Noise auto-correlation spectroscopy with coherent Raman scattering

Ultrafast lasers have become one of the most powerful tools in coherent nonlinear optical spectroscopy. Short pulses enable direct observation of fast molecular dynamics, whereas broad spectral bandwidth offers ways of controlling nonlinear optical processes by means of quantum interferences. Special care is usually taken to preserve the coherence of laser pulses as it determines the accuracy of a spectroscopic measurement. Here we present a new approach to coherent Raman spectroscopy based on deliberately introduced noise, which increases the spectral resolution, robustness and efficiency. We probe laser induced molecular vibrations using a broadband laser pulse with intentionally randomized amplitude and phase. The vibrational resonances result in and are identified through the appearance of intensity correlations in the noisy spectrum of coherently scattered photons. Spectral resolution is neither limited by the pulse bandwidth, nor sensitive to the quality of the temporal and spectral profile of the pulses. This is particularly attractive for the applications in microscopy, biological imaging and remote sensing, where dispersion and scattering properties of the medium often undermine the applicability of ultrafast lasers. The proposed method combines the efficiency and resolution of a coherent process with the robustness of incoherent light. As we demonstrate here, it can be implemented by simply destroying the coherence of a laser pulse, and without any elaborate temporal scanning or spectral shaping commonly required by the frequency-resolved spectroscopic methods with ultrashort pulses.Comment: To appear in Nature Physic

Dispersive, superfluid-like shock waves in nonlinear optics

In most classical fluids, shock waves are strongly dissipative, their energy being quickly lost through viscous damping. But in systems such as cold plasmas, superfluids, and Bose-Einstein condensates, where viscosity is negligible or non-existent, a fundamentally different type of shock wave can emerge whose behaviour is dominated by dispersion rather than dissipation. Dispersive shock waves are difficult to study experimentally, and analytical solutions to the equations that govern them have only been found in one dimension (1D). By exploiting a well-known, but little appreciated, correspondence between the behaviour of superfluids and nonlinear optical materials, we demonstrate an all-optical experimental platform for studying the dynamics of dispersive shock waves. This enables us to observe the propagation and nonlinear response of dispersive shock waves, including the interaction of colliding shock waves, in 1D and 2D. Our system offers a versatile and more accessible means for exploring superfluid-like and related dispersive phenomena.Comment: 21 pages, 6 figures Revised abstrac

Guided-mode phase-matching strategies for organic nonlinear optics

Waveguide strategies of phase-matching secondharmonic generation in nonlinear organic materials are examined. The mismatches of propagation constants of guided modes in planar waveguides are expressed through waveguide parameters, and the ability of multimode waveguides to phase-match nonlinear-optical processes in organic materials is assessed. The mismatch of propagation constants of the TE4/TM4 mode of the second harmonic and the TE0/TM0 mode of the pump field as a function of the size of the waveguiding layer with n(p)(w) = 1.50 and n(P)(2w) = 1.55 (solid line), 1.60 (dashed line), and 1.65 (dash-dotted line). The pump wavelength is I pm

Saturation of third-harmonic generation in a plasma of self-induced optical breakdown due to the self-action of 80-fs light pulses

Generation of the second and third harmonics of 80-fs 1-mJ pulses from a Ti:sapphire laser in the plasma of self-induced optical breakdown in atmospheric air is studied. Spatial self-action of fundamental radiation accompanied by the broadening of spectra of fundamental radiation and optical harmonics is revealed. The self-action of light leads to the saturation of the efficiency of third-harmonic generation as a function of the energy of fundamental radiation. An efficiency of third-harmonic generation up to 1.7x10(-3) is achieved with 1-kHz laser pulses

Generation of the second and third harmonics in a laser-produced plasma with 1-kHz 90-fs light pulses

Generation of the second and third harmonics of a Ti:sapphire laser in the plasma of self-induced optical breakdown in atmospheric air is studied. The efficiency of third-harmonic generation up to 1.2 x 10(-3) is achieved in the field of 1-kHz laser pulses with a pulse duration of 90 fs and a pulse energy of 1 mJ. A spatial structure characteristic of self-phase modulation is revealed in the intensity distribution of the light beam transmitted through the plasma. The self-action of light is demonstrated to have a noticeable influence on the energies of the second and third harmonics as functions of the energy of fundamental radiation

Coherent four-photon spectroscopy of excited atoms in a laser-produced plasma: From point-by-point to multipoint two-dimensional mapping

An experimental technique for the two-dimensional mapping of the relative populations of excited states of atoms and ions in a low-temperature plasma of optical breakdown is developed on the basis of coherent four-wave mixing (FWM) with hyper-Raman resonances. Conditions when FWM in a plasma occurs in the phase-matched regime and is not subject to significant influence of one-photon absorption are experimentally determined. A folded FWM scheme for single-pulse two-dimensional imaging of spatial distributions of atoms and ions in a laser-produced plasma is discussed. Copyright © 1997 by MAHK Hayka/Interperiodica Publishing

X-SEA-F-SPIDER characterization of over octave spanning pulses in the infrared range.

International audienceWe show a practical implementation of a pulse characterization method for sub-cycle pulse measurements in the infrared spectral range based on spectral shearing interferometry. We employ spatially-encoded arrangement filter-based spectral phase interferometry for direct electric field reconstruction with external ancila pulses (X-SEA-F-SPIDER). We show merits and limitations of the setup and an in-depth comparison to another widely used temporal characterization technique-Second-Harmonic Generation Frequency Resolved Optical Gating (SHG-FROG). The X-SEA-F-SPIDER implementation presented in this paper allows measurement of sub-cycle pulses with over one octave wide spectrum spanning the 900-2400 nm range without adding any extra dispersion due to the pulse characterization apparatus

Quantum technologies in Russia

Remarkable advancements in the ability to create, manipulate, and measure quantum systems are paving the way to build next generations of devices based on quantum physics. Quantum technologies in Russia are on the list of strategically important cross-cutting directions in the framework of the National Technology Initiative programs and the Digital Economy National Program. The broad focus includes quantum computing and simulation, quantum communications, quantum metrology and sensing. This paper reviews existing research on quantum science and technologies in Russia and summarizes the main goals for the next few years that form the basis of an upcoming major national initiative