Oleg I. Medvedkov

Laser-diode-pumped phosphosilicate-fiber Raman laser with an output power of 1 W at 1.48 mum.

An all-fiber 1.48-mum generator based on a laser-diode-pumped Yb-doped double-clad laser and a cascaded Raman wavelength converter has been developed. Second-order Raman Stokes radiation was generated in a phosphosilicate-fiber resonator formed by two pairs of Bragg gratings. A slope efficiency of the Raman converter of 48% with respect to the power emitted by the double-clad Yb laser has been achieved. We obtained an output power of 1 W at a slope efficiency of 34% with respect to the laser-diode array power, with a total optical-to-optical efficiency of 23%.

Mid-infrared Raman-soliton continuum pumped by a nanotube-mode-locked sub-picosecond Tm-doped MOPFA.

We demonstrate a mid-infrared Raman-soliton continuum extending from 1.9 to 3 µm in a highly germanium-doped silica-clad fiber, pumped by a nanotube mode-locked thulium-doped fiber system, delivering 12 kW sub-picosecond pulses at 1.95 µm. This simple and robust source of light covers a portion of the atmospheric transmission window.

Refractive-index gratings written by near-ultraviolet radiation

This is the first report, to our knowledge, of refractive-index grating side writing in 10 mol.% GeO(2)-doped fiber by the near-UV light of a cw Ar(+) laser (333-364 nm). An induced-index magnitude as large as 1.9 x 10(-4) at 1.7x10(5) W/cm(2) UV power density has been achieved. The observed gratings have exhibited the same temperature stability as gratings written by a KrF excimer laser (248 nm).

Bi-doped fiber lasers and amplifiers for a spectral region of 1300–1470 nm

Bismuth-doped fiber lasers operating in the range 1300-1470 nm have been demonstrated for the first time, to our knowledge. It has been shown that Bi-doped alumina-free phosphogermanosilicate fibers reveal optical gain in a wavelength range of 1240-1485 nm with pumping at 1205, 1230, or 808 nm.

Performance of Bragg and long-period gratings written in N- and Ge-doped silica fibers under /spl gamma/-radiation

In-fiber Bragg and long-period gratings as well as Mach-Zehnder interferometers based on germanium- and nitrogen-doped silica fibers have been investigated under /spl gamma/-rays. The majority of the experimental results suggest that both types of gratings in both types of fibers are stable with respect to /spl gamma/-ray doses of up to 1.47 MGy.

Optical amplification in 1430-1495 nm range and laser action in Bi-doped fibers.

An emission band with a maximum at 1430 nm and a FWHM of 100 nm was observed in a Bi-doped fiber under core-pumping in the 1340- 1370 nm wavelength range. Net gain in 1430-1490 nm and laser action in 1443-1459 nm wavelength range in the Bi-doped aluminosilicate fiber have been demonstrated for the first time to our knowledge.

Germania-glass-core silica-glass-cladding modified chemical-vapor deposition optical fibers: optical losses, photorefractivity, and Raman amplification

Germania-glass-core silica-glass-cladding single-mode fibers (deltan as great as 0.143) with a minimum loss of 20 dB/km at 1.85 microm were fabricated by modified chemical-vapor deposition. The fibers exhibit strong photorefractivity, with type IIa index modulation of 2 x 10(-3). A Raman gain of 300 dB/(kmW) was determined at 1.12 microm. Only 3 m of such fibers is sufficient for constructing the 10-W Raman laser at 1.12 microm with a 13-W pump at 1.07 microm.

Stabilization of Fiber Bragg Gratings Against Gamma Radiation

The effect of gamma-radiation on the spectral characteristics of FBGs has been studied experimentally. The FBGs were fabricated in optical fibers with a GeO2 concentration in the core in a range from several to 99 mol.%. Various pre- and post-fabrication treatments were applied with the aim to improve the radiation tolerance of the FBGs. The best result was obtained for a Type IIa annealed grating written in SM310 fiber, where the Bragg peak shift saturated at a 12 pm level and an amplitude change of 0.04 dB with the maximal dose of about 50 kGy.

Bismuth-doped silica-based fiber lasers operating between 1389 and 1538 nm with output power of up to 22 W

An efficient CW bismuth fiber laser operating around 1.46 μm with an efficiency of >50% and an output power of >20 W has been developed on a bismuth-doped GeO(2)-SiO(2) fiber. The laser demonstrates weak dependence of the output power on temperature in comparison with bismuth lasers operating near 1.15 and 1.3 μm. The laser generation has been obtained in the range 1.39 to 1.54 μm. The first linearly polarized bismuth-doped fiber laser at 1.46 μm based on a PANDA-type fiber has been demonstrated.

Absorption, Gain, and Laser Action in Bismuth-Doped Aluminosilicate Optical Fibers

In this study, bismuth-doped fiber lasers operating at the wavelength of 1179 nm with an optical efficiency of up to 28% are realized. The fiber gain upon 1-¿m pumping declines, while the unsaturable absorption increases with increasing the small-signal absorption. We conclude that up-conversion and excited-state absorption are responsible for limiting the efficiency of such lasers.