TY - JOUR AU - Babai-Hemati, Jonas AU - vom Bruch, Felix AU - Herrmann, Harald AU - Silberhorn, Christine ID - 51339 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Tailored second harmonic generation inTi-diffused PPLN waveguides usingmicro-heaters ER - TY - JOUR AB - Superconducting nanowire single-photon detectors (SNSPDs) show near unity efficiency, low dark count rate, and short recovery time. Combining these characteristics with temporal control of SNSPDs broadens their applications as in active de-latching for higher dynamic range counting or temporal filtering for pump-probe spectroscopy or LiDAR. To that end, we demonstrate active gating of an SNSPD with a minimum off-to-on rise time of 2.4 ns and a total gate length of 5.0 ns. We show how the rise time depends on the inductance of the detector in combination with the control electronics. The gate window is demonstrated to be fully and freely, electrically tunable up to 500 ns at a repetition rate of 1.0 MHz, as well as ungated, free-running operation. Control electronics to generate the gating are mounted on the 2.3 K stage of a closed-cycle sorption cryostat, while the detector is operated on the cold stage at 0.8 K. We show that the efficiency and timing jitter of the detector is not altered during the on-time of the gating window. We exploit gated operation to demonstrate a method to increase in the photon counting dynamic range by a factor 11.2, as well as temporal filtering of a strong pump in an emulated pump-probe experiment. AU - Hummel, Thomas AU - Widhalm, Alex AU - Höpker, Jan Philipp AU - Jöns, Klaus AU - Chang, Jin AU - Fognini, Andreas AU - Steinhauer, Stephan AU - Zwiller, Val AU - Zrenner, Artur AU - Bartley, Tim ID - 36471 IS - 1 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Nanosecond gating of superconducting nanowire single-photon detectors using cryogenic bias circuitry VL - 31 ER - TY - JOUR AB - Since high-order harmonic generation (HHG) from atoms depends sensitively on the polarization of the driving laser field, the polarization gating (PG) technique was developed and applied successfully to generate isolated attosecond pulses from atomic gases. The situation is, however, different in solid-state systems as it has been demonstrated that due to collisions with neighboring atomic cores of the crystal lattice strong HHG can be generated even by elliptically- and circularly-polarized laser fields. Here we apply PG to solid-state systems and find that the conventional PG technique is inefficient for the generation of isolated ultrashort harmonic pulse bursts. In contrast, we demonstrate that a polarization-skewed laser pulse is able to confine the harmonic emission to a time window of less than one-tenth of the laser cycle. This method provides a novel way to control HHG and to generate isolated attosecond pulses in solids. AU - Song, Xiaohong AU - Yang, Shidong AU - Wang, Guifang AU - Lin, Jianpeng AU - Wang, Liang AU - Meier, Torsten AU - Yang, Weifeng ID - 45704 IS - 12 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Control of the electron dynamics in solid-state high harmonic generation on ultrafast time scales by a polarization-skewed laser pulse VL - 31 ER - TY - JOUR AB - Interference between single photons is key for many quantum optics experiments and applications in quantum technologies, such as quantum communication or computation. It is advantageous to operate the systems at telecommunication wavelengths and to integrate the setups for these applications in order to improve stability, compactness and scalability. A new promising material platform for integrated quantum optics is lithium niobate on insulator (LNOI). Here, we realise Hong-Ou-Mandel (HOM) interference between telecom photons from an engineered parametric down-conversion source in an LNOI directional coupler. The coupler has been designed and fabricated in house and provides close to perfect balanced beam splitting. We obtain a raw HOM visibility of (93.5 ± 0.7) %, limited mainly by the source performance and in good agreement with off-chip measurements. This lays the foundation for more sophisticated quantum experiments in LNOI. AU - Babel, Silia AU - Bollmers, Laura AU - Massaro, Marcello AU - Luo, Kai Hong AU - Stefszky, Michael AU - Pegoraro, Federico AU - Held, Philip AU - Herrmann, Harald AU - Eigner, Christof AU - Brecht, Benjamin AU - Padberg, Laura AU - Silberhorn, Christine ID - 45850 IS - 14 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Demonstration of Hong-Ou-Mandel interference in an LNOI directional coupler VL - 31 ER - TY - JOUR AB - A reliable, but cost-effective generation of single-photon states is key for practical quantum communication systems. For real-world deployment, waveguide sources offer optimum compatibility with fiber networks and can be embedded in hybrid integrated modules. Here, we present what we believe to be the first chip-size fully integrated fiber-coupled heralded single photon source (HSPS) module based on a hybrid integration of a nonlinear lithium niobate waveguide into a polymer board. Photon pairs at 810 nm (signal) and 1550 nm (idler) are generated via parametric down-conversion pumped at 532 nm in the LiNbO3 waveguide. The pairs are split in the polymer board and routed to separate output ports. The module has a size of (2 × 1) cm^2 and is fully fiber-coupled with one pump input fiber and two output fibers. We measure a heralded second-order correlation function of g_h(2)=0.05 with a heralding efficiency of η_h=3.5% at low pump powers AU - Kießler, Christian AU - Conradi, Hauke AU - Kleinert, Moritz AU - Quiring, Viktor AU - Herrmann, Harald AU - Silberhorn, Christine ID - 46644 IS - 14 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Fiber-coupled plug-and-play heralded single photon source based on Ti:LiNbO3 and polymer technology VL - 31 ER - TY - JOUR AB - We report a titanium indiffused waveguide resonator featuring an integrated electro-optic modulator for cavity length stabilisation that produces close to 5 dB of squeezed light at 1550 nm (2.4 dB directly measured). The resonator is locked on resonance for tens of minutes with 70 mW of SH light incident on the cavity, demonstrating that photorefraction can be mitigated. Squeezed light production concurrent with cavity length stabilisation utilising the integrated EOM is demonstrated. The device demonstrates the suitability of this platform for squeezed light generation in network applications, where stabilisation to the reference field is typically necessary. AU - Stefszky, M. AU - vom Bruch, F. AU - Santandrea, M. AU - Ricken, R. AU - Quiring, V. AU - Eigner, C. AU - Herrmann, H AU - Silberhorn, C ID - 48349 IS - 21 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Lithium niobate waveguide squeezer with integrated cavity length stabilisation for network applications VL - 31 ER - TY - JOUR AB - Quantum photonic processing via electro-optic components typically requires electronic links across different operation environments, especially when interfacing cryogenic components such as superconducting single photon detectors with room-temperature control and readout electronics. However, readout and driving electronics can introduce detrimental parasitic effects. Here we show an all-optical control and readout of a superconducting nanowire single photon detector (SNSPD), completely electrically decoupled from room temperature electronics. We provide the operation power for the superconducting detector via a cryogenic photodiode, and readout single photon detection signals via a cryogenic electro-optic modulator in the same cryostat. This method opens the possibility for control and readout of superconducting circuits, and feedforward for photonic quantum computing. AU - Thiele, Frederik AU - Hummel, Thomas AU - McCaughan, Adam N. AU - Brockmeier, Julian AU - Protte, Maximilian AU - Quiring, Victor AU - Lengeling, Sebastian AU - Eigner, Christof AU - Silberhorn, Christine AU - Bartley, Tim ID - 48399 IS - 20 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - All optical operation of a superconducting photonic interface VL - 31 ER - TY - JOUR AU - Widhalm, Alex AU - Golla, Christian AU - Weber, Nils AU - Mackwitz, Peter AU - Zrenner, Artur AU - Meier, Cedrik ID - 29716 IS - 4 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Electric-field-induced second harmonic generation in silicon dioxide VL - 30 ER - TY - JOUR AB - Highly directive antennas with the ability of shaping radiation patterns in desired directions are essential for efficient on-chip optical communication with reduced cross talk. In this paper, we design and optimize three distinct broadband traveling-wave tantalum pentoxide antennas exhibiting highly directional characteristics. Our antennas contain a director and reflector deposited on a glass substrate, which are excited by a dipole emitter placed in the feed gap between the two elements. Full-wave simulations in conjunction with global optimization provide structures with an enhanced linear directivity as high as 119 radiating in the substrate. The high directivity is a result of the interplay between two dominant TE modes and the leaky modes present in the antenna director. Furthermore, these low-loss dielectric antennas exhibit a near-unity radiation efficiency at the operational wavelength of 780 nm and maintain a broad bandwidth. Our numerical results are in good agreement with experimental measurements from the optimized antennas fabricated using a two-step electron-beam lithography, revealing the highly directive nature of our structures. We envision that our antenna designs can be conveniently adapted to other dielectric materials and prove instrumental for inter-chip optical communications and other on-chip applications. AU - Farheen, Henna AU - Yan, Lok-Yee AU - Quiring, Viktor AU - Eigner, Christof AU - Zentgraf, Thomas AU - Linden, Stefan AU - Förstner, Jens AU - Myroshnychenko, Viktor ID - 31329 IS - 11 JF - Optics Express KW - tet_topic_opticalantenna SN - 1094-4087 TI - Broadband optical Ta2O5 antennas for directional emission of light VL - 30 ER - TY - JOUR AB - We demonstrate for the first time, to the best of our knowledge, reconfigurable and real-time orthogonal time-domain detection of a high-bandwidth Nyquist signal with a low-bandwidth silicon photonics Mach-Zehnder modulator based receiver. As the Nyquist signal has a rectangular bandwidth, it can be multiplexed in the wavelength domain without any guardband as a part of a Nyquist-WDM superchannel. These superchannels can be additionally multiplexed in space and polarization. Thus, the presented demonstration can open a new possibility for the detection of multidimensional parallel data signals with silicon photonics. No external pulse source is needed for the receiver, and frequency-time coherence is used to sample the incoming Nyquist signal with orthogonal sinc-shaped Nyquist pulse sequences. All parameters are completely tunable in the electrical domain. The feasibility of the scheme is demonstrated through a proof-of-concept experiment over the entire C-band (1530 nm–1560 nm), employing a 24 Gbaud Nyquist QPSK signal due to experimental constraints on the transmitter side electronics. However, the silicon Mach-Zehnder modulator with a 3-dB bandwidth of only 16 GHz can process Nyquist signals of 90 GHz optical bandwidth, suggesting a possibility to detect symbol rates up to 90 GBd in an integrated Nyquist receiver. AU - Misra, Arijit AU - Kress, Christian AU - Singh, Karanveer AU - Meier, Janosch AU - Schwabe, Tobias AU - Preussler, Stefan AU - Scheytt, J. Christoph AU - Schneider, Thomas ID - 34235 IS - 8 JF - Optics Express SN - 1094-4087 TI - Reconfigurable and real-time high-bandwidth Nyquist signal detection with low-bandwidth in silicon photonics VL - 30 ER - TY - JOUR AB - We present the design and experimental characterization of a silicon nitride pulse interleaver based on coupled resonator optical waveguide filters. In order to achieve a targeted free spectral range of 1.44 THz, which is large given the reduced optical confinement of the silicon nitride platform, individual ring resonators are designed with tapered waveguides. Its application to time-interleaved photonically-assisted ADCs is analyzed by combining experimental characterization of the photonic integrated circuit with a comprehensive model of the entire ADC. The impact of fundamental signal distortion and noise sources affecting the converter is investigated and suitable equalization techniques at the digital signal processing level are evaluated. The novel application of a simple but powerful equalization filter in the DSP domain allows for a significant improvement of the digitized signal SNR. An ENOB of 5 over a 75 GHz bandwidth (150 GS/s) and an ENOB of 4.3 over a 100 GHz bandwidth (200 GS/s) are expected to be achievable with compact and off-the-shelf single-section semiconductor mode locked lasers, that can be further improved with lower noise light sources. AU - Zazzi, Andrea AU - Müller, Juliana AU - Ghannam, Ibrahim AU - Battermann, Moritz AU - Rajeswari, Gayatri Vasudevan AU - Weizel, Maxim AU - Scheytt, J. Christoph AU - Witzens, Jeremy ID - 34230 IS - 3 JF - Optics Express SN - 1094-4087 TI - Wideband SiN pulse interleaver for optically-enabled analog-to-digital conversion: a device-to-system analysis with cyclic equalization VL - 30 ER - TY - JOUR AB - In this paper, the theory of phase-locking of a microwave oscillator on the interharmonics, i.e. non-integer harmonics, of the repetition rate of the optical pulse train of a mode-locked laser (MLL) is developed. A balanced optical microwave phase detector (BOMPD) is implemented using a balanced Mach-Zehnder modulator and is employed to discriminate the phase difference between the envelope of the optical pulses and the microwave oscillator. It is shown mathematically that the inherent nonlinear properties of BOMPD with respect to the microwave excitation amplitude can be used for interharmonic locking. The characteristic functions of the phase detector for interharmonic locking are derived analytically and are compared with the measurement results. An opto-electronic phase-locked loop (OEPLL) is demonstrated whose output frequency locks on interharmonics of the MLL repetition rate when an appropriate modulator bias and sufficient RF amplitude are applied. Thus, for the first time theory and experiment of reliable locking on interharmonics of the repetition rate of a MLL are presented. AU - Bahmanian, Meysam AU - Kress, Christian AU - Scheytt, J. Christoph ID - 34232 IS - 5 JF - Optics Express SN - 1094-4087 TI - Locking of microwave oscillators on the interharmonics of mode-locked laser signals VL - 30 ER - TY - JOUR AB - Recently, ferroelectric domain walls (DWs) have attracted considerable attention due to their intrinsic topological effects and their huge potential for optoelectronic applications. In contrast, many of the underlying physical properties and phenomena are not well characterized. In this regard, analyzing the vibrational properties, e.g. by Raman spectroscopy, provides direct access to the various local material properties, such as strains, defects or electric fields. While the optical phonon spectra of DWs have been widely investigated in the past, no reports on the acoustic phonon properties of DWs exist. In this work, we present a joint Raman and Brillouin visualization of ferroelectric DWs in the model ferroelectric lithium niobate. This is possible by using a combined Raman and virtually imaged phased array Brillouin setup. Here, we show that DWs can be visualized via frequency shifts observed in the acoustic phonons, as well. The observed contrast then is qualitatively explained by models adapted from Raman spectroscopy. This work, hence, provides a novel route to study ferroelectric DWs and their intrinsic mechanical properties. AU - Rix, Jan AU - Rüsing, Michael AU - Galli, Roberta AU - Golde, Jonas AU - Reitzig, Sven AU - Eng, Lukas M. AU - Koch, Edmund ID - 47980 IS - 4 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Brillouin and Raman imaging of domain walls in periodically-poled 5%-MgO:LiNbO3 VL - 30 ER - TY - JOUR AB - We present a combined experimental and numerical study of the far-field emission properties of optical travelling wave antennas made from low-loss dielectric materials. The antennas considered here are composed of two simple building blocks, a director and a reflector, deposited on a glass substrate. Colloidal quantum dots placed in the feed gap between the two elements serve as internal light source. The emission profile of the antenna is mainly formed by the director while the reflector suppresses backward emission. Systematic studies of the director dimensions as well as variation of antenna material show that the effective refractive index of the director primarily governs the far-field emission pattern. Below cut off, i.e., if the director’s effective refractive index is smaller than the refractive index of the substrate, the main lobe results from leaky wave emission along the director. In contrast, if the director supports a guided mode, the emission predominately originates from the end facet of the director. AU - Leuteritz, T. AU - Farheen, H. AU - Qiao, S. AU - Spreyer, F. AU - Schlickriede, Christian AU - Zentgraf, Thomas AU - Myroshnychenko, Viktor AU - Förstner, Jens AU - Linden, S. ID - 21821 IS - 10 JF - Optics Express KW - tet_topic_opticalantenna SN - 1094-4087 TI - Dielectric travelling wave antennas for directional light emission VL - 29 ER - TY - JOUR AU - Weizel, Maxim AU - Scheytt, J. Christoph AU - Kärtner, Franz X. AU - Witzens, Jeremy ID - 23476 JF - Optics Express SN - 1094-4087 TI - Optically clocked switched-emitter-follower THA in a photonic SiGe BiCMOS technology ER - TY - JOUR AB - Uniaxial anisotropy in nonlinear birefringent crystals limits the efficiency of nonlinear optical interactions and breaks the spatial symmetry of light generated in the parametric down-conversion (PDC) process. Therefore, this effect is usually undesirable and must be compensated for. However, high gain may be used to overcome the destructive role of anisotropy in order to generate bright two-mode correlated twin-beams. In this work, we provide a rigorous theoretical description of the spatial properties of bright squeezed light in the presence of strong anisotropy. We investigate a single crystal and a system of two crystals with an air gap (corresponding to a nonlinear SU(1,1) interferometer) and demonstrate the generation of bright correlated twin-beams in such configurations at high gain due to anisotropy. We explore the mode structure of the generated light and show how anisotropy, together with crystal spacing, can be used for radiation shaping. AU - Riabinin, M. AU - Sharapova, Polina AU - Meier, Torsten ID - 37334 IS - 14 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Bright correlated twin-beam generation and radiation shaping in high-gain parametric down-conversion with anisotropy VL - 29 ER - TY - JOUR AB - Domain walls (DWs) in ferroelectric (FE) and multiferroic materials possess an ever-growing potential as integrated functional elements, for instance in optoelectronic nanodevices. Mandatory, however, is the profound knowledge of the local-scale electronic and optical properties, especially at DWs that are still incompletely characterized to date. Here, we quantify the refractive index of individual FE DWs in periodically-poled LiNbO3 (PPLN) single crystals. When applying polarization-sensitive optical coherence tomography (PS-OCT) at 1300 nm using circular light polarization, we are able to probe the relevant electro-optical properties close to and at the DWs, including also their ordinary and extraordinary contributions. When comparing to numerical calculations, we conclude that the DW signals recorded for ordinary and extraordinary polarization stem from an increased refractive index of at least Δn > 2·10−3 that originates from a tiny region of < 30 nm in width. PS-OCT hence provides an extremely valuable tool to decipher and quantify subtle changes of refractive index profiles for both inorganic and biomedical nanomaterial systems. AU - Golde, Jonas AU - Rüsing, Michael AU - Rix, Jan AU - Eng, Lukas M. AU - Koch, Edmund ID - 47974 IS - 21 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Quantifying the refractive index of ferroelectric domain walls in periodically poled LiNbO3 single crystals by polarization-sensitive optical coherence tomography VL - 29 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 - Ansari, Vahid AU - Donohue, John M. AU - Brecht, Benjamin AU - Silberhorn, Christine ID - 21024 IS - 19 JF - Optics Express SN - 1094-4087 TI - Remotely projecting states of photonic temporal modes VL - 28 ER - TY - JOUR AB - A stepwise angular spectrum method (SASM) for curved interfaces is presented to calculate the wave propagation in planar lens-like integrated optical structures based on photonic slab waveguides. The method is derived and illustrated for an effective 2D setup first and then for 3D slab waveguide lenses. We employ slab waveguides of different thicknesses connected by curved surfaces to realize a lens-like structure. To simulate the wave propagation in 3D including reflection and scattering losses, the stepwise angular spectrum method is combined with full vectorial finite element computations for subproblems with lower complexity. Our SASM results show excellent agreement with rigorous numerical simulations of the full structures with a substantially lower computational effort and can be utilized for the simulation-based design and optimization of complex and large scale setups. AU - Ebers, Lena AU - Hammer, Manfred AU - Förstner, Jens ID - 20372 IS - 24 JF - Optics Express KW - tet_topic_waveguides SN - 1094-4087 TI - Light diffraction in slab waveguide lenses simulated with the stepwise angular spectrum method VL - 28 ER -