@article{63827, abstract = {{Light-emitting diodes (LEDs) are becoming increasingly important across various sectors of the lighting industry and are being used more frequently. In the field of symbolic projection, research is increasingly focusing on implementing light modulation using energy-efficient, incoherent LEDs rather than lasers. Since light modulation in micro- and nano-optics is typically achieved through phase modulation, Finite-Difference Time-Domain (FDTD) simulations are employed for analysis. The objective of this article is to investigate different approaches for approximating incoherent monochromatic light sources within FDTD simulations. To this end, two approaches based on dipole sources are considered, as well as a method involving plane waves with modulated wavefronts based on Cosine–Fourier functions and a method based on the superposition of Gaussian beams. These methods are evaluated in terms of their accuracy using a two-dimensional double-slit configuration and are compared against a fully incoherent analytical reference.}}, author = {{Metzner, Dominik and Potthoff, Jens and Zentgraf, Thomas and Förstner, Jens}}, issn = {{2304-6732}}, journal = {{Photonics}}, keywords = {{tet_topic_opticalantenna, tet_topic_numerics, tet_topic_meta}}, number = {{2}}, publisher = {{MDPI AG}}, title = {{{Approximating Incoherent Monochromatic Light Sources in FDTD Simulations}}}, doi = {{10.3390/photonics13020128}}, volume = {{13}}, year = {{2026}}, } @article{63532, abstract = {{Room-temperature lasing is a key milestone in the development of miniaturized optoelectronic and photonic devices. We present a simple approach to synthesize phase-pure quasi-2D layered tin perovskite nanowires with varying quantum well thicknesses (n = 1 to 4). By incorporating a new organic spacer capable of forming a hydrogen-bonded organic framework, this method promoted anisotropic crystal growth and enhanced lattice rigidity. Furthermore, introducing molecular intercalants enabled controlled crystallization into well-defined nanowires that function as Fabry–Pérot cavities. Cavities made from n = 2 to 4 perovskites support efficient and robust near-infrared, room-temperature optically pumped lasing with the threshold as low as 75.8 μJ/cm2, cavity quality factor over 3000, and negligible degradation over 106 pulses. A cleaved coupled nanolaser was fabricated as a proof-of-concept device for photonic applications.}}, author = {{Kim, Jeong Hui and Simon, Jeffrey and Shao, Wenhao and Nian, Zhichen and Yang, Hanjun and Chen, Peigang and Triplett, Brandon and Li, Zhixu and Wu, Pengfei and Chen, Yuheng and Farheen, Henna and Pagadala, Karthik and Choi, Kyu Ri and Fruhling, Colton B. and Förstner, Jens and Boltasseva, Alexandra and Savoie, Brett M. and Shalaev, Vladimir M. and Dou, Letian}}, issn = {{0002-7863}}, journal = {{Journal of the American Chemical Society}}, keywords = {{tet_topic_opticalantenna}}, pages = {{jacs.5c14431}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Hydrogen-Bonded Organic Framework Enables Phase-Pure Layered Tin Perovskite Nanowires for Room-Temperature Lasing}}}, doi = {{10.1021/jacs.5c14431}}, year = {{2026}}, } @article{55989, abstract = {{Phased arrays are vital in communication systems and have received significant interest in the field of optoelectronics and photonics, enabling a wide range of applications such as LiDAR, holography, wireless communication, etc. In this work, we present a blazed grating antenna that is optimized to have upward radiation efficiency as high as 80% with a compact footprint of 3.5 μm × 2 μm at an operational wavelength of 1.55 μm. Our numerical investigations demonstrate that this antenna in a 64 × 64 phased array configuration is capable of producing desired far-field radiation patterns. Additionally, our antenna possesses a low side lobe level of -9.7 dB and a negligible reflection efficiency of under 1%, making it an attractive candidate for integrated optical phased arrays.}}, author = {{Farheen, Henna and Joshi, Suraj and Scheytt, J. Christoph and Myroshnychenko, Viktor and Förstner, Jens}}, issn = {{2515-7647}}, journal = {{Journal of Physics: Photonics}}, keywords = {{tet_topic_opticalantenna}}, pages = {{045010}}, publisher = {{IOP Publishing}}, title = {{{An efficient compact blazed grating antenna for optical phased arrays}}}, doi = {{10.1088/2515-7647/ad6ed4}}, volume = {{6}}, year = {{2024}}, } @article{50012, abstract = {{Silicon photonics, in conjunction with complementary metal-oxide-semiconductor (CMOS) fabrication, has greatly enhanced the development of integrated optical phased arrays. This facilitates a dynamic control of light in a compact form factor that enables the synthesis of arbitrary complex wavefronts in the infrared spectrum. We numerically demonstrate a large-scale two-dimensional silicon-based optical phased array (OPA) composed of nanoantennas with circular gratings that are balanced in power and aligned in phase, required for producing elegant radiation patterns in the far-field. For a wavelength of 1.55 μm, we optimize two antennas for the OPA exhibiting an upward radiation efficiency as high as 90%, with almost 6.8% of optical power concentrated in the field of view. Additionally, we believe that the proposed OPAs can be easily fabricated and would have the ability to generate complex holographic images, rendering them an attractive candidate for a wide range of applications like LiDAR sensors, optical trapping, optogenetic stimulation, and augmented-reality displays.}}, author = {{Farheen, Henna and Strauch, Andreas and Scheytt, J. Christoph and Myroshnychenko, Viktor and Förstner, Jens}}, issn = {{1569-4410}}, journal = {{Photonics and Nanostructures - Fundamentals and Applications}}, keywords = {{tet_topic_opticalantenna}}, pages = {{101207}}, publisher = {{Elsevier BV}}, title = {{{Optimized, Highly Efficient Silicon Antennas for Optical Phased Arrays}}}, doi = {{10.1016/j.photonics.2023.101207}}, volume = {{58}}, year = {{2023}}, } @inproceedings{43052, abstract = {{We demonstrate a large-scale two dimensional silicon-based optical phased array (OPA) composed of nanoantennas with circular gratings that are balanced in power and aligned in phase, required for producing desired radiation patterns in the far-field. The OPAs are numerically optimized to have an upward efficiency of up to 90%, targeting radiation concentration mainly in the field of view. We envision that our OPAs have the ability of generating complex holographic images, rendering them an attractive candidate for a wide range of applications like LiDAR sensors, optical trapping, optogenetic stimulation and augmented-reality displays.}}, author = {{Farheen, Henna and Strauch, Andreas and Scheytt, J. Christoph and Myroshnychenko, Viktor and Förstner, Jens}}, booktitle = {{Integrated Optics: Devices, Materials, and Technologies XXVII}}, editor = {{García-Blanco, Sonia M. and Cheben, Pavel}}, keywords = {{tet_topic_opticalantenna}}, pages = {{124241D }}, publisher = {{SPIE}}, title = {{{Optimized silicon antennas for optical phased arrays}}}, doi = {{10.1117/12.2658716}}, year = {{2023}}, } @inproceedings{50466, abstract = {{A key challenge in designing efficient optical phased arrays is the lack of a well-designed radiator. This work explores horn antennas numerically optimized to target high upward radiation efficiency to be employed in silicon-based phased arrays capable of producing elegant radiation patterns in the far-field.}}, author = {{Farheen, Henna and Joshi, S. and Scheytt, J. Christoph and Myroshnychenko, Viktor and Förstner, Jens}}, booktitle = {{2023 IEEE Photonics Conference (IPC)}}, keywords = {{tet_topic_opticalantenna}}, publisher = {{IEEE}}, title = {{{Increasing the upward radiation efficiency of optical phased arrays using asymmetric silicon horn antennas}}}, doi = {{10.1109/ipc57732.2023.10360519}}, year = {{2023}}, } @inproceedings{43051, abstract = {{We demonstrate the numerical and experimental realization of optimized optical traveling-wave antennas made of low-loss dielectric materials. These antennas exhibit highly directive radiation patterns and our studies reveal that this nature comes from two dominant guided TE modes excited in the waveguide-like director of the antenna, in addition to the leaky modes. The optimized antennas possess a broadband nature and have a nearunity radiation efficiency at an operational wavelength of 780 nm. Compared to the previously studied plasmonic antennas for photon emission, our all-dielectric approach demonstrates a new class of highly directional, low-loss, and broadband optical antennas.}}, author = {{Farheen, Henna and Yan, Lok-Yee and Leuteritz, Till and Qiao, Siqi and Spreyer, Florian and Schlickriede, Christian and Quiring, Viktor and Eigner, Christof and Silberhorn, Christine and Zentgraf, Thomas and Linden, Stefan and Myroshnychenko, Viktor and Förstner, Jens}}, booktitle = {{Integrated Optics: Devices, Materials, and Technologies XXVII}}, editor = {{García-Blanco, Sonia M. and Cheben, Pavel}}, keywords = {{tet_topic_opticalantenna}}, pages = {{124241E}}, publisher = {{SPIE}}, title = {{{Tailoring the directive nature of optical waveguide antennas}}}, doi = {{10.1117/12.2658921}}, year = {{2023}}, } @article{28413, abstract = {{Optical traveling wave antennas offer unique opportunities to control and selectively guide light into a specific direction, which renders them excellent candidates for optical communication and sensing. These applications require state-of-the-art engineering to reach optimized functionalities such as high directivity and radiation efficiency, low sidelobe levels, broadband and tunable capabilities, and compact design. In this work, we report on the numerical optimization of the directivity of optical traveling wave antennas made from low-loss dielectric materials using full-wave numerical simulations in conjunction with the particle swarm optimization algorithm. The antennas are composed of a reflector and a director deposited on a glass substrate, and an emitter placed in the feed gap between them serves as an internal source of excitation. In particular, we analyze antennas with rectangular- and horn-shaped directors made of either hafnium dioxide or silicon. The optimized antennas produce highly directional emissions due to the presence of two dominant guided TE modes in the director in addition to leaky modes. These guided modes dominate the far-field emission pattern and govern the direction of the main lobe emission, which predominately originates from the end facet of the director. Our work also provides a comprehensive analysis of the modes, radiation patterns, parametric influences, and bandwidths of the antennas, which highlights their robust nature.}}, author = {{Farheen, Henna and Leuteritz, Till and Linden, Stefan and Myroshnychenko, Viktor and Förstner, Jens}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, keywords = {{tet_topic_opticalantenna}}, number = {{1}}, pages = {{83}}, title = {{{Optimization of optical waveguide antennas for directive emission of light}}}, doi = {{10.1364/josab.438514}}, volume = {{39}}, year = {{2022}}, } @article{31329, abstract = {{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.}}, author = {{Farheen, Henna and Yan, Lok-Yee and Quiring, Viktor and Eigner, Christof and Zentgraf, Thomas and Linden, Stefan and Förstner, Jens and Myroshnychenko, Viktor}}, issn = {{1094-4087}}, journal = {{Optics Express}}, keywords = {{tet_topic_opticalantenna}}, number = {{11}}, pages = {{19288}}, publisher = {{Optica Publishing Group}}, title = {{{Broadband optical Ta2O5 antennas for directional emission of light}}}, doi = {{10.1364/oe.455815}}, volume = {{30}}, year = {{2022}}, } @article{21821, abstract = {{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.}}, author = {{Leuteritz, T. and Farheen, Henna and Qiao, S. and Spreyer, F. and Schlickriede, Christian and Zentgraf, Thomas and Myroshnychenko, Viktor and Förstner, Jens and Linden, S.}}, issn = {{1094-4087}}, journal = {{Optics Express}}, keywords = {{tet_topic_opticalantenna}}, number = {{10}}, title = {{{Dielectric travelling wave antennas for directional light emission}}}, doi = {{10.1364/oe.422984}}, volume = {{29}}, year = {{2021}}, } @article{680, author = {{Peter, Manuel and Hildebrandt, Andre and Schlickriede, Christian and Gharib, Kimia and Zentgraf, Thomas and Förstner, Jens and Linden, Stefan}}, issn = {{1530-6984}}, journal = {{Nano Letters}}, keywords = {{tet_topic_opticalantenna}}, number = {{7}}, pages = {{4178--4183}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Directional Emission from Dielectric Leaky-Wave Nanoantennas}}}, doi = {{10.1021/acs.nanolett.7b00966}}, volume = {{17}}, year = {{2017}}, } @article{35, author = {{Linnenbank, Heiko and Grynko, Yevgen and Förstner, Jens and Linden, Stefan}}, issn = {{2047-7538}}, journal = {{Light: Science & Applications}}, keywords = {{tet_topic_opticalantenna, tet_topic_shg}}, number = {{1}}, pages = {{e16013}}, publisher = {{Springer Nature}}, title = {{{Second harmonic generation spectroscopy on hybrid plasmonic/dielectric nanoantennas}}}, doi = {{10.1038/lsa.2016.13}}, volume = {{5}}, year = {{2016}}, } @inproceedings{3939, abstract = {{Optical and infrared antennas provide a promising way to couple photons in and out of nanoscale structures. As counterpart to conventional radio antennas, they are able to increase optical felds in sub-wavelength volumes, to enhance excitation and emission of quantum emitters or to direct light, radiated by quantum emitters. The directed emission of these antennas has been mainly pursued by surface plasmon based devices, e.g. Yagi-Uda like antennas, which are rather complicated due to the coupling of several metallic particles. Also, like all metallic structures in optical or infrared regime, these devices are very sensitive to fabrication tolerances and are affected by strong losses. It has been shown recently, that such directed emission can be accomplished by dielectric materials as well. In this paper we present an optimization of nanoscopic antennas in the near infrared regime starting from a metallic Yagi-Uda structure. The optimization is done via a particle-swarm algorithm, using full time domain finite integration simulations to obtain the characteristics of the investigated structure, also taking into account substrates. Furthermore we present a dielectric antenna, which performs even better, due to the lack of losses by an appropriate choice of the dielectric material. These antennas are robust concerning fabrication tolerances and can be realized with different materials for both the antenna and the substrate, without using high index materials.}}, author = {{Hildebrandt, Andre and Reichelt, Matthias and Meier, Torsten and Förstner, Jens}}, booktitle = {{Ultrafast Phenomena and Nanophotonics XVIII}}, editor = {{Betz, Markus and Elezzabi, Abdulhakem Y. and Song, Jin-Joo and Tsen, Kong-Thon}}, keywords = {{tet_topic_opticalantenna}}, pages = {{89841G--8941G--6}}, publisher = {{SPIE}}, title = {{{Engineering plasmonic and dielectric directional nanoantennas}}}, doi = {{10.1117/12.2036588}}, volume = {{8984}}, year = {{2014}}, }