Curvilinear motion of laser soliton complexes

Conditions under which the center of inertia of stable complexes of dissipative optical solitons moves curvilinearly have been determined. Such a character of the motion of dissipative structures is caused by asymmetry in the distribution of the intensity and energy fluxes, and it is pronounced for laser solitons with strong interaction. The results of the numerical simulation of these complexes in the model of surface emitting lasers or laser amplifiers with saturated amplification and absorption are presented. Such complexes may be observed in various spatially distributed nonlinear dissipative systems, in particular, in the form of discrete solitons.     

On three-dimensional dissipative optical solitons: Collisions of laser bullets and topological solitons

Results of numerical simulation of collisions of two fundamental laser bullets—three-dimensional solitons formed in a medium with saturable amplification and absorption and frequency dispersion—are presented. A new collision regime resulting in the formation and the propagation of a switching wave is revealed. The existence of a metastable topological (with a wave front dislocation and an annular intensity distribution) three-dimensional dissipative optical soliton is demonstrated.     

Low noise dual-wavelength erbium fiber laser in single-longitudinal-mode operation

A new stable dual-wavelength fiber-ring laser based on erbium-doped fiber amplification is reported. The laser is based on ring resonators and employs fiber Bragg gratings to select the operation wavelengths. The topology of the laser has a significant influence in its performance: allowing an independent control of the losses for both lasing wavelengths and achieving a low noise configuration. As a result, it is experimentally demonstrated that both emission lines work in single-longitudinal-mode operation and the topology offers a better stability and higher optical signal-to-noise ratios than similar configurations.     

Femtosecond hybrid mode-locked semiconductor laser and amplifier dynamics

We describe the generation of femtosecond high power optical pulses using hybrid passive-active mode-locking techniques. Angle stripe geometry GaAs/AlGaAs semiconductor laser amplifiers are employed in an external cavity including prisms and a stagger-tuned quantum-well saturable absorber. An identical amplifier also serves as an optical power amplifier in a stretched pulse amplification and recompression sequence. After amplification and pulse compression this laser system produces 200 fs, 160 W peak power pulses. We discuss and extend our theory, and supporting phenomenological models, of picosecond and subpicosecond optical pulse amplification in semiconductor laser amplifiers which has been successful in calculating measured spectra and time-resolved dynamics in our amplifiers. We have refined the theory to include a phenomenological model of spectral hole-burning for finite intraband thermalization time. Our calculations are consistent with an intra-band time of approximately 60 fs. This theory of large signal subpicosecond pulse amplification will be an essential tool for understanding the mode-locking dynamics of semiconductor lasers and for analysis of high speed multiple wave-length optical signal processing and transmission devices and systems based on semiconductor laser amplifiers.     

Generation of fs laser pulses from a ps pulse-pumped optical parametric amplifier with a beat-wave seed signal

We describe a method of ultrashort-pulse and ultrafast-pulse-train generation through optical parametric amplification of a laser beat wave. Numerical simulation shows that 250-fs laser pulses at 1.55 μm are generated from a beat-wave seeded optical parametric amplifier pumped by a 30-ps laser at 1064 nm. The pulse compression is attributable to sideband generation and parametric amplification under group velocity mismatch. Our experimental result confirms efficient generation of comb-like sidebands for the mixing waves from such an optical parametric amplifier.     

用于宽带啁啾脉冲光参量放大系统精确同步的新方法

基于非共线光参量放大,以波长800 nm飞秒激光的倍频光为抽运光,以激光二极管640 nm连续波激光为信号光,产生了与800 nm飞秒激光精确同步的无直流本底的1064 nm脉冲光。实验结果显示该1064 nm的光脉冲在脉冲能量和空间光束质量上均可作为1064 nm波长脉冲放大器的种子光。仅通过一级简单紧凑的非共线参量放大就可实现光周期量级的光参量啁啾脉冲放大系统的抽运激光和种子光的精确同步。     

Regular and stochastic motion of dissipative optical solitons

Investigations of the motion of dissipative optical solitons and their complexes in wide-aperture nonlinearly optical (with coherent pump radiation) and laser (with incoherent pump radiation) systems have been reviewed. An important characteristic of dissipative solitons is the topology of the energy fluxes, which determines the internal structure of individual solitons and makes it possible to certainly separate the cases of the weak and strong interactions between the solitons. It has been shown that the character of the regular motion of dissipative soliton structures in a homogeneous system is determined by the symmetry of the transverse distributions of the intensity and energy flux; the motion of asymmetric structures is curvilinear. This is also valid for complexes of three-dimensional dissipative optical solitons, “laser bullets.” The extreme possibilities of localization of solitons are determined by quantum noises. The corresponding Brownian motion of the center of the dissipative optical soliton is characterized by a much lower level of the statistic dispersion of the coordinates of its center and velocity than that in the case of conservative solitons.     

GaN基蓝光半导体激光器的发展

文章介绍了下一代光存储用半导体激光器——GaN蓝光激光器的发展状况．对衬底材料的发展现状、外延片的生长技术以及激光器的制作工艺都作了论述．阐明了GaN激光器的一些技术路线，如GaN同质生长衬底的发展，侧向外延生长技术的采用以及湿法腐蚀腔面等．另外还介绍了GaN半导体激光器数字多功能光盘(DVD)的实用化进程．     

Yb:CaF2 — a new old laser crystal

Here is presented and discussed the history, the spectroscopic, the thermo-mechanical and the laser properties of the new old laser crystal Yb:CaF₂, of its Sr and Ba isotypes as well as of an Yb and Na codoped compound. It will be shown that Yb:CaF₂ is a very particular luminescent material, in which the laser-active center probably consists of a complex hexameric cluster, that it is the most promising Yb-doped fluoride material for large-scale, high-power and high-energy laser systems and that it can compete in several aspects with the currently used Yb-doped oxide crystals and glasses. The opportunity of operating the crystals at cryogenic temperatures and the recently achieved improvements in the field of femtosecond pulsed laser operation and high peak power laser amplification is highlighted and evaluated.     

Ultrashort pulse generation and measurement techniques

The first section will discuss the generation of picosecond and femtosecond laser pulses, their propagation and compression in optical fibers, and their amplification for nonlinear spectroscopic applications. Laser systems for different wavelength regimes and pulse measurement techniques will be described. The second section will extend the discussion of picosecond and femtosecond measurement to studies of ultrafast processes in materials. Pump-probe and transient four-wave-mixing methods will be analyzed. Examples of application to both molecular and solid state systems will be presented.     

Quantum‐optical analogies using photonic structures

Engineered photonic waveguides have provided in the past decade an extremely rich laboratory tool to visualize with optical waves the classic analogues of a wide variety of coherent quantum phenomena encountered in atomic, molecular or condensed‐matter physics. As compared to quantum systems, optics offers the rather unique advantage of a direct mapping of the wave function evolution in coordinate space by simple fluorescence imaging or scanning tunneling optical microscopy techniques. In this contribution recent theoretical and experimental advances in the field of quantum‐optical analogies are reviewed. Special attention is devoted to some relevant optical analogies based on the use of curved photonic structures, including: coherent destruction of tunneling in driven bistable potentials; coherent population transfer and adiabatic passage in laser‐driven multilevel atomic systems; quantum decay control and Zeno dynamics; electronic Bloch oscillations and Zener tunneling, Anderson localization and dynamic localization in crystalline potentials.     

Generation and amplification of dual-color femtosecond pulses by a noncollinear optical parametric up-conversion process

Noncollinear optical parametric up-conversion generation and amplification are realized in a thick β-barium borate (BBO) crystal, and a couple of visible femtosecond up-conversion laser pulses can be achieved by a femtosecond pulse at 800 nm as the pump sources. The theoretical and experimental results indicate that there exist phase-matching conditions for dual-color noncollinear parametric up-conversion generation and amplification, and their wavelengths can be tuned by rotating the BBO crystal. This parametric up-conversion generation and amplification can be attributed to three and five-wave mixing in a thick BBO crystal, and it shows the potential application on optical parametric chirped pulse amplification (OPCPA) to generate multi-color ultraviolet or visible femtosecond laser pulses pumped directly by femtosecond fundamental laser pulses without frequency-doubling or tripling.     

Bipartite entanglement induced by classically-constrained quantum dissipative dynamics

The properties of some complex many body systems can be modeled by introducing in the dissipative dynamics of each single component a set of kinetic constraints that depend on the state of the neighbor systems. Here, we characterize this kind of dynamics for two quantum systems whose independent dissipative evolutions are defined by a Lindblad equation. The constraints are introduced through a set of projectors that restrict the action of each single dissipative Lindblad channel to the state of the other system. Conditions that guarantee a classical interpretation of the kinetic constraints are found. The generation and evolution of entanglement is studied for two optical qubits systems. Classically constrained dissipation leads to a stationary state whose degree of entanglement depends on the initial state. Nevertheless, independently of the initial conditions, a maximal entangled state is generated when both systems are subjected to the action of local Hamiltonian fields that do not commutate with the constraints. The underlying physical mechanism is analyzed in detail.     

Trends in ultrashort and ultrahigh power laser pulses based on optical parametric chirped pulse amplification

Since the proof-of-principle demonstration of optical parametric amplification to efficiently amplify chirped laser pulses in 1992,optical parametric chirped pulse amplification(OPCPA)became the most promising method for the amplification of broadband optical pulses.In the meantime,we are witnessing an exciting progress in the development of powerful and ultrashort pulse laser systems that employ chirped pulse parametric amplifiers.The output power and pulse duration of these systems have ranged from a few gigawatts to hundreds of terawatts with a potential of tens of petawatts power level.Meanwhile,the output pulse duration based on optical parametric amplification has entered the range of fewoptical-cycle field.In this paper,we overview the basic principles,trends in development,and current state of the ultrashort and laser systems based on OPCPA,respectively.     

Photonic sensing technology is opening new frontiers in biophotonics

In advanced sensing photonics it is of great importance to explore the detection limits of extremely weak optical signals and imaging using state-of-the art technology. In this paper we describe recent progress in photonic sensing technology achieved in practice in the standard quantum limit of optical detection imposed by the signal-limited shot noise, which can be realized by both the optical heterodyne detection and photon counting techniques. Then, with particular attention on imaging of ultraweak photonic signals by these techniques, their applications in developing new frontiers in the field of biophotonics such as laser computed tomography, and the imaging and characterization of ultraweak biophoton emission phenomena are described and discussed as one of the typical examples of future trends in this field.     

Cascade parametric light amplification with low-frequency pumping

Cascade parametric amplification in a regular domain structure is examined theoretically taking the variations in phase of all the interacting waves in a dissipative medium into account. Analytic expressions are obtained for the conversion efficiency of the laser energy with low-frequency pumping. The dependence of the parametric amplification efficiency on the number of layers is given. Ways of increasing the frequency conversion efficiency are discussed. The presence of a nonzero input intensity at the sum frequency is found to cause a nonlinear increase in the high-frequency signal at the output of the structure. As the losses of the interacting waves increase, both the frequency conversion efficiency and the optimum domain length decrease.     

Stability criterion for dissipative soliton solutions of the one-, two-, and three-dimensional complex cubic-quintic Ginzburg-Landau equations

The generation and nonlinear dynamics of multidimensional optical dissipative solitonic pulses are examined. The variational method is extended to complex dissipative systems, in order to obtain steady state solutions of the (D + 1)-dimensional complex cubic-quintic Ginzburg-Landau equation (D = 1, 2, 3). A stability criterion is established fixing a domain of dissipative parameters for stable steady state solutions. Following numerical simulations, evolution of any input pulse from this domain leads to stable dissipative solitons.     

Widely-wavelength-tunable few-cycle optical pulse generation from an all-fiber erbium-doped laser system

A scheme for the construction of fiber laser systems for the generation of tunable ultrashort optical pulses is proposed. The scheme is based on the self-Raman shift of the soliton frequency in dispersion-decreasing fibers with the subsequent spectral broadening owing to the supercontinuum generation in a short highly nonlinear fiber and the compression in the corresponding fiber compressor. An all-fiber laser system for the generation of ultrashort laser pulses in the wavelength range 1.6–2.0 μm is experimentally demonstrated. In particular, the shortest pulses with a duration of 24 fs are generated at wavelengths of 1.8–1.9 μm, which corresponds to less than four optical cycles.     

The stability of the stationary generation of a multichannel laser

Stable generation of multi-channel lasers that find application in optical communication systems with spectral multiplexing is studied theoretically. A computational model to determine the frequencies and increments of self-oscillating perturbations depending on the key laser parameters and the characteristics of the channels cross-saturation is proposed. It is shown that for typical conditions of an erbium-doped fiber laser, multichannel generation with a large number of channels (more than ten), although stable, is characterized by large fluctuations of channel power due to the very small decay increments of perturbations caused by small technical fluctuations of the laser parameters.