Search results for "Parametric oscillator"
showing 10 items of 36 documents
Driven Bose-Hubbard Model with a Parametrically Modulated Harmonic Trap
2016
We investigate a one-dimensional Bose–Hubbard model in a parametrically driven global harmonic trap. The delicate interplay of both the local interaction of the atoms in the lattice and the driving of the global trap allows us to control the dynamical stability of the trapped quantum many-body state. The impact of the atomic interaction on the dynamical stability of the driven quantum many-body state is revealed in the regime of weak interaction by analyzing a discretized Gross–Pitaevskii equation within a Gaussian variational ansatz, yielding a Mathieu equation for the condensate width. The parametric resonance condition is shown to be modified by the atom interaction strength. In particul…
Linear Oscillator with Time-Dependent Frequency
2001
Here is another important example of a path integral calculation, namely the time-dependent oscillator whose Lagrangian is given by $$\displaystyle{ L = \frac{m} {2} \dot{x}^{2} -\frac{m} {2} W(t)x^{2}\;. }$$ (21.1) Since L is quadratic, we again expand around a classical solution so that later on we will be dealing again with the calculation of the following path integral: $$\displaystyle{ \int _{x(t_{i})\,=\,0}^{x(t_{f})\,=\,0}[dx(t)]\text{exp}\left \{ \frac{\text{i}} {\hslash }\,\frac{m} {2} \int _{t_{i}}^{t_{f} }dt\left [\left (\frac{dx} {dt} \right )^{\!2} - W(t)x^{2}\right ]\right \}\;. }$$ (21.2) Using \(x(t_{i}) = 0 = x(t_{f}),\) we can integrate by parts and obtain $$\displaystyle{…
Enhanced supercontinuum generation in tapered tellurite suspended core fiber
2015
Abstract We demonstrate 400-THz (0.6–3.3 µm) bandwidth infrared supercontinuum generation in a 10 cm-long tapered tellurite suspended core fiber pumped by nJ-level 200-fs pulses from an optical parametric oscillator. The increased nonlinearity and dispersion engineering extended by the moderate reduction of the fiber core size are exploited for supercontinuum optimization on both frequency edges (i.e., 155-THz overall gain), while keeping efficient power coupling into the untapered fiber input. The remaining limitation of supercontinuum bandwidth is related to the presence of the high absorption beyond 3 µm whereas spectral broadening is expected to fully cover the glass transmission window…
Four-wave mixing and vacuum squeezing in polariton microcavities
2017
In a recent paper [1] it has been shown how a bichromatic fast driving of optomechanical (optical domain) and superconducting circuit systems (microwave domain), operating in a limit where they present a non-linear Kerr-type interaction, can give rise to very strong vacuum squeezing. The driving with two close frequencies of a Kerr cavity changes the usual bistability bifurcation behaviour that takes place under monochromatic driving, into a degenerate four-wave mixing bifurcation, where a phase-bistable component starts oscillating spontaneously at a frequency that lies halfway between the two driving frequencies [2]. This resembles the physics of the optical parametric oscillator threshol…
Rescattering and vibrations in homonuclear diatomic molecules in a strong electromagnetic field
2009
Abstract The electron of a H 2 + driven by a strong electromagnetic field induces molecular vibrations. Numerical and analytical results show that the molecule behaves as a parametric oscillator and can be treated as a kicked oscillator. The results are discussed from the point of view of the electron's periodic dressing and undressing processes.
Faraday patterns in bose-Einstein condensates.
2002
Temporal periodic modulation of the interatomic s-wave scattering length in Bose-Einstein condensates is shown to excite subharmonic patterns of atom density through a parametric resonance. The dominating wavelength of the spatial structures is shown to be primarily selected by the excitation frequency but also affected by the depth of the spatial modulation via a nonlinear resonance. These phenomena represent macroscopic quantum analogues of the Faraday waves excited in vertically shaken liquids.
Supercontinuum Generation in Tellurite Optical Fibers
2017
This chapter presents a state of the art of infrared supercontinuum generation in heavy oxide tellurite optical fibers from the experimental results published by the international community. As a first part, a bibliographic table gathers the literature on which this work is based. Then, the second part briefly returns on the tellurite glass compositions, the third part presents the different fiber structures (microstructured, suspended core or step-index fibers, tapered fibers), the fourth part discusses the pumping sources in relation with the fiber chromatic dispersion as well as coupling issues, the supercontinuum performances are presented in the fifth part, and the sixth part deals wit…
Phase-bistable pattern formation in oscillatory systems via rocking: application to nonlinear optical systems
2014
We present a review, together with new results, of a universal forcing of oscillatory systems, termed ‘rocking’, which leads to the emergence of a phase bistability and to the kind of pattern formation associated with it, characterized by the presence of phase domains, phase spatial solitons and phase-bistable extended patterns. The effects of rocking are thus similar to those observed in the classic 2 : 1 resonance (the parametric resonance) of spatially extended systems of oscillators, which occurs under a spatially uniform, time-periodic forcing at twice the oscillations' frequency. The rocking, however, has a frequency close to that of the oscillations (it is a 1 : 1 resonant forcing) …
Expanding Two-Photon Intravital Microscopy to the Infrared by Means of Optical Parametric Oscillator
2010
Chronic inflammation in various organs, such as the brain, implies that different subpopulations of immune cells interact with the cells of the target organ. To monitor this cellular communication both morphologically and functionally, the ability to visualize more than two colors in deep tissue is indispensable. Here, we demonstrate the pronounced power of optical parametric oscillator (OPO)-based two-photon laser scanning microscopy for dynamic intravital imaging in hardly accessible organs of the central nervous and of the immune system, with particular relevance for long-term investigations of pathological mechanisms (e.g., chronic neuroinflammation) necessitating the use of fluorescent…
Mid-infrared 2000-nm bandwidth supercontinuum generation in suspended-core microstructured Sulfide and Tellurite optical fibers
2012
International audience; In this work, we report the experimental observation of supercontinua generation in two kinds of suspended-core microstructured soft-glass optical fibers. Low loss, highly nonlinear, tellurite and As2S3 chalcogenide fibers have been fabricated and pumped close to their zero-dispersion wavelength in the femtosecond regime by means of an optical parametric oscillator pumped by a Ti:Sapphire laser. When coupled into the fibers, the femtosecond pulses result in 2000-nm bandwidth supercontinua reaching the Mid-Infrared region and extending from 750 nm to 2.8 mu m in tellurite fibers and 1 mu m to 3.2 mu m in chalcogenide fibers, respectively.