Before the 1960s, all anti-Stokes emissions, which were known to exist, involved emission energies in excess of excitation energies by only a few kT. They were linked to thermal population of energy states above excitation states by such an energy amount. It was the well-known case of anti-Stokes emission for the so-called thermal bands or in the Raman effect for the well-known anti-Stokes sidebands. Thermoluminescence, where traps are emptied by excitation energies of the order of kT, also constituted a field of anti-Stokes emission of its own. Superexcitation, i.e., raising an already excited electron to an even higher level by excited-state absorption (ESA), was also known but with very weak emissions. These types of well-known anti-Stokes processes have been reviewed in classical textbooks on luminescence.1 All fluorescence light emitters usually follow the well-known principle of the Stokes law which simply states that excitation photons are at a higher energy than emitted ones or, in other words, that output photon energy is weaker than input photon energy. This, in a sense, is an indirect statement that efficiency cannot be larger than 1. This principle is

Upconversion and Anti-Stokes Processes with f and d Ions in Solids

Through thermal treatment of a fluoroaluminosilicate glass codoped with Er3+‐Yb3+ at a suitable temperature, microcrystallites were successfully precipitated in the glass matrix but little change was observed in the optical transmission spectra even around the ultraviolet edge, meanwhile the green upconversion luminescence due to the 4 S 3/2‐4 I 15/2transition of Er3+ increased by a factor of ∼100 when a 097 μm laser diode(LD) (5 mW) was used for excitation The infrared to green or to red upconversion efficiencies for the vitroceramics are evaluated to be nearly 2 or 10 times as high as fluoride glasses, respectively Also higher mechanical and chemical stabilities and laser damage threshold over fluoride glasses or crystals are expected for the vitroceramics

New transparent vitroceramics codoped with Er3+ and Yb3+ for efficient frequency upconversion

Ytterbium-doped silica fibers exhibit very broad absorption and emission bands, from /spl sim/800 nm to /spl sim/1064 nm for absorption and /spl sim/970 nm to /spl sim/1200 nm for emission. The simplicity of the level structure provides freedom from unwanted processes such as excited state absorption, multiphonon nonradiative decay, and concentration quenching. These fiber lasers therefore offer a very efficient and convenient means of wavelength conversion from a wide variety of pump lasers, including AlGaAs and InGaAs diodes and Nd:YAG lasers. Efficient operation with narrow linewidth at any wavelength in the emission range can be conveniently achieved using fiber gratings. A wide range of application for these sources can be anticipated. In this paper, the capabilities of this versatile source are reviewed. Analytical procedures and numerical data are presented to enable design choices to be made for the wide range of operating conditions. >

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Ytterbium-doped silica fiber lasers: versatile sources for the 1-1.2 /spl mu/m region

Whispering gallery mode (WGM) optical microresonators have attracted intense interests in the past decades. The combination of high quality factors (Q) and small mode volumes of modes in WGM resonators significantly enhances the light-matter interactions, making them excellent cavities for achieving low threshold and narrow linewidth lasers. In this Review, the progress in WGM microcavity lasers is summarized, and the laser performance considering resonator geometries and materials as well as lasing mechanisms is discussed. Label-free detection using WGM resonators has emerged as highly sensitive detection schemes. However, the resolution is mainly limited by the cavity Q factor which determines the mode linewidth. Microcavity lasers, due to their narrow laser spectral width, could greatly improve the detection resolution. Some recent developments in sensing using microcavity lasers are discussed.

Whispering gallery microcavity lasers

Photon avalanche upconversion in rare earth laser materials

The authors report what they believe to be the first single-wavelength pumped, CW, room-temperature, blue upconversion laser. This 480 nm laser uses Tm/sup 3+/ as the active ion in a fluorozirconate glass fibre. Up to 60 mW of output power has been observed with a slope efficiency of 18% with respect to coupled pump power.<
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K. W. Bennett

Papers

CW room-temperature blue upconversion fibre laser

Cw room-temperature blue upconversion laser

CW room-temperature blue upconversion fibre laser