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Holmium-doped congruent-composition lithium niobate (LiNbO3:Ho, LN:Ho) crystals were grown by the Czochralski method. The absorption of the LN:1at% Ho3+ crystal was recorded at room temperature. On the basis of the analysis of emission and absorption spectra of the LN:1at% Ho3+ crystal, the possibilities of obtaining, at room temperature, radiation-balanced (RB) lasing in the region of 640–670 nm wavelengths corresponding to the inter-Stark transitions of manifolds 5F5 and 5I8 was theoretically investigated. The RB lasing parameters were calculated and the optimal pump and laser wavelengths were determined: λ O P = 652.1   n m , λ O L = 653.6   n m . The values for the RB lasing efficiency and radiation amplification in the considered wavelength region were obtained: F e f f = 3.23 × 10 − 22 c m 2 ,   F g a i n = 6.08 × 10 − 22   c m 2 . [ABSTRACT FROM AUTHOR]

Photoinduced charge transport in lithium niobate for standard illumination, composition and temperature conditions occurs by means of small polaron hopping either on regular or defective lattice sites. Starting from Marcus-Holstein's theory for polaron hopping frequency we draw a quantitative picture illustrating two underlying microscopic mechanisms besides experimental observations, namely direct trapping and migration-accelerated polaron trapping transport. Our observations will be referred to the typical outcomes of transient light induced absorption measurements, where the kinetics of a polaron population generated by a laser pulse then decaying towards deep trap sites is measured. Our results help to rationalize the observations beyond simple phenomenological models and may serve as a guide to design the material according to the desired specifications. [ABSTRACT FROM AUTHOR]

A simple and effective technique to characterize the photoconductivity (PC) of lithium niobate is presented. The technique is based on the modulation of the external field and on the observation of the optical response of the material as a function of the intensity of a gaussian beam using a Tardy's polarimetric setup in the r 22 configuration. When the temporal period of the modulation is larger than the Maxwell time of the material, the effect of the PC can be detected observing the kinetics of the screening effect of the external applied field. This approach allows measuring a wide dynamic range up to high light intensities with good accuracy using a standard oscilloscope and with no need for charge collection electrodes. The technique is demonstrated by comparing two samples, the first possessing a standard congruent composition, the second being doped with Zn in order to boost the PC. [ABSTRACT FROM AUTHOR]

We present a novel plasmonic hydrogen sensor consisting of an array of gold nanodisks produced by lithography. The size, height, and spacing of the disks were optimized using finite element simulation to generate a sharp localized surface plasmon resonance peak in the near-infrared wavelength region. The reported results show the possibility of developing an optical gas sensors-based bare Au nanostructures operating at a low temperature. [ABSTRACT FROM AUTHOR]

Small-polaron hopping involved in charge transport in Fe-doped congruent lithium niobate is investigated as a function of temperature and composition by means of light-induced transient absorption spectroscopy. The relaxation dynamics of the light-induced polaron population is characterized by individual activation energies within different temperature ranges. A numerical investigation carried out by Monte Carlo simulations reveals that these findings may be understood in terms of the varying abundance of the different types of hops that the polarons may perform among regular or defective lattice sites. The role of the temperature and of the sample composition on the distribution of the different hop types is thus explored for a wide range of parameters, allowing one to preview the charge transport properties for a given set of experimental conditions. [ABSTRACT FROM AUTHOR]