times more efficient in self-gain compression, cross-gain compression, and four-wave mixing processes, respectively, due to its travelling-wave nature. It is shown that, using dual (pump and signal) external optical injections into the ring laser cavity, multiple modes can be locked in phase via the strong four wave mixing phenomenon. This results in modulation of the light wave at the mode beating frequencies which could be used for RF optical carrier generation.

All-Optical Directional Switching in Bistable Semiconductor-Ring Lasers

We investigate the operation of directionally bistable semiconductor-ring lasers as all-optical flip-flops. We demonstrate fast switching between the two lasing directions by injection of optical pulses acting as set and reset control signals with switching times as fast as 20 ps, delay times as short as 60 ps, and switching energy of 150 fJ.

The frequency noise and spectral linewidth in semiconductor ring lasers

Numerical analyses for power spectral density of frequency noise (FN) and spectral linewidth in monolithic semiconductor ring laser (SRL) operating in the bistable unidirectional regime are performed in this paper. The Langevin noise sources for electric field and carrier density fluctuations are also taken into account in the frequency-domain theoretical model. The influences of several important physical parameters on the FN properties and laser linewidth are clearly demonstrated, including the injection current, linewidth enhancement factor and the particular backscattering coefficient. Due to the particular backscattering in SRLs, the calculated linewidths are relatively higher than that from the conventional Henry formula. The laser linewidth shows an exponential relationship with the backscattering strength.

Oscillations and multistability in two semiconductor ring lasers coupled by a single waveguide

We theoretically study the dynamical behavior of semiconductor ring lasers coupled by a single bus waveguide, both when weakly coupled and when strongly coupled. We provide a detailed analysis of the multistable landscape in the coupled system, analyze the stability of all solutions, and relate the internal dynamics in the individual lasers to the field effectively measured at the output of the waveguide. We show that coupling phases close to $\ensuremath{\pi}/2$ generally promote instabilities. Finally, our analysis enables us to discuss the advantages and disadvantages for optical memory operation of coupled semiconductor ring lasers versus solitary ones.

Low-Frequency Fluctuations in Semiconductor Ring Lasers With Optical Feedback

In this paper, we experimentally and numerically study the dynamics of semiconductor ring lasers that are subjected to long delay and moderate self-feedback. Through varying the pump current or the feedback strength or both, we study the appearance and parameter dependence of low frequency fluctuations in these systems. In particular, we observe different routes to the building up of the initial power amplitude.

Chaos generation in a semiconductor ring laser with an optical injection

Two chaos generation schemes are demonstrated numerically based on a semiconductor ring laser (SRL) with either a constant or a chaotic optical injection from an external distributed feedback (DFB) laser. Under a certain bias current, the chaotic output can be generated by the SRL with appropriate injection parameters. Parameter map is achieved numerically to show types of oscillation in the SRL. Bifurcation diagrams and Lyapunov exponent spectra roughly describe the routes to chaos for the SRL with disturbance. A bandwidth-enhanced chaos generation can be describes based on the chaotic optical injection scheme. The bandwidth of the bandwidth-enhanced chaos generated is about 12GHz, which achieves approximately a two-fold increase compared with the constant injection scheme.

Controlled multiwavelength emission using semiconductor ring lasers with on-chip filtered optical feedback

We report on an integrated approach to obtain multiwavelength emission from semiconductor ring lasers with filtered optical feedback. The filtered feedback is realized on-chip employing two arrayed-waveguide gratings to split/recombine light into different wavelength channels. Through experimental observations and numerical simulations, we find that the effective gain of the different modes is the key parameter which has to be balanced in order to achieve multiwavelength emission. This can be achieved by tuning the injection current in each amplifier.

Theoretical investigation of a semiconductor ring laser driven by Chua’s oscillator

The modeling and numerical investigation of the dynamical behavior of a semiconductor ring laser (SRL) driven by Chua’s oscillator are reported. By increasing the coupling strength between the SRL and Chua’s oscillator at a fixed bias current, the SRL exhibits an intermittency route to anti-phase chaos. However, for a fixed value of the coupling strength, we report a period-doubling route to out-of-phase and anti-phase chaos when varying one of the parameters of the Chua’s oscillator are reported. We also demonstrate that a SRL driven by the chaotic output of Chua’s oscillator generates a more complex chaos compared to the one found in a SRL subject to a sinusoidally modulated current. This new way of modulation of semiconductor lasers would not only bring a general benefit in the physical equipment and reduce their cost but could have an impact for some relevant engineering applications.

Chaotic Optical Communication Performance Based on Semiconductor Ring Laser

We build up a model of chaotic optical communication based on semiconductor ring laser (SRL). The modulation and demodulation technique is numerically applied in order to demonstrate the communication performance and the security effect. The results indicate that good transmission and security performance can be achieved with the appropriate transmission data rate and modulation depth in SRL-based chaotic optical communication.

Bandwidth and unpredictability properties of semiconductor ring lasers with chaotic optical injection

The bandwidth and unpredictability properties of chaotic semiconductor ring lasers (SRLs) are numerically investigated. The SRL is brought to chaotic behaviors by utilizing chaotic optical injection from a master laser with optical feedback. The bandwidth and unpredictability degree of chaotic signal are examined for parameter regions of injection strength and frequency detuning. The chaos unpredictability degree is evaluated quantitatively by permutation entropy (PE). It is shown that, chaos can be obtained in large parameter regions, and simultaneous enhancement of bandwidth and unpredictability degree could be achieved for proper injection parameters. Such results are important for carrying out chaos-based communications and fast random number generations (RNGs).

Digitally tunable dual wavelength emission from semiconductor ring lasers with filtered optical feedback

We report on a novel integrated approach to obtain dual wavelength emission from a semiconductor laser based on on-chip filtered optical feedback. Using this approach, we show experiments and numerical simulations of dual wavelength emission of a semiconductor ring laser. The filtered optical feedback is realized on-chip by employing two arrayed waveguide gratings to split/recombine light into different wavelength channels. Semiconductor optical amplifiers are placed in the feedback loop in order to control the feedback strength of each wavelength channel independently. By tuning the current injected into each of the amplifiers, we can effectively cancel the gain difference between the wavelength channels due to fabrication and material dichroism, thus resulting in stable dual wavelength emission. We also explore the accuracy needed in the operational parameters to maintain this dual wavelength emission.

Multichannel Wavelength Conversion Using Four-Wave Mixing in Semiconductor Ring Lasers

We theoretically study all-optical simultaneous wavelength conversion of multiple channels by four-wave mixing in semiconductor ring lasers. Locking the semiconductor ring laser to a holding beam allows us to achieve large conversion efficiencies with good signal-to-noise ratio in several channels at multi-Gb/s bit rates. Cross-talk between signals, arising from the peculiar four-wave mixing cascade of modes in semiconductor ring lasers and their cross-gain saturation, is studied in detail. We show that it can be controlled by adjusting the intensity of the holding beam, the bias current of the laser, and the number, intensity, and wavelength of signals that one wants to convert.