Rasmus E. Christiansen
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View article: Tailoring robust photonic components using stochastic topology optimization
Tailoring robust photonic components using stochastic topology optimization Open
Nanophotonic systems that rely on strong resonances or near-unity transmission through individual components are highly sensitive to geometric imperfections introduced during fabrication. To address this challenge, we present a stochastic …
View article: Enhancement and Speed‐Up of Carrier Dynamics in A Dielectric Nanocavity with Deep Sub‐Wavelength Confinement
Enhancement and Speed‐Up of Carrier Dynamics in A Dielectric Nanocavity with Deep Sub‐Wavelength Confinement Open
Dielectric bowtie cavities represent a breakthrough in simultaneously achieving ultrahigh quality factors and ultra‐small mode volumes, providing new opportunities for enhancing light‐matter interactions. Experimental work has so far empha…
View article: 3D Imaging of Optical Modes in Dielectric Photonic Nanocavities with Sub-wavelength Field Confinement
3D Imaging of Optical Modes in Dielectric Photonic Nanocavities with Sub-wavelength Field Confinement Open
Dielectric optical cavities are emerging as viable platforms for efficiently concentrating light within extremely small volumes of sub-wavelength dimensions. This breaks with the notion that only plasmonic nanostructures can achieve this s…
View article: On the potential use of performance bounds based on semidefinite programs for topology optimization
On the potential use of performance bounds based on semidefinite programs for topology optimization Open
Topology optimization has matured to become a powerful engineering design tool capable of designing exceptional structures and materials for targeted applications. Despite its undeniable success unanswered questions remain, one of which be…
View article: Efficient first-principles inverse design of nanolasers
Efficient first-principles inverse design of nanolasers Open
We develop and demonstrate a first-principles approach, based on the nonlinear Maxwell-Bloch equations and steady-state ab-initio laser theory (SALT), for inverse design of nanostructured lasers, incorporating spatial hole-burning correcti…
View article: Morphogenesis of sound creates acoustic rainbows
Morphogenesis of sound creates acoustic rainbows Open
Sound is a crucial sensing element for many organisms in nature, with various species evolving organic structures that produce complex acoustic scattering and dispersion phenomena to emit and perceive sound clearly. To date, designing arti…
View article: Fabrication and characterization of shape- and topology-optimized optical cavities with deep sub-wavelength confinement for interfacing with colloidal quantum dots
Fabrication and characterization of shape- and topology-optimized optical cavities with deep sub-wavelength confinement for interfacing with colloidal quantum dots Open
We employ a combined shape- and topology-optimization strategy to design manufacturable two-dimensional photonic crystal-based optical nanocavities that confine light to length scales well below the resonance wavelength. We present details…
View article: Fabrication and Characterization of Shape- and Topology-Optimized Optical Cavities with Deep Sub-Wavelength Confinement for Interfacing with Colloidal Quantum Dots
Fabrication and Characterization of Shape- and Topology-Optimized Optical Cavities with Deep Sub-Wavelength Confinement for Interfacing with Colloidal Quantum Dots Open
View article: Enhancement and speed-up of carrier dynamics in a dielectric nanocavity with deep sub-wavelength confinement
Enhancement and speed-up of carrier dynamics in a dielectric nanocavity with deep sub-wavelength confinement Open
The emergence of dielectric bowtie cavities enable optical confinement with ultrahigh quality factor and ultra-small optical mode volumes with perspectives for enhanced light-matter interaction. Experimental work has so far emphasized the …
View article: Designing structures that maximize spatially averaged surface-enhanced Raman spectra: erratum
Designing structures that maximize spatially averaged surface-enhanced Raman spectra: erratum Open
This erratum corrects a misstatement regarding the absence of non-integrable singularities in 2d distributed Raman sensing applications and a formula [Eq. (9)] for one case of Raman enhancement. These changes do not impact the other result…
View article: On performance bounds for topology optimization
On performance bounds for topology optimization Open
Topology optimization has matured to become a powerful engineering design tool that is capable of designing extraordinary structures and materials taking into account various physical phenomena. Despite the method's great advancements in r…
View article: Engineering optical forces through Maxwell stress tensor inverse design
Engineering optical forces through Maxwell stress tensor inverse design Open
Precise spatial manipulation of particles via optical forces is essential in many research areas, ranging from biophysics to atomic physics. Central to this effort is the challenge of designing optical systems that are optimized for specif…
View article: Morphogenesis of sound creates acoustic rainbows
Morphogenesis of sound creates acoustic rainbows Open
Sound is an essential sensing element for many organisms in nature, and multiple species have evolved organic structures that create complex acoustic scattering and dispersion phenomena to emit and perceive sound unambiguously. To date, it…
View article: Orders-of-magnitude reduction in photonic mode volume by nano-sculpting
Orders-of-magnitude reduction in photonic mode volume by nano-sculpting Open
Three-dimensionally sculpted dielectric nanostructures supporting material(air) confined optical modes with single-emitter mode volumes three(four) orders of magnitude below the diffraction limit, $V_{\textbf{r}_0} \approx 0.0004 \left[λ/(…
View article: Topology Optimization of Thermal Initial Value Problems Exploiting Efficient Harmonic Analysis
Topology Optimization of Thermal Initial Value Problems Exploiting Efficient Harmonic Analysis Open
Topology optimization can be employed to manipulate transient thermal behavior for heat transfer devices. As a gradient-based approach, transient topology optimization faces challenges with the CPU cost of the associated forward and backwa…
View article: Omnidirectional gradient force optical trapping in dielectric nanocavities by inverse design
Omnidirectional gradient force optical trapping in dielectric nanocavities by inverse design Open
Optical trapping enables precise control of individual particles of different sizes, such as atoms, molecules, or nanospheres. Optical tweezers provide free-space omnidirectional optical trapping of objects in laboratories around the world…
View article: Inverse design and characterization of compact, broadband, and low-loss chip-scale photonic power splitters
Inverse design and characterization of compact, broadband, and low-loss chip-scale photonic power splitters Open
The scalability of integrated photonics hinges on low-loss chip-scale components, which are important for classical applications and crucial in the quantum domain. An important component is the power splitter, which is an essential buildin…
View article: Experimental realization of deep sub-wavelength confinement of light in a topology-optimized InP nanocavity
Experimental realization of deep sub-wavelength confinement of light in a topology-optimized InP nanocavity Open
We experimentally demonstrate an InP nanocavity with a mode volume of 0.26 ( λ /2 n ) 3 . This is an order of magnitude smaller than the mode volumes previously demonstrated in photonic crystal point-defect cavities realized in III-V mater…
View article: Inverse design of optical mode converters by topology optimization: tutorial
Inverse design of optical mode converters by topology optimization: tutorial Open
This tutorial details the use of topology optimization (TopOpt) for the inverse design of electromagnetic mode-converters. First, the design problem under consideration is stated. Second, suitable models for the geometry and physics are fo…
View article: Hybrid achromatic microlenses with high numerical apertures and focusing efficiencies across the visible
Hybrid achromatic microlenses with high numerical apertures and focusing efficiencies across the visible Open
Compact visible wavelength achromats are essential for miniaturized and lightweight optics. However, fabrication of such achromats has proved to be exceptionally challenging. Here, using subsurface 3D printing inside mesoporous hosts we de…
View article: Efficient low-reflection fully etched vertical free-space grating couplers for suspended silicon photonics
Efficient low-reflection fully etched vertical free-space grating couplers for suspended silicon photonics Open
We design and fabricate a grating coupler for interfacing suspended silicon photonic membranes with free-space optics while being compatible with single-step lithography and etching in 220 nm silicon device layers. The grating coupler desi…
View article: Observation of strong backscattering in valley-Hall photonic topological interface modes
Observation of strong backscattering in valley-Hall photonic topological interface modes Open
The unique properties of light underpin the visions of photonic quantum technologies, optical interconnects and a wide range of novel sensors, but a key limiting factor today is losses due to either absorption or backscattering on defects.…
View article: Impact of figures of merit in photonic inverse design
Impact of figures of merit in photonic inverse design Open
The rates of optical processes, such as two-photon absorption and spontaneous photon emission, are strongly dependent on the environment in which they take place, easily varying by orders of magnitude between different settings. Using topo…
View article: Interfacing free-space beams and suspended silicon photonic waveguides with a low back-reflection fully etched grating coupler
Interfacing free-space beams and suspended silicon photonic waveguides with a low back-reflection fully etched grating coupler Open
View article: Inverse design of compact and broadband nanophotonic beamsplitters
Inverse design of compact and broadband nanophotonic beamsplitters Open
View article: On the trade-off between mode volume and quality factor in dielectric nanocavities optimized for Purcell enhancement
On the trade-off between mode volume and quality factor in dielectric nanocavities optimized for Purcell enhancement Open
This study explores the effect of geometric limitations on the achievable Purcell factor for single emitters in dielectric structures by employing topology optimization as an inverse design tool to maximize the local density of states. Nan…
View article: Trace formulation for photonic inverse design with incoherent sources
Trace formulation for photonic inverse design with incoherent sources Open
Spatially incoherent light sources, such as spontaneously emitting atoms, naively require Maxwell’s equations to be solved many times to obtain the total emission, which becomes computationally intractable in conjunction with large-scale o…
View article: Nanometer-scale photon confinement in topology-optimized dielectric cavities
Nanometer-scale photon confinement in topology-optimized dielectric cavities Open
View article: Designing structures that maximize spatially averaged surface-enhanced Raman spectra
Designing structures that maximize spatially averaged surface-enhanced Raman spectra Open
We present a general framework for inverse design of nanopatterned surfaces that maximize spatially averaged surface-enhanced Raman (SERS) spectra from molecules distributed randomly throughout a material or fluid, building upon a recently…
View article: Designing Structures that Maximize Spatially Averaged Surface-Enhanced Raman Spectra
Designing Structures that Maximize Spatially Averaged Surface-Enhanced Raman Spectra Open
We present a general framework for inverse design of nanopatterned surfaces that maximize spatially averaged surface-enhanced Raman (SERS) spectra from molecules distributed randomly throughout a material or fluid, building upon a recently…