Microjoule mode-locked oscillators: issues of stability and noise

In this work, for the first time to our knowledge, stability and noise of a thin-disk mode-locked Yb:YAG oscillator operating in both negative- (NDR) and positive-dispersion (PDR) regimes have been analyzed systematically within a broad range of oscillator parameters. It is found, that the scaling of output pulse energy from 7 $\mu$J up to 55 $\mu$J in the NDR requires a dispersion scaling from -0.013 ps$^{2}$ up to -0.31 ps$^{2}$ to provide the pulse stability. Simultaneously, the energy scaling from 6 $\mu$J up to 90 $\mu$J in the PDR requires a moderate dispersion scaling from 0.0023 ps$^{2}$ up to 0.011 ps$^{2}$. A chirped picosecond pulse in the PDR has a broader spectrum than that of a chirp-free soliton in the NDR. As a result, a chirped picosecond pulse can be compressed down to a few of hundreds of femtoseconds. A unique property of the PDR has been found to be an extremely reduced timing jitter. The numerical results agree with the analytical theory, when spectral properties of the PDR and the negative feedback induced by spectral filtering are taken into account.Comment: 12 pages, 11 figures, SPIE's International Symposium "Photonics Europe" (EPE10), 12-16 April 2010, Brussels, Belgiu

Theory of Laser Energy Harvesting at Femtosecond Scale

Energy scaling of femtosecond laser pulses has a lot of applications in nanoscale micromachining, precision time-resolution spectroscopy, high-harmonic generation, surgery, etc. Besides applied sciences and technology, there are fundamental applications of energy harvesting at femtosecond scale. In particular, it is possible to study and control intra-atom and molecular dynamics at attosecond level as well as to map the quantum processes directly with unprecedented spatial and temporal resolution. This “mesoscopic” union of classical and quantum phenomena provides with new insights into fundamental issues of quantum mechanics of open systems including possible application in the field of quantum computing. In this work, we consider a theory of femtosecond pulse energy harvesting using the dissipative soliton generation in both solid-state and fiber mode-locked lasers and the femtosecond pulse enhancement in an external resonator. The femtosecond pulse energy, width, and spectrum scaling laws are presented in the explicit and physically meaningful form

Chaotic, Stochastic Resonance, and Anti-Resonance Phenomena in Optics

Existence of different, frequently incommensurate scales is a common phenomenon in nature. Interactions between processes characterized by different scales can result in a multitude of emergent phenomena when a system cannot be described as a scale-separated hierarchy of underlying processes but presents a substantially new entity with qualitatively new properties and behavior. Striking examples are life, fractals, and chaos. Here, we shall demonstrate the quite nontrivial phenomena: chaotic and stochastic resonances and anti-resonance on examples of laser systems. The phenomena of resonant stochastization (stochastic anti-resonance), self-ordering (stochastic resonance), and resonant chaotization of coherent structures (dissipative solitons) are considered on the examples of mode-locked lasers and Raman fiber amplifiers. Despite a well-known effect of noise suppression and global regularization of dynamics due to the resonant interaction of noise and regular external periodic perturbation, here we report about the reverse situation when the regular and noise-like perturbations result in the emergent phenomena ranging from the coherent structure formation to the fine-grained chaotic/noisy dynamics. We guess that the nonlinear optical systems can be considered in this context as an ideal test-bed for “metaphorical modeling” in the area of deterministic and stochastic dynamics of resonance systems

The unified theory of chirped-pulse oscillators

A completely analytical theory of chirped-pulse oscillators is presented. The theory is based on an approximate integration of the generalized nonlinear complex Ginzburg-Landau equation. The obtained parametric space of a chirped-pulse oscillator allows easy tracing the characteristics of both solid-state and fiber oscillators operating in the positive dispersion regime.Comment: 12 pages; 9 figures; Conference EOO/SPIE 2009, Prague, Czech Republic; the mathematical apparatus is presented in detail in http://info.tuwien.ac.at/kalashnikov/NCGLE1.html, http://info.tuwien.ac.at/kalashnikov/NCGLE2.html and http://info.tuwien.ac.at/kalashnikov/genNCGLE.htm

Vacuum polarization instead of "dark matter" in a galaxy

We considered a vacuum polarization inside a galaxy in the eikonal approximation and found that two possible types of polarization exist. The first type is described by the equation of state $p=\rho/3$, similar to radiation. Using the conformally-unimodular metric allows constructing a nonsingular solution for this vacuum ``substance'', if a compact astrophysical object exists in the galaxy's center. As a result, a ``dark'' galactical halo appears that increases the rotation velocity of a test particle as a function of the distance from a galactic center. The second type of vacuum polarization has a more complicated equation of state. As a static physical effect, it produces renormalization of the gravitational constant, thus, causing no static halo. However, a nonstationary polarization of the second type, resulting from an exponential increase (or decrease) of the galactic nuclei mass with time in some hypothetical time-dependent process, produces a gravitational potential looking like a dark matter halo.Comment: 16 pages, 6 figure