Stability and noise properties of diode lasers with phase-conjugate feedback

For a diode laser subjected to filtered feedback from a phase-conjugating mirror, we present the first exact stability analysis and various noise spectra. The stability properties are intermediate between those of the injection laser and the laser with conventional optical feedback. The role of a finite response-time is to drastically enhance the steady-state stability For moderate feedback, the frequency noise is suppressed by several orders of magnitude, and the main relaxation frequency of the laser shows a crossover from the usual relaxation oscillation frequency to a new frequency determined by the amount of feedback. This may be of technological importance since it is expected to improve the modulation bandwidt

Experimental Study of Nonlinear Dynamics and Chaos in a 1550 nm-VCSEL Subject to Polarized Optical Injection

We report the experimental observation of nonlinear dynamics including chaos in a1550nm-VCSEL subject to parallel- and orthogonally-polarized optical injection

Optical injection-induced timing jitter reduction in gain-switched single-mode vertical-cavity surface-emitting lasers

We report an experimental and theoretical investigation of the effect of optical injection on the characteristics of optical pulses generated by gain-switching a 1550 nm single transverse mode vertical-cavity surface-emitting laser (VCSEL). Under continuous wave operation the VCSEL emits in a linear polarization along the whole current range. The experimental analysis of the effect of external optical injection on the timing jitter, maximum power, and pulse width of optical pulses generated by gain-switching the single mode VCSEL is performed for several repetition rates and for different values of the detuning between the frequency of the optical injection and the VCSEL. Experimental results show that for 1 GHz repetition frequency, jitter reductions greater than 70 % can be obtained over a 47 GHz frequency detuning range with a slight increase of 22% in pulse width with respect to the solitary case. A clear anticorrelation between the maximum power and pulse width is also obtained. A theoretical study is also performed by using a model that incorporates both spatial dependence of carrier density and optical field profiles. The two polarization modes are also taken into account in the model. The theoretical results are in good agreement with the experimental result

All-optical inverter based on polarization switching in long-wavelength VCSELs

All-optical processing of high-speed signals is expected to be a key technology in future photonic networks. VCSELs are very promising devices for these applications due to their inherent advantages. Nonlinear transfer functions can be obtained by using optical injection because it strongly affects the transverse mode and polarization characteristics of VCSELs [1]. Optical injection can be used to obtain polarization switching (PS) of single transverse mode VCSELs. When the polarization of an injected optical field is orthogonal to that of the solitary VCSEL (orthogonal optical injection), PS and bistability are observed [2]. PS by optical injection is expected to be fast and thus suitable for application in all-optical signal-processing systems. In this work we report, for the first time to our knowledge, all-optical inversion operation using PS in a 1550nm single-mode VCSEL induced by orthogonal optical injection. We demonstrate all-optical inversion for NRZ signals at a bit rate of 2.5 Gb/s. An all-fiber system has been developed in order to inject the light from a tunable laser into a commercial 1550nm-VCSEL (RayCan, Co.). The free-running VCSEL emits in the fundamental transverse mode with a linear polarization (parallel polarization) over the whole current range. The subsidiary orthogonal polarization is shifted 0.48 nm to the long wavelength side with respect to the dominant one. Pulsed optical injection was obtained by using a pulse pattern generator and a Mach-Zhender intensity modulator. © 2011 IEEE

Microwave signal generation using a dual-beam optically injected 1550 nm VCSEL

We report microwave signal generation using a 1550 nm single-mode VCSEL subject to two-frequency optical injection. Double injection locking is achieved. It is found that this generation system is independent of the master lasers polarization

Analysis of self--averaging properties in the transport of particles through random media

We investigate self-averaging properties in the transport of particles through random media. We show rigorously that in the subdiffusive anomalous regime transport coefficients are not self--averaging quantities. These quantities are exactly calculated in the case of directed random walks. In the case of general symmetric random walks a perturbative analysis around the Effective Medium Approximation (EMA) is performed.Comment: 4 pages, RevTeX , No figures, submitted to Physical Review E (Rapid Communication

Equilibrium between radiation and matter for classical relativistic multiperiodic systems. II. Study of radiative equilibrium with Rayleigh-Jeans radiation

We continue the study of the problem of equilibrium between radiation and classical relativistic systems begun previously Phys. Rev. D 27 1254 (1983). We consider the emission and absorption of energy by a relativistic pointlike particle immersed in a Rayleigh-Jeans radiation field. The particle is acted upon by a force which, if alone, would produce a multiply periodic motion. It is shown that radiative balance at each frequency holds. A discussion is given of the results reported in both papers

Polarization and Transverse Mode Selection in Quantum Well Vertical-Cavity Surface-Emitting Lasers: Index-and Gain-guided Devices

Abstract We study polarization switching and transverse mode competition in Vertical Cavity Surface Emitting Lasers in the absence of temperature e ects. We use a model that incorporates the vector nature of the laser eld, saturable dispersion, di erent carrier populations associated with di erent magnetic sublevels of the conduction and heavy hole valence bands in quantum well media, spin-ip relaxation processes and cavity birefringence and dichroism. We consider both index-guided and gain-guided VCSELs, and we nd that spin-ip dynamics and linewidth enhancement factor are crucial for the selection of the polarization state corresponding to a given injection current. For index-guided VCSELs the e ect of spatial hole burning on the polarization behavior within the fundamental mode regime is discussed. For gain-guided VCSELs, transverse mode and polarization selection is studied within a Maxwell-Bloch approximation which includes eld di raction and carrier di usion. Polarization switching is found in the fundamental mode regime. The rst order transverse mode starts lasing orthogonally 1 polarized to the fundamental mode. At larger currents polarization coexistence with several active transverse modes occurs

Multiple strain-induced phase transitions in LaNiO3 thin films

Strain effects on epitaxial thin films of LaNiO3 grown on different single crystalline substrates are studied by Raman scattering and first-principles simulation. New Raman modes, not present in bulk or fully-relaxed films, appear under both compressive and tensile strains, indicating symmetry reductions. Interestingly, the Raman spectra and the underlying crystal symmetry for tensile and compressively strained films are different. Extensive mapping of LaNiO3 phase stability is addressed by simulations, showing that a variety of crystalline phases are indeed stabilized under strain which may impact the electronic orbital hierarchy. The calculated Raman frequencies reproduce the principal features of the experimental spectra, supporting the validity of the multiple strain-driven structural transitions predicted by the simulations.Comment: 18 pages, 7 figure