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Refractive index of optical material of powder is measured not as easily as a bulk material. Here, the prism coupling technique in combination with the immersion method is proposed to measure the refractive index of an optical material of powder. First, the powder material to be measured was dispersed in α-bromonaphthalene (C10H7Br) liquid to form a suspension mixture. The refractive index of the mixture, together with that of pure C10H7Br, was then measured at the wavelengths of 632.8, 1311, and 1553 nm using a commercial prism coupler. From the measured index values of pure C10H7Br and powder-dispersed mixture, the refractive index of the powder material was obtained on the basis of the Maxwell-Garnett model. Microcrystal powder from a LiNbO3 single-crystal, which has the known refractive index values, has been exemplified to demonstrate the method. The results show that the method is feasible with an accuracy of ±0.05. [ABSTRACT FROM AUTHOR]

Multimode near-stoichiometric (NS) Ti:LiNbO3 planar waveguide was fabricated by Ti-diffusion followed by post-Li-rich vapor transport equilibration. The crystalline phase, composition and guided modes in the planar waveguide were characterized. The refractive index profile in the waveguide is constructed from the measured mode indices using the inverse Wentzel–Krames–Brillouin method and correlated with the Ti profile obtained from secondary ion mass spectroscopy analysis. The results show that the LiNbO3 phase dominates in the waveguide layer and the waveguide has an NS composition. The index increase has a linear relation to Ti-concentration for both cases of ordinary and extraordinary rays, and the relationship is considerably different from those of some congruent or NS bulk materials or waveguides. A comparison of various congruent and NS bulk materials or waveguides allows to conclude that the relationship changes from congruent to NS composition, from one fabrication method to another and from bulk material to waveguide configuration. [ABSTRACT FROM PUBLISHER]

Multi-mode Ti:LiNbO 3 planar waveguide was fabricated by in-diffusion of 100-nm-thick Ti-metal film coated onto a near-stoichiometric LiNbO 3 substrate prepared by vapor transport equilibration. The crystalline phase and composition in the waveguide were characterized. The guided modes in the planar waveguide were characterized by prism coupling technique. The refractive index profile is constructed from the measured mode indices using the inverse Wentzel–Krames–Brillouin method, and correlated with the Ti 4+ - concentration profile, which was obtained from secondary-ion-mass-spectroscopy analysis. The results show that the waveguide still retains the LiNbO 3 phase, its composition is near-stoichiometric. The index change and Ti 4+ -concentration follow an exponential relationship with a power index 0.4 for an ordinary ray and 1.07 for an extraordinary ray. A comparison of various congruent and near-stoichiometric bulk materials or waveguides allows to conclude that the relationship is different from congruent to near-stoichiometric composition, from one fabrication method to another, and from bulk material to waveguide configuration. The difference is explained qualitatively. [ABSTRACT FROM AUTHOR]

Diffusion properties of Sc3+ in LiNbO3 crystal were studied, together with other two related issues: Sc3+-doping effect on LiNbO3 refractive index and Li2 O out-diffusion arising from Sc3+ in-diffusion. To reach the goal, some Sc3+-doped LiNbO3 crystal plates were prepared by in-diffusion of Sc2 O3 film coated onto Z-cut congruent substrates in air at different temperatures ranging from 1030°C to 1130°C. After diffusion, the refractive indices at the doped and undoped parts of surface were measured by prism coupling technique and the surface composition was evaluated from the measured index. The results show that the Sc3+ doping has little contribution to the substrate index and the Li2 O out-diffusion is not measurable. The Sc3+ profile was analyzed by secondary ion mass spectrometry. Some characteristic parameters such as temperature-dependent diffusivity, diffusion constant, activation energy, and surface concentration are obtained. The Sc3+/ Ti4+ co-diffusion characteristics were also studied. Comparison shows that in the single-diffusion case, the Sc3+ diffusivity is considerably smaller than the Ti4+ diffusivity. In the Sc3+/ Ti4+ co-diffusion case, the Ti4+ co-diffusion results in substantial increase in Sc3+ diffusivity while the Ti4+ diffusivity changing little. The diffusion characteristics are qualitatively explained. The Ti4+-assisted Sc3+ diffusion would be utilizable in shortening the fabrication period of an optical-damage-resistant Ti-diffused LiNbO3 waveguide doped with Sc3+, and some considerations for the fabrication are given. [ABSTRACT FROM AUTHOR]

Photonic jet (PJ) is generated by illuminating a dielectric scatterer with symmetric four Airy beams (SFAiB). The PJ properties have been systematically studied as a function of characteristic parameters of both the SFAiB and the scatterer, including the geometric parameter D that controls lateral position of each Airy beam component, decay factor, focal point position of the SFAiB, as well as the refractive index of the scatterer. The results show that the PJ performance can be optimized by all of these parameters as a result that the diffraction and self-focusing effects of the SFAiB itself, and the scatterer's focusing function simultaneously play roles in the PJ generation in case of SFAiB illumination. The illumination by SFAiB has advantages over that by plane wave or Gaussian beam in flexibility of tailoring the PJ performance and in possibility of generating a photonic hook with asymmetric illumination caused by transverse offset of focal point of incident SFAiB. In addition, the SFAiB illumination makes it possible to generate a PJ outside a scatterer in case that the scatterer has a higher refractive index of n s > 2.0, increasing the flexibility in both material choice and structural design of scatterer for generation of a PJ for some potential applications. • Photonic jet (PJ) is generated by symmetric four Airy beams (SFAiB) illumination. • SFAiB's diffraction and self-focusing, scatter's focusing effects enable to tailor PJ performance. • SFAiB illumination has advantages over that by plane wave or Gaussian beam. • The merits include flexibility in tailoring PJ performance and possibility of generating a photonic hook with asymmetric illumination. • SFAiB illumination enables to generate a PJ outside a scatterer with a higher refractive index of n s > 2.0, increasing flexibility in material choice and structural design of scatterer. [ABSTRACT FROM AUTHOR]

Generation of multiple photonic hooks (PHs) at THz region in reflection mode by a multi-dielectric structure that consists of periodical or aperiodical scatterer units on top surface of a reflection screen has been systematically studied. The study focuses on effects of geometric and optical parameters of the multi-dielectric structure on characteristics of the PHs generated, especially the bending angle. These geometric and optical parameters include spacing between adjacent scatterer units, length of reflection screen, as well as the size, refractive index and number of scatterer units. The results show that these geometric and optical parameters are key factors in tailoring the performance of the multiple PHs generated. The spacing determines bending direction of PHs and there exists a critical spacing value. Smaller than this critical value, the PHs generated bend outwards. Larger than this critical value, the PHs bend inwards. In addition, the spacing can be also used to effectively adjust the intensity and bending angle of the PHs. Screen length affects mainly PH's bending. The size and refractive index differences between scatterer units introduce additional optical inhomogeneity that leads to the generation of asymmetrical multiple PHs. Finally, the possibility of generation of an arrayed PHs in the reflection mode is demonstrated. • Generation of photonic hooks (PHs) array in reflection mode is studied. • PHs formation is ascribed to optical inhomogeneity of multi-dielectric structure. • PHs performance can be effectively tailored by geometric and optical parameters. • PHs generated at smaller or larger spacing bend in opposite directions. • Optical-axis asymmetric structure generates asymmetrical PHs array. [ABSTRACT FROM AUTHOR]

Ti-diffused near-stoichiometric(NS) LiTaO 3 multimode planar waveguide was fabricated by diffusion of Ti-film coated onto a congruent LiTaO 3 substrate and post Li-rich vapor transport equilibration process. The crystalline phase in the Ti-diffused layer was analyzed by powder x-ray diffraction and the Li 2 O-content was evaluated from the measured birefringence. The Ti-concentration profile was analyzed by secondary ion mass spectrometry. The modes guided in the planar waveguide were characterized by prism-coupling technique. The refractive index profile was constructed from the measured mode indices, and correlated with the Ti-concentration profile. The results show that the waveguide retains the LiTaO 3 phase and is in an NS composition environment. Both the refractive index and Ti-concentration follow Gaussian profile. The extraordinary and ordinary index change profiles are almost same, implying that the electric field profile of the mode guided in the NS Ti:LiTaO 3 waveguide would be polarization-insensitive. The ordinary and extraordinary index changes and the Ti-concentration follow a similar exponential relationship with a power index ∼1.3. Comparison shows that the Ti:LiTaO 3 waveguide shows considerable differences from the Ti:LiNbO 3 in Ti diffusivity, index change profile and its relation to Ti-concentration, and polarization dependence of guided mode. [ABSTRACT FROM AUTHOR]

Dispersion relation is established for Er(NbO 3) 3 phosphor, which is an excellent candidate for optical thermometry based on thermal effect of Er3+ fluorescence intensity ratio. To achieve it, Er(NbO 3) 3 phosphor was dispersed into α-bromonaphthalene liquid to form a suspension. Then, refractive index values of the suspension were measured at wavelengths 473, 589.3, 632.8, 980, 1311 and 1553 nm by dropping it onto a plastic sheet. Subsequently, refractive indices of the Er(NbO 3) 3 phosphor were evaluated from these measured index values using Maxwell-Garnett relation. Finally, based on these Er(NbO 3) 3 index values, which have an error 0.03, a three-oscillator Sellmeier equation that considers contributions from Nb–O group, plasmons in far UV regime and phonons in infrared region is established. In parallel, a Cauchy dispersion equation is also established. Both equations can well fit the experimental data and the refractive indices predicted by the two equations can be regarded as identical within the error 0.03. Refractive indices of Er(NbO 3) 3 phosphor at different wavelengths ranging from 473 to 1553 nm have been obtained from the index values measured from an α-bromonaphthalene mixture suspended with Er(NbO 3) 3 phosphor grains. A three-oscillator Sellmeier equation n2(λ) = B UV - B IR λ2 + B 3 /(λ 3 −2-λ−2) is proposed that considers the contributions from plasmons in far UV, phonons in infrared region and the Nb–O group. A Cauchy dispersion equation n(λ) = A + B/λ2 + C/λ4 + D/λ6 is also attempted to fit the experimental data. The fitting results show that both equations can give accurate prediction of the refractive index value of the Er(NbO 3) 3 phosphor and have an accuracy better than 0.03 satisfying the demand for Judd-Ofelt spectroscopic analysis. Image 1 • Refractive indices of Er(NbO 3) 3 powder were measured at different wavelengths. • A three-oscillator Sellmeier equation n2(λ) = B UV -B IR λ2+B 3 /(λ 3 −2-λ−2) is suggested. • A Cauchy dispersion equation n(λ) = A + B/λ2+C/λ4+D/λ6 is also established. • Both equations give accurate prediction of refractive index value of Er(NbO 3) 3. • Both equations have an accuracy 0.03 satisfying demand for Judd-Ofelt analysis. [ABSTRACT FROM AUTHOR]

Electro-optic (EO) property of titanium-diffused LiNbO 3 optical waveguide was studied using prism coupling technique. The EO-effect-induced increment ΔN of effective refractive index (at the wavelength 1311 nm) was measured as a function of externally applied electric field E for TM 0 and TM 1 modes guided in the titanium-diffused LiNbO 3 planar waveguide. By using the linearity between ΔN and E, the EO coefficient r 33 is determined. For reference, the measurement was also performed on a bulk material of congruent LiNbO 3 , yielding r 33 = 24.9 ± 0.8 p.m./V, which is in qualitative agreement with that obtained by extrapolating previously reported result to the 1311 nm wavelength, ~24 p.m./V, confirming the feasibility of the measurement method. Measurements on the titanium-diffused planar waveguide give r 33 = 25.7 ± 0.6 p.m./V for the TM 0 mode and 25.7 ± 0.4 p.m./V for the TM 1 mode. Both values can be considered as identical within the error, and are the same as that of the bulk material, indicating that the EO property is well preserved in the titanium-diffused LiNbO 3 waveguide. The main reason is that the LiNbO 3 crystalline phase is well preserved in the titanium-diffused waveguide layer. • Electro-optic (EO) property of Ti:LiNbO 3 planar waveguide is studied. • The study uses the linearity between refractive index change and electric field. • The study shows that EO property is well preserved in Ti:LiNbO 3 waveguide. • Little effect of Ti-diffusion doping on EO property is qualitatively explained. [ABSTRACT FROM AUTHOR]