Leonid L. Losev

Ultrabroad bandwidth multifrequency raman generation

We report on the modeling of transient stimulated rotational Raman scattering in H(2) gas. We predict a multifrequency output, spanning a bandwidth greater than the pump frequency, that may be generated without any significant delay with respect to the pump pulses. The roles of dispersion and transiency are quantified.

KrF laser picosecond pulse source by stimulated scattering processes

A new short-pulse KrF laser source was developed by combining stimulated scattering processes, namely, Raman, Brillouin, and four-wave-mixing (FWM). Short pulses of 1.1 ps were obtained from 4 ns oscillator output. Only two commercial discharge KrF lasers are required for this system. This method is very simple and could be extended to an ArF laser wavelength in principle.

Multifrequency parametric infrared Raman generation in KGd(WO 4 ) 2 crystal with biharmonic ultrashort-pulse pumping

Mutlifrequency parametric Raman generation was carried out in a KGd(WO(4))(2) crystal by use of a dual-wavelength Ti:sapphire laser system. It was found that with femtosecond pump pulses the efficiency of Raman generation is low because of the onset of self-phase modulation. The mechanism for suppression of stimulated Raman scattering by self-phase modulation is discussed. Employing 2-ps-long chirped pulses generated four Stokes and one anti-Stokes component.

Raman compression of picosecond microjoule laser pulses in KGd(WO4)2 crystal

Abstract The process of compression of 20 ps laser pulse at the wavelength of 532 nm by backward stimulated Raman scattering in KGd(WO 4 ) 2 crystal has been studied experimentally. 1.7 ps, 1 μJ Stokes pulses at the wavelength of 555 nm were obtained at a pump laser pulse energy of 3 μJ. The relation between the pump energy and the spatial profile of the Stokes beam intensity has been established.

High-contrast ratio subpicosecond Nd:glass laser with Raman master oscillator☆

Abstract High-energy, high contrast ultrashot laser pulses have been generated by amplification of a Raman-shifted ruby laser radiation in a Nd:glass amplifier. This optical scheme exploits a fortuitous coincidence between the wavelengths of the separate lasers, and the output pulse is dramatically sharpened by two nonlinear Raman processes. A 0.8 ps, 0.15 mJ pulse at the wavelength of 1.056 μm was generated by stimulated Raman scattering of a 2 mJ, 25 ps mode-locked ruby laser pulse in liquid SF 6 and pressured hydrogen. Amplification of the pulse in Nd:phosphate glass rod amplifiers increased the energy to 20 mJ. The brightness of the amplified pulse is 5 × 10 17 W cm −2 sr −1 . The measured ratio of the amplified pulse brightness to that of ASE exceeded 10 12 .

Ultrabroadband parametric stimulated Raman scattering in a highly transient regime

Abstract A theory is presented to describe the dynamics of multiline parametric SRS (PSRS) in a highly transient regime. The PSRS conversion of the biharmonical pump at laser and 1st Stokes frequencies may generate Raman components filling the bandwidth up to Δ ν / ν = 1.4 (two octaves on level of 0.1 to peak) with a bandwidth buildup time much less than time T 2 of the Raman medium at modest experimental conditions.

On the generation of ultra-broad bandwidth light in air at atmospheric pressure

We predict that ultra-broadband light consisting of over 150 distinct frequencies of comparable energy can be generated in air at atmospheric pressure by stimulated Raman scattering using resonant symmetric pumping. Nanosecond input pulses and the highest available intensities are found to be optimal. Gain suppression analysis, incorporating a finite Stokes shift, gives a qualitative explanation of the pumping requirements.

High-power femtosecond Raman frequency shifter

We report on the generation of broadband, high-energy femtosecond pulses centered at 1.28 μm by stimulated Raman scattering in a pressurized hydrogen cell. Stimulated Raman scattering is performed by two chirped and delayed pulses originating from a multi-mJ Ti:sapphire amplifier. The Stokes pulse carries record-high energy of 4.4 mJ and is recompressed down to 66 fs by a reflective grating pair. We characterized the short-wavelength mid-infrared source in view of energy stability, beam profile, and conversion efficiency at repetition rates of 100 and 10 Hz. The demonstrated high-energy frequency shifter will benefit intense THz sources based on highly nonlinear organic crystals.

Ultra broadband UV generation by stimulated Raman scattering of two-color KrF laser in deuterium confined in a hollow fiber

Broad Raman-multi-frequency spectra were generated from the resonant two-color excitation of the deuterium molecule rotational Raman transition (J=0?2), using ultraviolet bi-harmonic lasers with a quartz hollow fiber. Fifty pure rotational Raman spectral lines (34 lines that have intensity within 10% of the strongest spectral line) from 230 to 290 nm were generated at a gas pressure of 30 kPa. Furthermore, vibrational-rotational Raman spectral lines of almost 300 lines from 220 to 600 nm were also generated by increasing the gas pressure to 60 kPa.

Simple Ultraviolet Short-Pulse Intensity Diagnostic Method Using Atmosphere

An ultraviolet (UV) short-pulse intensity diagnostic method using atmosphere as a nonlinear medium was developed. This diagnostic method is based on evaluating the ion charge of the two-photon ionization of atmospheric oxygen upon irradiation with a UV (238–299 nm) short-pulse laser. The observed ion signal increased proportionally to the input intensity to the power of ~2.2, during the two-photon ionization of atmospheric oxygen. An autocorrelator was constructed and used to successfully measure a UV laser pulse of ~400 fs duration. Since this diagnostic system is used in the open-air under windowless conditions, it can be set along the beam path and used as a UV intensity monitor.