A new infrared luminescence from bismuth-doped silica glass is discovered. Spectroscopic properties of this glass are different from those of previously reported Bi2+- or Bi3+-doped glasses or crystals. Its luminescence spectrum is wide (full-width at half maximum; about 200 nm), with the peak at 1140 nm with 500 nm excitation. Absorption bands exist between the visible and near-infrared region. The lifetime of bismuth-doped silica glass is 630 µs at room temperature, which is longer than the lifetimes of Bi3+ luminescence reported previously.

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We investigated an Laguerre-Gaussian (LG) beam that can carry an orbital angular momentum and has a doughnut-shaped intensity pattern. We developed a multilevel spiral phase plate (SPP) that generates an LG beam by applying the wave surface of a spiral structure directly to a Gaussian beam for application to microscopic laser material processing.We experimentally demonstrate, for the first time, that it is possible to generate an LG beam with the multilevel SPP that allows the use in high intensity laser pulses.

We demonstrated an amplification phenomenon in a bismuth-doped silica glass at 1.3 μm with 0.8-μm excitation. This luminescent material is a promising candidate for use as the core-fiber material of an optical amplifier at the natural zero-dispersion wavelength (1.3 μm) of silica glass fiber.

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