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

Polymer composites are one of the most attractive near-term means to exploit the unique properties of carbon nanotubes and graphene. This is particularly true for composites aimed at electronics and photonics, where a number of promising applications have already been demonstrated. One such example is nanotube-based saturable absorbers. These can be used as all-optical switches, optical amplifier noise suppressors, or mode-lockers to generate ultrashort laser pulses. Here, we review various aspects of fabrication, characterization, device implementation and operation of nanotube-polymer composites to be used in photonic applications. We also summarize recent results on graphene-based saturable absorbers for ultrafast lasers.

Nanotube–Polymer Composites for Ultrafast Photonics

Computational Materials Science X

In this review, the major achievements and research and development (R&D) trends from the last decade in the field of single crystal scintillator materials are described. Two material families are included, namely, those of halide and oxide compounds. In most cases, the host crystals are doped with Ce3+, Pr3+ or Eu2+ rare earth ions. Their spin- and parity-allowed 5d–4f transitions enable a rapid scintillation response, on the order of tens to hundreds of nanoseconds. Technological recipes, extended characterization by means of optical and magnetic spectroscopies, and theoretical studies are described. The latter provide further support to experimental results and provide a better understanding of the host electronic band structure, energy levels of specific defects, and the emission centers themselves. Applications in medical imaging and dosimetry, security measures, high-energy physics and the high-tech industry, in which X(γ)-rays or particle beams are used and monitored, are recognized as the main driving factor for R&D activities in this field.

Recent R&D Trends in Inorganic Single-Crystal Scintillator Materials for Radiation Detection

We report a ring-cavity thulium fiber laser mode locked with a single-wall carbon nanotube absorber used in transmission. A carboxymethyl cellulose polymer film with incorporated carbon nanotubes synthesized by the arc discharge method has an absorption coinciding with in the amplification bandwidth of a Tm-doped fiber. This laser is pumped by an erbium fiber laser at 1.57 μm wavelength and produces a 37 MHz train of mode-locked 1.32 ps pulses at 1.93 μm wavelength with an average output power of 3.4 mW.

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Mode-locked 1.93 μm thulium fiber laser with a carbon nanotube absorber

Continuous wave diode pumped intracavity doubled Nd:GdVO4 laser with 840 mW output power at 456 nm

The refractive indices of new Nd3+ : GdVO4, Tm3+ : GdVO4, and Er3+ : GdVO4 laser crystals were determined with an error of ±5×10-5 in the range 400–1100 nm. The birefringence of these crystals was on the average 0.24, and the dispersion was described by the formula 1/Δn2 = a+ b/λ2. The thermal conductivity of the Nd : GdVO4 crystal (atomic neodymium concentration 1.3%) was determined in the temperature range 77-300 K. At 300 K the conductivity along the direction was 11.7 W m-1 K-1, which was higher than the conductivity of Nd : YAG crystals.

https://iopscience.iop.org/article/10.1070/QE1995v025n12ABEH000556/pdf

GdVO4 as a new medium for solid-state lasers: some optical and thermal properties of crystals doped with Cd3+, Tm3+, and Er3+ ions

A flash-lamp pumped passively mode-locked neodymium-doped vanadate lasers operated at 1.34 μm wavelength have been developed using a novel saturable absorber consisted of single-wall carbon nanotubes incorporated in a polymer matrix. Laser pulses with the output energy up to 50 μJ and the duration of 30 ps were generated.

Passive mode-locking with carbon nanotube saturable absorber in Nd:GdVO4 and Nd:Y0.9Gd0.1VO4 lasers operating at 1.34 μm

Self-Raman frequency conversion in a diode-pumped passively Q-switched Nd:GdVO4 laser has been demonstrated. The use of LiF:F2- crystal as a saturable absorber has provided effective Q-switching of the Nd:GdVO4 laser with high pulse energy. The laser pulse duration at the 1st Stokes wavelength 1174 nm was as short as 500 ps. Diode-to-Raman optical conversion efficiency more than 2 % at the pulse peak power of 9 kW was achieved.

http://iopscience.iop.org/article/10.1002/lapl.200410057/pdf

Yu. D. Zavartsev

Papers

Continuous wave diode pumped intracavity doubled Nd:GdVO4 laser with 840 mW output power at 456 nm

GdVO4 as a new medium for solid-state lasers: some optical and thermal properties of crystals doped with Cd3+, Tm3+, and Er3+ ions

Passive mode-locking with carbon nanotube saturable absorber in Nd:GdVO4 and Nd:Y0.9Gd0.1VO4 lasers operating at 1.34 μm

Diode pumped 500-picosecond Nd:GdVO4 Raman laser

Czochralski growth and characterization of (Lu1 − xGdx)2SiO5 single crystals for scintillators