@article{55751, abstract = {{Lateral leakage of TM modes in dielectric optical waveguides of rib/ridge or strip-loaded types can be fully suppressed, if the waveguide core is formed not through a strip that protrudes at one side (up) from the remaining lateral guiding slab, but through parallel strips on both sides (up and down), such that the resulting cross section becomes vertically symmetric. The fairly general arguments underlying the leakage suppression apply to TM modes of all orders simultaneously, and are independent of wavelength. These plus-shaped waveguides support strictly guided, non-leaky TM modes for, in principle, arbitrarily shallow etching.}}, author = {{Üstün, Necati and Farheen, Henna and Hammer, Manfred and Förstner, Jens}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, keywords = {{tet_topic_waveguide}}, number = {{9}}, pages = {{2077}}, publisher = {{Optica Publishing Group}}, title = {{{Symmetry-protected TM modes in rib-like, plus-shaped optical waveguides with shallow etching}}}, doi = {{10.1364/josab.528729}}, volume = {{41}}, year = {{2024}}, } @article{42679, abstract = {{The Saharan desert ant Cataglyphis bombycina is densely covered with shiny silver setae (hair-like structures). Their appearance was explained by geometric optics and total internal reflection. The setae also increase the emissivity of the ant, as they form an effective medium. This work provides additional data on microstructural details of the setae that are used to simulate the scattering of an individual seta to explain their influence on the optical properties. This is achieved by characterization of their structure using light microscopy and scanning/transmission electron microscopy. How the microstructural features influence scattering is investigated wave-optically within the limits of finite-difference time-domain simulations from the ultraviolet to the mid-infrared spectral range to elucidate the optical effects beyond ray optics and effective medium theory. The results show that Mie scattering plays an important role in protecting the ant from solar radiation and could be relevant for its thermal tolerance.}}, author = {{Schwind, Bertram and Wu, Xia and Tiemann, Michael and Fabritius, Helge-Otto}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, keywords = {{Atomic and Molecular Physics, and Optics, Statistical and Nonlinear Physics}}, number = {{3}}, pages = {{B49 -- B58}}, publisher = {{Optica Publishing Group}}, title = {{{Broadband Mie scattering effects by structural features of setae from the Saharan silver ant Cataglyphis bombycina}}}, doi = {{10.1364/josab.474899}}, volume = {{40}}, year = {{2023}}, } @article{43245, abstract = {{High-contrast slab waveguide Bragg gratings with 1D periodicity are investigated. For specific oblique excitation by semi-guided waves at sufficiently high angles of incidence, the idealized structures do not exhibit any radiative losses, such that reflectance and transmittance for the single port mode add strictly up to one. We consider a series of symmetric, fully and partly etched finite gratings, for parameters found in integrated silicon photonics. These can act as spectral filters with a reasonably flattop response. Apodization can lead to more box shaped reflectance and transmittance spectra. Together with a narrowband Fabry–Perot filter, these configurations are characterized by reflection bands, or transmittance peaks, with widths that span three orders of magnitude.}}, author = {{Hammer, Manfred and Farheen, Henna and Förstner, Jens}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, keywords = {{tet_topic_waveguide}}, number = {{4}}, pages = {{862}}, publisher = {{Optica Publishing Group}}, title = {{{How to suppress radiative losses in high-contrast integrated Bragg gratings}}}, doi = {{10.1364/josab.485725}}, volume = {{40}}, 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{21932, abstract = {{Gaussian-beam-like bundles of semi-guided waves propagating in a dielectric slab can excite modes with high-order optical angular momentum supported by a circular fiber. We consider a multimode step-index fiber with a high-index coating, where the waves in the slab are evanescently coupled to the modes of the fiber. Conditions for effective resonant interaction are identified. Based on a hybrid analytical–numerical coupled mode model, our simulations predict that substantial fractions of the input power can be focused into waves with specific orbital angular momentum, of excellent purity, with a clear distinction between degenerate modes with opposite vorticity.}}, author = {{Hammer, Manfred and Ebers, Lena and Förstner, Jens}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, keywords = {{tet_topic_waveguides}}, number = {{5}}, pages = {{1717}}, title = {{{Resonant evanescent excitation of guided waves with high-order optical angular momentum}}}, doi = {{10.1364/josab.422731}}, volume = {{38}}, year = {{2021}}, } @article{12908, author = {{Hammer, Manfred and Ebers, Lena and Förstner, Jens}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, keywords = {{tet_topic_waveguides}}, pages = {{2395}}, title = {{{Oblique quasi-lossless excitation of a thin silicon slab waveguide: a guided-wave variant of an anti-reflection coating}}}, doi = {{10.1364/josab.36.002395}}, volume = {{36}}, year = {{2019}}, } @article{13348, author = {{Luk, Samuel M. H. and Lewandowski, P. and Kwong, N. H. and Baudin, E. and Lafont, O. and Tignon, J. and Leung, P. T. and Chan, Ch. K. P. and Babilon, M. and Schumacher, Stefan and Binder, R.}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, number = {{1}}, title = {{{Theory of optically controlled anisotropic polariton transport in semiconductor double microcavities}}}, doi = {{10.1364/josab.35.000146}}, volume = {{35}}, year = {{2018}}, } @article{3828, abstract = {{The 3D implementation of a hybrid analytical/numerical variant of the coupled-mode theory is discussed. Eigenmodes of the constituting dielectric channels are computed numerically. The frequency-domain coupled-mode models then combine these into fully vectorial approximations for the optical electromagnetic fields of the composite structure. Following a discretization of amplitude functions by 1D finite elements, pro- cedures from the realm of finite-element numerics are applied to establish systems of linear equations for the then- discrete modal amplitudes. Examples substantiate the functioning of the technique and allow for some numerical assessment. The full 3D simulations are highly efficient in memory consumption, moderately demanding in com- putational time, and, in regimes of low radiative losses, sufficiently accurate for practical design. Our results include the perturbation of guided modes by changes of the refractive indices, the interaction of waves in parallel, horizontally or vertically coupled straight waveguides, and a series of crossings of potentially overlapping channels with fairly arbitrary relative positions and orientations.}}, author = {{Hammer, Manfred and Alhaddad, Samer and Förstner, Jens}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, keywords = {{tet_topic_waveguide, tet_topic_numerics}}, number = {{3}}, pages = {{613--624}}, publisher = {{The Optical Society}}, title = {{{Hybrid coupled-mode modeling in 3D: perturbed and coupled channels, and waveguide crossings}}}, doi = {{10.1364/josab.34.000613}}, volume = {{34}}, year = {{2017}}, } @article{15855, author = {{Kwong, N. H. and Tsang, C. Y. and Luk, M. H. and Tse, Y. C. and Lewandowski, P. and Chan, Chris K. P. and Leung, P. T. and Schumacher, Stefan and Binder, R.}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, title = {{{Patterns and switching dynamics in polaritonic quantum fluids in semiconductor microcavities [Invited]}}}, doi = {{10.1364/josab.33.00c153}}, year = {{2016}}, } @article{3937, abstract = {{The relevance of our definition for sensitivity in refractometric sensing, being the relative change in the transmittance of a certain output channel of an optical device over the change in the refractive index of the probed material, is discussed. It is compared to one based on spectral shift per refractive index unit change. Further, there is discussion on how group delay and sensitivity are interrelated and can be converted into each other and which physical quantities are relevant for high sensitivity. As a by-product of the theory presented, a general expression relating group delay and the ratio of the time-averaged optical energy and the input power is presented.}}, author = {{Hoekstra, Hugo J. W. M. and Hammer, Manfred}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, keywords = {{tet_topic_waveguide}}, number = {{7}}, publisher = {{The Optical Society}}, title = {{{General relation for group delay and the relevance of group delay for refractometric sensing}}}, doi = {{10.1364/josab.31.001561}}, volume = {{31}}, year = {{2014}}, } @article{22953, abstract = {{The generation of specific high harmonics for an optical two-level system is elucidated. The desired emitted radiation can be induced by a carefully designed excitation pulse, which is found by a multiparameter optimization procedure. The presented mechanism can also be applied to semiconductor structures for which the calculations result in much higher emission frequencies. The optimization procedure is either performed using a genetic algorithm or a rigorous mathematical optimization technique.}}, author = {{Reichelt, Matthias and Walther, Andrea and Meier, Torsten}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, number = {{2}}, title = {{{Tailoring the high-harmonic emission in two-level systems and semiconductors by pulse shaping}}}, doi = {{10.1364/josab.29.000a36}}, volume = {{29}}, year = {{2012}}, } @article{23493, abstract = {{A microscopic analysis is presented for the extreme nonlinear optical response of semiconductor quantum wells and wires after intense excitation with femtosecond laser pulses. In this regime, the light–matter interaction is the dominant eneregy scale, leading to a number of interesting effects such as carrier-wave Rabi flopping, Mollow splitting, and the creation of higher harmonics. The results presented here were obtained by evaluating the semiconductor Bloch equations without the rotating wave approximation. The electronic dispersion of semiconductor nanostructures is shown to have a characteristic influence on the extreme nonlinear optical response, whereas the relative importance of the carrier Coulomb interaction decreases with increasing excitation intensities.}}, author = {{Golde, Daniel and Meier, Torsten and Koch, Stephan W.}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, number = {{12}}, pages = {{2559--2565}}, title = {{{Microscopic analysis of extreme nonlinear optics in semiconductor nanostructures}}}, doi = {{10.1364/josab.23.002559}}, volume = {{23}}, year = {{2006}}, } @article{23506, abstract = {{The optical properties of semiconductor quantum wells embedded in one-dimensional photonic crystal structures are analyzed by a self-consistent solution of Maxwell’s equations and a microscopic many-body theory of the material excitations. For a field mode spectrally below the photonic band edge it is shown that the optical absorption and gain are enhanced, exceeding by more than 1 order of magnitude the values of a homogeneous medium. For the photonic crystal structure inside a microcavity the gain increases superlinearly with the number of wells and for more than five wells exceeds the gain of a corresponding vertical-cavity surface-emitting laser.}}, author = {{Pasenow, Bernhard and Reichelt, Matthias and Stroucken, Tineke and Meier, Torsten and Koch, Stephan W. and Zakharian, Aramis R. and Moloney, Jerome V.}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, number = {{9}}, pages = {{2039--2048}}, title = {{{Enhanced light-matter interaction in semiconductor heterostructures embedded in one-dimensional photonic crystals}}}, doi = {{10.1364/josab.22.002039}}, volume = {{22}}, year = {{2005}}, }