Valery M. Mashinsky

Bismuth-doped-glass optical fibers—a new active medium for lasers and amplifiers

Optical fibers with bismuth-doped silicate and germanate glass cores were fabricated by the modified chemical vapor deposition technique (solution and vapor-phase Bi incorporation). The fibers revealed an efficient luminescence with a maximum in the 1050-1200 nm spectral range, FWHM up to 200 nm, and a lifetime of the order of 1 ms.

Germania-based core optical fibers

Germania-glass-based core silica glass cladding single-mode fibers (/spl Delta/n up to 0.143) with a minimum loss of 20 dB/km at 1.9 /spl mu/m were fabricated by the modified chemical vapor deposition (MCVD) method. The fibers exhibit strong photorefractivity with the type-IIa-induced refractive-index modulation of 2/spl times/10/sup -3/. The Raman gain of 300 to 59 dB/(km/spl middot/W) was determined at 1.07 to 1.6 /spl mu/m, respectively, in a 75 mol.% GeO/sub 2/ core fiber. Only 3 m of such fibers are enough for the creation of a 10-W Raman laser at 1.12 /spl mu/m with a 13-W pump at 1.07 /spl mu/m. Raman generation in optical fiber at a wavelength of 2.2 /spl mu/m was obtained for the first time.

Yb-Bi pulsed fiber lasers

A new type of pulsed fiber laser is suggested and developed - Yb-Bi lasers. In such lasers the Yb fiber laser is Q-switched by use of a saturable absorber, a Bi-doped fiber placed in its own resonator, and pulsed lasing is obtained in both fiber lasers. Continous-wave diode-clad pumping of the Yb-Bi lasers at a 975 nm wavelength with power up to 16.5 W results in pulsed laser action in a spectral diapason of 1050-1200 nm with a maximum pulse energy of up to 100 microJ, an average power up to 7.5 W, and a repetition rate up to 100 kHz.

Efficient Bismuth-Doped Fiber Lasers

Bismuth-doped fiber lasers with efficiency of up to 32% at room temperature and up to 52% at 77 K have been developed. The dependence of the efficiency on the pump power and the pump wavelength is interpreted on the basis of spectroscopic measurements.

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.

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.

Effects of exposure to photons of various energies on transmission of germanosilicate optical fiber in the visible to near IR spectral range

Abstract The origins of optical absorption induced in germanosilicate-core optical fiber by exposure to visible, ultraviolet and γ-radiation have been investigated. The effects of exposure to 5.0 eV photons and γ quanta were found to be identical and strongly different from the effect of visible-range excitation. Based on the results of the photo- and thermal-bleaching experiments, the absorption components belonging to the dominant color centers were identified. In case of 5.0 eV photons or γ-irradiation, a new band was revealed at 2.6 eV (480 nm) and ascribed to electron traps Ge X. In the case of visible-range excitation, the so-called low absorption tail dominated, caused by irreversible structural changes in glass. The effects of loss increase with heat treatment are compared between an as drawn fiber and a fiber exposed to visible light.

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.

Mode-locked Bi-doped fiber laser

Mode locking is obtained for what we believe to be the first time in a Bi-doped fiber laser. Stable 50 ps laser pulses with a pulse repetition rate of 13 MHz are generated at a wavelength of 1161.6 nm with a 2 mW average power.