In this work, we have demonstrated the use of different technologies to fabricate straight channel waveguides, S-bend waveguides, Y-splitter and Mach-Zehnder (MZ) structures on RbTiOPO4 crystals and its isomorphs. We used reactive ion etching (RIE), inductively coupled plasma-RIE (ICP-RIE), femtosecond pulse laser micro-fabrication and ion diffusion techniques to structure these crystals. Computer simulations have been carried out and compared with the optical characterization of the waveguides which are in agreement with each other.
The optical damage behaviour of different LiNbO3 optical waveguides has been experimentally studied by measuring the intensity output of a single beam as a function of the intensity input. Parallel measurements of photovoltaic currents have been carried out as a function of the input intensity and they have been correlated with the optical damage data. The following LiNbO3 guides have been studied and compared: proton exchanged (PE) belonging to the phases alpha, beta1, beta2 and reverse proton exchanged (RPE), and Zn in-diffused waveguides. The greatest intensity thresholds for optical damage, about 2x103 times greater than that of the substrate, have been obtained in RPE guides (they support ordinary polarization and have similar nonlinear optic activity as the substrate) and beta2 guides which support extraordinary polarization (they have no nonlinear optic activity). On the other hand, the lowest photovoltaic currents have been measured in beta1,2-phases. As a function of the light intensity, the photovoltaic current exhibits a superlinear behaviour, strong in alpha-phase and weaker in Zn in-diffused and RPE guides. The results for optical damage are discussed in connection with those of photovoltaic currents, paying particular attention to the main mechanisms involved.
Fabrication characterization and operation stability of Zn-indiffused integrated optical devices in lithium niobate are described. Two examples of the operation of active waveguides fabricated by this technique are presented: laser operation of Nd3+ doped channel waveguides, and blue light generation by Quasi Phase Matching (QPM) using periodically structured substrates. In both cases ne-polarized high power denstiy CW-optical beams are involved and stable room temperature operation is sustained.
We report the fabrication, characterization and comparison of waveguides in Z-cut Erbium-doped LiNbO3, obtained by Proton Exchange, Anneal Proton Exchange and Reverse Proton Exchange (RPE). We found that even in the very low proton concentration (α-phase) waveguides, the radiative lifetime reduction, hence the fluorescence quenching, of the 4I13/2 yields 4I15/2 laser transition due to OH phonons is dramatic. At the contrary, in the RPE waveguides we measured a nearly unaffected lifetime as the ordinary polarized modes are supported by a surface layer nearly free of proton. As it is known that the ordinary polarization is largely advantageous in terms of pump absorption efficiency and relative signal amplification, such waveguides appear to be a workable solution for amplification/lasing around 1.5 μm, provided that the losses due to leakage through the index barrier can be sufficiently reduced.
Switching characteristics of ferroelectric thin films (103 to 104 angstrom) at the crossover field from subsonic (via domain wall motion) to supersonic (via random reversal of individual dipoles) switching is investigated. The switching behavior of TGS (singlecrystal) and PZT (ceramic) films is discussed.
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