Praseodymium-Doped Ge20In5Sb10Se65 Films Based on Argon Plasma Cosputtering for Infrared-Luminescent Integrated Photonic Circuits.

In this paper, we report on the infrared luminescence of amorphous praseodymium-doped Ge20In5Sb10Se65 waveguides, which can be used as infrared sources in photonic integrated circuits on silicon substrates. Amorphous chalcogenide thin films were deposited by radiofrequency magnetron cosputtering using an argon plasma whose deposition parameters were optimized for chalcogenide materials. The micropatterning as ridge waveguides of the chalcogenide cosputtered films was performed using photolithography and plasma-coupled reactive ion etching techniques. The influence of the rare earth concentration within those thin films on their optical properties and rare earth spectroscopic properties was investigated. Using an excitation wavelength of 1.55 µm, the mid-infrared luminescence of Pr3+ ions from 2.5 to 5.5 µm was clearly demonstrated for studied chalcogenide materials. A wide range of waveguide widths and doping ratios were tested, assessing the ability of the cosputtering technique to preserve the luminescence properties of the rare earth ions initially observed in the bulk glass through the thin-film deposition and patterning process.

In-band pumped Tm,Ho:LiYF4 waveguide laser.

A 4.5 at.% Tm, 0.5 at.% Ho:LiYF4 planar waveguide (thickness: 25 µm) grown by Liquid Phase Epitaxy is in-band pumped by a Raman fiber laser at 1679 nm (the 3H6 → 3F4 Tm3+ transition). A continuous-wave waveguide laser generates a maximum output power of 540 mW at 2051nm with a slope efficiency of 32.6%, a laser threshold of 337 mW and a linear laser polarization (π). This represents the highest output power extracted from any Tm,Ho waveguide laser. No parasitic Tm3+ colasing is observed. The waveguide propagation losses are determined to be as low as 0.19 dB/cm.

Watt-level visible laser in double-clad Pr3+-doped fluoride fiber pumped by a GaN diode.

We report on a red praseodymium fiber laser delivering 1.07 W at 634.5 nm with a slope efficiency of 20.7% (versus the incident pump), a laser threshold of 0.55 W, and a single-mode output (Mx,y2<1.1) in the quasi-continuous-wave regime. It is based on a 0.6 mol.% Pr3+-doped ZBLAN double-clad fiber with a 5.5 µm core, a double D-shaped (diameters, 115/125 µm) inner cladding, and a length of 5.0 m. The fiber is pumped by a multimode 443 nm GaN diode. The laser design is optimized using a numerical model. The proposed concept is suitable for the development of diode-pumped high brightness watt-level visible praseodymium fiber lasers.

Watt-level efficient 2.3 µm thulium fluoride fiber laser.

We report on an efficient mid-infrared thulium (Tm) fiber laser operating on the 3H4→3H5 transition and featuring an upconversion pumping scheme. This laser comprises a heavily Tm3+-doped (2.50 mol. %) zirconium fluoride glass fiber pumped by a tunable Yb fiber laser around 1.05 µm corresponding to the 3F4→3F2,3 excited-state absorption transition. The laser generates 1.24 W at 2269-2282 nm with a slope efficiency of 37% in the quasi-continuous-wave regime. The Tm-glass fiber exhibits a broadband 3H4→3H5 emission with a bandwidth of 173 nm, making it very promising for femtosecond fiber oscillators at ∼2.3µm.

Watt-level diode-pumped thulium lasers around 2.3 µm.

We report on efficient diode-pumped mid-infrared lasers based on Tm:LiYF4, Tm:Y3Al5O12, and Tm:YAlO3 crystals. These lasers operate in the continuous-wave (CW) regime and deliver watt-level output power at the wavelengths of 2.2-2.3 µm (the 3H4→3H5Tm3+ transition). In particular, a 1.8 at. % Tm:YAlO3 laser pumped at 789 nm generates a maximum CW output power of 1.32 W at 2272-2277 nm with a slope efficiency of 33.1% (with respect to the absorbed pump power), a linear laser polarization (E∥b), and a fundamental transverse output mode (the measured Mx2=1.26, My2=1.68). In the quasi-CW regime, the output peak power is scaled up to 2.69 W. The pump quantum efficiency and the fractional heat loading are estimated and discussed.

Comparative study of Er3+-doped Ga-Ge-Sb-S thin films fabricated by sputtering and pulsed laser deposition.

Despite the renewed interest in rare earth-doped chalcogenide glasses lying mainly in mid-infrared applications, a few comprehensive studies so far have presented the photoluminescence of amorphous chalcogenide films from visible to mid-infrared. This work reports the fabrication of luminescent quaternary sulfide thin films using radio-frequency sputtering and pulsed laser deposition, and the characterization of their chemical composition, morphology, structure, refractive index and Er3+ photoluminescence. The study of Er3+ 4I13/2 level lifetimes enables developing suitable deposition parameters; the dependency of composition, structural and spectroscopic properties on deposition parameters provides a way to tailor the RE-doped thin film properties. The surface roughness is very low for both deposition methods, ensuring reasonable propagation optical losses. The effects of annealing on the sulfide films spectroscopy and lifetimes were assessed. PLD appears consistent composition-wise, and largely independent of the deposition conditions, but radiofrequency magnetron sputtering seems to be more versatile, as one may tailor the film properties through deposition parameters manipulation. The luminescence via rare earth-doped chalcogenide waveguiding micro-structures might find easy-to-use applications concerning telecommunications or on-chip optical sensors for which luminescent sources or amplifiers operating at different wavelengths are required.

7 to 8 µm emission from Sm3+ doped selenide fibers.

We report on the observation of the long wave-infrared (LWIR) emission centered at 7.3 µm of Sm3+ doped chalcogenide fibers. The chemical composition of the selenide glass host matrix (Ga5Ge20Sb10Se65) enables the drawing of 500 ppm and 1000 ppm Sm3+ doped fibers. By means of conventional glass elaboration methods, these Sm3+ doped fibered materials exhibit a significant emission band from 6.5 to 8.5 µm with a maximum emission around 7.3 µm whether they are excited at 1.45 µm or at 2.05 µm. Absorption spectra, Judd-Ofelt analysis, NIR, MWIR and LWIR luminescence spectra are presented and discussed.

8 µm luminescence from a Tb3+ GaGeSbSe fiber.

In this Letter, we report for the first time, to the best of our knowledge, on an emission at 8 µm from Tb3+-doped Ga5Ge20Sb10Se65 chalcogenide fibers with doping levels at 1000 ppm and 500 ppm. These fibers were drawn following conventional melt-quenching methods and pumped at 2.05 µm using a Tm3+: YAG laser. The spectroscopic properties of the emitting F47 manifold are investigated to rule out any parasitic signal mimicking the real Tb3+ 8 µm emission. Time-resolved spectroscopic experiments are presented to build a comprehensive study of this 8 µm fluorescence recorded with a clear signal-to-noise ratio.

Design of praseodymium-doped chalcogenide micro-disk emitting at 4.7 µm.

A compact amplifier based on chalcogenide Pr3+-doped micro-disk coupled to two ridge waveguides is designed and refined by means of a home-made computer code. The gain G ≈ 7.9 dB is simulated for a Pr3+ concentration of 10 000 ppm, input signal power of -30 dBm at the wavelength 4.7 µm and input pump power of 50 mW at the wavelength 1.55 µm. In the laser behavior, i.e. without input signal, the maximum slope efficiency S = 8.1 × 10-4 is obtained for an input pump power of 2 mW. This value is about six times higher than that simulated for an optimized erbium-doped micro-disk.

Green, orange, and red Pr(3+)∶YLiF(4) epitaxial waveguide lasers.

Efficient guided laser oscillation in the visible spectral region is demonstrated with praseodymium-doped YLiF(4) layers grown by liquid phase epitaxy. By exciting Pr(3+) ions at 479.2 nm with an optically pumped semiconductor laser, maximum slope efficiencies of 40% at 639 nm and 32% at 604 nm are obtained in a cw regime. Green laser oscillation at 522.5 nm, in a quasi-cw regime, with an average output power of 66 mW, is demonstrated for the first time, to our knowledge, in a crystalline fluoride epitaxial waveguide. Furthermore, a record efficiency of 60% at 639 nm in the quasi-cw regime is reported.

2.8 W end-pumped Yb3+:LiYF4 waveguide laser.

Continuous wave, room temperature laser oscillation around 1 µm is reported for the first time (to our knowledge) from an Yb(3+)-doped fluoride crystalline waveguide fabricated by using the liquid phase epitaxy technique. Maximum slope efficiencies of 76% and 41% were obtained for laser emissions at 994 and 1020 nm, respectively. A maximum output power of 2.8 W was obtained at 1020 nm by pumping around 980 nm with a high-brightness fiber laser in an 87 mm long V-shaped cavity.

Red and orange Pr3+:LiYF4 planar waveguide laser.

In this Letter we report on room temperature continuous wave laser operation in the red (639 nm, (3)P(0)→(3)F(2)) and orange (604 nm, (3)P(0)→(3)H(6)) spectral regions of Pr(3+)-doped LiYF(4) planar waveguides fabricated by liquid phase epitaxy. Output powers of 25 and 12 mW and slope efficiencies of 5% and 6% were achieved at 639 and 604 nm, respectively, by pumping with an optically pumped semiconductor laser operating at 479.2 nm.

Tm:LiYF4 planar waveguide laser at 1.9 µm.

Continuous wave laser operation at 1.87 µm of liquid-phase epitaxially (LPE) grown Tm(3+)-doped YLiF(4) (Tm:YLF) layers is demonstrated. The waveguide laser delivers 560 mW by pumping with a Ti:Sapphire laser at 780 nm leading to an efficiency of 76% with respect to the absorbed pump power. This constitutes the first Tm(3+)-doped crystalline fluoride waveguide laser ever demonstrated as well as a record in efficiency and output power for an LPE grown waveguide laser operating in the 2 µm spectral range.