Sergei V. Firstov

Bi-Doped Optical Fibers and Fiber Lasers

The current state of the art in infrared Bi-doped fiber laser research is reviewed. The relevant fiber glass compositions and fiber technologies are introduced. Lasers operating on transitions ranging from 1.15 to 1.55 μm occurring in the bismuth active centers and their energy level schemes are discussed on the basis of the spectroscopic properties of these centers. Continuous-wave fundamental-mode power levels ranging from a few mW near 1.55 μm up to 16 W near 1.16 μm and 22 W near 1.46 μm have been demonstrated in recent years.

A 23-dB bismuth-doped optical fiber amplifier for a 1700-nm band

It is now almost twenty-five years since the first Erbium-Doped Fiber Amplifier (EDFA) was demonstrated. Currently, the EDFA is one of the most important elements widely used in different kinds of fiber-optic communication systems. However, driven by a constantly increasing demand, the network traffic, growing exponentially over decades, will lead to the overload of these systems (“capacity crunch”) because the operation of the EDFA is limited to a spectral region of 1530–1610 nm. It will require a search for new technologies and, in this respect, the development of optical amplifiers for new spectral regions can be a promising approach. Most of fiber-optic amplifiers are created using rare-earth-doped materials. As a result, wide bands in shorter (1150–1530 nm) and longer wavelength (1600–1750 nm) regions with respect to the gain band of Er-doped fibers are still uncovered. Here we report on the development of a novel fiber amplifier operating in a spectral region of 1640–1770 nm pumped by commercially available laser diodes at 1550 nm. This amplifier was realized using bismuth-doped high-germania silicate fibers fabricated by MCVD technique.

Photobleaching effect in bismuth-doped germanosilicate fibers

Photoinduced reduction of absorption (photobleaching) in bismuth-doped germanosilicate fibers irradiated with 532-nm laser has been observed for the first time. It was demonstrated that bismuth-related active centers having the absorption bands at wavelengths of 1400 and 1700 nm degrade under photoexcitation at 532 nm. The photobleaching process rate was estimated using conventional stretched exponential technique. It was found that the photobleaching rate in bismuth-doped germanosilicate fibers does not depend on type of bismuth-related active center. The possible underlying mechanism of photobleaching process in bismuth-doped fibers is discussed.

Anti-Stokes luminescence in Bismuth-doped silica and germania-based fibers

Luminescence excitation spectra of active centers in bismuth-doped vitreous SiO(2) and vitreous GeO(2) optical fibers under the two-step excitation have been obtained for the first time. The results revealed only one bismuth-related IR active center formed in each of these fibers. The observed IR luminescence bands at 1430 nm (1650 nm) and 830 nm (950 nm), yellow-orange (red) band at 580 nm (655 nm), violet (blue) band at 420 nm (480 nm) belong to this bismuth-related active center in the vitreous SiO(2) (vitreous GeO(2)), correspondingly.

1700 nm dispersion managed mode-locked bismuth fiber laser.

We demonstrate the first 1.7 μm bismuth-doped fiber laser generating ultrashort pulses via passive mode-locking. Pulse operation has been achieved for both anomalous and normal dispersion of the laser cavity owing to broadband characteristics of carbon nanotube saturable absorber. The laser delivered 1.65 ps pulses in net anomalous dispersion regime. In normal dispersion regime, the laser delivered 14 ps pulses which could be compressed to 1.2 ps using external fiber compressor.

Laser-induced bleaching and thermo-stimulated recovery of luminescent centers in bismuth-doped optical fibers

In this paper, we report the detailed study of photobleaching and recovery in bismuth-doped fibers that proved to be a unique laser media for the near IR spectral regions unreachable for rare-earth-doped lasers. The laser-induced bleaching and recovery dynamics of the characteristic absorption and emission bands assigned to different types of the bismuth-related active centers were obtained. By analyzing the Raman-scattering spectra of the bleached bismuth-doped fibers, the intensity-dependence of the photobleaching rate and the experimentally determined activation energy of the recovery process and underlying mechanisms of these phenomena are discussed. Furthermore, a bleaching–recovery cycling and “memory effect” are demonstrated.

Luminescence and laser generation in Bi-doped fibers in a spectral region of 1300–1520 nm

Optical properties of Bi-doped phosphogermanosilicate fibers were investigated. It was demonstrated that fiber lasers based on fibers of this type can generate radiation in a broad-band range of 1300–1520 nm.

Effect of gamma-irradiation on the optical properties of bismuth-doped germanosilicate fibers

In this paper we present the results on the effect of γ-irradiation on the optical properties of bismuth-doped germanosilicate fibers. It has been revealed that the absorption and emission bands of the bismuth-related active centers are mildly affected by γ-radiation with a dose ranging from 1 to 8 kGy. Experimental data on the radiation-induced absorption (RIA) dynamics of Bi-doped fibers under irradiation and post-irradiation recovery have been obtained. The RIA spectra of the Bi-doped germanosilicate fibers have been measured. The effect of Bi concentration on the RIA level is discussed.

Bismuth-doped optical fiber amplifier and watt-level CW laser for the spectral region 1600–1800 nm

The first bismuth-doped fiber amplifier (BDFA) for 1640-1770-nm region was developed. The BDFA diode-pumped at 1550 nm is characterized by 23-dB peak gain at 1710 nm, noise figure~7 dB, Δλ_1/2=40 nm and g=0.1 dB/mW.

Bismuth-doped Optical Fibers: Advances and New Developments

Recent results on luminescence properties of various Bi-doped fibers, the nature of Bi-related NIR emitting centers and the development of efficient Bi-doped fiber laser and optical amplifiers are presented.