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

The invention provides methods, compositions, and apparatus for performing sensitive detection of analytes, such as biological macromolecules and other analytes, by labeling a probe molecule with an up-converting label The up-converting label absorbs radiation from an illumination source and emits radiation at one or more higher frequencies, providing enhanced signal-to-noise ratio and the essential elimination of background sample autofluorescence The methods, compositions, and apparatus are suitable for the sensitive detection of multiple analytes and for various clinical and environmental sampling techniques

Up-converting reporters for biological and other assays using laser excitation techniques

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

Upconversion laser processes

Photon avalanche upconversion in rare earth laser materials

CW tunable green laser emission between 540 and 553nm (5S2 → 5I8) has been achieved in Ho3+-doped fluorozirconate fibre by upconversion pumping at room temperature, with output powers in excess of 10mW Laser emission at 075μm (3S2 → 5I7) was also observed at the same excited level

Room temperature CW tunable green upconversion holmium fibre laser

Upconversion lasing is obtained at 455 and 480 nm in a Tm3+-doped fluorozirconate fibre co-pumped at 676.4 and 647.1 nm. Lasing at 1.51 μm by two-photon absorption is also observed. Pumping schemes and dynamics of the lasing transitions are clarified.

Blue upconversion fluorozirconate fibre laser

50mW of green power and slope efficiency against launched pump power of 15% have been obtained at room temperature in an erbium doped fluorozirconate fibre pumped at 0.97μm. Lasing tunability domain, pump wavelength tunability and the role of colasing at 1.55μm are described.

Tunable green upconversion erbium fibre laser

Room temperature upconversion lasing has been obtained at 635 nm in Yb : Pr codoped fluoride fibre pumped in the 0.8μm region. Yb3+ is excited by ground state absorption and transfers energy to the 1G4 level of Pr3+, which is then brought into the 3P0 level by excited state absorption. Extracted powers in excess of 20 mW at 635 nm and a slope efficiency of 10% were observed for 840–850 nm.

M. Monerie

Papers

Room temperature CW tunable green upconversion holmium fibre laser

Blue upconversion fluorozirconate fibre laser

Blue upconversion fluorozirconate fibre laser

Tunable green upconversion erbium fibre laser

Red upconversion Yb-sensitised Pr fluoride fibre laser pumped in 0.8 μm region