@article{62862, abstract = {{Exciton polariton condensates are macroscopic coherent states in which topological excitations can be observed. In this work, we observe the excitation of the vortices and realize tuning the topological charge by manipulating the pumping configurations. Using a digital micromirror device, we constructed an annular pumping pattern where the inner and outer rings can be easily tuned. Both the number and the topological charge of the vortices can be changed by slightly tuning the inner ring position against the outer ring. The experimental results can be reproduced in theory by the Gross–Pitaevskii equation. Our work offers to generate and manipulate vortices in exciton polariton condensates using a straightforward optical method.}}, author = {{Ai, Qiang and Ma, Xuekai and Barkhausen, Franziska and Zhai, Xiaokun and Xing, Chunzi and Yang, Xinmiao and Wang, Peilin and Liu, Tianyu and Zhang, Yong and Gu, Yazhou and Li, Peigang and Li, Zhitong and Hatzopoulos, Zacharias and Savvidis, Pavlos G. and Schumacher, Stefan and Gao, Tingge}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, number = {{12}}, publisher = {{AIP Publishing}}, title = {{{Tuning polariton vortices in an asymmetric ring potential}}}, doi = {{10.1063/5.0287076}}, volume = {{127}}, year = {{2025}}, } @article{57028, abstract = {{Lithium niobate and lithium tantalate are among the most widespread materials for nonlinear, integrated photonics. Mixed crystals with arbitrary Nb–Ta ratios provide an additional degree of freedom to not only tune materials properties, such as the birefringence but also leverage the advantages of the singular compounds, for example, by combining the thermal stability of lithium tantalate with the larger nonlinear or piezoelectric constants of lithium niobate. Periodic poling allows to achieve phase-matching independent of waveguide geometry and is, therefore, one of the commonly used methods in integrated nonlinear optics. For mixed crystals, periodic poling has been challenging so far due to the lack of homogeneous, mono-domain crystals, which severely inhibit domain growth and nucleation. In this work, we investigate surface-near (<1μm depth) domain inversion on x-cut lithium niobate tantalate mixed crystals via electric field poling and lithographically structured electrodes. We find that naturally occurring head-to-head or tail-to-tail domain walls in the as-grown crystal inhibit domain inversion at a larger scale. However, periodic poling is possible if the gap size between the poling electrodes is of the same order of magnitude or smaller than the average size of naturally occurring domains. This work provides the basis for the nonlinear optical application of lithium niobate tantalate mixed crystals.}}, author = {{Bollmers, Laura and Babai-Hemati, Tobias and Koppitz, Boris and Eigner, Christof and Padberg, Laura and Rüsing, Michael and Eng, Lukas M. and Silberhorn, Christine}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, number = {{15}}, publisher = {{AIP Publishing}}, title = {{{Surface-near domain engineering in multi-domain x-cut lithium niobate tantalate mixed crystals}}}, doi = {{10.1063/5.0210972}}, volume = {{125}}, year = {{2024}}, } @article{54967, abstract = {{Ferroelectric domain wall conductivity (DWC) is an intriguing and promising functional property that can be elegantly controlled and steered through a variety of external stimuli such as electric and mechanical fields. Optical-field control, as a noninvasive and flexible tool, has rarely been applied so far, but it significantly expands the possibility for both tuning and probing DWC. On the one hand, as known from second-harmonic or Raman micro-spectroscopy, the optical approach provides information on DW distribution and inclination, while simultaneously probing the DW vibrational modes; on the other hand, photons might be applied to directly generate charge carriers, thereby acting as a functional and spectrally tunable probe to deduce the local absorption properties and bandgaps of conductive DWs. Here, we report on investigating the photo-induced DWC (PI-DWC) of three lithium niobate crystals, containing a very different number of DWs, namely: (A) none, (B) one, and (C) many conductive DWs. All three samples are inspected for their current–voltage behavior in darkness and for different illumination wavelengths swept from 500 nm down to 310 nm. All samples show their maximum PI-DWC at 310 nm; moreover, sample (C) reaches PI-DWCs of several microampere. Interestingly, a noticeable PI-DWC is also observed for sub-bandgap illumination, hinting toward the existence and decisive role of electronic in-gap states that contribute to the electronic charge transport along DWs. Finally, complementary conductive atomic force microscopy investigations under illumination proved that the PI-DWC indeed is confined to the DW area and does not originate from photo-induced bulk conductivity.}}, author = {{Ding, L. L. and Beyreuther, E. and Koppitz, B. and Kempf, K. and Ren, J. H. and Chen, W. J. and Rüsing, Michael and Zheng, Y. and Eng, L. M.}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, number = {{25}}, publisher = {{AIP Publishing}}, title = {{{Comparative study of photo-induced electronic transport along ferroelectric domain walls in lithium niobate single crystals}}}, doi = {{10.1063/5.0205877}}, volume = {{124}}, year = {{2024}}, } @article{43421, abstract = {{The achievement of a flat metasurface has realized extraordinary control over light–matter interaction at the nanoscale, enabling widespread use in imaging, holography, and biophotonics. However, three-dimensional metasurfaces with the potential to provide additional light–matter manipulation flexibility attract only little interest. Here, we demonstrate a three-dimensional metasurface scheme capable of providing dual phase control through out-of-plane plasmonic resonance of L-shape antennas. Under circularly polarized excitation at a specific wavelength, the L-shape antennas with rotating orientation angle act as spatially variant three-dimensional tilted dipoles and are able to generate desire phase delay for different polarization components. Generalized Snell's law is achieved for both in-plane and out-of-plane dipole components through arranging such L-shape antennas into arrays. These three-dimensional metasurfaces suggest a route for wavefront modulation and a variety of nanophotonic applications.}}, author = {{Li, Tianyou and Chen, Yanjie and Wang, Yongtian and Zentgraf, Thomas and Huang, Lingling}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, keywords = {{Physics and Astronomy (miscellaneous)}}, number = {{14}}, publisher = {{AIP Publishing}}, title = {{{Three-dimensional dipole momentum analog based on L-shape metasurface}}}, doi = {{10.1063/5.0142389}}, volume = {{122}}, year = {{2023}}, } @article{31480, abstract = {{Optical geometric phase encoded by in-plane spatial orientation of microstructures has promoted the rapid development of numerous functional meta-devices. However, pushing the concept of the geometric phase toward the acoustic community still faces challenges. In this work, we utilize two acoustic nonlocal metagratings that could support a direct conversion between an acoustic plane wave and a designated vortex mode to obtain the acoustic geometric phase, in which an orbital angular momentum conversion process plays a vital role. In addition, we realize the acoustic geometric phases of different orders by merely varying the orientation angle of the acoustic nonlocal metagratings. Intriguingly, according to our developed theory, we reveal that the reflective acoustic geometric phase, which is twice the transmissive one, can be readily realized by transferring the transmitted configuration to a reflected one. Both the theoretical study and experimental measurements verify the announced transmissive and reflective acoustic geometric phases. Moreover, the reconfigurability and continuous phase modulation that covers the 2π range shown by the acoustic geometric phases provide us with the alternatives in advanced acoustic wavefront control.}}, author = {{Liu, Bingyi and Zhou, Zhiling and Wang, Yongtian and Zentgraf, Thomas and Li, Yong and Huang, Lingling}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, keywords = {{Physics and Astronomy (miscellaneous)}}, number = {{21}}, publisher = {{AIP Publishing}}, title = {{{Experimental verification of the acoustic geometric phase}}}, doi = {{10.1063/5.0091474}}, volume = {{120}}, year = {{2022}}, } @article{36414, abstract = {{ Recently, microcavities with anisotropic materials were shown to be able to create bands with non-zero local Berry curvature. The anisotropic refractive index of the cavity layer is believed to be critical in opening an energy gap at the tilted Dirac points. In this work, we show that the anticrossing between a cavity mode and a Bragg mode can also be realized within an empty microcavity without any birefringent materials in the cavity layer. Nondispersive bands are observed within the energy gap due to the particular refractive index distribution of the sample. The intrinsic TE-TM splitting and XY splitting of DBR mirrors induce the squeezing of the cavity modes in momentum space, so that the nondispersive bands are tilted and spin-dependent. Our results pave the way to investigate interesting physical phenomena of photonic modes close to or in the nondispersive bands without anisotropic cavity layers. }}, author = {{Gao, Ying and Li, Yao and Ma, Xuekai and Gao, Meini and Dai, Haitao and Schumacher, Stefan and Gao, Tingge}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, keywords = {{Physics and Astronomy (miscellaneous)}}, number = {{20}}, publisher = {{AIP Publishing}}, title = {{{Tilting nondispersive bands in an empty microcavity}}}, doi = {{10.1063/5.0093908}}, volume = {{121}}, year = {{2022}}, } @article{47982, abstract = {{Spontaneous Raman spectroscopy (SR) is a versatile method for analysis and visualization of ferroelectric crystal structures, including domain walls. Nevertheless, the necessary acquisition time makes SR impractical for in situ analysis and large scale imaging. In this work, we introduce broadband coherent anti-Stokes Raman spectroscopy (B-CARS) as a high-speed alternative to conventional Raman techniques and demonstrate its benefits for ferroelectric domain wall analysis. Using the example of poled lithium niobate, we compare the spectral output of both techniques in terms of domain wall signatures and imaging capabilities. We extract the Raman-like resonant part of the coherent anti-Stokes signal via a Kramers–Kronig-based phase retrieval algorithm and compare the raw and phase-retrieved signals to SR characteristics. Finally, we propose a mechanism for the observed domain wall signal strength that resembles a Čerenkov-like behavior, in close analogy to domain wall signatures obtained by second-harmonic generation imaging. We, thus, lay here the foundations for future investigations on other poled ferroelectric crystals using B-CARS.}}, author = {{Reitzig, Sven and Hempel, Franz and Ratzenberger, Julius and Hegarty, Peter A. and Amber, Zeeshan H. and Buschbeck, Robin and Rüsing, Michael and Eng, Lukas M.}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, keywords = {{Physics and Astronomy (miscellaneous)}}, number = {{16}}, publisher = {{AIP Publishing}}, title = {{{High-speed hyperspectral imaging of ferroelectric domain walls using broadband coherent anti-Stokes Raman scattering}}}, doi = {{10.1063/5.0086029}}, volume = {{120}}, year = {{2022}}, } @article{34094, author = {{Gao, Ying and Li, Yao and Ma, Xuekai and Gao, Meini and Dai, Haitao and Schumacher, Stefan and Gao, Tingge}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, keywords = {{Physics and Astronomy (miscellaneous)}}, number = {{20}}, publisher = {{AIP Publishing}}, title = {{{Tilting nondispersive bands in an empty microcavity}}}, doi = {{10.1063/5.0093908}}, volume = {{121}}, year = {{2022}}, } @article{27099, abstract = {{In our work, we have engineered low capacitance single quantum dot photodiodes as sensor devices for the optoelectronic sampling of ultrafast electric signals. By the Stark effect, a time-dependent electric signal is converted into a time-dependent shift of the transition energy. This shift is measured accurately by resonant ps laser spectroscopy with photocurrent detection. In our experiments, we sample the laser synchronous output pulse of an ultrafast CMOS circuit with high resolution. With our quantum dot sensor device, we were able to sample transients below 20 ps with a voltage resolution in the mV-range.}}, author = {{Widhalm, Alex and Krehs, Sebastian and Siebert, Dustin and Sharma, Nand Lal and Langer, Timo and Jonas, Björn and Reuter, Dirk and Thiede, Andreas and Förstner, Jens and Zrenner, Artur}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, keywords = {{tet_topic_qd}}, pages = {{181109}}, title = {{{Optoelectronic sampling of ultrafast electric transients with single quantum dots}}}, doi = {{10.1063/5.0061358}}, volume = {{119}}, year = {{2021}}, } @article{63156, abstract = {{GaAs quantum dots (QDs) have recently emerged as state-of-the-art semiconductor sources of polarization-entangled photon pairs, however, without site-control capability. In this work, we present a systematic study of epitaxially grown GaAs/AlxGa1-xAs site-controlled pyramidal QDs possessing unrivaled excitonic uniformity in comparison to their InGaAs counterparts or GaAs QDs fabricated by other techniques. We have experimentally and systematically investigated the binding energy of biexcitons, highlighting the importance of the uniformity of all excitonic lines, rather than concentrating solely on the uniformity of the neutral exciton as a typical figure of merit, as it is normally done in the literature. We present optical signatures of GaAs QDs within a range of ∼250 meV with a remarkable uniformity within each individual sample, the ability to excite the biexciton state resonantly, and a systematic study of the fine-structure splitting (FSS) values—features important for polarization entangled photon emission. While, in general, we observe relatively large FSS distribution and associated non-uniformities, we discuss several strategies to suppress the average FSS values to <15 μeV.}}, author = {{Ranjbar Jahromi, Iman and Juska, Gediminas and Varo, Simone and Basso Basset, Francesco and Salusti, Francesco and Trotta, Rinaldo and Gocalinska, Agnieszka and Mattana, Francesco and Pelucchi, Emanuele}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, number = {{7}}, publisher = {{AIP Publishing}}, title = {{{Optical properties and symmetry optimization of spectrally (excitonically) uniform site-controlled GaAs pyramidal quantum dots}}}, doi = {{10.1063/5.0030296}}, volume = {{118}}, year = {{2021}}, } @article{17433, author = {{Wang, D. Q. and Reuter, Dirk and Wieck, A. D. and Hamilton, A. R. and Klochan, O.}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, title = {{{Two-dimensional lateral surface superlattices in GaAs heterostructures with independent control of carrier density and modulation potential}}}, doi = {{10.1063/5.0009462}}, year = {{2020}}, } @article{17995, author = {{Riha, Christian and Buchholz, Sven S. and Chiatti, Olivio and Wieck, Andreas D. and Reuter, Dirk and Fischer, Saskia F.}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, title = {{{Excess noise in Al x Ga 1 − xAs/GaAs based quantum rings}}}, doi = {{10.1063/5.0002247}}, year = {{2020}}, } @article{17322, author = {{Mukherjee, Amlan and Widhalm, Alex and Siebert, Dustin and Krehs, Sebastian and Sharma, Nandlal and Thiede, Andreas and Reuter, Dirk and Förstner, Jens and Zrenner, Artur}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, keywords = {{tet_topic_qd}}, pages = {{251103}}, title = {{{Electrically controlled rapid adiabatic passage in a single quantum dot}}}, doi = {{10.1063/5.0012257}}, volume = {{116}}, year = {{2020}}, } @article{40271, author = {{Vergyris, Panagiotis and Babin, Charles and Nold, Raphael and Gouzien, Elie and Herrmann, Harald and Silberhorn, Christine and Alibart, Olivier and Tanzilli, Sébastien and Kaiser, Florian}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, keywords = {{Physics and Astronomy (miscellaneous)}}, number = {{2}}, publisher = {{AIP Publishing}}, title = {{{Two-photon phase-sensing with single-photon detection}}}, doi = {{10.1063/5.0009527}}, volume = {{117}}, year = {{2020}}, } @article{54086, abstract = {{Planar nanostructures allow near-ideal extraction of emission from a quantum emitter embedded within, thereby realizing deterministic single-photon sources. Such a source can be transformed into M single-photon sources by implementing active temporal-to-spatial mode demultiplexing. We report on the realization of such a demultiplexed source based on a quantum dot embedded in a nanophotonic waveguide. Efficient outcoupling (>60%) from the waveguide into a single mode optical fiber is obtained with high-efficiency grating couplers. As a proof-of-concept, active demultiplexing into M = 4 spatial channels is demonstrated by the use of electro-optic modulators with an end-to-end efficiency of >81% into single-mode fibers. Overall, we demonstrate four-photon coincidence rates of >1 Hz even under nonresonant excitation of the quantum dot. The main limitation of the current source is the residual population of other exciton transitions, which corresponds to a finite preparation efficiency of the desired transition. We quantitatively extract a preparation efficiency of 15% using the second-order correlation function measurements. The experiment highlights the applicability of planar nanostructures as efficient multiphoton sources through temporal-to-spatial demultiplexing and lays out a clear path way of how to scale up toward demonstrating quantum advantages with the quantum dot sources.}}, author = {{Hummel, Thomas and Ouellet-Plamondon, Claudéric and Ugur, Ela and Kulkova, Irina and Lund-Hansen, Toke and Broome, Matthew A. and Uppu, Ravitej and Lodahl, Peter}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, number = {{2}}, publisher = {{AIP Publishing}}, title = {{{Efficient demultiplexed single-photon source with a quantum dot coupled to a nanophotonic waveguide}}}, doi = {{10.1063/1.5096979}}, volume = {{115}}, year = {{2019}}, } @article{3427, abstract = {{We report on the coherent phase manipulation of quantum dot excitons by electric means. For our experiments, we use a low capacitance single quantum dot photodiode which is electrically controlled by a custom designed SiGe:C BiCMOS chip. The phase manipulation is performed and quantified in a Ramsey experiment, where ultrafast transient detuning of the exciton energy is performed synchronous to double pulse p/2 ps laser excitation. We are able to demonstrate electrically controlled phase manipulations with magnitudes up to 3p within 100 ps which is below the dephasing time of the quantum dot exciton.}}, author = {{Widhalm, Alex and Mukherjee, Amlan and Krehs, Sebastian and Sharma, Nandlal and Kölling, Peter and Thiede, Andreas and Reuter, Dirk and Förstner, Jens and Zrenner, Artur}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, keywords = {{tet_topic_qd}}, number = {{11}}, pages = {{111105}}, title = {{{Ultrafast electric phase control of a single exciton qubit}}}, doi = {{10.1063/1.5020364}}, volume = {{112}}, year = {{2018}}, } @article{21029, author = {{Allgaier, Markus and Ansari, Vahid and Eigner, Christof and Quiring, Viktor and Ricken, Raimund and Donohue, John Matthew and Czerniuk, Thomas and Aßmann, Marc and Bayer, Manfred and Brecht, Benjamin and Silberhorn, Christine}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, title = {{{Streak camera imaging of single photons at telecom wavelength}}}, doi = {{10.1063/1.5004110}}, volume = {{112}}, year = {{2018}}, } @article{23630, author = {{Liu, Ning and Steinrück, Hans-Georg and Osvet, Andres and Yang, Yuyun and Schmuki, Patrik}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, pages = {{072102}}, title = {{{Noble metal free photocatalytic H2 generation on black TiO2: On the influence of crystal facets vs. crystal damage}}}, doi = {{10.1063/1.4976010}}, volume = {{110}}, year = {{2017}}, } @article{22568, author = {{Layes, V. and Monje, S. and Corbella, C. and Trieschmann, J. and de los Arcos de Pedro, Maria Teresa and von Keudell, A.}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, title = {{{Species transport on the target during high power impulse magnetron sputtering}}}, doi = {{10.1063/1.4976999}}, year = {{2017}}, } @article{13361, author = {{Lafont, O. and Luk, S. M. H. and Lewandowski, P. and Kwong, N. H. and Leung, P. T. and Galopin, E. and Lemaitre, A. and Tignon, J. and Schumacher, Stefan and Baudin, E. and Binder, R.}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, title = {{{Controlling the optical spin Hall effect with light}}}, doi = {{10.1063/1.4975681}}, year = {{2017}}, }