We have experimentally investigated the generation of tunable and broadband Optical Frequency Comb (OFC) based on a gain-switching vertical-cavity surface emitting laser driven by a square wave signal under optical injection. During the experiment, the influences of modulation frequency fm and injection light wavelength λion OFC performances are analyzed systematically. The experimental results indicate that under suitable operation parameters, an OFC with bandwidth of 77.0 GHz within 10 dB power variation and single sideband phase noise of -115.7 dBc/Hz @ 10 kHz can be generated. Also, during the modulation frequency range of 1.5 GHz - 2.8 GHz, broadband OFCs with bandwidth exceeding 70.0 GHz can be obtained based on the square-current modulated VCSEL under optical injection.
Based on a vertical-cavity surface-emitting laser with saturated absorber (VCSEL-SA) subject to optical injection, we proposed an ultrafast pattern recognition scheme of four-bit binary data and theoretically investigated the recognition performances. The results show that, patterns recognition of different four-bit binary data at Gb/s rate can be realized by adjusting the injection weight of each bit number and optimal weight values can be determined. Although noise has some influences on the patterns recognition speed and accuracy, this proposed system has a certain robustness to noise on the whole. These results provide a promising application prospect for VCSEL-SA based ultrafast photonic neuromorphic system in pattern recognition field.
KEYWORDS: Microwave radiation, Microwave photonics, Photonic microstructures, Semiconductor lasers, Modulation, Microsoft Foundation Class Library, Signal generators, Frequency combs, Phase shift keying, Nonlinear dynamics
Semiconductor lasers (SLs) under external disturbances can be driven into diverse nonlinear dynamical states such as period-one, period-two, multi-period, and chaos. Based on the period-one nonlinear dynamical state in an optically injected semiconductor laser, tunable single-tone microwave signal, ultra-broadband microwave frequency combs, and frequency-modulated continuous wave can be generated. Moreover, through introducing optical feedback, a SL under pulsed current modulation can output pulsed chaotic signal, which can be applied in anti-interference radar.
A system for generating ultra-broadband microwave frequency combs (MFCs) is proposed and investigated. In such a system, a current modulated distributed feedback semiconductor laser (DFB-SL) is utilized to generate a seed resource of MFC, whose comb space can be tuned but bandwidth is relatively narrow. Then, the seed resource of MFC is injected into another DFB-SL for enhancing the bandwidth. The results demonstrate that, after being injected into another DFB-SL, the bandwidth of seed resource of the MFC can be enhanced greatly, and the MFC with bandwidth over 70 GHz can be obtained under suitable injection parameters.
High-quality photonic microwave generation is experimentally demonstrated based on the period-one (P1) dynamical state output from an optically injected 1550 nm vertical-cavity surface-emitting laser (1550 nm-VCSEL) subject to optoelectronic negative feedback. The experimental results show that, under suitable injection condition, the 1550 nm-VCSEL can generate a photonic microwave signal with single sideband optical spectrum structure, but the linewidth of the microwave signal is relatively wide (on the order of MHz). After further introducing optoelectronic negative feedback, the linewidth of the microwave signal can be narrowed two orders of magnitude to 105.7 kHz. Furthermore, for the case that the feedback strength is set at an optimized value, the frequency of the microwave signal can be tuned continuously within a certain range through simply adjusting the injection strength.
A bidirectional chaos communication system, composed of 1550nm semiconductor lasers (SLs) and fiber links, is
experimentally and numerically investigated. Based on the robust chaos synchronization between two authorized SLs,
0.5Gbits/s pseudo-random data bidirectional message transmission between the two SLs has been preliminarily realized
experimentally. Moreover, related theoretical simulations are also given, which basically conforms to our experimental
observations.
In this paper, after taking into account two situations that the polarization of the injection light is parallel or orthogonal
with the solitary vertical-cavity surface-emitting laser (VCSEL) output light, the nonlinear dynamic characteristics of an
optical injection VCSEL are investigated numerically. The simulated results show that VCSEL can exhibit periodic
oscillations, deterministic chaos and other complex instabilities under optical injection. For parallel or orthogonal optical
injection, the same injection coefficients have different effects on the output of VCSEL. By properly adjusting the
injection strength or detuning frequency, the dynamical state of the laser output can be controlled to a fixed state, and the
polarization of the VCSEL output light can also be controlled.
Based on the theoretical model of the synchronization system with incoherent optical feedback, the influence of the
internal parameter mismatch on the synchronized characteristics of the chaotic system has been investigated. The result
shows that the chaotic system with incoherent optical feedback can be realized more easily than the complete
synchronized system, and has higher security than injection locking synchronization system. Using encoding of chaos
shift keying, the message can be hidden efficiently during the transmission in the system and decoded easily in receiver.
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