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A scheme for generating wideband optical frequency comb (OFC) is proposed and experimentally investigated based on a master-slave system. In such a system, a tunable optical resource and a distributed feedback semiconductor laser are utilized as master lasers (MLs), and their outputs provide dual optical injection (DOI) into a slave laser (SL) which is a 1550 nm multi-transverse mode vertical-cavity surface-emitting laser (1550 nm-VCSEL) operating at gain-switched state. For the 1550 nm-VCSEL biased at a relatively high current, two low-order transverse modes LP01 and LP11 can simultaneously lase and possess comparable powers. After loaded a large signal modulation, the 1550 nm-VCSEL can be driven into gain-switched state, and two separated sub-combs originating from two transverse modes can be generated. Through further introducing DOI to the gain-switched 1550 nm-VCSEL, the two sub-combs can link up to form an overall OFC under suitable operation parameters. The experimental results show that, through selecting optimized operating parameters, the bandwidth of the integral OFC within 10 dB amplitude variation can achieve 150.0 GHz. Additionally, the effects of the wavelengths of the two injection lights on the bandwidth of the overall OFC are also analyzed.

Taking the broadband chaotic output from a weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) under filtered feedback as a chaotic entropy source, we propose and experimentally demonstrate a scheme for generating fast physical random bits (PRBs) at a rate up to 240 Gbits/s. First, we investigate the dependence of the dynamical properties of the filtered feedback WRC-FPLD on the system parameters, and determine the optimized parameter region for generating wavelength-tunable and broadband chaotic signals. Second, a broadband chaotic signal with a bandwidth beyond 20 GHz output from the WRC-FPLD is sampled and transferred to a digital bit sequence by an 8-bit analog-to-digital converter at a rate of 40 GS/s. Finally, by utilizing multi-bit post-processing method, PRBs is generated at a rate up to 240 Gbits/s, which can pass all the 15 NIST statistics tests and meet the strict criteria of the statistical bias and the serial correlation coefficient.

We investigate experimentally and theoretically the communication of inhibited spiking dynamics between two interlinked photonic neurons based upon the vertical-cavity surface-emitting lasers (VCSELs). We show that the sub-nanosecond speed spiking dynamics fired by a Transmitter-VCSEL (T-VCSEL) can be inhibited under the arrival of suitable external stimuli and that the inhibited spiking behaviors are propagated into another Receiver-VCSEL (R-VCSEL). Both VCSELs exhibit analogous inhibited spiking dynamics in response to stimuli with different temporal durations and strength. In addition, a very good agreement is found between theoretical simulations and experiments. These results offer greater prospects for future networks of VCSEL-based photonic neurons for neuromorphic computing platforms.

In this work, a novel optoelectronic oscillator (OEO) structure is proposed for generating widely tunable photonic microwave. In this structure, an optical injection semiconductor laser (OISL) functions as an active tunable microwave photonic filter (MPF). Through controlling the injection power and frequency detuning, the OISL is driven into period-one dynamics whose oscillation frequency can be widely tuned from 10.43 to 65.82 GHz. As a result, the OISL can be regarded as a widely tunable active MPF. By introducing an optical feedback loop, the filtered bandwidth of the widely tunable active MPF can be further reduced. Taking the OISL under optical feedback as a widely tunable narrow-bandwidth MPF and a seeding laser source to establish an OEO structure, widely tunable narrow-linewidth photonic microwave can be generated. The experimental results demonstrate that widely tunable photonic microwaves ranging from 10.43 to 39.10 GHz with linewidths below 0.1 MHz and phase variances below 10-2 (rad2) can be achieved.

We have experimentally demonstrated and characterized the generation of tunable and ultra-broadband microwave frequency combs (MFCs) based on a slave laser (SL) subject to regular pulse injection from a current modulated master laser (ML). Under modulation frequency fm = 1.2 GHz and modulation power Pm = 22 dBm, the current modulated ML is driven into a regular pulse state, and a seed MFC with 14.4 GHz bandwidth within a ±5 dB amplitude variation can be obtained. Such a seed MFC is then injected into the SL for producing final MFC with higher performances. For a fixed detuning frequency fi = 0 GHz and optimized injection power Pi = 2060 μW, the bandwidth of the final MFC is increased to 33.6 GHz, and the single-sideband phase noises of all comb lines of the MFC within the bandwidth can be decreased to below -90.9 dBc/Hz@10 kHz. Additionally, the influences of Pi and fm on the MFC bandwidth are also analyzed. The experimental results are in agreement with numerical simulations to a certain extent.

We experimentally demonstrate multi-channel physical random bits (PRBs) generation by utilizing chaotic outputs from two linear polarization modes in a vertical-cavity surface-emitting laser (VCSEL) under a chaotic optical injection. The polarization-resolved chaotic signal is obtained with a master-VCSEL subject to optical feedback, and then injects into a slave-VCSEL for driving its two linear polarization modes into chaotic state. We analyze the influences of injection parameters on bandwidth, complexity, and the correlation of two-channel chaotic signals. By using the two chaotic signal outputs from the slave-VCSEL under optimized parameters as entropy sources, we have obtained the PRBs at the dual-channel rate of 160 Gbits/s by adopting the m least significant bits extraction with logical exclusive-OR (XOR) post-processing. Further utilizing the n-bit cross-merging method, the PRB at a rate of 320 Gbits/s could be obtained.

The polarization bistability (PB) features in a 1550 nm vertical-cavity surface-emitting laser (1550 nm-VCSEL) subject to variable polarization optical injection (VPOI) are experimentally investigated. We have investigated the influence of polarization angle θ, of optical injection on PBs induced by scanning the power (power-induced PB) and the frequency of injected light (frequency-induced PB) along with different routes. The experimental results show that, for the fixed frequency of the injection laser and by scanning the injection power within a certain region, there exists a determined range of θ, in which power-induced PB in the 1550 nm-VCSEL subject to VPOI can be observed. For VPOI with θ, located within the determined range, the power-induced PB possesses larger hysteresis width, as compared with orthogonally polarized optical injection. The hysteresis width will be larger for a smaller value of θ,. Under the condition of fixed injection power and continuously varying the frequency of the injection laser, two frequency-induced hysteresis cycles can be observed, of which one is located at negative frequency detuning, and the other is located at positive frequency detuning. The variations of the two hysteresis width with θ, exhibit different trends. Also, when the bias current of the 1550 nm-VCSEL increases, the hysteresis width can be further broadened for the power-induced PB, and the broadening effect is relatively weak for the frequency-induced PB.

We have demonstrated and characterized the generation of ultra-broadband microwave frequency combs (MFCs) based on a current modulated distributed feedback semiconductor laser (DFB-SL) subject to optical injection, and the comb spacing of MFCs can be tuned easily through adjusting the modulation frequency fm. For the DFB-SL under only current modulation with modulation frequency fm = 1.2 GHz and modulation power Pm = 22 dBm, the generated MFC has a bandwidth of about 15.6 GHz within ±5.0 dB amplitude variation. Further, introducing continuous-wave optical injection into the current modulated DFB-SL with injection power Pi = 1170 μW and no frequency detuning between the injection light frequency and the oscillation frequency of the free-running DFB-SL, the bandwidth of MFC can be increased to 57.6 GHz. Through measuring the single sideband (SSB) phase noises of some representative comb lines, the performances of the MFCs generated before and after introducing optical injection are compared, and the SSB phase noises at 10 kHz offset frequency can be increased by 10 dB for the harmonics with frequencies of more than 40fm after adopting optical injection. Moreover, the influences of operation parameters on the bandwidths of MFCs are analyzed, and the optimized parameter range for generating ultra-broadband MFCs has been determined.

Bistability in a single-mode distributed feedback semiconductor laser (DFB-SL) with positive optoelectronic feedback (POEF) is observed experimentally. For a given biased current, the output dynamical states of DFB-SL with POEF are critically dependent on variation routes of the laser-biased current. Different routes of biased current variation lead to a bistability characterized by states of different time series, power spectra, and phase portraits. [ABSTRACT FROM PUBLISHER]

A long-distance isochronous chaos synchronization system, composed of a driving chaotic semiconductor laser and twin semiconductor lasers, is demonstrated experimentally. Via a driven chaotic signal which is generated by the driving chaotic semiconductor laser subject to external feedback and then injects into the twin semiconductor lasers by a pair of 20-km single-mode fibers, respectively, isochronous synchronization between the twin semiconductor lasers is experimentally observed. Further results show that high-quality isochronous synchronization can still be maintained even though the correlation coefficient between the driving laser and twin lasers is low. In addition, the bandwidth of synchronized chaotic signals is enhanced to more than 10 GHz although the bandwidth of driving signal is about 5.7 GHz. [ABSTRACT FROM PUBLISHER]