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This paper delves into the indoor performance analysis of Perovskite/Silicon Tandem Solar Cells (PSSTC) through a detailed exploration utilizing numerically modeled energy band diagrams. The primary objective is to uncover the potential of PSSTC for solar energy conversion in indoor settings. Various tandem cell configurations are scrutinized under diverse artificial lighting spectra, with an innovative Li4Ti5O12/CsPbCl3/MAPbBr3/CH3NH3PbI3/Si architecture achieving an exceptional maximum power conversion efficiency of 25.25%. This represents a substantial efficiency enhancement of nearly 7% compared to standalone Silicon cells. The study underscores the significance of design optimization in maximizing performance. The energy band diagram analysis reveals a strong correlation with the I-V characteristics, providing valuable insights into solar cell performance under varied optical injections. Notably, the Xenon light source exhibits a higher deviation of the quasi-Fermi level, resulting in increased current density surpassing the AM1.5G conditions by approximately 2.5 mA/cm2. These findings underscore the promising potential of PSSTC for highly efficient indoor solar energy conversion and emphasize the critical role of design optimization in unlocking peak performance. [ABSTRACT FROM AUTHOR]

In a laser diode (LD) system with optical injection, the effects of gain saturation of the LD on the orbital instability of the system are analyzed numerically. For the optical injection LD system without signal application, it is shown that the effect of optical injection is suppressed in the system with gain saturation and small optical injection, and that a higher amount of optical injection is necessary to obtain similar dynamics. Next, in the optical injection LD system with a pseudo-random signal applied to the LD drive current, it is confirmed that when the dynamics are a periodic window between chaotic and chaotic regions, chaotic dynamics are actualized as the standard deviation of the applied signal becomes larger. Furthermore, it is suggested that this phenomenon can be explained by linear stability analysis, and it is shown by introducing randomly varying tentative gain coefficients that gain fluctuations that lead to an expansion of the chaotic region. Hence, the results of this study provide research on the effects of gain saturation on chaotic oscillation in LDs with pseudo-random signals applied and contribute to the generation of more complex chaotic signals, chaotic secure communication, and random number generation. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive numerical investigation on the generation of a microwave frequency comb (MFC) using a semiconductor laser subjected to periodic-modulated optical injection. To enhance performance, optoelectronic feedback is incorporated through a dual-drive Mach–Zehnder modulator. The results show that the first optoelectronic feedback loop, with a delay time inversely proportional to the modulation frequency, can optimize MFC generation through a mode-locking effect and the second optoelectronic feedback loop with a multiple delay time of the first one can further enhance the performance of the MFC. The comb linewidth appears to decrease with the increase in the second-loop delay time in the power function. These results are consistent with experimental observations reported in the literature. We also explore the impact of the feedback index on comb contrast, the statistical characteristics of the central 128 lines within the MFC, and side peak suppression. The simulation results demonstrate the presence of an optimal feedback index. The study also reveals that linewidth reduction, through increasing the feedback index and delay time, comes at the cost of declining side peak suppression. These findings collectively contribute to a deeper understanding of the factors influencing MFC generation and pave the way for the design and optimization of high-performance MFC systems for various applications. [ABSTRACT FROM AUTHOR]

For silicon-based epitaxial quantum dot lasers (QDLs), the mismatches of the lattice constants and the thermal expansion coefficients lead to the generation of threaded dislocations (TDs), which act as the non-radiative recombination centers through the Shockley–Read–Hall (SRH) recombination. Based on a three-level model including the SRH recombination, the nonlinear properties of the silicon-based epitaxial QDLs under optical injection have been investigated theoretically. The simulated results show that, through adjusting the injection parameters including injection strength and frequency detuning, the silicon-based epitaxial QDLs can display rich nonlinear dynamical states such as period one (P1), period two (P2), multi-period (MP), chaos (C), and injection locking (IL). Relatively speaking, for a negative frequency detuning, the evolution of the dynamical state with the injection strength is more abundant, and an evolution path P1-P2-MP-C-MP-IL has been observed. Via mapping the dynamical state in the parameter space of injection strength and frequency detuning under different SRH recombination lifetime, the effects of SRH recombination lifetime on the nonlinear dynamical state of silicon-based epitaxial QDLs have been analyzed. [ABSTRACT FROM AUTHOR]

We theoretically investigate the frequency shift of a free-running semiconductor laser when optically injected by an optical frequency comb. By numerical integration of the laser rate equations, we have identified two types of frequency shifts, frequency pulling, and frequency pushing. The free-running slave laser seems to switch between pulling and pushing in a regular manner. We have systematically determined the dependence of these shifts on comb parameters, including comb spacing and number of lines. We have found that the occurring frequency pushing seems to be almost independent of comb signals and comb spacing, while in contrast, the frequency pulling shows weak dependence on comb signals but largely affected by comb spacing. We have also shown that carrier density dynamic is the origine of these phenomena.

In a laser diode (LD) system with optical injection, the effects of gain saturation of the LD on the orbital instability of the system are analyzed numerically. For the optical injection LD system without signal application, it is shown that the effect of optical injection is suppressed in the system with gain saturation and small optical injection, and that a higher amount of optical injection is necessary to obtain similar dynamics. Next, in the optical injection LD system with a pseudo-random signal applied to the LD drive current, it is confirmed that when the dynamics are a periodic window between chaotic and chaotic regions, chaotic dynamics are actualized as the standard deviation of the applied signal becomes larger. Furthermore, it is suggested that this phenomenon can be explained by linear stability analysis, and it is shown by introducing randomly varying tentative gain coefficients that gain fluctuations that lead to an expansion of the chaotic region. Hence, the results of this study provide research on the effects of gain saturation on chaotic oscillation in LDs with pseudo-random signals applied and contribute to the generation of more complex chaotic signals, chaotic secure communication, and random number generation.

This study presents a comprehensive numerical investigation on the generation of a microwave frequency comb (MFC) using a semiconductor laser subjected to periodic-modulated optical injection. To enhance performance, optoelectronic feedback is incorporated through a dual-drive Mach–Zehnder modulator. The results show that the first optoelectronic feedback loop, with a delay time inversely proportional to the modulation frequency, can optimize MFC generation through a mode-locking effect and the second optoelectronic feedback loop with a multiple delay time of the first one can further enhance the performance of the MFC. The comb linewidth appears to decrease with the increase in the second-loop delay time in the power function. These results are consistent with experimental observations reported in the literature. We also explore the impact of the feedback index on comb contrast, the statistical characteristics of the central 128 lines within the MFC, and side peak suppression. The simulation results demonstrate the presence of an optimal feedback index. The study also reveals that linewidth reduction, through increasing the feedback index and delay time, comes at the cost of declining side peak suppression. These findings collectively contribute to a deeper understanding of the factors influencing MFC generation and pave the way for the design and optimization of high-performance MFC systems for various applications.

For silicon-based epitaxial quantum dot lasers (QDLs), the mismatches of the lattice constants and the thermal expansion coefficients lead to the generation of threaded dislocations (TDs), which act as the non-radiative recombination centers through the Shockley–Read–Hall (SRH) recombination. Based on a three-level model including the SRH recombination, the nonlinear properties of the silicon-based epitaxial QDLs under optical injection have been investigated theoretically. The simulated results show that, through adjusting the injection parameters including injection strength and frequency detuning, the silicon-based epitaxial QDLs can display rich nonlinear dynamical states such as period one (P1), period two (P2), multi-period (MP), chaos (C), and injection locking (IL). Relatively speaking, for a negative frequency detuning, the evolution of the dynamical state with the injection strength is more abundant, and an evolution path P1-P2-MP-C-MP-IL has been observed. Via mapping the dynamical state in the parameter space of injection strength and frequency detuning under different SRH recombination lifetime, the effects of SRH recombination lifetime on the nonlinear dynamical state of silicon-based epitaxial QDLs have been analyzed.

The study theoretically investigates the dynamic of an injection-locked semiconductor laser with zero linewidth enhancement factor. The stability map of the injection locking process is drawn, and bifurcation diagrams are generated. Carrier density dynamics are also investigated. The study has reported different periodical and chaotic behaviour and revealed the dynamics of carriers with zero linewidth enhancement factor.

Two microwave photonic signal processing structures, which are capable to realise microwave frequency division with a tunable integer or non-integer division ratio, are presented. They are based on applying an RF signal into a Mach Zehnder modulator, which is biased to generate a carrier-suppressed double sideband (DSB) or single sideband (SSB) optical signal. The carrier-suppressed DSB optical signal consists of the upper and lower $1^{\rm st}$ order sidebands with a separation of two times the input RF signal frequency. The carrier of the SSB optical signal is suppressed by a fibre Bragg grating (FBG) connected to the modulator output. Hence the FBG output consists of the upper $1^{\rm st}$ order and lower $2^{\rm nd}$ order sidebands with a separation of three times the input RF signal frequency. The carrier-suppressed DSB or SSB optical signal is injected into a semiconductor laser. The semiconductor laser is oscillated in the period-one state that generates a number of equally spaced frequency components, which are frequency locked by the injection light wave. Beating of these optical frequency components at the photodetector produces an RF signal with a frequency of 2/ $N$ or 3/ $N$ times the input RF signal frequency where $N$ can be between 3 and 6. Hence the 2/ $N$ frequency divider can realise 2/3, 1/2, 2/5 and 1/3 frequency division operation, and the 3/ $N$ frequency divider can realise 3/4, 3/5 and 1/2 frequency division operation. The proposed 2/ $N$ and 3/ $N$ frequency dividers have a very simple structure compared to the reported photonics-based microwave frequency divider that can realise both integer and non-integer frequency divisions. The frequency division ratio can be tuned by simply adjusting the forward bias current of the semiconductor laser subject to optical injection. Experimental results demonstrate the two proposed structures can realise microwave frequency division with a tunable integer and non-integer division ratio for different input RF signal frequencies of 10 to 18 GHz, and over 60 dB output signal-to-noise ratio performance. More than 27 dB suppression in the unwanted frequency components around the frequency divided signal is also demonstrated.

This paper presents a detailed experimental investigation of the nonlinear dynamics of a dual-beam optically injected semiconductor laser. Unlike previous works, we focus on the situation where the power and the frequency of the injection light wave are fixed and the free running frequency of the laser subject to optical injection is in between the two injection beams that have a large frequency separation. The nonlinear dynamics of the slave laser (SL), i.e., the laser subject to optical injection, for different SL forward bias currents are examined. Results show, in addition to the regenerated injection light wave, a fundamental oscillation together with its harmonics are generated when the SL interacts with its nearby injection beam. The SL output frequency components are stabilised when one of the harmonics of the fundamental oscillation is located at the injection beam that is far away from the free running SL. More than six-fold improvement in the frequency stability of the resultant output microwave signal, compared to that generated by optical mixing, is obtained. Experimental results also show the SL nonlinear dynamics have different behaviours when the two injection beams have different frequency separations.

Photonic reservoir computing has been demonstrated to be able to solve various complex problems. Although training a reservoir computing system is much simpler compared to other neural network approaches, it still requires considerable amounts of resources which becomes an issue when retraining is required. Transfer learning is a technique that allows us to re-use information between tasks, thereby reducing the cost of retraining. We propose transfer learning as a viable technique to compensate for the unavoidable parameter drift in experimental setups. Solving this parameter drift usually requires retraining the system, which is very time and energy consuming. Based on numerical studies on a delay-based reservoir computing system with semiconductor lasers, we investigate the use of transfer learning to mitigate these parameter fluctuations. Additionally, we demonstrate that transfer learning applied to two slightly different tasks allows us to reduce the amount of input samples required for training of the second task, thus reducing the amount of retraining.

Photonic reservoir computing has been demonstrated to be able to solve various complex problems. Although training a reservoir computing system is much simpler compared to other neural network approaches, it still requires considerable amounts of resources which becomes an issue when retraining is required. Transfer learning is a technique that allows us to re-use information between tasks, thereby reducing the cost of retraining. We propose transfer learning as a viable technique to compensate for the unavoidable parameter drift in experimental setups. Solving this parameter drift usually requires retraining the system, which is very time and energy consuming. Based on numerical studies on a delay-based reservoir computing system with semiconductor lasers, we investigate the use of transfer learning to mitigate these parameter fluctuations. Additionally, we demonstrate that transfer learning applied to two slightly different tasks allows us to reduce the amount of input samples required for training of the second task, thus reducing the amount of retraining. [ABSTRACT FROM AUTHOR]

The study theoretically investigates the dynamic of an injection-locked semiconductor laser with zero linewidth enhancement factor. The stability map of the injection locking process is drawn, and bifurcation diagrams are generated. Carrier density dynamics are also investigated. The study has reported different periodical and chaotic behaviour and revealed the dynamics of carriers with zero linewidth enhancement factor. [ABSTRACT FROM AUTHOR]

Based on the cascade relaxation model of the quantum dot (QD) lasers, the nonlinear dynamics of a two-state QD laser subject to optical injection is numerically studied. The simulation results show that, for a two-state QD laser operating at the ground-state (GS) and excited-state (ES) emission simultaneously, through adjusting the injection parameters, the two emission states can display the stable (S), injection locking (IL), suppression (SP), period-one (P1), period-two (P2), multi-period (MP), and chaotic pulse (CP) states when the frequency of the injection light is close to the GS lasing frequency. Further mapping of these dynamic states in the parameter space of frequency detuning and injection strength, it is found that the complex dynamic behaviors are mainly distributed in the negative frequency detuning region. In addition, the complexity of the chaotic signal is qualified by the permutation entropy (PE) calculating, and the high complexity signal with PE value over 0.95 is obtained. Moreover, within a certain frequency detuning range, the ES emission can be effectively suppressed by increasing the injection strength. [ABSTRACT FROM AUTHOR]

We propose and experimentally demonstrate an RF signal multiplier based on optical injection locking in a semiconductor laser followed by an optoelectronic oscillator (OEO). In the proposed scheme, the modulated master laser is injected into a slave laser, a single mode Fabry-Pérot laser diode (SMFP-LD), in such a way that one of the harmonics of the modulated beam is locked to the corresponding mode of the SMFP-LD. By optical beating at the output of the SMFP-LD, stable multiple RF signals with ahigh signal-to-noise ratio (SNR) are generated due to SMFP-LD, which provides a sufficient gain to the RF signal. Further, we employ an OEO structure at the output of the SMFP-LD to optimize one of the generated multiple RF signals which are determined by the electrical bandpass filter (EBPF) and the low noise amplifier (LNF) in the OEO loop. As the gain of the OEO loop is higher than the loss, a high-purity oscillating signal, which is the selected multiple RF frequency, can be generated. In the experiment, a sextuple frequency (20 GHz) of the modulated signal is observed with an SNR and the phase noise of 54.44 dB and −102.44 dBc/Hz@10 kHz, respectively. Compared with other photonic schemes, the proposed method provides high SNR, higher multiplication factor, and low phase noise.

An all-optical photonic microwave frequency divider (PMFD) is presented. It is based on injecting an RF phase modulated optical signal into a semiconductor laser oscillating in the period-two state. New optical frequency components with frequency separation of half of the input RF signal frequency are generated at the laser output. A frequency divided signal can be obtained by the beating of these optical frequency components at a photodetector. Large harmonic suppression can be achieved by using an optical filter to select only two optical frequency components to be detected by the photodetector. The proposed PMFD is free of electrical components and does not suffer from the modulator bias drift problem. It has the potential to operate over a 100 GHz frequency range. System parameters required to realise divide-by-two frequency division operation for different input RF signal frequencies are investigated. Experimental results are presented for the novel PMFD, which demonstrate the generation of a 1/2 frequency component for different input RF signal frequencies by controlling the forward bias current of an off-the-shelf semiconductor laser, and which also show the important advantages of large harmonic suppression and high signal-to-noise ratio performance. Wide input RF signal power range and high output stability performance are also demonstrated experimentally.

We have numerically investigated the dynamics of frequency shifts in semiconductor lasers under the injection of a frequency comb. We have studied the effect of comb spacing on the locking bandwidth. Frequency comb spacing was found to play an important role in the boundaries of the locking bandwidth as well as in the frequency shift of the SL peak. [ABSTRACT FROM AUTHOR]

Artificial neural networks are very time consuming and energy intensive to train, especially when increasing the size of the neural network in an attempt to improve the performance. In this paper, we propose to preprocess the input data of a deep neural network using a reservoir, which has originally been introduced in the framework of reservoir computing. The key idea of this paper is to use such a reservoir to transform the input data into a state in a higher dimensional state-space, which allows the deep neural network to process the data with improved performance. We focus on photonic reservoirs because of their fast computation times and low-energy consumption. Based on numerical simulations of delay-based reservoirs using a semiconductor laser, we show that using such preprocessed data results in an improved performance of deep neural networks. Furthermore, we show that we do not need to carefully fine-tune the parameters of the preprocessing reservoir.

We theoretically propose and demonstrate photonic microwave signal generation with a very broad tunability range from below 2.5 GHz to around 100 GHz. The proposed scheme is based on sustained oscillation dynamics produced in spin-VCSELs under right circularly polarized optical injection. The generated microwave frequencies can be tuned by detuning the frequency of the optical injection signal. The system also takes the advantage of polarization switching phenomena to generate broader microwave frequencies where the generated frequencies are equal to the sum of the absolute detuning frequency and the birefringence split between the spin-VCSEL modes which is 47.7 GHz. Sustained oscillation dynamics provokes tunable periodical oscillations through the adjustment of the frequency detuning and injection strength which can be used as a microwave signal generator. Enhancement of the RF power of the oscillations can be achieved by increasing the injection strength towards the locking regions. The microwave linewidth is reduced from 58 MHz to a medium linewidth of about 14 MHz under optical injection technique. This simple configuration paves the way for potential uses of spin-VCSELs in Radio-over-Fiber (RoF) applications and future technologies.

We theoretically investigate the behavior of carrier density variation in optically injected semiconductor lasers when varying the linewidth enhancement factor. The variation of carrier appears independent of the LEF in the positive detuning side, while decreased in the negative detuning side with any growth in the LEF. This variation is found to be enhanced when the injection level is boosted. [ABSTRACT FROM AUTHOR]

In order to study the performance of the photonic microwave signal generated by a semiconductor laser (SL) under optical injection, based on the rate equation of SL and the fiber Bragg grating (FBG) filter theory, the optical spectra, power spectra, and linewidth under different injection parameters were obtained by numerical simulation and theoretical analysis, and the effect of the feedback parameters on the microwave linewidth was also studied. Considering that the generated microwave signal has wide linewidth, a FBG optical feedback was further introduced to narrow the microwave linewidth. The results show that, for the SL subject to optical injection only, the microwave frequency can be continuously tuned and the microwave intensity can be maximized by changing the injection parameters; the microwave linewidth gradually decreases with the increase of feedback strength. Through properly adjusting the feedback parameters, the microwave linewidth can be compressed below 10kHz. The results can provide a theoretical reference for the application of semiconductor laser in the photonic microwave signals generation. [ABSTRACT FROM AUTHOR]

We theoretically and systematically study the dynamics of carrier density in optically injected VCSELs and correlate it to the observed frequency shift outside the locking region. We also show the dependence of carrier dynamics on all major parameters including frequency detuning, injection level and the linewidth enhancement factor (LEF). [ABSTRACT FROM AUTHOR]

The current research work presents an evidence on overall synchronization of loosely bound strength in chaotic systems along with a new coupled design based on dual quantum dot light-emitting diodes (QDLEDs) in order to generate n-scroll attractors. To characterize these phenomena, the researchers used a theoretical approach on the basis of time series and phase space maps, i.e., attractors. In case of coupled QDLED attractors, the phases are generally locked during synchronous regime while the amplitudes are correlated. With the proposed construction scheme, both frequency detuning and coupling strength of two systems can be tuned independently. Further, chaotic attractors with even or else odd count of scrolls can also be easily generated. The study also demonstrated distinct attractors with n scrolls obtained using coupled design. [ABSTRACT FROM AUTHOR]

We numerically study the behavior of a semiconductor ring laser subject to bidirectional delayed optical feedback, when the isolated laser is in the quasi-unidirectional regime. The optical feedback, provided by two external reflectors located in front of the ring output waveguides, can modify the laser regime produced by the cross-saturation between the clockwise and the counter-clockwise mode. Thus, the system exhibits new different regimes, most of which are asymmetric and bidirectional, with alternating dominant mode. Two of these regimes are of special interest in view of applications, because the laser switching period, between the clockwise and the counter-clockwise mode, is linearly related to the time of flight from the laser to one or both reflectors. In these operating conditions, the laser is thus suitable to implement a telemeter. A convenient electrical output signal is obtained by a photodiode located behind one (partially reflecting) fixed mirror, or by measuring the voltage drop across the laser junction. Simulations are performed by mathematical models based on rate-equations, assuming typical literature parameters for a 1 mW ring laser. [ABSTRACT FROM AUTHOR]

This paper presents a novel microwave photonic (MWP) radar scheme that is capable of optically generating and processing broadband linear frequency-modulated (LFM) microwave signals without using any radio-frequency (RF) sources. In the transmitter, a broadband LFM microwave signal is generated by controlling the period-one (P1) oscillation of an optically injected semiconductor laser. After targets reflection, photonic de-chirping is implemented based on a dual-drive Mach-Zehnder modulator (DMZM), which is followed by a low-speed analog-to-digital converter (ADC) and digital signal processer (DSP) to reconstruct target information. Without the limitations of external RF sources, the proposed radar has an ultra-flexible tunability, and the main operating parameters are adjustable, including the central frequency, bandwidth, frequency band, and temporal period. In the experiment, a fully photonics-based radar with a bandwidth of 4 GHz is established for high-resolution and fast detection. The results show that a high range resolution reaching ∼1.88 cm, and a two-dimensional (2D) imaging resolution as high as ∼1.88 cm × ∼2.00 cm is achieved with a sampling rate of 100 MSa/s in the receiver. The flexible tunability of the radar is also experimentally demonstrated. The proposed radar scheme features low cost, simple structure, and high reconfigurability, which may pave the way for future multifunction adaptive and miniaturized radars. [ABSTRACT FROM AUTHOR]

A semiconductor laser with optical feedback and optical injection is an appealing scheme to construct the time-delay reservoir computing (TDRC) networks. Quantum dot (QD) lasers are compatible to the silicon platform, and hence is helpful to develop fully on-chip TDRCs. This work theoretically demonstrates a parallel TDRC based on a Fabry-Perot QD laser with multiple longitudinal modes. These modes act as connected physical neurons, which process the input signal in parallel. The interaction strength of the modes is characterized by the cross-gain saturation effect. We show that the neuron interaction strength affects the performance of various benchmark tasks, including the memory capacity, time series prediction, nonlinear channel equalization, and spoken digit recognition. In comparison with the one-channel TDRC with the same number of nodes, the parallel TDRC runs faster and its performance is improved on multiple benchmark tasks. [ABSTRACT FROM AUTHOR]

A delay-laser-based reservoir computer (RC) usually has its processing speed limited by the transient response of laser dynamics. Here, we study a simple all-optical approach to enhancing the processing speed by introducing optical injection to the reservoir layer of conventional RC that consists of a semiconductor laser with a delay loop. Using optical injection, the laser's transient response effectively accelerates due to the speeded carrier-photon resonance. In the chaotic time-series prediction task, the proposed RC achieves good performance in a flexible range of injection detuning frequency under sufficient injection rate. Using proper injection parameters, the prediction error is significantly reduced and stabilized when using high processing speed. For achieving a prediction error below 0.006, the optical injection enhances the processing speed by an order of magnitude of about 5 GSample/s. Moreover, the proposed RC extends the advantage to the handwritten digit recognition task by achieving better word error rate. [ABSTRACT FROM AUTHOR]

Due to the advantages of rich dynamics, small size, and easy integration, semiconductor lasers have many applications in microwave photonics. With a proper perturbation to invoke period-one (P1) nonlinear laser dynamics, a widely tunable microwave signal can be generated. In this paper, we concentrate on the realization and application of photonic microwave signal generation based on the P1 oscillation state of semiconductor lasers. Recent developments in P1 dynamics-based tunable microwave signal generation techniques are reviewed with an emphasis on the optical injection system, which has a large frequency tuning range that is far beyond the intrinsic relaxation oscillation frequency. In order to improve the spectral purity and stability of the generated microwave signal, two typical approaches are introduced, i.e., microwave modulation stabilization, and delayed feedback stabilization. Various applications of the P1 dynamics-based microwave signal generator in diverse signal generation and photonic microwave signal processing are described. Development trends of the P1 dynamics-based photonic microwave signal generator are also discussed. [ABSTRACT FROM AUTHOR]

In this paper, microwave photonic signal generation based on the period-one dynamic of optically injected discrete mode (DM) semiconductor lasers has been experimentally demonstrated and numerically simulated. The results show that the frequency of the generated microwave increases linearly with the frequency detuning or optical injection ratio. In addition, a single optical feedback loop is sufficient to reduce the microwave linewidth without significantly deteriorating side mode suppression. The simulation results using a model considering the nonlinear dependencies of the carrier recombination agree well with the experimental results, which indicates that the nonlinear carrier recombination effect is important in determining the nonlinear dynamics of optically injected DM lasers. [ABSTRACT FROM AUTHOR]

Semiconductor lasers (SLs) that are subject to delayed optical feedback and external optical injection have been demonstrated to perform information processing using the photonic reservoir computing paradigm. Optical injection or optical feedback can under some conditions induce bandwidth-enhanced operation, expanding their modulation response up to several tens of GHz. However, these conditions may not always result in the best performance for computational tasks, since the dynamical and nonlinear properties of the reservoir might change as well. Here we show that by using strong optical injection we can obtain an increased frequency response and a significant acceleration in the information processing capability of this nonlinear system, without loss of performance. Specifically, we demonstrate numerically that the sampling time of the photonic reservoir can be as small as 12 ps while preserving the same computational performance when compared to a much slower sampling rate. We also show that strong optical injection expands the reservoir’s operating conditions for which we obtain improved task performance. The latter is validated experimentally for larger sampling times of 100 ps. The above attributes are demonstrated in a coherent optical communication decoding task.

We present experiments and numerical simulations of optical frequency combs generated by gain-switching a single mode laser diode when subject to optical injection. Our analysis focuses on the combs with a frequency separation fR in the GHz range. We present experimental maps in the parameter space spanned by the detuning and the strength of the optical injection that identify the boundaries between regions with different dynamical states. A rich variety of nonlinear behaviors including injection-locked, unlocked and irregular combs are observed and analyzed. The dynamical state corresponding to an injection locked comb, PN, is characterized by an optical phase oscillation with a well defined amplitude in such a way that repeats or changes in 2π with an N/fR period, where N is a natural number. Different regions of locked combs with a tongue shape around detuning values given by multiples of fR appear in the maps. P1 and P2 are the most widespread locked states for large values of the modulation amplitude. As this amplitude decreases a much larger variety of PN states with large values of N appear in small area regions of the map. Our numerical simulations are in very good agreement with experimental results.

In this paper, a high-speed switchable dual-passband microwave photonic filter (MPF) using a single mode Fabry-Perot laser diode (SMFP-LD) is proposed and experimentally demonstrated. Benefiting from the wavelength selective amplification in the SMFP-LD, the +1st sideband of two external beams injected after phase modulation can be amplified in the gain spectrum of the SMFP-LD. Hence, an MPF with two tunable passbands is generated. The switching of the generated passbands is obtained through the switching signal of 1 Gbps applied to the modulator, which controls the power of one of the external beams. By properly setting the external beams’ injection parameters, the passbands of MPF can switch from single passband to no passband, single passband to dual passband, and one passband to another passband. In this experiment, the maximum center frequency and tuning range of the passbands is 45.0 GHz and 35.0 GHz, respectively. The out-of-band rejection ratio and 3 dB bandwidth of the proposed filter are 29.62 dB and 83 MHz, respectively. [ABSTRACT FROM AUTHOR]

The dynamics of a single-mode semiconductor laser under the optical injection of three signals is theoretically investigated. 3D maps of injection locking are drawn and compared when the master signals are injected at different operating points. The maps show the injection-locking bandwidth, frequency pulling region and secondary locking regions (SLR) in one picture to reveal the complete dynamics of the injected laser. Cascaded SLR are also demonstrated in the maps and explained in terms of other dynamics. [ABSTRACT FROM AUTHOR]

We have numerically investigated the dynamics of frequency shifts in semiconductor lasers under the injection of a frequency comb. We have studied the effect of comb spacing on the locking bandwidth. Frequency comb spacing was found to play an important role in the boundaries of the locking bandwidth as well as in the frequency shift of the SL peak.

The effect of the linewidth enhancement factor (LEF) on the frequency pulling behavior in optically injected lasers is theoretically investigated. The frequency pulling is found to be exponentially dependent on the LEF. This dependence is systematically revealed and explained.

In this article, we propose and investigate a novel scheme to generate optical frequency combs (OFCs) by using a three-stage generator, which is based on optical injection–induced dynamics cascaded by subharmonic electro-optic modulation and the four-wave mixing (FWM) effect. A primary seed OFC is rooted from the nonlinear dynamics in the optically injected semiconductor laser, and its performance is improved using a two-stage booster based on subharmonic electro-optic modulation and the FWM effect. The comb spacing can be easily tuned by adjusting that of the primary seed OFC or through electro-optic modulation by the use of subharmonics with different orders. Moreover, it becomes stabilized because the phase relationship between the comb teeth can be fixed in the process of subharmonic electro-optic modulation. Its optical spectrum continues to be broadened in the following FWM process. Finally, robust OFCs with a comb spacing of 4 GHz and a comb teeth number of 23 and a comb spacing of 5 GHz and a comb teeth number of 21 are experimentally demonstrated.

Period-one (P1) dynamics induced by an optically injected semiconductor laser oscillate at microwave frequencies. The oscillation frequency of a P1 dynamic can be rendered nearly insensitive to small-signal parameter fluctuations and intrinsic laser noise at appropriate operating conditions of the master and slave lasers. In this paper, the noise-canceling properties of the various low-sensitivity (LS) operating points is demonstrated through their dependency on the noise fluctuation frequency and power. The three different types of LS operating points show their effectiveness in suppressing not only P1 intensity and frequency fluctuations caused by narrowband laser perturbations but also intensity and frequency noise caused by broadband intrinsic and extrinsic noise sources.

In this letter, we experimentally demonstrate multi-band linear frequency modulation (LFM) signal generation subjected to multi-input optical injection in an external cavity-based Fabry-Pérot laser diode (ECFP-LD). The ECFP-LD is a specially designed FP-LD with a self-injected single longitudinal mode tuned up to 10 nm. The non-linear dynamics in period-one oscillation in ECFP-LD subjected to multi-input optical injection shows unique characteristics for multi-band linear frequency modulation. In the proposed scheme, four external input beams are injected to ECFP-LD, among which one is power modulated with the saw-tooth like waveform, and others are with the constant power. The varying power beam red-shifts the self-injected mode of ECFP-LD and mode-hopping on attaining a particular power level. Hence, multi-band LFM signals are generated by beating self-injected and multi-input injected beams with a large time-bandwidth product (TBWP). The total bandwidths of 12GHz (LFM1: 33–36 GHz, LFM2: 29–32 GHz, LFM3: 25–28 GHz, LFM4: 22–25 GHz) for four-band linear frequency modulation signals with a TBWP of 12000 is measured. The generated multi-band LFM signal provides flexibility on central frequency tunability and dynamic chirp rate for a multifunctional radar system. [ABSTRACT FROM AUTHOR]

This letter demonstrates a tunable multi-band linear frequency modulation (LFM) signal with improved and unidentical bandwidths subjected to optical injection in a distributed-feedback (DFB) laser. In the proposed scheme, an optical beam is divided into two paths, one modulating with a baseband LFM signal and another with a power-varying signal. The basic principle of the proposed scheme is the optical beating of the carrier-suppressed ± 1st sidebands in one path and the red-shifted emission mode of the DFB laser after optical injection in another path. In the experiment, the generated three LFM signals have the bandwidths of 11.5 GHz (from 23.0 to 34.5 GHz), 7.5 GHz (from 15.0 to 22.5 GHz), and 4 GHz (from 8.0 to 12.0 GHz) in one period of 1 μs. Moreover, we analyze the effect of the injected beam’s frequency and power on the bandwidth tunability of the generated LFM signals. [ABSTRACT FROM AUTHOR]

A delay-laser-based reservoir computer (RC) usually has its processing speed limited by the transient response of laser dynamics. Here, we study a simple all-optical approach to enhancing the processing speed by introducing optical injection to the reservoir layer of conventional RC that consists of a semiconductor laser with a delay loop. Using optical injection, the laser’s transient response effectively accelerates due to the speeded carrier-photon resonance. In the chaotic time-series prediction task, the proposed RC achieves good performance in a flexible range of injection detuning frequency under sufficient injection rate. Using proper injection parameters, the prediction error is significantly reduced and stabilized when using high processing speed. For achieving a prediction error below 0.006, the optical injection enhances the processing speed by an order of magnitude of about 5 GSample/s. Moreover, the proposed RC extends the advantage to the handwritten digit recognition task by achieving better word error rate.

Nonlinear dynamics of mutually injected twin-microring semiconductor lasers are studied numerically and experimentally. For the twin-microring laser, a bridge waveguide directly connecting two identical microrings is utilized to realize mutual optical injection or mode coupling. The coupling coefficient is related to the waveguide parameter and influences the mutual injection process dramatically. By adjusting the frequency offset between two microrings, four-wave mixing, injection locking, periodic, and multi-period oscillation states are observed from the experimental lasing spectra. The plentiful nonlinear dynamical states are induced by the mode interaction between the two microrings and can be well explained by the rate equations with mutual optical injection. [ABSTRACT FROM AUTHOR]

Dynamics of the broad-area laser with time-periodic modulation of the pump parameter and external optical radiation injection is theoretically studied. It is shown that injection efficiently suppresses transverse instabilities resulting from pump modulation. The injected signal parameters at which transverse instabilities are efficiently suppressed are determined. [ABSTRACT FROM AUTHOR]