Abstract Achieving laser-driven relativistic light sails would represent a tremendous breakthrough for humankind. Numerous sail designs have been proposed, but none satisfy all the stringent optical, mechanical, and mass constraints. Here we demonstrate a class of nanolaminate sails with strong and flexible hexagonally-corrugated microstructures. Our prototypes, fabricated from alumina and molybdenum disulfide using scalable semiconductor processing techniques, feature areal densities of < 1 g ⋅ m −2 , achieve experimentally-measured broadband reflectivities of > 50%, and feature broadband absorptivities of < 4% with a measurement uncertainty that overlaps with zero - indicative of our sail class’s potential for fast acceleration and ultra-low photon absorption. Moreover, we propose a sail’s maximum achievable relative velocity as a performance benchmark, and analyze optical, mechanical, and mass constraints for our design and others in the literature to highlight the strong potential of our class of sails. Our approach represents a promising step toward plausible relativistic interstellar propulsion.

Single-photon addition enables “lossless” amplification and preparation of non-Gaussian and arbitrary quantum states using nonlinear optical processes and tabletop optics. While photon addition can be implemented in free space using bulk optics, often these discrete components can lead to compounded input and output losses, which detract from amplification. Furthermore, arbitrary quantum states are an essential resource for photonic quantum computing, which will be more accessible if created on-chip. We present a conceptual chip-based device for deterministic single-photon addition and integrated superconducting nanowire-based detection, with a focus on how this device facilitates “lossless” amplification in phase-based interferometry. Our model using on-chip, deterministic photon addition overcomes the classical signal-to-noise ratio (SNR) limits of coherent and thermal light by 2.3× and 3.5×, respectively. These gains increase with additional single-photon addition events. Through careful device design and optimization, we limit total system loss to −1.15 dB. We estimate this device could produce a waveguide-coupled deterministic single-photon in 21% of pulsed signals, far outperforming the probability rates of probabilistic sources. Finally, we show that the benefits of on-chip, deterministic single-photon addition for SNR amplification outweigh chip input losses.

In this study, we explore cocatalyst-free, single-crystalline, and epitaxial thin film zinc telluride (ZnTe) as a photocathode for CO2-to-CO conversion. The study systematically examines the impact of electronic properties and crystal orientation using nitrogen-doped, p-type ZnTe (ZnTe:N) photocathodes grown on GaAs substrates by molecular beam epitaxy (MBE). Heavily doped ZnTe:N ([p] congruent to 10(20) cm(-3)) with a (100) orientation achieves a selective CO2-to-CO Faradaic efficiency of 62% over a 200-mV potential window (with current densities of similar to 0.1 mA & centerdot;cm(-2)) without additional surface modifications. ZnTe:N of (100), (110), and (111) crystal orientations demonstrate different photoactivity, with the (100) and (110) orientations exhibiting three times higher photocurrent density compared to the (111) orientation despite their similar electronic properties. Overall, this study provides a foundation for further development of ZnTe-based tandem devices for photoelectrochemical CO2 reduction.

Electrically tunable metasurfaces enable dynamic control of light in ultrathin optical platforms. Most solid-state implementations rely on reflection-mode operation to achieve strong light-matter interaction, which limits their compatibility with transmissive and monolithically integrated photonic systems. In this work, we demonstrate a solid-state, electrically tunable transmissive metasurface based on a metal-oxide-semiconductor (MOS) architecture that overcomes this constraint by engineering vertical optical confinement in transmission mode. The metasurface consists of plasmonic gold nanoantennas separated from a semitransparent gold layer by an Al2O3/indium tin oxide (ITO) stack, with an additional amorphous silicon layer beneath the semitransparent metal. This vertical heterostructure forms a Fabry-Perot cavity that couples to a gap plasmon resonance supported by the nanoantennas, enabling strong electric-field confinement within the electrically gated ITO accumulation layer while preserving forward transmission. Electrical bias drives the ITO into the epsilon-near-zero regime, producing a pronounced modulation of the transmitted intensity. The device experimentally exhibits a peak transmittance of 24.4% and a relative transmission modulation of 9.4% at a wavelength of 1494 nm under a low driving voltage of under +/- 3.5 V bias, in good agreement with numerical simulations. High-speed measurements reveal a -3 dB modulation bandwidth of 7.7 MHz, primarily limited by device capacitance. The fully solid-state, CMOS-compatible architecture provides a compact platform for high-speed transmissive optical modulation, with potential applications in beam steering and free-space optical communications.

Achieving highly directive thermal emission across a broad spectral range remains a fundamental challenge in photonics. While recent advances have demonstrated broadband directional emission via Berreman modes, their operation is restricted to transverse-magnetic polarization. In this work, we present a framework for dual-polarized, spectrally broadband directive thermal emission by identifying the role of phase-matching leaky modes. By engineering the relative permittivity ratio between adjacent layers, broadband angular confinement is achieved without relying on strongly dispersive epsilon-near-zero resonances. A Si/Ge tandem structure supports dual-polarized directive emission inside a high-index medium, and a hemispherical extraction geometry preserves the emission angle upon outcoupling. This work provides a scalable strategy for broadband directional thermal emission in mid-infrared systems.

Solar-driven electrochemical CO2 reduction (eCO2R) is a promising approach for producing value-added chemicals from renewable energy sources. While integrated solar fuel reactors have been primarily studied under fixed conditions, their real-world deployment outdoors introduces significant challenges due to dynamic conditions such as fluctuating irradiance. We investigate the performance of a Cu gas diffusion electrode (GDE) as a model system for eCO2R under simulated diurnal conditions. We find that under varying irradiance conditions, degradation of the Cu GDE can arise from the day-to-night transition, which occurs over extended time periods under “off” conditions. Operando X-ray tomography reveals that pressure variations during this transition can trigger electrolyte incursion into the microporous layer, leading to increased hydrogen evolution. This work enhances our understanding of phenomena that may occur for CO2R during diurnal operation of a GDE and suggests operational strategies for solar-driven eCO2R devices to improve durability and reliability.

Transition metal dichalcogenide (TMD) solar cells are promising candidates for high-specific-power photovoltaics due to their strong light-matter interactions, such as their high absorption coefficients. The performance of many TMD solar devices is limited by recombination losses at the semiconductor and metal electrode interface. Recent studies with silicon and perovskite solar cells overcome this challenge by employing two carrier-selective contacts to improve carrier separation and collection. In this work, we design and demonstrate the first dual selective contact TMD solar cell with both electron and hole transport layers. Resembling inverted perovskite device architectures, this solar cell consists of a vertical-junction 10-nm-thick WS2 absorber layer, C60 electron-selective contact, and PTAA hole-selective contact. This photovoltaic device exhibits an AM1.5 G open-circuit voltage of 523 mV and a power conversion efficiency of 2.4%. We characterize the carrier dynamics in the dual selective contact solar cell, which include achieving balanced transport with symmetric carrier-selective contact conductance to achieve high fill factors. We demonstrate this by showing that S-shaped I-V curves can be eliminated through reducing the thickness of the low-conductance contact. From theoretical calculations, we find that the TMD carrier lifetime limits the open-circuit voltage of TMD solar cells. To move towards the voltage limit and achieve higher solar performance, we outline steps for improving the dual selective contact solar cell architecture.

Swings in pH can be achieved by electrically polarizing a bipolar membrane (BPM) to drive water dissociation at the BPM junction for electrochemical conversion and separation processes. BPM junction design is critical to tailor performance for specific applications; however, characterization techniques capable of resolving the nanometer scale physical structure of the junction are limited. We present sample preparation, imaging, and analysis workflows that are adaptable to a variety of BPM junction architectures. Atomic force microscopy produces BPM junction images with nanometer scale lateral resolution for samples with and without a graphene oxide water dissociation catalyst in the junction. Subsequent image segmentation and analysis quantify line edge roughness and catalyst layer thickness as descriptors of junction structure. Comparison of pre- and post-electrodialysis junctions suggests electric field-induced alignment of catalyst particles during electrodialysis. This characterization workflow can inform manufacturing protocols, computational modeling, and failure mode analysis for next-generation BPMs.

Accessing diverse polarization states across the Poincaré sphere via electrical control is highly desirable in optical communications, bio-imaging and quantum information processing, where fast continuous switching, compactness, and ease of integration into photonikic circuits are essential. Layered anisotropic 2D materials enable polarization modulation in a fast and compact manner, thereby overcoming the speed and size limitations of liquid-crystal based spatial light modulators and electro-optic Pockels cell modulators. Here, we report a Fabry-Perot cavity that integrates two cross-aligned black phosphorus layers, with each layer being independently gated to access the inherently two-dimensional range of polarization states across the Poincaré sphere surface. Our heterostructure design predicts electronic access to 86% of the Poincaré sphere at its S-band operating wavelength. We experimentally validate the design by fabricating and testing such a device in reflection, where we demonstrate independent, two-parameter electronic control of the output polarization.

We report simple and potentially low-cost techniques for creating high-quality n-type gallium arsenide (GaAs) and GaAs p/n junctions and fabricate GaAs p/n junction solar cells. Detailed-balance modeling suggests that 20% AM1.5G efficiency p/n homojunction devices may be possible if the surface doping concentration can be limited to values less than similar to 5 & times; 10(19) cm(-3). Our process exploits an open-tube, vapor-phase, deposition-free, zinc diffusion technique for forming p-type layers in melt-grown n-GaAs substrates that results in sheet resistances less than 1 k Omega/square. In addition, we have improved the minority carrier diffusion lengths of melt-grown GaAs from less than one micron to over five microns using an open-tube, vacuum-free, annealing process which reduces the density of EL2 midgap defects. Finally, we have combined these advances to fabricate epitaxy-free, GaAs solar cells with a validated AM1.5G efficiency of 15.3%.

Achieving spatiotemporal control of light at subwavelength and subcycle scales is an important milestone in the development of new photonic materials for signal processing, pulse shaping and ultrafast imaging. Spatiotemporal light modulation currently relies on electronic interband and intraband transitions that yield pronounced refractive index changes but typically suffer from slow, picosecond response times due to carrier relaxation. Here we show that by leveraging resonant light-matter interactions in a high-quality factor metasurface it is possible to use the optical Kerr effect, a weaker but subfemtosecond optoelectronic polarization effect, to achieve ultrafast, reconfigurable light modulation. By the subwavelength all-optical tuning of the refractive index of the dielectric metasurface unit cells with a spatially structured pump beam, we experimentally demonstrate pulse-limited beam steering with a 74-fs response time at angles up to ±13° in the near-infrared, where the deflection angles are programmable by the pump pattern. The steering originates from the Kerr effect, with a background contribution arising from a slower two-photon-excited free carrier absorption. Additionally, we observe pump self-modulation and self-diffraction, linear frequency conversion, and demonstrate arbitrary subpicosecond spatial light modulation in two dimensions.

The emission and absorption of thermal radiation are usually coupled via Kirchhoff's law or reciprocity, stated as the equality of spectral directional emissivity and absorptivity. Magneto-optical materials have recently been identified as a promising route to lifting the constraint of reciprocity, with multiple experimental demonstrations using doped InAs. However, these demonstrations have been limited to p-polarized light in the Voigt configuration, whereas thermal radiation from a blackbody is unpolarized. Therefore, to break reciprocity in both polarization channels, we design a nanophotonic, dual-polarized nonreciprocal absorber operating in the mid-infrared spectral range (11-20 x03BCm), consisting of an a-Si photonic crystal slab on top of a doped InAs substrate described by an antisymmetric, nonreciprocal dielectric tensor under an applied magnetic field. The photonic crystal slab supports eigenmodes that couple to both s- and p-polarized light, resulting in absorption peaks that frequency shift in opposite directions for forward- and backward-propagating lightx2014a signature of nonreciprocity in planar, subwavelength systems. We fabricate our design, then measure its room-temperature absorptance using magnetic-field-integrated absorptance spectroscopy, experimentally demonstrating nonreciprocal absorption for both polarizations. Our design is a step toward the complete control of light as heat, which could improve photonic energy conversion, thermal management, and mid-infrared optical isolation and circulation.

The dynamic, on-demand generation of different polarization states of light has diverse applications in optical communications, imaging, sensing, and quantum information processing. Such active polarization control is typically achieved using active metasurfaces or spatial light modulators based on liquid crystal media that have limited switching speeds and conversion efficiency. Layered van der Waals low-dimensional materials provide new avenues for more versatile polarization control with an operating frequency several orders of magnitude higher than that for liquid crystal devices. Here, we report the design of a heterostructure for efficient, polarization-selective free-space phase modulation or amplitude modulation by integrating electrically tunable, optically anisotropic black phosphorus (BP) into high quality factor (Q similar to 7500 to 11000) distributed Bragg reflector-based Fabry-Perot cavities. These devices achieve a respective phase tuning range of 210 degrees and an amplitude tuning range of 99%. We also introduce designs for BP heterostructures that employ two twisted cross-aligned BP layers that are able to access polarization states covering 75% of the Poincare sphere from voltage tuning alone. Finally, we introduce a design for an active metasurface polarization beam splitter based on our cavity heterostructures with an electrically tunable angle of diffraction that leverages spatially engineered polarization gradients. These structures open a pathway for further structuring of light by controlling the phase and amplitude along independent orthogonal directions.

We present an open-source code for calculating proton damage to solar cells through thin radiation shields with relevance to space based solar power delivered from geostationary orbit. In contrast to EQFLUX, we use Monte-Carlo calculations for proton transmission instead of analytic range formula. In contrast to MC-SCREAM, we use experimental relative damage coefficients instead of theoretical non-ionizing energy loss function. We demonstrate the numerical convergence of our results and we predict that 30 g/m2 of silica or 20g/m2 of polyethylene is sufficient to grant InP solar cells 80% end-of-life remaining power after 15 years in geostationary orbit.

Luminescent Solar Concentrators (LSCs) are a class of ultralight solar technology, comprising a waveguide embedded with quantum dots (QDs), that absorb and downshift incident spectra, that is then guided towards a band-gap matched solar cell, via total internal reflection (TIR). However, TIR accounts for >25% of losses. To mitigate these losses, an Emissive LSC (eLSC) model is proposed, that modifies the waveguide to support only the two fundamental modes, with a guided mode resonance (GMR) structure, such that the photoluminescence (PL) from the embedded QDs is instantly redirected towards an external PV cell through diffractive outcoupling of the GMR. This combined nanophotonic-PV device presents a novel method to improve LSC efficiency, while maintaining low mass and cost characteristics necessary for large scale production.

Indium phosphide (InP) thin film solar cells have considerable potential for low-cost space photovoltaic applications due to their efficiency ultralight weight form factor. However, InP cells have received less attention than their GaAs counterparts for space photovoltaic application. Future low-cost ultralight space photovoltaics with specific power greater than 1 kW/kg will require a shift away from vacuum-based layer growth and device processing. We investigate here a diffusion doping process for InP space photovoltaics using cadmium phosphide (Cd3P2) and zinc phosphide (Zn3P2). Then, we evaluate the process considerations to achieve higher efficiencies. We fabricated Cd-doped cells with efficiencies up to 4.94%, exhibiting a VOC of 762.3 mV, a JSC of 8.96 mA/cm2, a FF of 72.4%, and a dark current density J0 of 1. 74*10-6 mA/cm2. We fabricated Zn-doped cells with efficiencies up to 1.88%, exhibiting a VOC of 738.0 mV, a JSC of 3.86 mA/cm2, a FF of 66.1%, and a dark current density J0 of 2.89*10-6 mA/cm2.