@article{64864, abstract = {{Probing novel properties, arising from twisted interfaces, has traditionally relied on the stacking of exfoliated two-dimensional materials and the spontaneous formation of van der Waals bonds. So far, investigations involving intimate covalent or ionic bonds have not been a focus. Yet, we show here that an established technique, involving thermocompressional wafer bonding, works well for creating twisted non-van der Waals interfaces. We have successfully bonded z-cut lithium niobate single crystals to create ferroelectric oxide interfaces with strong polar discontinuities and have mapped the associated emergent interfacial conductivity. In some instances, a dramatic change in microstructure occurs, involving local dipolar switching. A twist-induced collapse in the capability of the system to effec8tively screen interfacial bound charge is implied. Importantly, this only occurs around specific moiré twist angles with sparse coincident lattices and associated short-range aperiodicity. In quasicrystals, aperiodicity is known to induce pseudo-bandgaps and we suspect a similar phenomenon here.}}, author = {{Rogers, Andrew and Holsgrove, Kristina and Schäfer, Nils A. and Koppitz, Boris and McCluskey, Conor J. and Yedama, Shivani and Lynch, Ronan and Sloan, Keelan and Porter, Barry and Sykes, Adam and Catalan Daniels, Alex and Silva, Romualdo S. and Bruno, Flavio Y. and Seddon, Sam D. and Lu, Haidong and Rüsing, Michael and Fink, Christa and Fahler-Muenzer, Philipp and Fearn, Sarah and Heutz, Sandrine E. M. and Hadjimichael, Marios and Ramasse, Quentin M. and Alexe, Marin and Kumar, Amit and McQuaid, Raymond G. P. and Gruverman, Alexei and Sanna, Simone and Eng, Lukas M. and Gregg, J. Marty}}, issn = {{2041-1723}}, journal = {{Nature Communications}}, number = {{1}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{Polar discontinuities, emergent conductivity, and critical twist-angle-dependent behaviour at wafer-bonded ferroelectric interfaces}}}, doi = {{10.1038/s41467-026-68553-7}}, volume = {{17}}, year = {{2026}}, } @article{65094, abstract = {{ The development of practical sensors for optical coherence tomography (OCT) with undetected photons requires miniaturization via integration. To be practical, these sensors must exhibit a large spectral bandwidth and a high brightness, which are linked to a high axial resolution and a sufficient signal-to-noise ratio, respectively. Here, we combine these requirements in a scheme for OCT measurements with undetected photons based on nonlinear Ti : Li Nb O 3 waveguides. We investigate the performance benchmarks of the commonly used SU(1,1) scheme in comparison to an induced-coherence scheme and find that the latter is actually better suited when implementing measurements with undetected photons in integrated systems. In both schemes, we perform pump-gain optimization and OCT measurements with undetected photons with an axial resolution as low as 28 μ m . }}, author = {{Roeder, Franz and Pollmann, René and Quiring, Viktor and Eigner, Christof and Brecht, Benjamin and Silberhorn, Christine}}, issn = {{2331-7019}}, journal = {{Physical Review Applied}}, number = {{3}}, publisher = {{American Physical Society (APS)}}, title = {{{Toward integrated sensors for optimized optical coherence tomography with undetected photons}}}, doi = {{10.1103/cwsx-42c4}}, volume = {{25}}, year = {{2026}}, } @article{65096, abstract = {{ Precise measurements of both the arrival time and carrier frequency of light pulses are essential for time–frequency-encoded quantum technologies. Quantum mechanics, however, imposes fundamental limits on the simultaneous determination of these quantities. In this work, we derive and experimentally verify the quantum uncertainty bounds governing joint time–frequency measurements. We show that when detection is restricted to finite time windows, the problem is naturally described by a quantum rotor, rendering the commonly used Heisenberg uncertainty relation inapplicable. We further propose an optimal detection scheme that saturates these fundamental limits. By sampling the Q -function, we demonstrate the reconstruction of the Wigner function beyond the harmonic oscillator. Using an experimental implementation based on a quantum pulse gate, we confirm that the proposed scheme approaches the ultimate quantum limit for simultaneous time–frequency measurements. These results provide a framework for joint time–frequency detection with direct implications for precision measurements and quantum information processing. }}, author = {{Folge, Patrick Fabian and Serino, Laura Maria and Mišta, Ladislav and Brecht, Benjamin and Silberhorn, Christine and Řeháček, Jaroslav and Hradil, Zdeněk}}, issn = {{2334-2536}}, journal = {{Optica}}, number = {{3}}, publisher = {{Optica Publishing Group}}, title = {{{Quantum-limited detection of the arrival time and the carrier frequency of time-dependent signals}}}, doi = {{10.1364/optica.579459}}, volume = {{13}}, year = {{2026}}, } @article{63451, abstract = {{Superconducting nanowire single-photon detectors (SNSPDs) can enable photon-number resolution (PNR) based on accurate measurements of the detector’s response time to few-photon optical pulses. In this work, we investigate the impact of the optical pulse shape and duration on the accuracy of this method. We find that Gaussian temporal pulse shapes yield cleaner arrival-time histograms and, thus, more accurate PNR, compared to bandpass-filtered pulses of equal bandwidth. For low system jitter and an optical pulse duration comparable to the other jitter contributions, photon numbers can be discriminated in our system with a commercial SNSPD. At 60 ps optical pulse duration, photon-number discrimination is significantly reduced. Furthermore, we highlight the importance of using the correct arrival-time histogram model when analyzing photon-number assignment. Using exponentially modified Gaussian distributions, instead of the commonly used Gaussian distributions, we can more accurately determine photon-number misidentification probabilities. Finally, we reconstruct the positive operator-valued measures of the detector, revealing sharp features that indicate the intrinsic PNR capabilities.}}, author = {{Schapeler, Timon and Mischke, Isabell and Schlue, Fabian and Stefszky, Michael and Brecht, Benjamin and Silberhorn, Christine and Bartley, Tim}}, issn = {{2835-0103}}, journal = {{APL Quantum}}, number = {{1}}, publisher = {{AIP Publishing}}, title = {{{Practical considerations for assignment of photon numbers with SNSPDs}}}, doi = {{10.1063/5.0304127}}, volume = {{3}}, year = {{2026}}, } @article{65095, abstract = {{ We provide experimental validation of tight entropic uncertainty relations for the Shannon entropies of observables with mutually unbiased eigenstates in high dimensions. In particular, we address the cases of dimensions d = 3 , 4, and 5 and consider from 2 to d + 1 mutually unbiased bases. The experiment is based on pulsed frequency bins measured with a multioutput quantum pulse gate, which can perform projective measurements on a complete high-dimensional basis in the time-frequency domain. Our results fit the theoretical predictions: the bound on the sum of the entropies is never violated and is saturated by the states that minimize the uncertainty relations. }}, author = {{Serino, Laura Maria and Chesi, Giovanni and Brecht, Benjamin and Maccone, Lorenzo and Macchiavello, Chiara and Silberhorn, Christine}}, issn = {{2469-9926}}, journal = {{Physical Review A}}, number = {{3}}, publisher = {{American Physical Society (APS)}}, title = {{{Experimental entropic uncertainty relations in dimensions three to five}}}, doi = {{10.1103/f6c4-jtlc}}, volume = {{113}}, year = {{2026}}, } @article{65847, abstract = {{Simulating vibronic spectra is a central task in physical chemistry, offering insight into important properties of molecules. Recently, it has been experimentally demonstrated that photonic platforms based on Gaussian boson sampling (GBS) are capable of performing these simulations. However, whether an actual GBS approach is required depends on the molecule under investigation. To develop a better understanding on the requirements for simulating vibronic spectra, we explore connections between theoretical approximations in physical chemistry and their photonic counterparts. Mapping these approximations into photonics, we show that for certain molecules the GBS approach is unnecessary. We place special emphasis on the linear coupling approximation, which in photonics corresponds to sampling from multiple coherent states. By implementing this approach in experiments, we demonstrate improved similarities over previously reported GBS results for formic acid and identify the particular attributes that a molecule must exhibit for this, and other approximations, to be valid. These results highlight the importance in forming deeper connections between traditional methods and photonic approaches.}}, author = {{Eickmann, Jan-Lucas and Luo, Kai-Hong and Roiz, Mikhail and Lammers, Jonas and Atzeni, Simone and Pandey, Cheeranjiv and Lütkewitte, Florian and Shirazi, Reza G. and Schlue, Fabian and Brecht, Benjamin and Rybkin, Vladimir V. and Stefszky, Michael and Silberhorn, Christine}}, issn = {{2056-6387}}, journal = {{npj Quantum Information}}, number = {{1}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{Bridging chemistry and Gaussian boson sampling: a photonic hierarchy of approximations for molecular vibronic spectra}}}, doi = {{10.1038/s41534-026-01250-x}}, volume = {{12}}, year = {{2026}}, } @article{66741, abstract = {{Abstract We study theoretically how high-gain effects affect the measurement outcome of visible signal spectra in undetected photon measurement schemes. We consider two interferometric configurations: firstly, the SU(1,1) interferometer where the idler incurs loss and additional dispersion in between two identical, lossless, squeezers; secondly, the induced coherence interferometer where the idler incurs loss and additional dispersion in between two identical, lossless, squeezers and where the second squeezer is seeded by the idler and a vacuum ancilla mode. Furthermore, we consider a distributed loss configuration where the idler incurs loss as it propagates in the nonlinear medium. Motivated by experimental evidence and due to the fact that broadband sources are ideal for these measurement schemes, we use the dispersive data of a third-order dispersion engineered integrated waveguide parametric down conversion (PDC) source presented in Roeder et al (2024 New J. Phys. 26 123025) to model the PDC spectra in the three configurations. For each configuration we consider the case of idler-only (i) absorption, (ii) additional dispersion, and (iii) the combined effects. We obtain results which outline the strength and weaknesses of the different configurations at different operation points. }}, author = {{Houde, Martin and Roeder, Franz and Silberhorn, Christine and Brecht, Benjamin and Quesada, Nicolás}}, issn = {{1367-2630}}, journal = {{New Journal of Physics}}, number = {{7}}, publisher = {{IOP Publishing}}, title = {{{High-gain effects in broadband continuous-wave parametric down conversion sources and measurements with undetected photons}}}, doi = {{10.1088/1367-2630/ae8692}}, volume = {{28}}, year = {{2026}}, } @article{66740, abstract = {{Abstract We theoretically compare the quantum Fisher information (QFI) for three configurations of absorption spectroscopy with undetected idler photons: an SU(1,1) interferometer with inter-source idler loss, an induced-coherence (IC) setup in which the idler partially seeds a second squeezer together with a vacuum ancilla, and a distributed-loss (DL) scheme with in-medium attenuation. We calculate the QFI as a function of parametric gain for both full and signal-only detection access. For losses below 99% and low to moderate gain, the SU(1,1) configuration provides the largest QFI. At high gain and intermediate loss, the IC scheme performs best, while under extreme attenuation (transmission < 1%) the DL model becomes optimal. These results delineate the measurement regimes in which each architecture is optimal in terms of information theory. }}, author = {{Houde, Martin and Roeder, Franz and Silberhorn, Christine and Brecht, Benjamin and Quesada, Nicolás}}, issn = {{2515-7647}}, journal = {{Journal of Physics: Photonics}}, number = {{3}}, publisher = {{IOP Publishing}}, title = {{{Quantum fisher information analysis for absorption measurements with undetected photons}}}, doi = {{10.1088/2515-7647/ae82a2}}, volume = {{8}}, year = {{2026}}, } @article{66877, abstract = {{Integrated photon-pair sources, providing scalability solutions, are crucial for large-scale realizations of quantum photonic technologies. Their traditional fabrication techniques, such as etching, are often complex, require long development cycles, and are resource inefficient in case of fabrication imperfections or failures. The two-photon polymerization (2PP) technique can offer a rapid, efficient, and reproducible alternative for the fabrication of integrated photonic devices. Here, we demonstrate an integrated photon-pair source based on a 2PP-defined strip-loaded waveguide on a periodically poled thin-film lithium niobate (TFLN) platform. The device generates photon pairs through type-II spontaneous parametric down-conversion (SPDC), employing first-order quasi-phase matching (QPM) with TM-polarized excitation light. The device achieves an on-chip pair generation rate of 4.357 MHz and a coincidence-to-accidental ratio (CAR) of ∼404. To prove the flexibility and versatility of the fabrication technique, the waveguides were erased from the LN substrate and reprinted, reaching comparable performance. This work demonstrates the potential of 2PP as a rapid production technique for high-performance integrated photon-pair sources, offering a practical solution to the limitations of traditional fabrication techniques and showcasing both reproducibility of the fabrication and the reusability of the substrate.}}, author = {{Sewidan, Muhamed A. and Rittmeier, Alexandra and Bollmers, Laura and Babel, Silia and Chatzizyrli, Elisavet and Duran Gomez, Juan S. S. and Padberg, Laura and Eigner, Christof and Silberhorn, Christine and Bremner, Douglas and Wienke, Andreas and Kracht, Dietmar and Hinkelmann, Moritz and Kues, Michael}}, issn = {{1094-4087}}, journal = {{Optics Express}}, number = {{16}}, publisher = {{Optica Publishing Group}}, title = {{{High-performance photon-pair source using a two-photon-polymerized strip-loaded lithium niobate waveguide}}}, doi = {{10.1364/oe.596879}}, volume = {{34}}, year = {{2026}}, } @article{66939, abstract = {{Many quantum optical applications in spectroscopy, communication and signal analysis rely on spectrally-engineered nonlinear optical interactions to target specific wavelengths or bandwidth. Here, in an established material platform like lithium niobate the achievable wavelength and bandwidth combinations are usually limited by the material’s dispersion and its birefringence. In this regard, mixed crystals of lithium niobate tantalate (LNT) promise a novel material platform, because they allow tuning the birefringence, which is central for type II phase matching devices. Crucially, LNT offers crystal compositions without any birefringence, which still retain their second-order optical nonlinearity. Despite recent progress in the growth and fabrication of LNT, so far no works have investigated the unique properties of LNT for use in electro-optics, nonlinear or quantum optics. In this study, we explore nonlinear optical devices based on LNT for broad- and narrowband nonlinear optical interactions based on recently measured Sellmeier coefficients. Most interestingly, we find that compositions without birefringence allow the design of broadband, degenerate type II phase matching sources spanning the whole near- to mid-infrared range by only changing the poling period and pump wavelength. Such devices are not easily realizable in pure lithium niobate or lithium tantalate. This could potentially allow for more flexible light sources and nonlinear devices in quantum metrology, quantum spectroscopy and quantum communication.}}, author = {{Roeder, Franz and Rüsing, Michael and Hehemann, Tobias and Gnanavel, Abira and Eigner, Christof and Brecht, Benjamin and Imlau, Mirco and Silberhorn, Christine}}, issn = {{2159-3930}}, journal = {{Optical Materials Express}}, number = {{8}}, publisher = {{Optica Publishing Group}}, title = {{{Lithium niobate tantalate mixed crystals: a versatile platform for nonlinear quantum processes}}}, doi = {{10.1364/ome.592892}}, volume = {{16}}, year = {{2026}}, } @article{66942, abstract = {{Raman imaging, based on incoherent spontaneous Raman scattering (SR) or coherent techniques such as broadband coherent anti-Stokes Raman spectroscopy (BCARS), is a powerful tool for visualizing local lattice distortions. It can thus be employed, e.g., to identify and visualize ferroelectric (FE) domain walls (DWs). While SR-based DW imaging relies on small changes in the intensity or position of Raman peaks at the DW, BCARS measurements may detect DW signatures with a drastically increased contrast and orders of magnitude faster imaging speed. However, while SR-based contrasts can be predicted from existing models, the increased DW contrasts in BCARS remain poorly understood. In this work, we develop a first-principles approach for the simulation of CARS spectra to investigate the origin of this BCARS signal contrast at periodically poled stoichiometric lithium niobate (sPPLN) DWs. Combining these atomistic simulations with strain modeling allows us to explore how strain affects the CARS signal generation at FE DWs. We then apply polarization-sensitive BCARS to image sPPLN DWs for different polarization configurations. Our results reveal additional Raman peaks specific to the DWs across all investigated polarization combinations, yielding a strong DW-to-bulk contrast that enables in situ identification and localization of DWs in two-dimensional BCARS maps. This study demonstrates the practical utility of polarization-sensitive BCARS for fast DW imaging and provides fundamental insights into the BCARS contrast mechanism in FE materials, both in strained regions and in the unstrained bulk.}}, author = {{Buschbeck, Robin and Pionteck, Mike N. and Herrmann, Naomi and Rüsing, Michael and Kehr, Susanne C. and Sanna, Simone and Eng, Lukas M.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{3}}, publisher = {{American Physical Society (APS)}}, title = {{{Ab initio modeling and experimental analysis of contrast in broadband coherent anti-Stokes Raman spectroscopy: A case study on ferroelectric domain walls}}}, doi = {{10.1103/m1xq-rlft}}, volume = {{114}}, year = {{2026}}, } @article{66941, abstract = {{Understanding and controlling the optical properties of lithium niobate tantalate solid solutions (LiNb1−xTaxO3, 0 ≤ x ≤ 1) is essential for their use in integrated quantum and nonlinear photonics. This material system allows for composition-dependent tuning of key optical parameters such as refractive indices and birefringence. While lithium niobate (LiNbO3, x = 0) and lithium tantalate (LiTaO3, x = 1) are well characterized, reliable dispersion data for intermediate compositions remain scarce, limiting accurate modeling and refractive index engineering. Here, we address this gap by experimentally determining the ordinary and extraordinary refractive indices of LiNb1−xTaxO3 over the spectral range of 405 − 1550 nm using an interferometric technique. As a result, composition-dependent refractive index dispersion and Sellmeier coefficients are derived and discussed in relation to previous studies and structural aspects. In particular, a monotonic decrease of the ordinary refractive index with increasing Tantalum concentration is observed. The present Sellmeier coefficients further allow discussion of zero birefringence dispersion and its composition dependence in lithium niobate tantalate.}}, author = {{Hehemann, Tobias and Dömer, Niklas and Sauerwein, Felix and Rüsing, Michael and Ganschow, Steffen and Imlau, Mirco}}, issn = {{2159-3930}}, journal = {{Optical Materials Express}}, number = {{7}}, publisher = {{Optica Publishing Group}}, title = {{{Composition-dependent refractive index dispersion and Sellmeier coefficients for lithium niobate tantalate solid solutions}}}, doi = {{10.1364/ome.592118}}, volume = {{16}}, year = {{2026}}, } @article{66094, abstract = {{The two-qubit controlled-not (C-NOT) gate is an essential component for gate-based quantum circuits. In fact, its operation, combined with single qubit rotations allows to realise any quantum circuit. Several strategies have been adopted in order to build quantum gates. Among them, photonics offers the dual advantage of excellent isolation from the environment and ease of manipulation at the single qubit level. Here we adopt a scalable time-multiplexed approach in order to build a fully reconfigurable architecture capable of implementing a post-selected C-NOT gate with a fidelity of (93.8 ± 1.4)%. We then show how our time-multiplexed platform can be employed to combine a C-NOT and a single qubit gate in order to generate the four Bell states.}}, author = {{Pegoraro, Federico and Held, Philip and Lammers, Jonas and Brecht, Benjamin and Silberhorn, Christine}}, issn = {{2041-1723}}, journal = {{Nature Communications}}, keywords = {{Photonic Quantum Computing, Time-multiplexing, Quantum Information}}, number = {{1}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{Demonstration of a quantum C-NOT gate in a time-multiplexed fully reconfigurable photonic processor}}}, doi = {{10.1038/s41467-026-74861-9}}, volume = {{17}}, year = {{2026}}, } @article{63734, abstract = {{Quantum dots (QDs) are a promising source of single photons mainly due to their on-demand operation. However, their emission wavelength depends on their size and immediate surroundings in the solid-state environment. By applying a serrodyne electro-optic phase modulation, we achieve a spectral shift up to 0.01 nm (3.5 GHz) while preserving the purity and indistinguishability of the photons. This method provides an efficient and scalable approach for tuning the emission wavelength of QDs without relying on nonlinear frequency mixing or probabilistic processes. Our results show that the electro-optic phase modulation enables stable and tunable spectral shifts, making it suitable for applications such as quantum communication, quantum key distribution, and primarily integrating remote quantum dot sources into large-scale quantum networks.}}, author = {{Kapoor, Sanjay and Rodek, Aleksander and Mikołajczyk, Michał and Szuniewicz, Jerzy and Sośnicki, Filip Maksymilian and Kazimierczuk, Tomasz and Kossacki, Piotr and Karpiński, Michał}}, issn = {{2192-8614}}, journal = {{Nanophotonics}}, number = {{11}}, pages = {{1775--1782}}, publisher = {{Walter de Gruyter GmbH}}, title = {{{Electro-optic frequency shift of single photons from a quantum dot}}}, doi = {{10.1515/nanoph-2024-0550}}, volume = {{14}}, year = {{2025}}, } @article{63732, abstract = {{Time lenses have been recognized as crucial components for manipulating ultrafast optical pulses in various applications, from ultrafast spectroscopy to the interfacing of optical quantum systems. A time lens is characterized by its chirp rate, which determines the focusing strength of the time lens, and accurate knowledge of this chirp is critical for precise dispersion compensation and minimizing aberrations. Here, we introduce a tunable time aperture model for sinusoidal time lenses that provides a more accurate estimate of the effective chirp rate without modifying the device. We derive a closed-form expression for the maximum phase error and show how it depends on the time aperture. We experimentally demonstrate a 1.6-fold improvement in spectral bandwidth compression of Gaussian pulses compared to the conventional approach. Our framework offers a practical tool for designing efficient temporal optical systems, benefiting applications in both classical and quantum optics where accurate spectro-temporal shaping is essential.}}, author = {{Kapoor, Sanjay and Sośnicki, Filip Maksymilian and Karpiński, Michał}}, issn = {{2378-0967}}, journal = {{APL Photonics}}, number = {{9}}, publisher = {{AIP Publishing}}, title = {{{Aberration-optimized electro-optic time lens model using a tunable aperture}}}, doi = {{10.1063/5.0270904}}, volume = {{10}}, year = {{2025}}, } @article{61338, abstract = {{Conductive ferroelectric domain walls (DWs) represent a promising topical system for the development of nanoelectronic components and device sensors to be operational at elevated temperatures. DWs show very different properties as compared to their hosting bulk crystal, in particular with respect to the high local electrical conductivity. The objective of this work is to demonstrate DW conductivity up to temperatures as high as 400 °C which extends previous studies significantly. Experimental investigation of the DW conductivity of charged, inclined DWs is performed using 5 mol % MgO-doped lithium niobate single crystals. Current–voltage ( ) curves are determined by DC electrometer measurements and impedance spectroscopy and found to be identical. Moreover, impedance spectroscopy enables to recognize artifacts such as damaged electrodes. Temperature dependent measurements over repeated heating cycles reveal two distinct thermal activation energies for a given DW, with the higher of the activation energies only measured at higher temperatures. Depending on the specific sample, the higher activation energy is found above 160 °C to 230 °C. This suggests, in turn, that more than one type of defect/polaron is involved, and that the dominant transport mechanism changes with increasing temperature. First principles atomistic modeling suggests that the conductivity of inclined domain walls cannot be solely explained by the formation of a 2D carrier gas and must be supported by hopping processes. This holds true even at temperatures as high as 400 °C. Our investigations underline the potential to extend DW current based nanoelectronic and sensor applications even into the so-far unexplored temperature range up to 400 °C.}}, author = {{Wulfmeier, Hendrik and Yakhnevych, Uliana and Boekhoff, Cornelius and Diima, Allan and Kunzner, Marlo and Verhoff, Leonard M. and Paul, Jonas and Ratzenberger, Julius and Beyreuther, Elke and Gössel, Joshua and Kiseleva, Iuliia and Rüsing, Michael and Sanna, Simone and Eng, Lukas M. and Fritze, Holger}}, issn = {{0167-2738}}, journal = {{Solid State Ionics}}, publisher = {{Elsevier BV}}, title = {{{Demonstration of domain wall current in MgO-doped lithium niobate single crystals up to 400°C}}}, doi = {{10.1016/j.ssi.2025.116949}}, volume = {{429}}, year = {{2025}}, } @misc{62639, author = {{Kruse, Stephan and Silberhorn, Christine and Brecht, Benjamin and Schwabe, Tobias}}, title = {{{Optisch basierter Digital-Analog-Umsetzer}}}, year = {{2025}}, } @article{62749, abstract = {{Coherent Raman scattering techniques as coherent anti-Stokes Raman scattering (CARS), offer significant advantages in terms of pixel dwell times and speed as compared to spontaneous Raman scattering for investigations of crystalline materials. However, the spectral information in CARS is often hampered by the presence of a nonresonant contribution to the scattering process that shifts and distorts the Raman peaks. In this work, we apply a method to obtain nonresonant background-free spectra based on time-delayed, broadband CARS (TD-BCARS) using an intrapulse excitation scheme. In particular, this method can measure the phononic dephasing times across the full phonon spectrum at once. We test the methodology on amorphous SiO2 (glass), which is used to characterize the setup-specific and material-independent response times, and then apply TD-BCARS to the analysis of single crystals of diamond and ferroelectrics of potassium titanyl phosphate (KTP) and potassium titanyl arsenate (KTA). For diamond, we determine a dephasing time of 𝜏=7.81 ps for the single 𝑠⁢𝑝3 peak.}}, author = {{Hempel, F. and Rüsing, Michael and Vernuccio, F. and Spychala, K. J. and Buschbeck, R. and Cerullo, G. and Polli, D. and Eng, L. M.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{22}}, publisher = {{American Physical Society (APS)}}, title = {{{Phonon dephasing times determined with time-delayed broadband coherent anti-Stokes Raman scattering}}}, doi = {{10.1103/1ctr-csjy}}, volume = {{112}}, year = {{2025}}, } @article{62911, abstract = {{In this paper, we theoretically study the spectral and temporal properties of pulsed spontaneous parametric down-conversion (SPDC) generated in lossy waveguides. Our theoretical approach is based on the formalism of Gaussian states and the Langevin equation, which is elaborated for weak parametric down-conversion and photon-number-unresolved click detection. Using the example of frequency-degenerate type-II SPDC generated under the pump-idler group-velocity-matching condition, we show how the joint-spectral intensity, mode structure, normalized second-order correlation function, and Hong-Ou-Mandel interference pattern depend on internal losses of the SPDC process. We found that the joint-spectral intensity is almost insensitive to internal losses, while the second-order correlation function shows a strong dependence on them, being different for the signal and idler beams in the presence of internal losses. Based on the sensitivity of the normalized second-order correlation function, we show how its measurement can be used to experimentally determine internal losses.}}, author = {{Kopylov, Denis A. and Stefszky, Michael and Meier, Torsten and Silberhorn, Christine and Sharapova, Polina R.}}, issn = {{2643-1564}}, journal = {{Physical Review Research}}, number = {{3}}, publisher = {{American Physical Society (APS)}}, title = {{{Spectral and temporal properties of type-II parametric down-conversion: The impact of losses during state generation}}}, doi = {{10.1103/zp72-7qwl}}, volume = {{7}}, year = {{2025}}, } @article{62269, abstract = {{The titanium in-diffused lithium niobate waveguide platform is well-established for reliable prototyping and packaging of many quantum photonic components at room temperature. Nevertheless, compatibility with certain quantum light sources and superconducting detectors requires operation under cryogenic conditions. We characterize alterations in phase-matching and mode guiding of a non-degenerate spontaneous parametric down-conversion process emitting around 1556 nm and 950 nm, under cryogenic conditions. Despite the effects of pyroelectricity and photorefraction, the spectral properties match our theoretical model. Nevertheless, these effects cause small but significant variations within and between cooling cycles. These measurements provide a first benchmark against which other nonlinear photonic integration platforms, such as thin-film lithium niobate, can be compared.}}, author = {{Lange, Nina Amelie and Lengeling, Sebastian and Mues, Philipp and Quiring, Viktor and Ridder, Werner and Eigner, Christof and Herrmann, Harald and Silberhorn, Christine and Bartley, Tim}}, issn = {{1094-4087}}, journal = {{Optics Express}}, number = {{24}}, publisher = {{Optica Publishing Group}}, title = {{{Widely non-degenerate nonlinear frequency conversion in cryogenic titanium in-diffused lithium niobate waveguides}}}, doi = {{10.1364/oe.578108}}, volume = {{33}}, year = {{2025}}, }