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In this paper, epitaxial layers of Rb1-xBaxTi1-y-zYbyNbzOPO4 have been successfully grown on (001) oriented RbTiOPO4 substrates. Although the Ba2+ contents in these layers was very low, the contrasts in refractive indices between the epitaxial layer and the substrate were high enough to allow the propagation of one TE and three TM modes, at the wavelength of 632.8 nm, using a 5 μm thickness epilayer. These light propagation modes were first simulated, using the refractive indices of the layer and the substrate measured previously. The TE and TM dark-mode spectra obtained experimentally, using the prism coupler method and a He-Ne laser beam, agree well with the simulation results. Finally, type II Second Harmonic Generation experiments were carried out with pumping at 1130 nm and obtaining green light at 565 nm. The experimental efficiency in the Second Harmonic Generation experiments was of 69%/mWcm2. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The present paper shows epitaxial layers grown by liquid phase epitaxy of RbTiOPO4 doped with Yb3+ on substrates of RTP. The layers were grown on (0 0 1) plane, which contains the phase matching direction for type-II second harmonic generation for the Yb3+ emission wavelength range. The layer guides polarized light parallel to c crystallographic direction. A 10 m-thickness epitaxial layer guides five modes which had been observed by dark-mode spectrum. The measured losses were about 0.7 dB/cm.

This paper summarizes the main results we obtained in our laboratories in relation with crystalline layers obtained by Liquid Phase Epitaxial growth of lanthanide doped KLu(WO 4 ) 2 and Nb:RbTiOPO 4 grown on KLu(WO 4 ) 2 and RbTiOPO 4 substrates, respectively. Macroscopic defect free epitaxial layers were grown and characterized in terms of their compositional homogeneity, structural stress in the layer/substrate interface and laser and waveguiding performances.

In this paper epitaxial layers of RbTiOPO 4 doped with Y b 3+ on substrates of RbTiOPO 4 have been grown by Liquid Phase epitaxy on the (001) plane, which contains the phase matching direction for Type II Second Harmonic Generation for the Y b 3+ emission wavelength range. These layers can guide polarized light parallel to the c crystallographic direction. A 5 μm-thickness epitaxial layer can guide 3 propagation modes as it has been observed by the dark-mode spectrum. The sample was polished in both end-faces to visualize the TM modes of the waveguides. The near field pattern was recorded by a CCD camera, using a green diode laser at a wavelength of 532 nm, coupled into, and out from the waveguide using two microscope objectives. The demonstration of good guiding at a wavelength of 532 nm in Y b:Nb:RbTiOPO 4 waveguides is one of the important steps to obtain Self Frequency Doubling laser waveguides.

Coelectroosmotic micellar electrokinetic chromatography (coelectroosmotic MEKC) has been investigated for the separation of twelve aromatic sulfonate compounds. The advantage of this method is that it combines the efficient separation characteristic of MEKC and the short analysis time of the coelectroosmotic mode. MEKC was performed with either cetyltrimethylammonium bromide (CTAB) or polyethylene glycol dodecyl ether (Brij 35) surfactants as pseudostationary phases and 2-propanol as organic modifier. The electroosmotic Flow (EOF) was reversed by adding two types of EOF modifier, an alkylammonium salt (cetyltrimethylammonium bromide, CTAB) or a cationic polyelectrolyte (hexadimetrine bromide, HDB). The surfactant concentration, applied voltage, and temperature were optimized, the influence of 2-propanol on the MEKC resolution of the compounds was studied. The effect of the osmotic modifier on the separation was also investigated.

Coelectroosmotic capillary zone electrophoresis (CZE) has been investigated as a means of rapid analysis of twelve aromatic sulphonate compounds. The main factors affecting reversal of electroosmotic flow (EOF)—type of osmotic modifier and concentration-were studied. Two types of osmotic modifier, an alkylammonium salt (cetyltrimethylammonium bromide, CTAB) and a cationic polyelectrolyte (hexadimentrine bromide, HDB) were investigated. The composition of the running buffers was optimized according to the characteristics of each osmotic modifier. A concentration of HDB as low as 0.0001% (w/v) was used successfully to provide a stable and reversed EOF.

Two modes of capillary electrophoresis (CE), capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC), were investigated for the separation of 12 aromatic sulphonate compounds. In CZE, although the voltage applied, the buffer concentration and the pH were optimized for effective separation of the compounds studied, under the best conditions four of the five amino compounds coeluted, as did naphthalene-1-sulphonic acid and naphthalene-2-sulphonic acid. In MEKC, sodium dodecyl sulphate (SDS) and Brij 35 were chosen as the anionic and nonionic surfactants and the effect of the concentration of micelles was examined. The effect of adding methanol as the organic modifier was also investigated with each of these micellar systems. All the analytes, including the isomers, were completely separated by use of MEKC with Brij 35 but when SDS was used only 11 compounds were separated because two amino compounds coeluted.

In this work we show the ultrafast laser fabrication of ridge waveguides in a (Yb, Nb):RbTiOPO4 (RTP) epilayer grown on a RTP substrate by liquid phase epitaxy [1]. The ribs are produced by machining trenches on the surface of the (Yb, Nb):RTP epilayer. In order to improve the verticality and roughness of the walls of the trenches, we have used the approximation scanning technique [2]. This approach has been enhanced in terms of speed and flexibility by using a Spatial Light Modulator (SLM) to multiplex the irradiation beam.

Summary form only given. RbTiOPO4 (RTP) belongs to the KTiOPO4 (KTP) family of crystals and has similarly useful nonlinear optical properties. In addition, RTP allows higher doping of rare-earth elements, such as Yb3+, when compared to KTP, a 2 times larger damage threshold than KTP, a very large electro-optic coefficient, a low dielectric constant and high chemical stability, which makes these materials very interesting for active photonics applications. In particular, Yb3+-doped RTP exhibits a broad fluorescence spectrum that has been exploited to demonstrate ultrafast operation, with pulses as short as 155 fs being generated [1]. Recently, planar waveguiding has been demonstrated in an (Yb3+, Nb5+):RTP film grown by liquid phase epitaxy [2], opening the possibility of planar integrated devices based on this highly functional material.Channel waveguides based on this thin-film technology would be of considerable interest for realising, for example, compact ultrafast lasers with GHz repetition rates [3] with applications in optical frequency metrology, optical sampling and biological imaging, or self-frequency-doubled lasers for visible laser sources. In this work we discuss the reactive ion etching (RIE) of RTP and the process optimisation to fabricate single-mode channel waveguides for lasing application around 1 micron. A 200-nm layer of chromium (Cr) was deposited on a number of RTP substrates grown by the top-seeded solution growth method (TSSG), after which it was photolithographically patterned to give a Cr mask with waveguide features of widths 1 μm to 10 μm. The masked substrates were etched in an OPT Plasmalab 80 plus RIE system (Oxford Instruments) with an RF frequency of 13.56 MHz. SF6 and Ar were used to etch the substrates in order to study the interplay between chemical and physical etching processes, respectively. The gas flow rates, gas pressures and RF power were systematically varied to get a good balance between etch rate and RMS surface roughness. The dependence of the etch rate and surface roughness on each parameter is shown in figure 1. Based on these graphs the optimum conditions were chosen to be: RF power of 250 W, gas pressure of 40 mTorr and gas flow rate of 10 sccm for both SF6 and Ar (giving a total gas flow rate of 20 sccm). A 6-μm-thick (Yb,Nb): RTP thin-film was grown on an undoped RTP substrate by liquid phase epitaxy and then etched for 135 minutes with the optimised conditions. It was then end polished to give a 6-mm-long waveguide. An SEM image of the end face of a 9.8-μm-wide channel is shown in the inset of figure 1. The sidewall angle was measured to be 63° and the etch depth was 1.4 μm. Waveguiding experiments were carried out by end-fire coupling a 981nm fiber-coupled single-mode laser diode into the channels. The output was found to be single-mode, with 1/e2 mode diameters measured to be 16.4 μm and 8 μm in the x and y directions respectively and is in good agreement with the simulated values of 15.2 μm and 6.8 μm.

We present the fabrication of single-mode rib waveguides in (Yb,Nb):RbTiOPO4 ((Yb,Nb):RTP) by reactive ion etching (RIE) with a combination of SF6 and Ar gases. The influence of the gas pressure, RF power and gas ratio on the etch rate and surface quality was studied to optimize the etching of RTP. Optimized parameters were used to fabricate rib waveguides in a (Yb,Nb):RTP film, grown by liquid phase epitaxy, with an etch rate of 10 nm/min. Channel waveguide propagation was demonstrated for the first time in an RIE etched (Yb,Nb):RTP rib structure.

In this Letter we report Cs(+) ion exchange channel waveguides on RbTiOPO(4) (RTP) for what we believe is the first time. A Ti channel mask was fabricated on an RTP substrate by conventional photolithography. The ion exchange process was carried out in a CsNO(3) melt, and the channels produced ranged from 6 to 11 μm in width. The near-field pattern of the modes was recorded, and type II second harmonic generation in waveguide regime was obtained, producing 512.5 nm green light. The optical characterization shows optical losses of 3.8 dB/cm.

In this paper we present the fabrication and characterization of rib waveguides made on (Yb,Nb):RbTiOPO4/RbTiOPO4 epitaxial layers. Liquid phase epitaxy (LPE) was used to grow planar thin films followed by Ar+ ion milling for surface rib fabrication. Here, we report the detailed fabrication procedure and characterization of the ribs. The study reveals good optical confinement and that type II second harmonic generation inside the rib was obtained, showing the generation of green light at 570 nm.

Efficient Type II phase-matching second-harmonic generation of a 1125 nm fundamental beam has been obtained using Ba:Yb:Nb:RbTiOPO(4)/RbTiOPO(4) waveguides grown by liquid phase epitaxy. The refractive indices of the epitaxial layer have been measured at different wavelengths, and the Sellmeier coefficients of the chromatic dispersion curves have been obtained. The phase-matching curve shows that the Ba(2+) doping in RbTiOPO(4) contributes to increase the phase-matching range until 900 nm. The measured effective refractive indices of the propagation modes agree well with the theoretical calculations.

In this paper we report the growth of RbTi1−x−yYbxNbyOPO4/RbTiOPO4 epitaxial layers by the liquid phase epitaxy method and discuss their structural and optical characterization. The layers were grown on (001) oriented substrates because this plane contains the phase-matching direction for Yb3+ type-II second-harmonic generation. In RbTi0.971Yb0.015Nb0.014OPO4/RbTiOPO4 epitaxial layers we obtained enough contrast of refractive indices (Δnz = 0.007 at 632.8 nm) to guide the light in TM polarization. The maximum Yb3+ concentration obtained in these layers was 1.43 × 1020 atoms per cm3, which may be suitable for laser action. The lattice mismatch between the epitaxial layers and the substrates was low enough to obtain high quality epitaxial layers. Confinement of the light at 532 and 632.8 nm was demonstrated and there was good agreement between theoretical calculations, dark-mode spectra and modes of propagation.