Demultiplexing chaos from multimode semiconductor lasers

We show numerically that the injection of two chaotic modes of a multimode semiconductor laser with optical feedback into two single-mode stand-alone semiconductor lasers leads to chaotic synchronization between the respective intensities. The effect of parameter mismatch between the transmitter and receiver lasers is examined, and it is concluded that the observed synchronization is a consequence of injection locking. Under these conditions, the possibility of using this demultiplexing scheme for message transmission is examined.     

Time-wavelength multiplexing of mode-locked external-cavity semiconductor lasers

A technique for obtaining multicolor operation of mode-locked lasers has been applied to an external-cavity semiconductor laser. The generation of two perfectly synchronized optical pulse trains of different wavelengths from such a laser is demonstrated.     

Antiphase dynamics of selectively coupled multimode semiconductor lasers

We analyze the experiment of A. Uchida et al. (2001) reporting on the synchronization of multimode semiconductor lasers coupled unidirectionally through one of the transmitter modes. We show that only the coupled modes are synchronized and that the dynamical regimes of the two lasers are different, though leading to similar power spectra.     

Coherence properties of gain- and index-guided semiconductor lasers

The spectral linewidth of the longitudinal laser modes has been measured as a function of mode power for different types of gain-guided as well as index-guided (GaAl)As double heterostructure laser diodes. Various effects contributing to line broadening, such as spontaneous emission, carrier density fluctuations, changes of the resonator parameters, and mode competition are discussed.     

高功率半导体二极管阵列激光器

半导体二极管阵列激光器是高效、小型、全固态源.本文论述高功率二极管阵列激光器的性能和关键技术,并给出了它最新的进展和未来的应用.     

光注入多模半导体激光器的混沌及其同步

为了在光纤通信中实现多模同步传输以提高通信容量,构建了一个光注入多模半导体激光器开环混沌通信系统,并利用MATLAB数值仿真了系统的同步性能。结果表明,选取合适的系统参量,多模半导体激光器混沌通信系统能够实现完全同步;发射激光器和接收激光器对应模式可以实现完全同步,而且系统对内部参量失配具有较好的容忍性。     

975 nm multimode semiconductor lasers with high-order Bragg diffraction gratings

The 975 nm multimode diode lasers with high-order surface Bragg diffraction gratings have been simulated and calculated using the 2D finite difference time domain(FDTD) algorithm and the scattering matrix method(SMM).The periods and etch depth of the grating parameters have been optimized.A board area laser diode(BA-LD) with high-order diffraction gratings has been designed and fabricated.At output powers up to 10.5 W,the measured spectral width of full width at half maximum(FWHM) is less than 0...     

Bandwidth of linearized electrooptic modulators

Many schemes have been proposed to make high dynamic range analog radio frequency (RF) photonic links by linearizing the transfer function of the link's modulator. This paper studies the degrading effects of finite transit time and optical and electrical velocity dispersion on such linearization schemes. It further demonstrates that much of the lost dynamic range in some modulators may be regained by segmenting and rephasing the RF transmission line     

Operation mechanism of electrooptic multimode X-switches

The operation mechanism of electrooptic multimode switches using crossing channel waveguides (X-switch) is investigated theoretically and experimentally. The light propagation through the X-structure as well as the switching behavior of the device is explained in terms of local normal modes. The theoretical model is confirmed by numerical calculations (BPM) and by experiments using Ti:LiNbO3multimode channel waveguides. The results indicate that the generally applied model of total internal reflection (TIR) is not suited to explain the low voltage operation of multimode X-switches.     

Wavelength-locking and coherence-collapsed operation of multimode semiconductor lasers induced by external injection

We have experimentally and theoretically demonstrated that residual power from a fiber Bragg grating-stabilized 980-nm pump laser in a coherence-collapsed state can be used to lock the wavelength of another solitary 980-nm pump. The coherence collapsed operation is transferred to the slave laser.     

Spectral investigation of multimode fiber Bragg grating based external-cavity semiconductor lasers

The output spectra of external-cavity semiconductor lasers (ECSLs) formed by using different antireflection (AR) coated laser diodes (LDs) with multimode fiber Bragg gratings (MMFBGs), are studied systematically. It is found that the side mode suppression ratio (SMSR) of the output spectra of ECSL is dependent on the relative position of the Bragg wavelength and the intracavity modes of the LD, and this effect is more apparent when the reflectivity of AR coating of LD is increased. Numerical simulations are provided to explain the experimental observations. Furthermore, the requirements of wavelength locking of ECSLs with MMFBGs are found to be different from those with single-mode fiber Bragg gratings (SMFBGs). The conditions of wavelength locking of the MMFBG-based ECSLs in terms of gain margin between the material gain peak and the gain corresponding to the selected Bragg wavelength, reflectivity of AR coating of LD and reflectivities of the Bragg wavelengths of MMFBG are comprehensively investigated, and compared with the experimental results.     

Proposed wide-band and low-drive-power electrooptic modulators

Novel methods for the wide-band and low-drive-power electrooptic modulators are proposed. This wide-band and low-drive-power performance is obtained by the utilization of relative electrical and optical delays. Both a lumped and a traveling-wave configuration are described.     

Optical time-division multiplexing signal processing using electro-optic modulators

We present some optical signal processing methods for optical time-division multiplexing, based on electro-optic modulators. Dual-parallel Mach–Zehnder modulator and time-lens-based signal processing for optical frequency comb generation, optical Nyquist pulse generation and time-domain demultiplexing are realized. Multifunctional optoelectronic oscillators which are capable of performing simultaneous electrical clock recovery, optical clock recovery and demultiplexing are demonstrated with modulators embedded as the key components.     

Fibre optic modulators using active multimode waveguide overlays

The evanescent field coupling between a singlemode optical fibre, side polished close to the core and a high index, multimode, planar waveguide overlay has been investigated as a means of realising inline modulators without interruption of the fibre. Oils of known refractive index and thin layers of polished lithium niobate have been used in the role of the overlay and an electro-optic inline intensity modulator based on the latter has been realised and tested. The results demonstrate the technical feasibility of fabricating rugged, low loss solid state devices offering performances which are realistic in terms of applications.<>     

Active mode locking of lasers using an electrooptic deflector

The deflector shows excellent loss modulation characteristics in a laser cavity under large signal operation. The mode locker is capable of generating very short optical pulses comparable to those obtained by passive mode locking. In experiments, an LiTaO₃ double-prism deflector is used as the mode locker for an Nd:glass laser. As a result, stable 6-ps pulses are obtained     

Analysis of circular-polarization electrooptic amplitude modulators

An analysis of electrooptic (EO) amplitude/IM modulators of light having the form of circular polarizer-sample-circular analyzer (CPSA) systems is presented. On the assumption of nonideal components, with the sample being a linear EO crystal, principal characteristics and performance parameters of the above modulators are derived and investigated as to the effect of azimuthal misalignments &thetas; in the crystal birefringence axes. The so obtained results are compared with those drawn from the study of linear-polarization EO amplitude modulators structured as linear polarizer-sample-linear analyzer (LPSA) systems in their optimized variety (45°-CLPSA modulators). From this comparison, it is found that a CPSA modulator in its optimized configuration (ACPSA modulator) is superior in EO-modulation sensitivity and considerably more stable against misalignments &thetas; than its 45°-CLPSA counterpart. On the other hand, both kinds of modulator exhibit identical behavior as regards harmonic distortion and maximum-nonlinearity parameters     

The dependence of carrier lifetime on spectral width in multimode semiconductor lasers

Comprehensive measurements of the dependence of the carrier lifetime, eye pattern, and power penalty on the spectral width in multimode semiconductor lasers for a gigabit lightwave transmission system are presented. The results show that the carrier lifetime, eye pattern, and power penalty caused by mode partition noise (MPN) are strongly dependent on the source spectral width. The lasers with shorter carrier lifetimes exhibit a narrow spectral width, and hence show less MPN, a better eye opening, and a lower power penalty. A theoretical calculation of the MPN-induced power penalty is in good agreement with the measured system penalties. The likely cause for narrow spectral width with shorter carrier lifetime of the lasers is due to the smaller linewidth enhancement factor a caused by a higher doping concentration in the lasers.     

The efficiency of thin-film optical-waveguide modulators using electrooptic films or substrates

This paper describes a new method for characterizing thin-film modulators which utilize TErightleftarrowsTM wave conversion. The conversion is described in terms of a coupled wave model. The coupling constantkdescribes the strength of the coupling between the TE and TM waves. It is expressed in the formk = k_{pw}Cwhere kpwis the coupling constant of plane waves traveling through the relevant bulk medium. The coefficientCcontains the parameters which characterize the guide. The model allows the comparison of structures utilizing electrooptic films and electrooptic substrates. Our results show that in general for single mode films (those approximately a half-wavelength thick), modulators of either type are about equally effective. It is tacitly assumed that kpwis identical for each structure. For films which can support several modes (films a few wavelengths thick), the coefficient for devices utilizing electrooptic substrates approach zero. In contrastCapproaches unity for similar thick-film devices which use electrooptic films.     

High-speed electrooptic phase modulators using InGaAs/InAlAsmultiple quantum well waveguides

High-speed phase modulation of waveguided InGaAs/InAlAs multiple-quantum-well optical modulators operating at 1.55 μm is described. The modulator requires a low voltage for π-phase-shift ( V_π=2.5 V) as well as a small intensity modulation depth of 1 dB. The measured electrical 3-dB bandwidth is 10 GHz, giving a bandwidth-to-voltage ratio of 4 GHz/V     

Synchronization bandwidth of capacitive transverse-field electrooptic modulators

Expressions are given that can be used to calculate the synchronization bandwidth of center-fed and end-fed, capacitive electrooptic modulators that employ a modulation field transverse to the direction of optical beam propagation.