Μm Amplification Research Articles

1.76 μm on-chip gain characteristics of Tm3+ in a rib waveguide based on Tm3+-doped LiNbO3 thin-film on insulator

A theoretical study has been performed on 1.76 μm on-chip amplification characteristics of Tm3+ in a rib waveguide of LiNbO3 on insulator (Tm:LNOI) under 795 nm wavelength pumping. Steady-state rate equations and propagation equations of signal and pump waves are established on the basis of a three-level model of Tm3+ system with the cross relaxation process 3H4→3F4: 3H6→3F4 included. The validity of the three-level model is demonstrated by referencing previously reported experiment result of Er3+-doped LNOI waveguide amplifier and by examining the effect of Tm3+ blue upconversion emissions on the 1.76 μm amplification. Besides the relations of signal gain to propagation length, launched pump power and input signal power, the effects of waveguide cross-section geometry and Tm3+ concentration on the gain characteristics are also studied. The results show that the waveguide cross-section geometry affects definitely the gain performance via its effect on mode field. The Tm3+ concentration affects the signal gain also via its effect on the 3H4→3F4: 3H6→3F4 cross relaxation coefficient, besides the conventional effect that higher active ion concentration yields larger signal gain. A comparison with conventional Ti4+(Zn2+)-diffused Tm3+-doped LN [Ti(Zn):Tm:LN] waveguide shows that the Tm:LNOI waveguide has much better gain performance than the Ti(Zn):Tm:LN waveguide, including much stronger pump power and propagation distance dependences of signal gain, much higher signal gain and much lower threshold pump power. These features are associated with significantly increased Tm3+ population inversion extent due to ultra-compact mode field and larger overlapping factor of mode field and Tm3+ population profiles in the Tm:LNOI waveguide.

Tm:YAG single-crystal fiber laser

In this Letter, to the best of our knowledge, we present the first thulium (Tm) single-crystal fiber (SCF) laser with free-space propagation of the laser beam only. The SCF is equipped with diffusion-bonded end caps of undoped YAG for better thermal management and enhancement of pump guiding. By utilizing mode matching and pump guiding in different SCF parts, an output power of 9.1 W is achieved at ∼2.02µm with a slope efficiency of 49.4%. This straightforward approach, which is also simple to realize and is based on combining the advantages of fiber-geometry structure and crystalline properties of Tm:YAG, is expected to be useful for 2 µm amplification stages in different time formats as well.

Deficient SUMO Attachment to Flp Recombinase Leads to Homologous Recombination-dependent Hyperamplification of the Yeast 2 μm Circle Plasmid

Many Saccharomyces cerevisiae mutants defective in the SUMO pathway accumulate elevated levels of the native 2 microm circle plasmid (2 microm). Here we show that accumulation of 2 microm in the SUMO pathway mutants siz1Delta siz2Delta, slx5Delta, and slx8Delta is associated with formation of an aberrant high-molecular-weight (HMW) form of 2 microm. Characterization of this species from siz1Delta siz2Delta showed that it contains tandem copies of the 2 mum sequence as well as single-stranded DNA. Accumulation of this species requires both the 2 microm-encoded Flp recombinase and the cellular homologous recombination repair (HRR) pathway. Importantly, reduced SUMO attachment to Flp is sufficient to induce formation of this species. Our data suggest a model in which Flp that cannot be sumoylated causes DNA damage, whose repair via HRR produces an intermediate that generates tandem copies of the 2 microm sequence. This intermediate may be a rolling circle formed via break-induced replication (BIR), because mutants defective in BIR contain reduced levels of the HMW form. This work also illustrates the importance of using cir(o) strains when studying mutants that affect the yeast SUMO pathway, to avoid confusing direct functions of the SUMO pathway with secondary effects of 2 microm amplification.

Synthesis and spectroscopic characterization of CaF2:Er3+ single crystal for highly efficient 1.53 μm amplification

A CaF2:Er3+ single crystal was grown by the Tammann–Stober method. The potential of this material as a laser crystal for 1530 nm emission was established by quantitative analysis of the optical absorption and emission spectra. Assuming the tetragonal symmetry of the Er3+ sites, the Bkq crystal field parameters, Racah parameters, spin–orbit interaction parameters, and configuration interaction parameters were derived by fitting the experimental absorption band positions with the model energy Hamiltonian. Judd–Ofelt parametrization was done to compute the radiative decay time and fluorescence branching ratio of various meta stable transitions. Using the measured fluorescence decay time and computed radiative decay time, 100% quantum efficiency is obtained for the 1530 nm band, which is reasonable due to the low multiphonon relaxation, and absence of nonradiative energy transfer processes at the 0.01 at.% Er3+ concentration. The narrow bandwidth (13 nm) and high stimulated emission cross section (3.2×10−20 cm2) support the suitability of CaF2:Er3+ for use in high gain optical amplifiers.

Solution synthesis and spectroscopic characterization of high Er3+ content LaF3 for broadband 1.5 μm amplification

Erbium-doped LaF3 transparent gels have been synthesized by the solution synthesis of metal inorganic precursors. The solid solubility of Er3+ can reach 60 mol %, which is almost double the solubility limit of Er3+ in LaF3 synthesized by the Bridgman technique. A quantitative analysis of the absorption and emission spectral data shows that the quantum efficiency of the 1.55 μm emission band is comparable to that of melt grown single crystal. However, the emission spectral width of the 1.55 μm band is found to be 40% greater than that of the melt grown single crystal, which extends the spectral bandwidth to 11 THz. The high solid solubility of Er3+ supports 36 cm−1 single pass optical gain, which is three times higher than that in zirconium barium lanthanum aluminum sodium glass. The high Er3+ concentration and spectral bandwidth enable LaF3:Er amplifiers to be made by a low-temperature solution-based technique.

Arsenic sulfide single mode fibres for 1.3 μm amplification.: Preparation – gain potential – power stability limits

Praseodymium doped arsenic sulfide based single mode fibres were prepared for 1.3 μm amplification. Despite of the high maximum gain coefficient (0.5 dBmW−1) the pump power stability limits the suitability of this glass matrix type for amplifier and laser applications. A 1.2 mol% germanium doped single mode fibres show a maximum pump power density limit of <15 kWcm−2. Investigations by pulsed pumping show that material degradation effects consist of reversible and irreversible portions, depending on the power pump density. By increasing the germanium concentration to more than 10 mol% the power stability limit can be remarkably improved. This indicates that the power sensitivity is determined by the main component arsenic sulfide in first place.

An insulating grid spacer for large-area MICROMEGAS chambers

We present a novel design for large-area gaseous detectors based on the MICROMEGAS technology. This technology incorporates an insulating grid, sandwiched between the micro-mesh and the anode-pad plane, which provides a uniform 200 μm amplification gap. The uniformity of the amplification gap thickness has been verified. The gain performances of the detector are presented and compared to the values obtained with detectors using cylindrical micro spacers. The new design presents several technical and financial advantages.

Effects of carbon, hydrocarbon and hydroxide impurities on praseodymium doped arsenic sulfide based glasses

In rare earth doped chalcogenide glasses, hydrocarbon and hydroxyl based impurities affect the absorption and fluorescence properties. Corresponding to Fourier transform infrared spectroscopy (FTIR) investigations sulfur is the main source of these impurities. The simultaneous occurrence of H, O, C impurities leads to an interaction influenced by the preparation conditions. Under melting conditions of arsenic sulfide and germanium/gallium doped arsenic sulfide (900°C, evacuated sealed quartz glass ampoules) hydrocarbon species tend to react with oxide impurities (As 2O 3, GeO 2) and hydroxyl with carbon oxysulfide and carbon dioxide. Excess of carbon appears as carbon disulfide (CS 2) in the FTIR spectra. The specific absorption coefficient of CS 2 is found to be 0.012±0.003 cm −1/ wt.ppm . Hydrocarbon impurities additionally increase the hydrosulfide content of samples. Based on the FTIR investigationes the specific absorption coefficient of the alkane C 24H 50 is estimated to be 0.006±0.001 cm −1/ wt.ppm . The `oxygen trap process' of carbon and hydrocarbon components in chalcogenide glasses is confirmed by thermodynamic calculations. The defined adjustment of hydrosulfide (500–1000 wt.ppm) and hydroxyl content (less 3 wt.ppm) of the As–Ge–Ga–S glass by carbon/hydrocarbon doping allowed us to prepare optimised fibers with attenuation 1.5–2 dB m −1 and a sufficient lifetime of the excited level 1 G 4 220–180 μs at 750 wt.ppm Pr 3+. The glass is introduced as core material in a single mode fiber for 1.3 μm amplification.

Spectroscopic properties of erbium-doped ultraphosphate glasses for 1.5 μm amplification

The spectroscopic properties of P2O5–Y2O3–Er2O3 and P2O5–Li2O–Al2O3–Y2O3–Er2O3 ultraphosphate glasses have been investigated. The concentration quenching rates of Er3+ in these two systems are lower compared with those in other oxide glasses. The spectral broadening of the measured fluorescence of 83.33P2O5–(16.67−x)Er2O3–xY2O3 (x=0.1 and 16.67) was observed by increasing temperature. Meanwhile, the lifetime of the I13/24 level shows the temperature dependence with increasing temperature, ascribed to the possible thermalization of higher-lying sublevels of the I13/24 level with faster radiative rates and the effect of radiation trapping. At room temperature, the deformation of the emission spectrum line shape has been observed with the increase of Er2O3 concentration due to the reabsorption effect. The 1.5-μm-amplification characteristics of P2O5–Y2O3–Er2O3 ultraphosphate glasses have been predicted from the calculated gain spectra at different pump powers.

Nanoscale Chemistry and Processing of Multifunctional Composites for Nanophotonics and Biophotonics

Multifunctional nanostructured materials and composites are of considerable interest for photonics, optoelectronics and biophotonics. This paper will focus on three topics. In the first part of the paper, we will focus on silica encapsulated multifunctional nanoparticles. These particles show enhanced optical properties as well as photo, chemical and thermal stability. In the second part of the paper, we investigate the Er3+ sol-gel multicomponent silica glass prepared with nanostructure control for 1.55 μm amplification. These glasses demonstrate the longest reported lifetime in sol-gel glasses to date, which we attribute to the reduction of the hydroxyl content in the glass. The third part of the paper discusses our work on photonic crystals.

Modification of the local phonon modes and electron–phonon coupling strengths in Dy 3+-doped sulfide glasses for efficient 1.3 μm amplification

The effect of changes in the local phonon modes and electron–phonon coupling strengths on the 1.31 μm fluorescence efficiency of Dy 3+-doped sulfide glass was investigated. An addition of 10 mole% CsBr resulted in a sharp increase in the 1.31 μm emission intensity at the expense of the 1.75 μm emission. The lifetime of the 1.31 μm emission level ( 6 F 11/2 – 6 H 9/2 ) increased to 1.58 ms, which was more than 40 times larger than that of the Ge–Ga–S host. Quantum efficiency increased from 17% to approximately 100%. These changes in the optical characteristics resulted from the large changes in the local phonon modes and electron-coupling strengths through the addition of CsBr to Ge 25Ga 10S 65 glass.

Small core high NA Pr-doped As-S glass fibres forefficient 1.3 µm amplification

Singlemode fibres for optical 1.3 µm amplification with 760 wt.ppm Pr3+ have been prepared for the first time in the As-S system. The fibres show low losses in the pump and signal region, good fluorescence behaviour and good mechanical properties.

Low Phonon Concentration Lasing Glasses for 1.3 μm Amplification

ABSTRACTGe-Ga-S-glasses doped with 15000 mole-ppm Pr3+ have been developed for applications in optical amplifiers for 1.3 μm. The formation of crystalline phase separations in Ge 25 Ga10 S65could be suppressed by modification of the glass composition with Sb. Samples have been prepared by melting in sealed silica ampoules at 950°C. Ge-Ga-Sb-S-glasses, doped with 15000 mole ppm Pr3+, were synthesized by addition of Sb2S3up to contents of 14.3 mole% to the composition Ge25,Ga10S65. (corresponding to 83,3GeS2-16,7Ga2S3) or by replacing up to 50 mole% of Ga by Sb. Transparent to opaque glasses were obtained which were free from crystalline phase separations. The modification of the glasses with Sb leads to a remarkable decrease of the transformation temperature of the glasses. However, the temperature working range remains almost unaffected. The transparent glasses exhibit with 15 – 18 μs the same fluorescence lifetimes and the same fluorescence maximum position (1340– 1341 nm) and FWHM (63 μm) as the unmodified Ge-Ga-S-glass. The preparation process for both glass systems could be optimized to obtain monoliths with lengths of several centimeters and intrin- sic optical losses of only 0.05 dB/cm at 1.3 μm (after correction of reflection), which is of very high importance for the future development of planar amplifiers with remarkable net gain.

Optical Fiber Amplifiers and Their Applications. 1.6.MU.m-Band Rare-Earth-Doped Fiber Amplifier.

1.6μm band fiber amplifiers must be developed for future optical transmission line monitoring systems and ultra-wide band wavelength division multiplexing systems. The 1.6μm band Er3+-doped fiber amplifier (EDFA) and the Tm3+-doped fluoride fiber amplifier have been proposed as candidates. The former can be realized by shifting the amplification band of a 1.55μm band EDFA, by using a long Er3+-doped fiber. The latter employs the tail of the 1.8μm amplification band of Tm3+-doped fluoride fiber by the doping of terbium ions in the cladding. This paper reviews the amplification mechanisms and basic characteristics of 1.6μm band EDFAs and TDFAs.

Comparison Between Standard and Modified Judd-Ofelt Theories in a Pr3+-Doped Fluoride Glass

Α method which takes into account normalized oscillator strengths is detailed for the calculation of parameters in Judd-Ofelt theory (B.R. Judd, Phys. Rev. 127, 750 (1962), G.S. Ofelt, J. Chem. Phys. 37, 511 (1962)). In the case of a Pr3+ -dopaed fluorozirconate glass, the Judd-Ofelt parameters obtained in this way do not depend strongly on the transitions included in the frt. Particularly, it is no longer necessary to exclude the 3H4 → 3Ρ2 transition from tle analysis. Three modifred theories (F. Auzel, S. Hubert, P. Delamoye, J. Lumin. 26, 251 (1982), A.A. Kornienko, A.A. Kaminskii, E.B. Dunina, Phys. Status Solidi B 157, 267 (1990)) are also considered but do not improve the calculated intensities when the energy of the 5d level is set to its experimentally determined value. Finally, in connection with 1.3 μm amplification, the 1.3 hn1 reabsorption ( 1i.4 → 1D2) oscillator strength is computed from the various models as well as the 1.3 /im emission branching ratio ( 1G4 --> 3H5/ 1G4 — 3H6). The best agreement with experiment is obtained with the standard Judd-Ofelt theory.

Praseodymium-doped cadmium mixed halide glasses for 1.3 μm amplification

In the search for suitable glass hosts for 1300 nm amplification, the field has been narrowed to Pr-doped fluorozirconate, fluoroindate, cadmium mixed halide and sulphide glasses. This paper presents data identifying the cadmium mixed halide system as a leading candidate, based on the lifetime and quantum efficiency of the1G4 →3H5 fluorescence of Pr3+ in this system. Compositional studies to develop cladding and core glasses suitable for high numerical aperture fiber, as well as relevant physical and optical properties, are also discussed.