5†µm CW Ce3+-doped chalcogenide glass fiber laser with 17% slope efficiency.

Efficient room temperature mid-infrared laser action in a Ce3+-doped chalcogenide fiber was demonstrated. The fiber had a doped selenide glass core in an undoped sulfide glass cladding. The pump source was a CW Fe2+:ZnSe laser emitting at 4.14 µm. The optimized fiber length allowed obtaining up to 7 mW of 5.06 µm output with 17% slope efficiency at room temperature.

Passively Q-switched 5-µm Ce3+-doped selenide glass laser using Fe:CdTe and Fe:CdSe as saturable absorbers.

The first, to the best of our knowledge, mid-infrared Q-switched Ce3+-doped glass laser is demonstrated. As saturable absorbers, Fe2+:CdSe and Fe2+:CdTe are used for the first time. When Q-switched by Fe:CdSe, the laser operates in a multi-pulse regime with an individual pulse width of 110 ns, centered at λ = 5.20 µm. With Fe:CdTe as saturable absorber, 1-3 giant pulses of 30 ns pulse width are generated at λ = 5.13 µm.

Mid-infrared laser performance of Ce3+-doped selenide glass.

An extensive study of a novel room-temperature mid-infrared Ce3+-doped Ge20Sb10Ga5Se65 glass laser is reported. An influence of output-coupler transmission on laser efficiency and emission spectra is investigated. Pumped by a pulsed Fe:ZnSe laser at 4.1 µm, a maximum output energy of 35 mJ is demonstrated at 5.2 µm, with a laser threshold of about 60 mJ and a slope efficiency of 21%. The tuning range of a mid-infrared Ce:glass laser is reported for the first time: with an intracavity prism, the laser is continuously tunable in the spectral range of 4.5-5.6 µm. The internal losses are determined to be below 9% per roundtrip.

Resonantly pumped Ce3+ mid-infrared lasing in selenide glass.

In high purity Ce3+-doped selenide glass pumped by a 4.08 µm Fe:ZnSe laser, 5.1-5.5 µm laser oscillations were observed. This is the first evidence of laser action corresponding to the 2F7/2→2F5/2 transition of Ce3+ ions.

Infrared luminescence in bismuth-doped AgCl crystals.

Experimental and computer-modeling studies of the spectral properties of crystalline AgCl doped with metal bismuth or bismuth chloride are performed. The broad near-IR luminescence band in the 0.8-1.2 µm range with time dependence described by two exponential components corresponding to the lifetimes of 1.5 and 10.3 µs is excited mainly by 0.39-0.44 µm radiation. Computer modeling of probable Bi-related centers in the AgCl lattice is performed. On the basis of experimental and calculation data, a conclusion is drawn that IR luminescence can be caused by Bi+ ion centers substituted for Ag+ ions.

Centers of near-IR luminescence in bismuth-doped TlCl and CsI crystals.

A comparative first-principles study of possible bismuth-related centers in TlCl and CsI crystals is performed and the results of computer modeling are compared with the experimental data. The calculated spectral properties of the bismuth centers suggest that the IR luminescence in TlCl:Bi is most likely caused by Bi(+)···V(Cl)(-) centers (Bi(+) ion in thallium site and a negatively charged chlorine vacancy in the nearest anion site). On the contrary, Bi(+) substitutional ions and Bi(2)(+) dimers are most likely responsible for the IR luminescence in CsI:Bi.

Near-infrared luminescence in TlCl:Bi crystal.

Experimental and theoretical studies of spectral properties of crystalline TlCl:Bi are performed. Two broad near-infrared luminescence bands with a lifetime of about 0.25 ms are observed: a strong band near 1.18 µm excited by 0.40, 0.45, 0.70, and 0.80 µm radiation and a weak band at ≳1.5 µm excited by 0.40 and 0.45 µm radiation. Computer modeling of Bi-related centers in TlCl lattice suggests that a Bi(+)…VCl(Cl)(-) center (Bi(+) in Tl site and a negatively charged Cl vacancy in the nearest anion site) is most likely responsible for the IR luminescence.

Spectral dependence of the refractive index of chemical vapor deposition ZnSe grown on substrate with an optimized temperature increase.

Precise measurement of the refractive index of chemical vapor deposition (CVD) ZnSe with the Fourier-transform interference refractometry method from 0.9 to 21.7microm (from 11,000 to 460cm(-1)) with 0.1cm(-1) resolution is described. For this measurement, structurally homogeneous ZnSe plates were grown on a substrate with an optimized temperature increase. Using three ZnSe plates of different thicknesses, we managed to raise the measurement accuracy of the refractive index up to 2x10(-5) (being nearly 1 order of magnitude better than the available data) in the near IR and most of the middle IR wavelength range from 0.9 to 12.5microm (wavenumber range of 11,000-800cm(-1)) and up to 1...4x10(-4) in the 12.5-21.7microm (800-460cm(-1)) region. The experimental results are approximated by a generalized Cauchy dispersion function of the 8th power. Spectral wavelength dependencies of the first- and second-order derivatives of the refractive index are calculated, and the zero material dispersion wavelength is found to be lambda(0)=4.84microm.

Origin of broadband near-infrared luminescence in bismuth-doped glasses.

Interstitial negative-charged bismuth dimers, Bi(-)(2) and Bi(2-)(2), are suggested as a model of broadband IR luminescence centers in bismuth-doped glasses. The model is based on quantum-chemical calculations of equilibrium configurations, absorption, luminescence, and luminescence excitation spectra of the dimers in an alumosilicate network and is supported by IR luminescence observed for the first time, to our knowledge, in bismuth-doped polycrystalline magnesium cordierite.

Increased solubility of molecular hydrogen in UV-exposed germanosilicate fibers.

Spectral properties of photoinduced fiber Bragg gratings written in germanosilicate fibers and subjected to hydrogen loading at a pressure of 150-170 MPa have been studied. It was observed, for the first time to our knowledge, that hydrogen dissolution in the glass network at such high pressures leads not only to a Bragg wavelength shift but also to a considerable alteration of the grating reflectivity. The relative magnitude of the latter effect is independent of the dissolved hydrogen concentration and is defined mainly by the core glass properties and the UV-irradiation conditions. The alteration of the grating reflectivity observed experimentally is explained by increased solubility of molecular hydrogen in UV-exposed germanosilicate glass.

Raman band intensities of tellurite glasses.

Raman spectra of TeO2-based glasses doped with WO3, ZnO, GeO2, TiO2, MoO3, and Sb2O3 are measured. The intensity of bands in the Raman spectra of MoO3-TeO2 and MoO3-WO3-TeO2 glasses is shown to be 80-95 times higher than that for silica glass. It is shown that these glasses can be considered as one of the most promising materials for Raman fiber amplifiers.

UV-irradiation-induced structural transformation in phosphosilicate glass fiber.

The Raman spectra of phosphosilicate core (P(2)O(5)-SiO(2)) fibers were investigated. Significant changes in the spectra were observed after UV irradiation of the fibers. An interpretation of the photostructural changes confirmed by computer simulation of phosphorus-related centers is proposed.

UV-irradiation-induced structural transformation of germanoscilicate glass fiber.

Raman spectra of germanosilicate core fibers before and after UV irradiation were investigated. Significant changes of the Raman spectra after irradiation indicate transformation of the glass structure. A possible interpretation of the observed changes is proposed.