TY - JOUR AB - We study the DC conductivity in potassium titanyl phosphate (KTiOPO4, KTP) and its isomorphs KTiOAsO4 (KTA) and Rb1%K99%TiOPO4 (RKTP) and introduce a method by which to reduce the overall ionic conductivity in KTP by a potassium nitrate treatment. Furthermore, we create so-called gray tracking in KTP and investigate the ionic conductivity in theses areas. A local unintended reduction of the ionic conductivity is observed in the gray-tracked regions, which also induce additional optical absorption in the material. We show that a thermal treatment in an oxygen-rich atmosphere removes the gray tracking and brings the ionic conductivity as well as the optical transmission back to the original level. These studies can help to choose the best material and treatment for specific applications. AU - Padberg, Laura AU - Quiring, Viktor AU - Bocchini, Adriana AU - Santandrea, Matteo AU - Gerstmann, Uwe AU - Schmidt, Wolf Gero AU - Silberhorn, Christine AU - Eigner, Christof ID - 33484 JF - Crystals SN - 2073-4352 TI - DC Ionic Conductivity in KTP and Its Isomorphs: Properties, Methods for Suppression, and Its Connection to Gray Tracking VL - 12 ER - TY - JOUR AU - Santandrea, Matteo AU - Stefszky, Michael AU - Silberhorn, Christine ID - 26218 JF - Journal of Optics SN - 2040-8978 TI - General analytic theory of classical collinear three-wave mixing in a monolithic cavity ER - TY - JOUR AU - Bartnick, Moritz AU - Santandrea, Matteo AU - Höpker, Jan Philipp AU - Thiele, Frederik AU - Ricken, Raimund AU - Quiring, Viktor AU - Eigner, Christof AU - Herrmann, Harald AU - Silberhorn, Christine AU - Bartley, Tim ID - 26221 JF - Physical Review Applied SN - 2331-7019 TI - Cryogenic Second-Harmonic Generation in Periodically Poled Lithium Niobate Waveguides ER - TY - CONF AB - We present a frequency multimode integrated SU (1,1) interferometer with a polarization converter and strong signal-idler photon correlations. Phase sensitivity below the shot noise limit is demonstrated, various filtering and seeding strategies are discussed. AU - Ferreri, A. AU - Santandrea, Matteo AU - Stefszky, Michael AU - Luo, Kai Hong AU - Herrmann, Harald AU - Silberhorn, Christine AU - Sharapova, Polina ID - 40374 T2 - Conference on Lasers and Electro-Optics TI - Multimode integrated SU(1,1) interferometer ER - TY - JOUR AU - Gil López, Jano AU - Santandrea, Matteo AU - Roland, Ganaël AU - Brecht, Benjamin AU - Eigner, Christof AU - Ricken, Raimund AU - Quiring, Viktor AU - Silberhorn, Christine ID - 22770 JF - New Journal of Physics SN - 1367-2630 TI - Improved non-linear devices for quantum applications ER - TY - JOUR AB - Nonlinear SU(1,1) interferometers are fruitful and promising tools for spectral engineering and precise measurements with phase sensitivity below the classical bound. Such interferometers have been successfully realized in bulk and fiber-based configurations. However, rapidly developing integrated technologies provide higher efficiencies, smaller footprints, and pave the way to quantum-enhanced on-chip interferometry. In this work, we theoretically realised an integrated architecture of the multimode SU(1,1) interferometer which can be applied to various integrated platforms. The presented interferometer includes a polarization converter between two photon sources and utilizes a continuous-wave (CW) pump. Based on the potassium titanyl phosphate (KTP) platform, we show that this configuration results in almost perfect destructive interference at the output and supersensitivity regions below the classical limit. In addition, we discuss the fundamental difference between single-mode and highly multimode SU(1,1) interferometers in the properties of phase sensitivity and its limits. Finally, we explore how to improve the phase sensitivity by filtering the output radiation and using different seeding states in different modes with various detection strategies. AU - Ferreri, Alessandro AU - Santandrea, Matteo AU - Stefszky, Michael AU - Luo, Kai Hong AU - Herrmann, Harald AU - Silberhorn, Christine AU - Sharapova, Polina R. ID - 26077 JF - Quantum SN - 2521-327X TI - Spectrally multimode integrated SU(1,1) interferometer ER - TY - JOUR AU - Luo, Kai Hong AU - Santandrea, Matteo AU - Stefszky, Michael AU - Sperling, Jan AU - Massaro, Marcello AU - Ferreri, Alessandro AU - Sharapova, Polina AU - Herrmann, Harald AU - Silberhorn, Christine ID - 26889 JF - Physical Review A SN - 2469-9926 TI - Quantum optical coherence: From linear to nonlinear interferometers ER - TY - JOUR AB - Potassium titanyl phosphate (KTP) is a nonlinear optical material with applications in high-power frequency conversion or quasi-phase matching in submicron period domain grids. A prerequisite for these applications is a precise control and understanding of the poling mechanisms to enable the fabrication of high-grade domain grids. In contrast to the widely used material lithium niobate, the domain growth in KTP is less studied, because many standard methods, such as selective etching or polarization microscopy, provides less insight or are not applicable on non-polar surfaces, respectively. In this work, we present results of confocal Raman-spectroscopy of the ferroelectric domain structure in KTP. This analytical method allows for the visualization of domain grids of the non-polar KTP y-face and therefore more insight into the domain-growth and -structure in KTP, which can be used for improved domain fabrication. AU - Brockmeier, Julian AU - Mackwitz, Peter Walter Martin AU - Rüsing, Michael AU - Eigner, Christof AU - Padberg, Laura AU - Santandrea, Matteo AU - Silberhorn, Christine AU - Zrenner, Artur AU - Berth, Gerhard ID - 23826 JF - Crystals SN - 2073-4352 TI - Non-Invasive Visualization of Ferroelectric Domain Structures on the Non-Polar y-Surface of KTiOPO4 via Raman Imaging ER - TY - JOUR AU - Santandrea, Matteo AU - Stefszky, Michael AU - Roeland, Ganaël AU - Silberhorn, Christine ID - 26223 JF - Optics Express SN - 1094-4087 TI - Interferometric method for determining the losses of spatially multi-mode nonlinear waveguides based on second harmonic generation ER - TY - JOUR AU - Stefszky, Michael AU - Santandrea, Matteo AU - vom Bruch, Felix AU - Krapick, S. AU - Eigner, Christof AU - Ricken, R. AU - Quiring, V. AU - Herrmann, Harald AU - Silberhorn, Christine ID - 22771 JF - Optics Express SN - 1094-4087 TI - Waveguide resonator with an integrated phase modulator for second harmonic generation ER - TY - JOUR AB - The characterisation of loss in optical waveguides is essential in understanding the performance of these devices and their limitations. Whilst interferometric-based methods generally provide the best results for low-loss waveguides, they are almost exclusively used to provide characterization in cases where the waveguide is spatially single-mode. Here, we introduce a Fabry-Pérot-based scheme to estimate the losses of a nonlinear (birefringent or quasi-phase matched) waveguide at a wavelength where it is multi-mode. The method involves measuring the generated second harmonic power as the pump wavelength is scanned over the phase matching region. Furthermore, it is shown that this method allows one to infer the losses of different second harmonic spatial modes by scanning the pump field over the separated phase matching spectra. By fitting the measured phase matching spectra from different titanium indiffused lithium niobate waveguides to the model presented in this paper, it is shown that one can estimate the second harmonic losses of a single spatial-mode, at wavelengths where the waveguides are spatially multi-mode. AU - Santandrea, Matteo AU - Stefszky, Michael AU - Roeland, Ganaël AU - Silberhorn, Christine ID - 38051 IS - 4 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Interferometric method for determining the losses of spatially multi-mode nonlinear waveguides based on second harmonic generation. VL - 28 ER - TY - JOUR AU - Eigner, Christof AU - Padberg, Laura AU - Santandrea, Matteo AU - Herrmann, Harald AU - Brecht, Benjamin AU - Silberhorn, Christine ID - 21025 IS - 22 JF - Optics Express SN - 1094-4087 TI - Spatially single mode photon pair source at 800 nm in periodically poled Rubidium exchanged KTP waveguides VL - 28 ER - TY - JOUR AU - Padberg, Laura AU - Santandrea, Matteo AU - Rüsing, Michael AU - Brockmeier, Julian AU - Mackwitz, Peter AU - Berth, Gerhard AU - Zrenner, Artur AU - Eigner, Christof AU - Silberhorn, Christine ID - 25920 JF - Optics Express SN - 1094-4087 TI - Characterisation of width-dependent diffusion dynamics in rubidium-exchanged KTP waveguides ER - TY - JOUR AU - Santandrea, Matteo AU - Stefszky, Michael AU - Roeland, Ganaël AU - Silberhorn, Christine ID - 26224 JF - New Journal of Physics SN - 1367-2630 TI - Characterisation of fabrication inhomogeneities in Ti:LiNbO3 waveguides ER - TY - JOUR AU - Santandrea, Matteo AU - Stefszky, Michael AU - Silberhorn, Christine ID - 26225 JF - Optics Letters SN - 0146-9592 TI - General framework for the analysis of imperfections in nonlinear systems ER - TY - JOUR AU - Santandrea, Matteo AU - Stefszky, Michael AU - Ansari, Vahid AU - Silberhorn, Christine ID - 26226 JF - New Journal of Physics SN - 1367-2630 TI - Fabrication limits of waveguides in nonlinear crystals and their impact on quantum optics applications ER - TY - JOUR AU - Luo, Kai-Hong AU - Ansari, Vahid AU - Massaro, Marcello AU - Santandrea, Matteo AU - Eigner, Christof AU - Ricken, Raimund AU - Herrmann, Harald AU - Silberhorn, Christine ID - 26237 JF - Optics Express SN - 1094-4087 TI - Counter-propagating photon pair generation in a nonlinear waveguide ER - TY - JOUR AU - Luo, Kai Hong AU - Ansari, Vahid AU - Massaro, Marcello AU - Santandrea, Matteo AU - Eigner, Christof AU - Ricken, Raimund AU - Herrmann, Harald AU - Silberhorn, Christine ID - 26052 JF - Optics Express SN - 1094-4087 TI - Counter-propagating photon pair generation in a nonlinear waveguide ER - TY - JOUR AU - Eigner, Christof AU - Santandrea, Matteo AU - Padberg, Laura AU - Volk, Martin F. AU - Rüter, Christian E. AU - Herrmann, Harald AU - Kip, Detlef AU - Silberhorn, Christine ID - 9614 JF - Optics Express SN - 1094-4087 TI - Periodically poled ridge waveguides in KTP for second harmonic generation in the UV regime ER - TY - JOUR AU - Ansari, V. AU - Roccia, E. AU - Santandrea, Matteo AU - Doostdar, M. AU - Eigner, Christof AU - Padberg, Laura AU - Gianani, I. AU - Sbroscia, M. AU - Donohue, J. M. AU - Mancino, L. AU - Barbieri, M. AU - Silberhorn, Christine ID - 9619 JF - Optics Express SN - 1094-4087 TI - Heralded generation of high-purity ultrashort single photons in programmable temporal shapes ER -