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A tapered Er-doped fiber amplifier for high peak power pulses amplification has been developed and tested. The core diameter changed from 15.8 µm (mode field diameter (MFD) 14.5 µm) to 93 µm (MFD 40 µm) along 3.7 m maintaining single-mode performance at 1555 nm (according to the S2-method, the part of the power of high-order modes does not exceed 1.5%). The amplification of 0.9 ns pulses with spectral width below 0.04 nm up to a peak power above 200 kW (limited by self-phase modulation) with a slope pump-to-signal conversion efficiency of 15.6% was demonstrated.

In this paper, we have developed Yb-doped fiber suitable for creation of all-fiber seed laser schemes operating near 977 nm. The fiber was based on a ring-doping design (cladding was partially doped with Yb-ions), which allowed us to fabricate a relatively small core and provide mode field diameter (MFD) of the active fiber comparable with standard fibers (to achieve small splicing losses with commercially available optical fibers) and, simultaneously, increase absorption from the cladding to keep a reasonably high lasing efficiency. So MFDx of the fiber was 12 μm, MFDy was 14 μm. Outer silica cladding of the active fiber was decreased to diameter of 80 μm and a special pump and signal combiner was used to inject pump and signal into the active fiber. Based on the developed Yb-doped fiber an all-fiber polarization maintaining mode-locked laser with central wavelength around 977 nm was demonstrated for the first time. SESAM was used as a saturable absorber. The laser was self-starting for pump powers above 4.6 W, with the output power of 3 mW. The autocorrelation was the best fitted with sech2 profile and pulse duration was estimated to be as long as 9.5 ps. The fundamental cavity frequency corresponded to the pulse repetition rate of 33.532 MHz. Signal-to-noise ratio measured in the radio frequency range was more than 50 dB, the line width was below 1 kHz, which indicate ultimate stability of the fabricated mode-lock laser. acceptedVersion

We developed a highly efficient double-clad Yb-doped polarization-maintaining fiber to be implemented for small-signal amplification near 0.976 μm. The fiber was designed to have a relatively small mode field diameter compatible with standard step-index single-mode optical fibers. Another feature of the fiber was a small threshold for 0.976 μm signal amplification, which was achieved by a creation of a thin inner cladding (80 μm diameter). The unique design of the fiber allowed us to construct successfully an all-fiber picoseconds mode-locked laser at 0.98 μm for the first time to the best of our knowledge.

Phosphate glass is an attractive material for rare-earth-doped fiber manufacturing because high doping levels are possible without introducing negative effects such as up-conversion or increased non-radiative recombination. In this paper we present a novel PM heavily Yb-doped polarization maintaining large mode area phosphate fiber and a < 100 W power level amplifier based on this fiber. The fiber was fabricated by a rod-in-tube technique. An 18 cm long piece of the fiber was used to build a high-power all-fiber amplifier. 106 W of output power at 1030 nm was achieved with 55 % slope efficiency with respect to the launched pump power. To the best of our knowledge, this is the highest average power ever demonstrated for short phosphate fiber lasers.

An all-fiber pulsed erbium laser with pulse width of 2.4 ns working in a MOPA configuration has been created. Cladding pumped double clad erbium doped large mode area fiber was used in the final stage amplifier. Peculiarity of the current work is utilization of custom-made multimode diode wavelength stabilized at 981±0.5 nm – wavelength of maximum absorption by Er ions. It allowed us to shorten Er-doped fiber down to 1.7 m and keep a reasonably high pump-to signal conversion efficiency of 8.4%. The record output peak power for all-fiber amplifiers of 84 kW was achieved within 1555.9±0.15 nm spectral range.

In this work we present cost effective all-fiber high power pump laser near 1530 nm. The laser was based on the novel Er-doped fiber with core/cladding diameter of 100/125 μm and optimized core composition. Exploiting of this fiber together with original laser scheme allowed us to reach wall-plug efficiency as high as ~17.5 % and, at the same time, provide robust wavelength-stabilized operation. Developed laser was tested as a pump source for single-mode Tefloncoated double-clad Er-doped fiber at 1585 nm. Slope efficiency of 45 % was demonstrated in MOPA configuration

In this work we present a monolithic lidar system, based on a newly-developed double-clad large mode area (LMA) polarization-maintaining Er-doped fiber and specially designed LMA passive components. Optimization of the fiber designs resulted in as high as 100 W of SBS limited peak power. The amplifier and its passive components (circulator and collimator) were integrated in an existing lidar system. The enhanced lidar system provides three times increase of scanning range compared to one based on standard telecom-grade amplifiers.

In this work we present results on the amplification of narrow-linewidth nanosecond pulses in a recently developed ytterbium-free erbium-doped large mode area fiber cladding pumped at 980 nm. At first, a co-propagating all fiber amplifier scheme was used. Using 1 m of active fiber length in such configuration a peak power of 4 kW limited by instabilities caused by stimulated Brillouin scattering (SBS) was achieved. To the best of our knowledge this is the highest peak power ever reported for single-frequency single mode silica-based fiber sources near 1550 nm. Then all fiber counter-pumped configuration with 6 m of active fiber was used and peak power of 900 W was obtained. In this case peak power was limited by SBS generation in a passive fiber at the laser output. Slope electrical-to-optical conversion efficiency of 8 % demonstrated in such scheme is a record value for kW-level single mode single-frequency Er-doped nanosecond fiber lasers.

In this Report, we present a record-high-peak-power single-frequency master oscillator power amplifier (MOPA) system based on a newly developed double-clad large-mode-area Yb-free Er-doped fiber (DC-LMA-EDF). A fiber Bragg grating wavelength-stabilized fiber-coupled diode laser at λ=1551 nm with ~2 MHz spectral width was used as the master oscillator. Its radiation was externally modulated with a 5 kHz repetition rate and 92 ns pulse duration and then amplified in a core-pumped Er-doped fiber amplifier up to an average power of 4 mW. The amplified spontaneous emission (ASE) generated at the last preamplifier stage was suppressed by a narrow-band (0.7 nm) DWDM filter. The last MOPA stage was based on the recently developed single-mode DC-LMA-EDF with a mode field diameter of 25 microns and pump clad-absorption of 3 dB/m at λ=980 nm. The pump and the signal were launched into this fiber through a commercial pump combiner in a co-propagating amplifier scheme. At first, we used a 3-m long DC-LMAEDF. In such configuration, a peak power of 800 W was achieved at the output of the amplifier together with a ~ 12 % pump conversion slope efficiency. Further power scaling was limited by SBS. After that we shortened the fiber length to 1 m. As a result, owing to large unabsorbed pump power, the efficiency decreased to ~5 %. However, a peak power of more than 3.5 kW was obtained before the SBS threshold. In this case, the pulse shape changed and its duration decreased to ~60 ns owing to inversion depletion after propagation of the forward front of the pulse. To the best of our knowledge, the peak power of more than 3.5 kW reported here is the highest value ever published for a single-frequency single-mode silica-based fiber laser system operating near λ=1550 nm.

The use of double-clad fibers for short pulses amplification requires high active ions concentration in order to keep the active fiber length short. In the case of Er-doped fibers an increase of concentration leads to a significant drop of efficiency due to Er ions clustering. We have demonstrated through numerical simulation that efficiency of amplifiers based on double-clad P2O5-Al2O3-SiO2 (PAS) Er-doped fibers decreases slower with Er-concentration growth if compared with standard Al2O3-SiO2 fibers. In this paper, we present single-mode large-mode-area heavily Er-doped double-clad fiber based on PAS glass matrix for short pulses amplification. The developed PAS fiber has a 36 μm singlemode core and a small signal cladding absorption of 3 dB/m at 980 nm leading to an optimal fiber length in range of 5-8 m depending on the central wavelength. At first, an all-fiber nanosecond MOPA at 1560 nm was built using our PAS fiber as the final amplifier. We obtained 28 W of average output power (efficiency of 25 % with respect to the launched pump power at 976) limited by amplified spontaneous emission. Pulse energy of 1.5 mJ was achieved at pump power level of ~120 W. We believe that it is the first demonstration of mJ-energy level single-mode nanosecond fiber system. Then, direct amplification of 100-fs source was performed using this fiber. We obtained 12 nJ pulse energy and 100 kW of peak power from the fiber which is close to the record value for Er-doped fiber amplifiers.

Power scaling of Yb-free Er-doped fiber lasers is extremely challenging due to low Er ion absorption cross-section and growth of unbleachable loss at high Er concentrations because of clustering effects. Hence, usual double-clad Er-doped fibers suffer from low efficiency. We present an efficient high power all-fiber amplifier based on our newly developed Yb-free Er-doped fiber. Proper core composition and relatively low Er3+ concentration mitigates clustering effect. Furthermore, large single-mode core diameter of 34 um increases the pump absorption and decreases the fiber length. Our amplifier consists in the specialty Er fiber pumped through a commercially available pump combiner by means of 6 pigtailed multimode diodes (D=105 um, NA=0.15, input pump power of 275W). The signal source is a low power continuous wave fiber laser spliced to the amplifier. Therefore we built truly all-fiber laser without any free space coupling. We obtained 103 W of amplified signal limited only by the available pump power. Pump conversion efficiency is as high as 37 %. To the best of our knowledge this is the highest power ever demonstrated for Yb-free Er-doped lasers pumped at 976 nm. This power level is similar to that obtained in resonantly pumped Er-doped fiber lasers.

In this paper, we propose a novel all-fiber laser scheme with the output wavelength of 1565 nm based on a new Er-doped fiber design. A conventional commercially available pump source at 980nm (D=105 P m, NA=0.2) is used for pumping. A high slope efficiency of 28% comparable with those in Er -Yb lasers was achieved owing to the utilization of the novel P 2 O 5 -Al 2 O 3 -SiO 2 (PAS) glass as the host for Er 3+ ions. A relatively low in-cavity fiber length (~14m) becomes possible owing to a small outer fiber diameter (80 P m) and the use of a fiber taper (105 P m to 80 P m) for launching the pump. Keywords: Er-doped fiber, fiber laser, double clad fiber 1. INTRODUCTION Among high power (>1W) fiber lasers operating near 1550nm, the most popular ones are fiber lasers and amplifiers based on Er-Yb optical fibers. A high absorption cross section of Yb 3+ ions allows pumping of optical fibers through the cladding by powerful and chip multimode laser sources at 915/976nm. The slope of the pump-to-signal conversion efficiency (slope efficiency) achieved at a medium power in Er-Yb lasers a nd amplifiers reach 30-40% (e.g. [1]-[5]). At the same time, significant disadvantage of Er-Yb lasers is the appearance of unwanted lasing near the wavelength of 1P m. Calculations show that in usual fibers with a core area of about 90 P m

Some experimental results of artificial airglow emission at 557.7 nm (green line) during HF pumping of the ionosphere with specially designed HF pulsing sequence are reported. Ionospheric radio pumping was performed at the "Sura" radio facility situated near Niznhny Novgord, Russia. The measurements of airglow were handled at the Astronomical Observatory of Kazan State University (220 km to the east of "Sura" facility) by the astronomical telescope AZT-14 connected with the electric photometer. During several "Sura" runs enhancements of the airglow intensity in time with pump wave pulses were observed after the pump wave switch from continuous transmission to low duty cycle pulse transmission.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Optical limiting effect has been investigated in polyimide- fullerene and polyimide-dye-fullerene systems. The second harmonic of a pulsed Nd:YAG laser was applied as an irradiation source. The laser radiation was attenuated at least by an order of magnitude. When fullerenes and dye were simultaneously introduced in polyimide, the most optical limiting effect was observed. It was established the fullerene-doped polyimide systems could be applied for limiting power to more than 4 J cm -2 .

We report electroluminescence (EL) of polyimides prepared from 9,10-bis(m-aminophenylthio)-anthracene (BPTA) and 1,3-bis(3,4- dicarboxyphenoxy)benzene or 2,2-bis[4-(3,4- dicarboxyphenoxy)phenyl]-propane dianhydrides. The new polyimide-type of polymers, aromatic polyimides with and without sulphur atoms in the backbone, were investigated as electron-hole transporting and light-emitting materials for use in single- and multilayer electroluminescent diodes. These polymers belong to a new class of donor-acceptor compounds and have some advantages over their counterparts. They are efficient electron and hole conductors and known as photoluminophores exhibiting intense photoluminescence of exciplex origin. Some of them were used earlier as hole conducting layers together with tris(8-quinolinolato)aluminum complex as an electron conducting layer in bilayer LEDs of high brightness. Donor-acceptor interactions determine optical, electrical and photoelectrical properties of these polymers. A direct correlation was revealed between transporting characteristics and electroluminescent properties for these electroactive materials. At room temperature, the electron and hole drift mobilities directly measured by conventional TOF techniques indicated effective bipolar transport. The simplicity of synthesis, high thermal stability, organic solvent solubility together with excellent film-forming properties make the polymers potentially of interest for technological applications. Properties of the uni- and bilayer LEDs based on these materials are discussed in terms of the band structure, bipolar transport and electron donor-acceptor interactions.

Hole drift mobilities (mu) were measured in a series of triphenylamine (TPA) molecules and oligomers dispersed into bisphenol-A polycarbonate (PC) by conventional time-of- flight techniques. The transport molecules were oligomeric triphenylamine (OTPA) containing 8-10 TPA units TPD and TPA. In PC doped with 50 wt percent OTPA, TPD, and TPA, (mu) values were of 1 X 10-7, 1 X 10-5, and 7 X 10-6 cm2/(V S) accordingly, at the electric field of F equals 5 $ MUL 105V/cm and room temperature. In order to elucidate the relationship between structure of transport site and mobility, the molecular orbital calculations were made for the TPA, TPD and OTPA molecules. For the calculations, the PM3 method was chosen because it gave better agreement between calculated and experimentally parameters than the AM1 method for the molecules studied. The result obtained from the hole mobility measurements and the quantum chemistry calculations demonstrate that the N-Ph-Ph-N fragment is a transporting center for both TPD and OTPA molecules. For OTPA, the end fragments of the molecule appear as transport sites.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The method of electrodigit diagnostics is based on registration of a picture luminescence of object, placed in a high-frequency high-voltage field. It lets to reveal surface heterogeneity of a various nature, defects conductor under a layer optical opaque dielectric or in most dielectric. Early (USSR author certificat N° 1563447) it is offered to replace traditionally used in this method halogensilver materials for vacuum thermal deposition (VTD) on dielectric of a substrate by thin layers organic dyes, that will make a method more technological and cheap. In the given work the spectral methods have qualitatively appreciated a role making of (electronic, X-ray, ultraviolet and visible radiations) in formation of the electrodigit image in VTD-films of Rhodamine 6G (R-6G) and dye of a class Oxazine (OX-1). It is established, that: 1) the contribution all making (except UV-radiation) in formation of a drawing in VTD-films of R-6G and OX-1 is insignificant; 2) the visible image in a VTD-film of R-6G will be formed for the account of decomposition of dye by rigid UV-radiation ; 3) the influence of I sec. of the crown discarge on 0,68-μm a VTD-film of OX-1 is equivalent of irradiation her 365 nm by a doze 0,8 J/cm 2 .

Light-addressed spatial light modulators with various photosensitive layers have been investigated using both holographic and projection techniques. The ways of reaching the compromise between high resolution and high speed of the device have pointed out.

Organic polymer photoconductors are considered as a perspective materials for optically addressed spatial light modulators. A few type of materials were tested. Approach to the choice of materials is suggested.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Peculiarities of 30...100 keV P+ and Ar+ ion implantation into dry vacuum resist on the base of -pyrone have been studied by x-ray photoelectron spectroscopy and Rutherford backscattering spectrometry. Phosphorus atom distribution profile has been shown to have an anomalous shape with two peaks, one of which is situated in a region of projected range, while the other is on the sample surface directly. Radiation-induced diffusion and solid phase reactions leading to phosphorus organic coating formation of about 40..50 Ao in thickness has been revealed to occur during phosphorus ion implantation.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.