Facile fabrication of single-crystal-diamond nanostructures with ultrahigh aspect ratio

Detector of UV light chirality based on a diamond metasurface

Circularly polarized light (CPL) finds diverse applications in fields such as quantum communications, quantum computing, circular dichroism (CD) spectroscopy, polarization imaging, and sensing. However, conventional techniques for detecting CPL face challenges related to equipment miniaturization, system integration, and high-speed operation. In this study, we propose a novel design that addresses these limitations by employing a quarter waveplate constructed from a diamond metasurface, in combination with a linear polarizer crafted from metallic aluminum. The diamond array, with specific dimensions (a = 84 nm, b = 52 nm), effectively transforms left-handed and right-handed circularly polarized light into two orthogonally linearly polarized beams who have a polarization degree of approximately 0.9. The aluminum linear polarizer then selectively permits the transmission of these transformed linearly polarized beams.Our proposed design showcases remarkable circular dichroism performance at a wavelength of 280 nm, concurrently maintaining high transmittance and achieving a substantial extinction ratio of 25. Notably, the design attains an ultraviolet wavelength transmission efficiency surpassing 80%. Moreover, our design incorporates a rotation mechanism that enables the differentiation of linearly polarized light and singly circularly polarized light. In essence, this innovative design introduces a fresh paradigm for ultraviolet circularly polarized light detection, offering invaluable insights and references for applications in polarization detection, imaging, biomedical diagnostics, and circular dichroic spectroscopy.

Coupling silicon vacancy centers in a thin diamond membrane to a silica optical microresonator

We report the development of a composite cavity QED system, in which silicon vacancy centers in a diamond membrane as thin as 100 nm couple to optical whispering gallery modes (WGMs) of a silica microsphere with a diameter of order 50 µm. The membrane induces a linewidth broadening of 3 MHz for equatorial and off-resonant WGMs, while the overall linewidth of the composite system remains below 40 MHz. Photoluminescence experiments in the cavity QED setting demonstrate the efficient coupling of optical emissions from silicon vacancy centers into the WGMs. Additional analysis indicates that the composite system can be used to achieve the good cavity limit in cavity QED, enabling an experimental platform for applications such as state transfer between spins and photons.

High-Q Nanophotonic Resonators on Diamond Membranes using Templated Atomic Layer Deposition of TiO2

Integrating solid-state quantum emitters with nanophotonic resonators is essential for efficient spin-photon interfacing and optical networking applications. While diamond color centers have proven to be excellent candidates for emerging quantum technologies, their integration with optical resonators remains challenging. Conventional approaches based on etching resonators into diamond often negatively impact color center performance and offer low device yield. Here, we developed an integrated photonics platform based on templated atomic layer deposition of TiO₂ on diamond membranes. Our fabrication method yields high-performance nanophotonic devices while avoiding etching wavelength-scale features into diamond. Moreover, this technique generates highly reproducible optical resonances and can be iterated on individual diamond samples, a unique processing advantage. Our approach is suitable for a broad range of both wavelengths and substrates and can enable high-cooperativity interfacing between cavity photons and coherent defects in diamond or silicon carbide, rare earth ions, or other material systems.

Mechanical Properties of 3D Nanostructures Obtained by Focused Electron/Ion Beam-Induced Deposition: A Review

This article reviews the state-of-the -art of mechanical material properties and measurement methods of nanostructures obtained by two nanoscale additive manufacturing methods: gas-assisted focused electron and focused ion beam-induced deposition using volatile organic and organometallic precursors. Gas-assisted focused electron and ion beam-induced deposition-based additive manufacturing technologies enable the direct-write fabrication of complex 3D nanostructures with feature dimensions below 50 nm, pore-free and nanometer-smooth high-fidelity surfaces, and an increasing flexibility in choice of materials via novel precursors. We discuss the principles, possibilities, and literature proven examples related to the mechanical properties of such 3D nanoobjects. Most materials fabricated via these approaches reveal a metal matrix composition with metallic nanograins embedded in a carbonaceous matrix. By that, specific material functionalities, such as magnetic, electrical, or optical can be largely independently tuned with respect to mechanical properties governed mostly by the matrix. The carbonaceous matrix can be precisely tuned via electron and/or ion beam irradiation with respect to the carbon network, carbon hybridization, and volatile element content and thus take mechanical properties ranging from polymeric-like over amorphous-like toward diamond-like behavior. Such metal matrix nanostructures open up entirely new applications, which exploit their full potential in combination with the unique 3D additive manufacturing capabilities at the nanoscale.

Optical coherence of implanted silicon vacancy centers in thin diamond membranes

We report the fabrication and optical characterization of thin diamond membranes implanted with negatively charged silicon vacancy (SiV^-) centers. The variations in the membrane thickness enable the experimental study of optical coherence of SiV^- centers as the membrane thickness is varied from 100 nm to 1100 nm. Photoluminescence excitation spectroscopy at low temperature shows that most of the SiV^- centers in these membranes feature an optical linewidth ranging between 200 and 300 MHz. Furthermore, there is no discernable dependence of the optical linewidth on the membrane thickness for membranes as thin as 100 nm, indicating the feasibility of incorporating SiV^- centers in a varity of diamond nanostructures and still maintaining the excellent optical coherence of these color centers.

Microscale 3D imaging by magnetic resonance force microscopy using full-volume Fourier- and Hadamard-encoding

Three-dimensional spatially resolved full-volume imaging by magnetic resonance force microscopy at room temperature is described. Spatial resolution in z-dimension is achieved by using the magnetic-field gradient of a ferromagnetic particle that is also used for the force detection of the magnetic resonance. The gradient of the radiofrequency pulses generated by two separate wire-bonded microcoils is used for spatial resolution in x- and y-dimension. To enhance the sensitivity of our measurement Hadamard- and Fourier-encoding schemes are applied due to their multiplex effect. Measurements were taken on a patterned (NH₄)₂SO₄ crystal sample. From the calculated magnetic field distributions, a 3D image was reconstructed with a voxel volume of about 5 μm³ (1.2 μm × 3.0 μm × 1.4 μm in x-, y- and z-dimension).

Nanoladder Cantilevers Made from Diamond and Silicon

We present a "nanoladder" geometry that minimizes the mechanical dissipation of ultrasensitive cantilevers. A nanoladder cantilever consists of a lithographically patterned scaffold of rails and rungs with feature size ∼100 nm. Compared to a rectangular beam of the same dimensions, the mass and spring constant of a nanoladder are each reduced by roughly 2 orders of magnitude. We demonstrate a low force noise of 158_-42⁺⁶² zN and 190_-33⁺⁴² zN in a 1 Hz bandwidth for devices made from silicon and diamond, respectively, measured at temperatures between 100-150 mK. As opposed to bottom-up mechanical resonators like nanowires or nanotubes, nanoladder cantilevers can be batch-fabricated using standard lithography, which is a critical factor for applications in scanning force microscopy.

Advances in diamond nanofabrication for ultrasensitive devices

This paper reviews some of the major recent advances in single-crystal diamond nanofabrication and its impact in nano- and micro-mechanical, nanophotonics and optomechanical components. These constituents of integrated devices incorporating specific dopants in the material provide the capacity to enhance the sensitivity in detecting mass and forces as well as magnetic field down to quantum mechanical limits and will lead pioneering innovations in ultrasensitive sensing and precision measurements in the realm of the medical sciences, quantum sciences and related technologies.

Fabrication of all diamond scanning probes for nanoscale magnetometry

The electronic spin of the nitrogen vacancy (NV) center in diamond forms an atomically sized, highly sensitive sensor for magnetic fields. To harness the full potential of individual NV centers for sensing with high sensitivity and nanoscale spatial resolution, NV centers have to be incorporated into scanning probe structures enabling controlled scanning in close proximity to the sample surface. Here, we present an optimized procedure to fabricate single-crystal, all-diamond scanning probes starting from commercially available diamond and show a highly efficient and robust approach for integrating these devices in a generic atomic force microscope. Our scanning probes consisting of a scanning nanopillar (200 nm diameter, 1-2 μm length) on a thin (<1 μm) cantilever structure enable efficient light extraction from diamond in combination with a high magnetic field sensitivity (ηAC≈50±20nT/Hz). As a first application of our scanning probes, we image the magnetic stray field of a single Ni nanorod. We show that this stray field can be approximated by a single dipole and estimate the NV-to-sample distance to a few tens of nanometer, which sets the achievable resolution of our scanning probes.

Scalable fabrication of high-quality, ultra-thin single crystal diamond membrane windows

High quality, ultra-thin single crystal diamond (SCD) membranes that have a thickness in the sub-micron range are of extreme importance as a materials platform for photonics, quantum sensing, nano/micro electro-mechanical systems (N/MEMS) and other diverse applications. However, the scalable fabrication of such thin SCD membranes is a challenging process. In this paper, we demonstrate a new method which enables high quality, large size (∼4 × 4 mm) and low surface roughness, low strain, ultra-thin SCD membranes which can be fabricated without deformations such as breakage, bowing or bending. These membranes are easy to handle making them particularly suitable for fabrication of optical and mechanical devices. We demonstrate arrays of single crystal diamond membrane windows (SCDMW), each up to 1 × 1 mm in dimension and as thin as ∼300 nm, supported by a diamond frame as thick as ∼150 μm. The fabrication method is robust, reproducible, scalable and cost effective. Microwave plasma chemical vapour deposition is used for in situ creation of single nitrogen-vacancy (NV) centers into the thin SCDMW. We have also developed SCD drum head mechanical resonator composed of our fully clamped and freely suspended membranes.

Circuit optomechanics: concepts and materials

Nanophotonic integrated circuits offer unique advantages for studying the interaction of light fields with mechanical structures. Because nanoscale waveguides are closely size-matched to nanomechanical devices, strong optomechanical interactions arise which can be harnessed in optical systems. The additional mechanical degrees of freedom provided by optomechanical devices are of particular interest for material systems in which tunability of the optical properties is not readily available. Here, suitable materials for the realization of chip-based optomechanical circuits are discussed and analyzed in terms of performance and the achievable quality factors. In particular, materials that offer large electronic band gaps are of interest, because in this case broadband optical transparency is achieved, combined with reduced free carrier effects. Several device geometries that can be used for enhancing optical forces are presented which address both an increase in the field gradient and the net optical force through resonant enhancement. Combining a variety of optomechanical components into full circuits thus provides a new route toward functional nanophotonic circuits with applications in sensing and optical signal processing in a chip-scale framework.

Subtractive 3D printing of optically active diamond structures

Controlled fabrication of semiconductor nanostructures is an essential step in engineering of high performance photonic and optoelectronic devices. Diamond in particular has recently attracted considerable attention as a promising platform for quantum technologies, photonics and high resolution sensing applications. Here we demonstrate the fabrication of optically active, functional diamond structures using gas-mediated electron beam induced etching (EBIE). The technique achieves dry chemical etching at room temperature through the dissociation of surface-adsorbed H2O molecules by energetic electrons in a water vapor environment. Parallel processing is possible by electron flood exposure and the use of an etch mask, while high resolution, mask-free, iterative editing is demonstrated by direct write etching of inclined facets of diamond microparticles. The realized structures demonstrate the potential of EBIE for the fabrication of optically active structures in diamond.