Fabrication of optical planar waveguides in KY(WO4)2KY(WO_4)_2 by He-ion implantation

In this paper, planar waveguides produced by He-ion implantation have been demonstrated in undoped and Yb-doped KY(WO/sub 4/)/sub 2/ crystals. The effective refractive indices of guided modes in surface planar waveguides were measured by dark m-line spectroscopy and the refractive index profiles were reconstructed by calculations based on the inverse WKB method. The end-faces of implanted crystals were polished and the waveguiding properties of the obtained planar structures were investigated using a laser diode at 980 nm and a CCD camera

Fabrication of optical planar and channel waveguides in Yb³⁺ doped KY(WO₄)₂ by He-ion implantation

Light ion implantation can be regarded as a universal tool for fabricating low-loss waveguide structures in optically active oxide materials. We have fabricated planar optical waveguides in $KY(WO_4)_2$:(2%)$Yb^{3+}$ crystals by implanting He+ ions at 1.5 MeV, with doses ranging from 1 to 3x10^16 ions/cm2. An optical barrier with a decreased effective refractive index was created at the end of the ions' tracks, situated approximately 3.5 μm below the surface. The change in refractive index with respect to the bulk value and its stability to thermal treatment were investigated by dark m-line spectroscopy. Surface channel waveguides were obtained by writing sidewalls into the planar guiding layer by implantation through a slit. The sidewalls were produced by keeping the ion energy fixed and varying the incident angle of implantation. Channel waveguides of 5-μm width and 4-μm depth were obtained in the regions between the implanted sidewalls. Beam-propagation parameters were measured by investigating the output profile of end-coupled, fundamental-mode laser light at 980 nm. The results of loss measurements will be presented at the conference

Assessing Lanthanide‐Dependent Methanol Dehydrogenase Activity: The Assay Matters

Artificial dye-coupled assays have been widely adopted as a rapid and convenient method to assess the activity of methanol dehydrogenases (MDH). Lanthanide(Ln)-dependent XoxF-MDHs are able to incorporate different lanthanides (Lns) in their active site. Dye-coupled assays showed that the earlier Lns exhibit a higher enzyme activity than the late Lns. Despite widespread use, there are limitations: oftentimes a pH of 9 and activators are required for the assay. Moreover, Ln-MDH variants are not obtained by isolation from the cells grown with the respective Ln, but by incubation of an apo-MDH with the Ln. Herein, we report the cultivation of Ln-dependent methanotroph Methylacidiphilum fumariolicum SolV with nine different Lns, the isolation of the respective MDHs and the assessment of the enzyme activity using the dye-coupled assay. We compare these results with a protein-coupled assay using its physiological electron acceptor cytochrome cGJ (cyt cGJ). Depending on the assay, two distinct trends are observed among the Ln series. The specific enzyme activity of La-, Ce- and Pr-MDH, as measured by the protein-coupled assay, exceeds that measured by the dye-coupled assay. This suggests that early Lns also have a positive effect on the interaction between XoxF-MDH and its cyt cGJ thereby increasing functional efficiency

Amplitude and phase modulation of time-energy entangled two-photon states

We experimentally demonstrate amplitude and phase modulation of a time-energy entangled two-photon wave function. The entangled photons are produced by spontaneous parametric down-conversion, spectrally dispersed in an prism compressor, modulated in amplitude and/or phase, and detected in coincidence by sum-frequency generation. First, we present a Fourier optical analysis of the optical setup yielding an analytic expression for the resulting field distribution at the exit plane of the shaping apparatus. We then introduce amplitude and/or phase shaping and present results which can only be obtained through a combination of the two. Specifically, we use a shaper-based interferometer to measure the two-photon interference of an almost bandwidth-limited two-photon wave function.Comment: 7 pages, 4 figure