The invention relates to phosphate-based glasses suitable for use as a solid laser medium, doped with Er3+ and sensitized with Yb, in “eye-safe” applications. In particular, the invention relates to improving the physical properties of such phosphate-based laser glass composition, particularly with regards to strength of the glass structure and improved thermal shock resistance.

Laser waveguides, methods and systems for forming a laser waveguide are provided. The waveguide includes an inner cladding layer surrounding a central axis and a glass core surrounding and located outside of the inner cladding layer. The glass core includes a laser-active material. The waveguide includes an outer cladding layer surrounding and located outside of the glass core. The inner cladding, outer cladding and/or core may surround a hollow central channel or bore and may be annular in shape.

An add-drop filter for transmitting at least one signal is provided. The add-drop filter includes at least two optical waveguides capable of carrying the at least one signal, and at least one active resonator coupled between the optical waveguides, wherein the at least one active resonator provides gain that counteracts losses for the at least one signal.

Ultrashort pulse fiber amplifier having a pulse width from 200 ps to 200 fs comprising a rare earth oxide doped multicomponent glass fibers for laser amplification, including a core and a cladding, the core comprising at least 2 weight percent glass network modifier selected from BaO, CaO, MgO, ZnO, PbO, K.sub.2O, Na.sub.2O, Li.sub.2O, Y.sub.2O.sub.3, or combinations; wherein the mode of the core is guided with step index difference between the core and the cladding, a numerical aperture of the fiber is between 0.01 and 0.04; core diameter is from about 60 microns to about 150 microns, and a length of the gain fiber is shorter than 60 cm.

An optical amplifier is provided in which adjacent ones of a plurality of cores each containing a rare-earth element and included in an amplifying multi-core optical fiber (MCF) serve as coupled cores at an amplifying wavelength, a connecting MCF is connected to the amplifying MCF, a pump light source is connected to the connecting MCF, and the pump light source pumps the rare-earth element in the amplifying MCF through the connecting MCF.

An amplification fiber which can generate a laser beam in a visible region even when a silica glass is used as a base material of a core of the amplification fiber is realized. An amplification fiber according to an embodiment of the present disclosure includes a core configured to generate a laser beam from an excitation beam in a visible region, and a cladding surrounding the core. The core is composed of a core material including Dy, one or more elements selected from Al, Ge, and P, and a silica glass.

A photodarkening-resistant ytterbium-doped quartz optical fiber and a method for prpearing such a fiber are provided. Glass of a photodarkening-resistant ytterbium-doped quartz optical fiber core rod includes at least Yb.sub.2O.sub.3, Al.sub.2O.sub.3, P.sub.2O.sub.5, SiO.sub.2. The proportions of Yb.sub.2O.sub.3, Al.sub.2O.sub.3, and P.sub.2O.sub.5 in the entire substance are Yb.sub.2O.sub.3: 0.05-0.3 mol %, Al.sub.2O.sub.3: 1-3 mol %, and P.sub.2O.sub.5: 1-5 mol %, respectively. In the preparation method for the photodarkening-resistant ytterbium-doped quartz optical fiber, a sol-gel method and an improved chemical vapor deposition method are combined. By using the molecular-level doping uniformity and the low preparation loss thereof respectively, ytterbium ions, aluminum ions and phosphorus ions are effectively doped in a quartz matrix, thereby effectively solving the problems in the optical fiber of high loss, photodarkening caused by cluster or the like, and a central refractive index dip.

A multi-clad optical fiber design is described in order to provide low optical loss, a high numerical aperture (NA), and high optical gain for the fundamental propagating mode, the linearly polarized (LP) 01 mode in the UV and visible portion of the optical spectrum. The optical fiber design may contain dopants in order to simultaneously increase the optical gain in the core region while avoiding additional losses during the fiber fabrication process. The optical fiber design may incorporate rare-earth dopants for efficient lasing. Additionally, the modal characteristics of the propagating modes in the optical core promote highly efficient nonlinear mixing, providing for a high beam quality (M.sup.2<1.5) output of the emitted light.

A first fiber is connected to a first end of a third fiber doped with a rare earth element, and a second fiber is connected to a second end of the third fiber. In the third fiber doped with the rare earth element, a central portion of a core is more heavily doped with the rare earth element than a peripheral portion of the core is.

Disclosed is a laser device containing a. compound represented by the following formula in a light-emitting layer, R.sup.1 and R.sup.5 each represent a substituent having a positive Hammett's σ.sub.p value, and R.sup.2 to R.sup.4, and R.sup.6 to R.sup.15 each represent a hydrogen atom or a substituent.

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