Vertical-cavity Surface-emitting Laser Subject Research Articles

Secure multi-channel information encryption based on integrated optical device

In allusion to the privacy and security problems, a secure multi-channel information protection scheme based on an integrated optical device is proposed in this paper. The information to be encrypted and shared is converted into a QR code. For supporting the multi-channel encryption, a 1-nw encryption algorithm is employed, which possesses the capability to map the original image information into nw seemingly random cipher images. In terms of hardware, an ultra-compact optical encryption device is designed, which consists of two rows of ring resonators coupled to the waveguide. This novel encryption device can output ten cipher images, each transmitted on a separate channel. Meanwhile, the vertical-cavity surface-emitting laser subject to optical injection and optical feedback is researched to generate optical chaos sequences, which are introduced for key generation and QR code encryption. Ultimately, combining the 1-nw encryption algorithm and optical chaos, information protection is implemented based on integrated optics. The simulation results demonstrate the practical feasibility and remarkable effectiveness of the proposed scheme. Furthermore, various security and robustness analyses are performed, and the results reveal that the proposed information protection scheme has a high level of security and robustness. This work is of great significance for the development of optical encryption chips and provides potential applications for secure data sharing.

Controlling the likelihood of extreme events in an optically pumped spin-VCSEL via chaotic optical injection.

We report on the manipulation of extreme events (EEs) in a slave spin-polarized vertical-cavity surface-emitting laser (spin-VCSEL) subject to chaotic optical injection from a master spin-VCSEL. The master laser is free-running but yielding a chaotic regime with obvious EEs, while the slave laser originally (i.e., without external injection) operates in either continuous-wave (CW), period-one (P1), period-two (P2), or a chaotic state. We systematically investigate the influence of injection parameters, i.e., injection strength and frequency detuning, on the characteristics of EEs. We find that injection parameters can regularly trigger, enhance, or suppress the relative number of EEs in the slave spin-VCSEL, where the large ranges of enhanced vectorial EEs and average intensity of both vectorial and scalar EEs can be achieved with suitable parameter conditions. Moreover, with the help of two-dimensional correlation maps, we confirm that the probability of occurrence of EEs in the slave spin-VCSEL is associated with the injection locking regions, outside which enhanced relative number of EEs regions can be obtained and expanded with augmenting the complexity of the initial dynamic state of the slave spin-VCSEL.

Broadband chaos generation in VCSELs with intensity-modulated optical injection

We propose and numerically demonstrate broadband chaos generation based on vertical-cavity surface-emitting lasers (VCSELs) subject to intensity-modulated (IM) optical injection. Herein, we consider two scenarios, i.e., parallelly-polarized IM optical injection (PPIOI) and orthogonally-polarized IM optical injection (OPIOI). Specifically, we investigate the effect of injection parameters (injection strength and frequency detuning) and modulation parameters (modulation depth and modulation frequency) on the chaotic dynamic behaviors. The results confirm that both PPIOI and OPIOI can enhance the chaotic regions, bandwidth, and correlation dimension (CD) compared with continuous-wave (CW) optical injection. Besides, OPIOI seems to be more beneficial for obtaining chaotic signals with broader bandwidth and higher dimension compared with PPIOI. Therefore, this study paves the way for prosperous potential in the chaos-based applications.

Characteristics of Polarization Switching and Bistability in Vertical-Cavity Surface-Emitting Laser Subject to Continuous Variable-Polarization Optical Injection

Characteristics of Polarization Switching and Bistability in Vertical-Cavity Surface-Emitting Laser Subject to Continuous Variable-Polarization Optical Injection

Generation of Broadband Optical Frequency Comb Based on a Gain-Switching 1550 nm Vertical-Cavity Surface-Emitting Laser under Optical Injection

In this work, broadband optical frequency comb (OFC) generation by a gain-switching vertical-cavity surface-emitting laser (VCSEL) subject to optical injection is investigated experimentally. During implementing the experiment, a 1550 nm VCSEL under a large signal current modulation is driven into the gain-switching state with a broad noisy spectrum. By further introducing an optical injection, a high performance OFC can be produced. The experimental results demonstrate that the power and wavelength of the injection light seriously affect the performance of the produced OFC. Under proper optical injection parameters, two sub-combs originating from two orthogonal polarization components of the VCSEL can splice into a broadband total-OFC. By selecting optimized operation parameters, a high quality total-OFC can be acquired, with stable comb lines, high coherence, wide bandwidth of 70.0 GHz (56.0 GHz) within 10 dB (3 dB) amplitude variation and low single sideband phase noise at the fundamental frequency below −120.6 dBc/Hz @ 10 kHz.

Experimental Investigations on Polarization Switching and Bistability in a 1550 nm VCSEL Subject to Orthogonal Optical Injection With Time-Varying Injection Power

Polarization switching (PS) and polarization bistability (PB) characteristics of a 1550 nm vertical-cavity surface-emitting laser (VCSEL) subject to orthogonal optical injection (OOI) with time-varying injection power are experimentally investigated for the first time. To implement the optical injection, a Mach-Zehnder modulator (MZM) modulated by a triangular radio wave is adopted, and the influences of some typical parameters on the performances of PS and PB are analyzed. Under suitable operation conditions, PB in the VCSEL subject to OOI with time-varying injection power can be observed only for the input power P0 of MZM locating within a determined range, and the width of hysteresis loop gradually decreases with the increase of P0 from the minimum P0, min to the maximum P0, max. Under different frequency detuning Δ ν between the injection light and the X polarization mode of the VCSEL, the determined ranges of P0 required for PB are different. With the variation of Δ ν from a negative value to a positive value, both P0, min and P0, max present a trend of decrease first and then increase. Additionally, with the increase of the modulation frequency, the hysteresis loop width firstly increases rapidly and then gradually tends saturation.

Enhanced memory capacity of a neuromorphic reservoir computing system based on a VCSEL with double optical feedbacks

In this paper, a neuromorphic reservoir computing (RC) system with enhanced memory capacity (MC) based on a vertical-cavity surface-emitting laser (VCSEL) subject to double optical feedbacks (DOF) is proposed and investigated numerically. The aim of this study is to explore the MC of the proposed system. For the purpose of comparison, the MC of the VCSEL-based RC system with single optical feedback (SOF) is also taken into account. It is found that, compared with the VCSEL-based RC system subject to SOF, enhanced MC can be obtained for the VCSEL-based RC system with DOF. Besides, the effects of feedback strength, injected strength, frequency detuning as well as injection current on the MC of the VCSEL-based RC system with DOF are considered. Moreover, the influence of feedback delays is also carefully examined. Thus, such proposed VCSEL-based RC system with DOF provides a prospect for the further development of the neuromorphic photonic system based on RC.

VCSEL-Based Optical Frequency Combs Expansion Induced by Polarized Optical Injection

The present theoretical work studies optical frequency combs (OFCs) associated with both linear polarizations of a gain switching vertical-cavity surface-emitting laser (VCSEL) subject to optical injection of arbitrary polarization. The overall OFC, formed by the two orthogonally polarized sub-combs, can have an expanded optical span in agreement with experiments reported by Prior et al. We show that the maximum optical span is obtained for a certain angle between the linearly polarized optical injection and the direction of emission of the main mode of the free-running VCSEL. We find that this angle decreases as the injection strength increases. We also characterize the maximum expansion of the optical span of the overall comb. For VCSELs with large birefringence splitting the maximum expansion is the optical span of the free-running OFC, while for small birefringence splitting VCSELs the maximum expansion is the value of the birefringence splitting.

Numerical investigations on multi-channel wideband chaotic signal generation by a multi-transverse mode vertical-cavity surface-emitting laser subject to chaotic optical injection.

A multi-channel wideband chaotic signal generation scheme is proposed and numerically investigated based on a slave multi-transverse mode vertical-cavity surface-emitting laser (SL) subject to chaotic optical injection from a master multi-transverse mode vertical-cavity surface-emitting laser (ML) with optical feedback. Taking two low-order transverse modes, LP01 and LP11, as an example for numerical calculations, the simulated results show that under suitable optical feedback both the LP01 and LP11 modes (two-channel) of a ML can be driven into the chaotic states where their bandwidths are relatively narrow at a level about 8 GHz. Further injecting the two chaotic signals into a SL, for the case of the globally chaotic optical injection, the SL can output two-channel chaotic signals with wide bandwidths above 20 GHz under appropriate operation parameters. Moreover, the case of SL with mode-selective chaotic optical injection is also analyzed.

Parallel information processing by a reservoir computing system based on a VCSEL subject to double optical feedback and optical injection.

In this work, we propose a scheme of reservoir computing (RC) for processing a Santa-Fe time series prediction task and a signal classification task in parallel, and the performances of the RC have been numerically investigated. For this scheme, a vertical-cavity surface-emitting laser (VCSEL) simultaneously subject to double optical feedback and optical injection is utilized as a nonlinear node, and the parallel information processing of the RC system is implemented based on the dynamical responses of X polarization component (X-PC) and Y polarization component (Y-PC) in the VCSEL. Considering that two different feedback frames (polarization-preserved optical feedback (PP-OF) or polarization-rotated optical feedback (PR-OF)) may be adopted in two feedback loops, four feedback combination cases are numerically analyzed. The simulated results show that the parallel processing ability of the proposed RC system depends on the feedback frames adopted in two loops. After comprehensively evaluating the parallel processing performances of the two tasks under different feedback combinations, the best parallel processing performance can be achieved by adopting PP-OFs in both two feedback loops. Under some optimized operation parameters, this proposed RC system can realize the lowest prediction error of 0.0289 and the lowest signal classification error of 2.78 × 10-5.

Real-time 850 nm multimode VCSEL to 1 550 nm single mode VCSEL data routing for optical interconnects

Short-reach optical interconnects among massive serves in data centers have attracted extensive research recently. Increasing capacity, cost and power efficiency as well as wavelength switching between data center network nodes are still key challenges for current optical interconnects. In this work, we experimentally demonstrate the real-time inter-mode optical wavelength switching technique, for high-speed wavelength flexible data center interconnects. A 10 Gbit/s 1 550 nm single mode vertical cavity surface emitting laser (VCSEL) is optically injected and used to control a 10 Gbit/s multimode VCSEL carrier at 850 nm. Results show that a clearly open eye diagram is achieved at back-to-back analysis, implying a successful wavelength switch and error-free operation at 10 Gbit/s. A fully optical wavelength conversion of a multimode VCSEL operation at 850 nm using a single mode VCSEL subject to external optical injection at 1 550 nm is reported. This work opens new perspectives towards the development of a cost effective high-speed real-time inter-band wavelength switching technique between servers and network devices operating at different transmission windows at network nodes, for current and future optical interconnects.

Electrically Controlled Neuron-Like Spiking Regimes in Vertical-Cavity Surface-Emitting Lasers at Ultrafast Rates

We report experimentally on the electrically controlled, tunable, and repeatable neuron-like spiking regimes generated in an optically injected vertical-cavity surface-emitting laser (VCSEL) operating at the telecom wavelength of 1300 nm. These fast spiking dynamics (obtained at sub-nanosecond speed rates) demonstrate different behaviors observed in biological neurons such as thresholding, phasic and tonic spiking, and spike rate and spike latency coding. The spiking regimes are activated in response to external stimuli (with controlled strengths and temporal duration) encoded in the bias current applied to a VCSEL subject to continuous wave optical injection. These results reveal the prospect for fast (>7 orders of magnitude faster than neurons), novel, electrically controlled spiking photonic modules for future neuromorphic computing platforms.

Intrinsically Stabilized Plastic Optical Fiber Link Subject to External Optical Feedback

We develop a graded-index plastic optical fiber (GI POF) that can significantly stabilize a multimode fiber (MMF) link with a vertical-cavity surface-emitting laser (VCSEL) subject to external optical feedback. It is demonstrated that the dominant mechanism for this stabilization effect is the strong mode coupling of the GI POF, which is closely related to the polymer-specific microscopic heterogeneities in the GI POF core material. Such mode coupling decreases correlation between the problematic reflected light field and VCSEL cavity field, increasing tolerance of the MMF link for external optical feedback. Our developed GI POF with specific microscopic heterogeneities prevents the external-optical-feedback-induced critical destabilization observed for silica GI MMFs. These results suggest that the stabilization effect can be controlled by microscopic properties regardless of the fiber attenuations and core refractive indices.

Frequency-induced polarization switching and bistability in a 1550 nm VCSEL subject to parallel optical injection

We experimentally investigate frequency-induced polarization switching (PS) and bistability (PB) characteristics in a 1550 nm vertical-cavity surface-emitting laser (1550 nm VCSEL) subject to parallel optical injection, for which the polarization direction of the injection light is along with the direction of dominant polarization mode in the solitary 1550 nm VCSEL. The results show that, for a 1550 nm VCSEL under parallel optical injection with frequency detuning ∆ν (= νinj − ν0, where νinj is the frequency of injection light and ν0 is the frequency of dominant polarization mode of the solitary 1550 nm VCSEL), type I PS (the dominant polarization mode switches from Y-polarization mode with a shorter wavelength to X-polarization mode with a longer wavelength) and type II PS (the dominant polarization mode switches from X-polarization mode to Y-polarization mode) can be observed through continuously scanning the frequency of injection light. Moreover, the values of ∆ν required for generating PSs are dependent on the variation route, namely frequency-induced PB phenomenon occurs. In the region with negative ∆ν, there exist two hysteresis loops, whose widths are seriously influenced by the injection power and the biased current.

Dynamics of a Bistable VCSEL Subject to Optical Feedback From a Vibrating Rough Surface

The paper presents an experimental study of the temporal behaviour of a bistable vertical cavity surface emitting laser (VCSEL) under the effect of optical feedback coming from vibrating diffusely-reflecting surface. We demonstrate that a VCSEL operating in the regime of polarization switchings caused by self-mixing effects can greatly enhance a responsivity of the detection of microvibrations. For small amplitudes of microvibrations (less than $\lambda$/2, where $\lambda$ is the operating wavelength of the laser), which cause only harmonic (or close to harmonic) oscillations in the laser output outside of the bistability region, the use of polarization switching can increase the responsivity up to 45 times. For the amplitudes larger then $\lambda$/2 the response of a bistable VCSEL well reproduces a fine temporal structure of the self-mixing signal. A procedure of the data processing in the switching regime for the correct determination of the direction of the displacement and for the reconstruction of the waveform of surface vibrations with a basic resolution of $\lambda$/2 is also shown.

Photonic Generation of Neuron-Like Dynamics Using VCSELs Subject to Double Polarized Optical Injection

We propose to generate excitatory and inhibitory neuron-like dynamics in vertical-cavity surface-emitting lasers (VCSELs) by applying simultaneously the orthogonally-polarized CW optical injection (OPCWOI) and parallelly-polarized pulse optical injection stimulus. Based on the spin flip model, excitatory and inhibitory neuron-like dynamics accompanying with reverse polarization switching is numerically investigated. It is found that, due to the injection locking effect or beating effect between two injected fields, the excitatory phasic and tonic spiking dynamics can be obtained in the originally dominated polarization mode. Moreover, the unwanted relaxation oscillation followed by the excitatory spiking dynamics at the end of the stimulus pulse, which is present in previous reported photonic neuron based on the VCSELs subject to a single orthogonally-polarized optical pulse injection, can be completely suppressed. In addition, the inhibition of tonic spiking dynamics can also be achieved, and the transition from tonic spiking dynamics to phasic bursting dynamics can be obtained, when the two injected fields have the same frequency. These results are interesting and valuable for the ultrafast photonic neuromorphic systems and neuron-inspired photonic information processing.

Complex-enhanced chaotic signals with time-delay signature suppression based on vertical-cavity surface-emitting lasers subject to chaotic optical injection

A chaotic system is constructed on the basis of vertical-cavity surface-emitting lasers (VCSELs), where a slave VCSEL subject to chaotic optical injection (COI) from a master VCSEL with the external feedback. The complex degree (CD) and time-delay signature (TDS) of chaotic signals generated by this chaotic system are investigated numerically via permutation entropy (PE) and self-correlation function (SF) methods, respectively. The results show that, compared with master VCSEL subject to optical feedback, complex-enhanced chaotic signals with TDS suppression can be achieved for S-VCSEL subject to COI. Meanwhile, the influences of several controllable parameters on the evolution maps of CD of chaotic signals are carefully considered. It is shown that the CD of chaotic signals for S-VCSEL is always higher than that for M-VCSEL due to the CIO effect. The TDS of chaotic signals can be significantly suppressed by choosing the reasonable parameters in this system. Furthermore, TDS suppression and high CD chaos can be obtained simultaneously in the specific parameter ranges. The results confirm that this chaotic system may effectively improve the security of a chaos-based communication scheme.

Attractor hopping between polarization dynamical states in a vertical-cavity surface-emitting laser subject to parallel optical injection.

We present experimental and theoretical results of noise-induced attractor hopping between dynamical states found in a single transverse mode vertical-cavity surface-emitting laser (VCSEL) subject to parallel optical injection. These transitions involve dynamical states with different polarizations of the light emitted by the VCSEL. We report an experimental map identifying, in the injected power-frequency detuning plane, regions where attractor hopping between two, or even three, different states occur. The transition between these behaviors is characterized by using residence time distributions. We find multistability regions that are characterized by heavy-tailed residence time distributions. These distributions are characterized by a -1.83±0.17 power law. Between these regions we find coherence enhancement of noise-induced attractor hopping in which transitions between states occur regularly. Simulation results show that frequency detuning variations and spontaneous emission noise play a role in causing switching between attractors. We also find attractor hopping between chaotic states with different polarization properties. In this case, simulation results show that spontaneous emission noise inherent to the VCSEL is enough to induce this hopping.

Key distribution based on unidirectional injection of vertical cavity surface emitting laser system

Random source is important for the security of key distribution. In this paper, a novel secure key distribution scheme based on unidirectional injection of vertical cavity surface emitting laser (VCSEL) system is proposed. In the proposed scheme, a chaotic signal without time delay signature is generated by a VCSEL subject to unidirectional optical injection, which is regarded as a master laser. The chaotic signal generated by the master VCSEL is further injected into two slave VCSELs to obtain synchronized bandwidth-enhanced chaotic signals. After that, by sampling, quantizing and XOR operation on the two synchronized chaotic signals, two key streams can be obtained. Based on the well-known spin-flip model, the time delay signature of chaotic signals generated by master VCSEL and the synchronization performance between the master VCSELs and two slave VCSELs are numerically investigated in detail. It is shown that by the unidirectional injection, the chaotic outputs can be achieved in the master VCSEL in a wide range of frequency detuning and coupling strength. More importantly, no time delay signature can be observed in the auto correlation function of the chaotic intensity time series generated by the master VCSEL. Besides, we find that high quality synchronization is achieved between the bandwidth-enhanced chaotic signals generated by two slave VCSELs under the common driving of master VCSEL. The synchronization coefficient between two slave VCSELs increases up to 0.99, and the synchronization coefficient between master VCSEL and salve VCSEL is only 0.74. Note that such a high quality synchronization between two slave VCSELs while relatively low quality synchronization between the master and slave VCSEL is conducible to ensuring the security of key distribution. In addition, the effects of tunable parameters on key bit error rate are considered, and two quantization methods are employed for comparison. Numerical simulation results show that the key bit error rate between two legitimate users is as low as 1%, and the key bit error rate between legitimate user and eavesdropper is higher than 10% in the single-threshold case; the bit error rate can even be as low as 10-6 in the double-threshold case. The influence of parameter mismatch on key bit error rate is also discussed, and it is suggested that two salve VCSELs should be finely matched to ensure low bit error rate. Finally, NIST randomness test is performed for the generated key streams. Hence, the proposed scheme enhances the security of key distribution, which is valuable for further developing the chaos communication systems.

Cascadable Neuron-Like Spiking Dynamics in Coupled VCSELs Subject to Orthogonally Polarized Optical Pulse Injection

The cascadability of spiking dynamics in coupled vertical-cavity surface-emitting lasers (VCSELs) subject to orthogonally polarized optical pulse injection (OPOPI) is investigated numerically based on the well-known spin-flip model. For the coupled VCSELs systems, different connection topologies are considered. The effects of stimuli strength, coupling strength, frequency detuning between two coupled VCSELs, and the pump current on the cascadable spiking dynamics are examined by extensive numerical bifurcation analysis. It is found that, the phasic spike generated in one VCSEL with OPOPI can also induce a similar phasic spike in another VCSEL in three considered connection topologies. Besides, such a cascadable spiking behavior can be achieved in wide range of stimuli strength, coupling strength, and frequency detuning. However, failure transfer of the phasic spike between two VCSELs may be caused when the pump currents are relatively large, and hence, low pump currents are desirable for both VCSELs to allow for successful cascadable spiking dynamics. This work is interesting and valuable for constructing reliable optical spiking information processing platform based on polarization dynamics of VCSELs.