Evgueni M. Dianov

Mode-locked 1.93 μm thulium fiber laser with a carbon nanotube absorber

We report a ring-cavity thulium fiber laser mode locked with a single-wall carbon nanotube absorber used in transmission. A carboxymethyl cellulose polymer film with incorporated carbon nanotubes synthesized by the arc discharge method has an absorption coinciding with in the amplification bandwidth of a Tm-doped fiber. This laser is pumped by an erbium fiber laser at 1.57 μm wavelength and produces a 37 MHz train of mode-locked 1.32 ps pulses at 1.93 μm wavelength with an average output power of 3.4 mW.

Inscription of fiber Bragg gratings by ultraviolet femtosecond radiation

We report on what is to our knowledge the first fabrication of fiber Bragg gratings by UV femtosecond radiation. The Bragg gratings, with photoinduced refractive-index modulation up to 1.92 x 10(-3) in H2-loaded SMF-28 and up to 1.05 x 10(-3) in Nufern GF1 fibers, were written by high-intensity (31-77-GW/cm2) femtosecond pulses at 264 nm. The dependence of the refractive-index modulation on intensity at equal fluences points to a two-photon absorption mechanism for grating inscription.

Near-infrared luminescence of RbPb2Cl5:Bi crystals.

A wideband near-IR (NIR) luminescence centered at 1080 nm was found in a RbPb(2)Cl(5):Bi single crystal grown by the Bridgman technique. Absorption, luminescence, and excitation of luminescence spectra were investigated at room and cryogenic temperatures. The luminescence was proposed to be due to the (3)P(1)-->(3)P(0) transition in Bi(+) ion.

High-speed photography, spectra, and temperature of optical discharge in silica-based fibers

The dynamics of fiber fuse effect including process of bubble formation in fiber core was investigated. Bubbles in the core were observed not later than 20/spl divide/70 /spl mu/s after the plasma forepart passed. For the first time, the temperature of optical discharge was measured for a wide range of laser radiation powers. For 40-W laser power, the temperature reached 10/sup 4/ K, the velocity of discharge propagation having increased to 10 m/s.

2.1 microm continuous-wave Raman laser in GeO2 fiber.

We report on 33 % efficient generation of the first Stokes in a high concentration GeO2 fiber Raman laser pumped by a 22 W Thulium doped fiber laser. An output power of 4.6 W at 2.105 um is demonstrated.We report 33% efficient generation of the first Stokes in a high-concentration GeO(2) fiber Raman laser pumped by a 22 W thulium-doped fiber laser. An output power of 4.6 W at 2.105 microm is demonstrated.

Optical spectroscopy of the RbPb 2 Cl 5 :Dy 3+ laser crystal and oscillation at 5.5 μm at room temperature

Oscillation at 5.5μm wavelength has been investigated in the low-phonon, moisture-resistant RbPb2Cl5:Dy3+ crystal in free-running mode at room temperature. In line with our knowledge this is the longest laser wavelength for a rare-earth doped crystal that does not require any special precautions for survival. Spectra and kinetics of luminescence of the new laser crystal were investigated under pumping to 1.3 μm absorption band, corresponding to lasing experiments. Emission cross sections were determined for mid-IR transitions. It was found that emission cross section on the 6H9/2+6F11/2→6H11/2 laser transition at 5.5 μm wavelength is as high as 0.6×10−20cm2.

Single-mode fiber with chromatic dispersion varying along the length

Single-mode fibers with chromatic dispersion varying along the length (VD SMF) are a promising medium for nonlinear fiber optics. In a theoretical paper1 VD SMFs were proposed for communication lines to compensate for the soliton pulse broadening caused by the influence of optical losses. We were, we believe, the first to produce fibers of this kind and to use them for the adiabatic compression of femtosecond solitons2 and for the generation of 0.2-THz soliton trains.3 This paper examines optical properties of VD SMF.

High-Power Narrow-Linewidth Continuous-Wave Raman Amplifier at 1.27

A high-power narrow-linewidth continuous-wave (CW) Raman fiber amplifier at 1.27 μm is demonstrated for remote sensing measurements of atmospheric oxygen (O2). The amplifier uses phosphosilicate fiber in both a standard single-mode design and with the core size varying in the longitudinal direction for stimulated Brillouin scattering (SBS) suppression. The highest reported power level at this wavelength to date, a total peak power of 3 W, has been achieved for online (2.4 W) and offline (580 mW) spectroscopic measurements, in agreement with theoretical predictions. Additionally, it is shown that when 60-kHz sinusoidal amplitude modulation is applied to the amplifier seed signal, the modulated wave form is preserved at the amplifier output with 1.8 W total average power being obtained.

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We exploit the anomalous dispersion generated by an index-guided photonic crystal fiber (PCF) for dispersion compensation in an ytterbium fiber laser passively mode-locked with a semiconductor saturable absorber. A PCF, reasonably compatible with standard fiber, and a Faraday rotator in the cavity allow for robust all-fiber subpicosecond operation at 1 m, insensitive to environmental disturbance.

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Cathodoluminescence (CL), photoreflection (PR), phototransmission (PT) of single and multiquantum wells (MQWs) and strain layer ZnCdSeZnSe superlattices (SLs) grown by molecular beam epitaxy (MBE) were studied. An increase of the Stokes shift with the number of quantum wells (QWs) and the appearance of new lines in CL and PT spectra were observed. Room temperature (RT) vertical-cavity surface-emitting laser (VCSEL) operation was achieved by using the SL structures. Output power up to 2.2 W in single longitudinal mode with λ = 493 nm was obtained. Cut facet laser wavelength of the same SL structure was 502 nm.