Diamond Waveguide Research Articles

Determining strain components in a diamond waveguide from zero-field optically detected magnetic resonance spectra of negatively charged nitrogen-vacancy-center ensembles

Determining strain components in a diamond waveguide from zero-field optically detected magnetic resonance spectra of negatively charged nitrogen-vacancy-center ensembles

Nonlinear Quantum Photonics with a Tin-Vacancy Center Coupled to a One-Dimensional Diamond Waveguide.

Color centers integrated with nanophotonic devices have emerged as a compelling platform for quantum science and technology. Here, we integrate tin-vacancy centers in a diamond waveguide and investigate the interaction with light at the single-photon level in both reflection and transmission. We observe single-emitter-induced extinction of the transmitted light up to 25% and measure the nonlinear effect on the photon statistics. Furthermore, we demonstrate fully tunable interference between the reflected single-photon field and laser light backscattered at the fiber end and show the corresponding controlled change between bunched and antibunched photon statistics in the reflected field.

Generation of macroscopic entanglement in ensemble systems based on silicon vacancy centers

Abstract Entanglement in macroscopic systems, as a fundamental quantum resource, has been utilized to propel the advancement of quantum technology and probe the boundary between the quantum and classical realms. This study focuses on a unique hybrid quantum system comprising of an ensemble of silicon vacancy (SiV) centers coupled to phononic waveguides in diamond via strain interactions. By employing two sets of time-dependent, non-overlapping driving fields, we investigate the generation process and dynamic properties of macroscopic quantum entanglement, providing fresh insights into the behavior of such hybrid quantum systems. Furthermore, it paves the way for new possibilities in utilizing quantum entanglement as an information carrier in quantum information processing and quantum communication.

A novel machine learning method for the design optimization of diamond waveguides fabricated by femtosecond laser writing

We report on a novel machine learning method for the design optimization of femtosecond (fs) laser written dielectric waveguides. Experimental results previously obtained from the optical characterization of fs laser written depressed cladding diamond waveguides have been used to form statistically generated regression models. Design variables such as core diameter and number of written tracks were varied to both minimize the propagation loss as well as to establish a full-factorial experimental design. The regression models were used to conduct a multi-objective optimization study to optimize the competing objectives such as maximizing the refractive index contrast while minimizing the propagation loss and V-number by using a genetic algorithm. Optimization was subject to a nonlinear Rayleigh range constraint to ensure that the structure was in the waveguiding regime. Results from the optimization revealed the optimum variables to achieve low-loss and nearly single-mode guiding for a fs laser written diamond waveguide. Using the solution sets of design parameters resulting from the optimization study and their corresponding objective function values, important correlations between the design parameters and the objective functions have been revealed. With this regard, it has been shown that the number of written tracks is a much more dominant parameter, when compared to core diameter, during the design of a fs laser written circular depressed cladding diamond waveguide. The proposed method should be applicable not only to diamond waveguides but also to a wide range of dielectric waveguides fabricated by fs laser writing.

Inverse design of mid-infrared diamond waveguide beam splitter.

Diamond is a supreme material for mid-infrared (MIR) integrated photonics as it has a transparency window up to 20 µm that covers the entire fingerprint region. However, its relatively low refractive index poses a challenge in designing an MIR diamond functional device with both small footprint and high transmission efficiency. Here we propose and demonstrate the inverse design of an MIR diamond waveguide beam splitter operating at the wavelength of 15 µm with a small footprint of ∼15 µm × ∼15 µm and a total transmission efficiency above 95%. Our work paves a new avenue for the design of compact and high-efficiency MIR diamond photonic devices.

Integrated phononic waveguides in diamond

Integrated phononic waveguides in diamond

A diamond nanophotonic interface with an optically accessible deterministic electronuclear spin register

A contemporary challenge for the scalability of quantum networks is developing quantum nodes with simultaneous high photonic efficiency and long-lived qubits. Here we present a fibre-packaged nanophotonic diamond waveguide hosting a tin-vacancy centre with a spin-1/2 117Sn nucleus. The interaction between the electronic and nuclear spins results in a signature 452(7) MHz hyperfine splitting. This exceeds the natural optical linewidth by a factor of 16, enabling direct optical nuclear spin initialization with 98.6(3)% fidelity and single-shot readout with 80.0(1)% fidelity. The waveguide-to-fibre extraction efficiency of our device of 57(6)% enables the practical detection of five-photon events. Combining the photonic performance with the optically initialized nuclear spin, we demonstrate a spin-gated single-photon nonlinearity with 11(1)% contrast in the absence of an external magnetic field. These capabilities position our nanophotonic interface as a versatile quantum node in the pursuit of scalable quantum networks.

Thin-Film Waveguide Laser Spectroscopy: A Novel Platform for Bacterial Analysis.

Bacterial sensing based on quantum cascade laser spectroscopy coupled with diamond or gallium arsenide thin-film waveguides is a novel analytical tool for gaining high-resolution infrared spectroscopic information of planktonic and sessile bacteria, as shown in the present study for Escherichia coli. During observation periods of up to 24 h, diamond and gallium arsenide thin-film waveguide laser spectroscopy was compared to information obtained via conventional Fourier transform infrared spectroscopy. The proliferation behavior of E. coli at those surfaces was complementarily investigated using atomic force microscopy and scanning electron microscopy.

Modular chip-integrated photonic control of artificial atoms in diamond waveguides

A central goal in creating long-distance quantum networks and distributed quantum computing is the development of interconnected and individually controlled qubit nodes. Atom-like emitters in diamond have emerged as a leading system for optically networked quantum memories, motivating the development of visible-spectrum, multi-channel photonic integrated circuit (PIC) systems for scalable atom control. However, it has remained an open challenge to realize optical programmability with a qubit layer that can achieve high optical detection probability over many optical channels. Here, we address this problem by introducing a modular architecture of piezoelectrically actuated atom-control PICs (APICs) and artificial atoms embedded in diamond nanostructures designed for high-efficiency free-space collection. The high-speed four-channel APIC is based on a splitting tree mesh with triple-phase shifter Mach–Zehnder interferometers. This design simultaneously achieves optically broadband operation at visible wavelengths, high-fidelity switching (>40dB) at low voltages, submicrosecond modulation timescales (>30MHz), and minimal channel-to-channel crosstalk for repeatable optical pulse carving. Via a reconfigurable free-space interconnect, we use the APIC to address single silicon vacancy color centers in individual diamond waveguides with inverse tapered couplers, achieving efficient single photon detection probabilities (∼15%) and second-order autocorrelation measurements g(2)(0)<0.14 for all channels. The modularity of this distributed APIC–quantum memory system simplifies the quantum control problem, potentially enabling further scaling to thousands of channels.

Espresso Science: Laser-Based Diamond Thin-Film Waveguide Sensors for the Quantification of Caffeine.

Diamond thin-film waveguides with a nanocrystalline diamond layer of approximately 20 μm thickness were used in the mid-infrared regime in combination with quantum cascade lasers to detect the IR signature of caffeine. The diamond thin-film waveguides were fundamentally characterized with respect to their morphological properties via AFM and SEM. Theoretical simulations confirmed the feasibility of using a larger sensing area of approximately 50 mm2 compared to conventionally used strip waveguides. A comprehensive and comparative analysis confirmed the performance of the diamond thin-film-waveguide-based sensing system vs data obtained via conventional attenuated total reflection Fourier transform infrared spectroscopy using a single-bounce diamond internal reflection element. Hence, the utility of innovative diamond thin-film-waveguide-based sensors coupled with quantum cascade laser light sources has been confirmed as an innovative analytical tool, which may be used in a wide range of application scenarios, ranging from environmental to medical sensing, taking advantage of the robustness and inertness of nanocrystalline diamond.

Analysis of ridges and grooves shape in grating coupler for optimization of integrated optics sensor structures.

The paper presents a theoretical analysis of a sensor structure based on a planar waveguide and grating coupler designed to determine selected physical properties of blood – hemoglobin concentration and oxidation level. In particular analysis were focused on optimization of selected geometrical properties of grating coupler (shape of ridges and grooves) to obtain maximum efficiency of uncoupling of light from the sensor structure. The analysis were carried out for three type of ridges and grooves shape in grating coupler: rectangular, triangular and sinusoidal. Full Text: PDF ReferencesI. . Singh, A.Weston, A. Kundur, G. Dobie, Haematology Case Studies with Blood Cell Morphology and Pathophysiology; Elsevier: Amsterdam, The Netherlands, (2017). DirectLink P. Jarolim, M. Lahav, SC. Liu, J. Palek, "Effect of hemoglobin oxidation products on the stability of red cell membrane skeletons and the associations of skeletal proteins: correlation with a release of hemin", Blood 76, 10 (1990). CrossRef E. Beutler, J. Waalen, "The definition of anemia: what is the lower limit of normal of the blood hemoglobin concentration?", Blood 107, 5 (2006). CrossRef M. Kiroriwal, P. Singal M. Sharma, A. Singal, "Hemoglobin sensor based on external gold-coated photonic crystal fiber", Optics & Laser Technology 149, 107817 (2022). CrossRef A. A. Boiarski, J. R. Busch, B. S. Bhullar, R. W. Ridgway, V. E. Wood, "Integrated optic sensor with macro-flow cell", Proc. SPIE Integrated Optics and Microstructures 1793 (1993). CrossRef L. Cheng, S. Mao, Z. Li, Y. Han and H. Y. Fu, "Grating Couplers on Silicon Photonics: Design Principles, Emerging Trends and Practical Issues", Micromachines 11, 666 (2020). CrossRef P. Struk, "Design of an Integrated Optics Sensor Structure Based on Diamond Waveguide for Hemoglobin Property Detection", Materials 12, 175 (2019). CrossRef P. Struk, "Numerical analysis of integrated photonics structures for hemoglobin sensor application", Phot. Lett. Poland 12, 2 (2020). CrossRef P.V. Lambeck, "Integrated optical sensors for the chemical domain", Meas. Sci. Technol. 17, (2006). CrossRef W. Lukosz, "Integrated optical chemical and direct biochemical sensors", Sens. Actuators B Chem 29 (1995). CrossRef P. Struk, T. Pustelny, K. Gołaszewska,E. Kaminska, M.A. Borysiewicz, M. Ekielski, A. Piotrowska, "Hybrid photonics structures with grating and prism couplers based on ZnO waveguides", Opto-Electron. Rev. 21, (2013). CrossRef P. Struk, "Design of an integrated optics sensor structure for hemoglobin property detection", Proc. SPIE 11204, (2019). CrossRef OptiFDTD Technical Background and Tutorials - Finite Difference Time Domain Photonics Simulation Software, Optiwave Systems Inc. (2008). DirectLink K. Yee, "Cutoff Frequencies of Eccentric Waveguides", IEEE Transactions 14, 3 (1966). CrossRef

Nonlinear optics in diamond-fin photonic nanowires: soliton formation and frequency comb generation.

We present a detailed study of the nonlinear optical properties of newly developed subwavelength diamond-fin waveguides, along with an analysis of soliton generation and pulse spectral broadening in these structures. Our rigorous mathematical model includes all the key linear and nonlinear optical effects that govern the pulse dynamics in these diamond waveguides. As a relevant application of our investigations, we demonstrate how these waveguides can be employed to efficiently generate frequency combs in the visible spectral domain.

Development of hard masks for reactive ion beam angled etching of diamond.

Diamond offers good optical properties and hosts bright color centers with long spin coherence times. Recent advances in angled-etching of diamond, specifically with reactive ion beam angled etching (RIBAE), have led to successful demonstration of quantum photonic devices operating at visible wavelengths. However, larger devices operating at telecommunication wavelengths have been difficult to fabricate due to the increased mask erosion, arising from the increased size of devices requiring longer etch times. We evaluated different mask materials for RIBAE of diamond photonic crystal nanobeams and waveguides, and how their thickness, selectivity, aspect ratio and sidewall smoothness affected the resultant etch profiles and optical performance. We found that a thick hydrogen silesquioxane (HSQ) layer on a thin alumina adhesion layer provided the best etch profile and optical performance. The techniques explored in this work can also be adapted to other bulk materials that are not available heteroepitaxially or as thin films-on-insulator.

Generation of Greenberger-Horne-Zeilinger states for silicon-vacancy centers using a decoherence-free subspace

Generating Greenberger-Horne-Zeilinger (GHZ) states of solid-state spins is of great significance for quantum metrology and quantum error correction. We propose here an efficient scheme for generating high fidelity GHZ states in a solid-state setup where multiple silicon-vacancy (SiV) centers are embedded in a quasi-one-dimensional acoustic diamond waveguide. The lattice distortion gives rise to a strong strain coupling between the orbital degree of freedom of SiV centers and the continuum phonon modes. Due to the permutation symmetry, we can take advantage of the decoherence-free subspace to avoid dissipation. Under the quantum Zeno regime, two control fields are used to achieve a ladderlike coupling structure in decoherence-free subspace along with an off-resonant two-photon Raman transition process. We calculate the pulse sequences for $N=4$ and at the same time analyze the effect of different collective decay rates. Moreover, we consider the disorder in the imperfect position of SiV centers and the inhomogeneous strain coupling. This paper may provide a feasible protocol for the generation of GHZ states in a solid-state system.

Spatially dense integration of micron-scale devices from multiple materials on a single chip via transfer-printing

The heterogeneous integration of devices from multiple material platforms onto a single chip is demonstrated using a transfer-printing (TP) technique. Serial printing of devices in spatially dense arrangements requires that subsequent processes do not disturb previously printed components, even in the case where the print head is in contact with those devices. In this manuscript we show the deterministic integration of components within a footprint of the order of the device size, including AlGaAs, diamond and GaN waveguide resonators integrated onto a single chip. Serial integration of semiconductor nanowire (NW) using GaAs/AlGaAs and InP lasers is also demonstrated with device to device spacing in the 1 μm range.

Suspended nanocrystalline diamond ridge waveguides designed for the mid-infrared

A comprehensive study and design of air-clad suspended ridge diamond waveguides for operation across the 2.5–16 µm spectral range is presented, specifically targeting nanocrystalline diamond (NCD) thin films directly grown on silicon substrates. Three film thicknesses of 520, 1000 and 2000 nm are considered, to cover overlapping sub-bands of 2.5–5, 4–9 and 8–16 µm, respectively. Within each sub-band, the waveguide dimensions for single mode quasi-TE operation are found and the waveguide material losses and bending losses are estimated at each design point. In addition, in each case the minimum required undercut depth and etch hole placement for optical isolation of the waveguide mode from the silicon substrate is also quantified. We also estimate the losses associated with scattering from surface roughness, which is an unavoidable byproduct of the NCD thin film growth process. Our results indicate that despite the relatively low film thickness-to-wavelength ratio, mechanically stable waveguides with good optical confinement and low material and bending losses can be realised to cover the full 2.5–16 µm range. In addition, scattering loss estimations predict a drastic drop in roughness-induced scattering losses above 6 µm, even for relatively rough films. In addition to highlighting the utility of suspended NCD as a versatile platform for mid-infrared integrated photonics, the approaches and results presented here can be used to inform the design of suspended air-clad waveguides in other material platforms.

Preparation of spin squeezed state in SiV centers coupled by diamond waveguide* *Project supported by the National Natural Science Foundation of China (Grant No. 11664029) and the Inner Mongolia Natural Science Foundation, China (Grant No. 2021MS01012).

Spin squeezing is a fascinating manifestation of many-particle entanglement and one of the most promising quantum resources. In this paper, we propose a novel realization of a solid-state quantum spin squeezing by applying SiV centers embedded in a diamond waveguide with the help of a microwave field. The phenomena about the generation of spin squeezing are analyzed numerically in Markovian environments. Our analysis shows that spin squeezing can be generated with the microwave field’s help under some realistic conditions, despite the presence of dephasing and mechanical damping. This solid-state spin squeezing based on SiV centers in diamonds might be applied to magnetometers, interferometry, and other precise measurements.

Design and optimization of diamond mid-infrared phase shifter

Herein, the mid-infrared (7.7–13.7 μm) diamond-based phase shifter was designed and optimized by finite-element analysis. The ridge-shaped diamond waveguide is designed and doped to form the internal p–n structure, and the internal carrier distribution is changed by applying forward and reverse voltages to change the effective refractive index to achieve the effect of π-phase shift. The results show that when p-doping concentration is 4 × 1017 cm−3 and n doping concentration is 1 × 1018 cm−3, upon the reverse voltage (8 V) is applied, the change of the real part of effective refractive index (ΔR) is 1.6 × 10−5, and the length of the phase shifter (L) required to realize the π-phase shift is 241 mm; upon the forward voltage (–8 V) is applied, ΔR increases to 3.2 × 10−4, and the length of the phase shifter required is shortened to 12.03 mm. Such a short length is relatively easy in industrial production. In order to make the refractive index distribution more uniform, the carrier concentration has been optimized as 1 × 1017 cm−3 for p-type and 4 × 1017 cm−3 for n-type, respectively.

High sensitivity infrared spectroscopy with a diamond waveguide on aluminium nitride

Mid-infrared waveguide spectroscopy promises highly sensitive detection and characterization of organic molecules. Different material combinations for waveguides and cladding have been demonstrated with promising results, each with its own strengths and weaknesses in terms of sensitivity, transmission window and robustness. In this article we present a 5 μm thick diamond planar waveguide on aluminium nitride cladding, using a new fabrication and polishing method. Diamond has a very wide transmission window in the infrared, and its hardness and high chemical stability allows for chemistries and cleaning protocols that may damage other materials. With an aluminium nitride cladding the waveguide has a useable range between 1000 and 1900 cm-1, which we demonstrate using a tunable quantum cascade laser (QCL). This is a large improvement over silicon dioxide cladding. Compared to previously demonstrated free-standing diamond waveguides, the robustness of the sensor is greatly improved, which allows for a thinner diamond layer and increased sensitivity. The new waveguide was used in a QCL-based optical setup to detect acetone in deuterium oxide and isopropyl alcohol in water. The measurements showed higher sensitivity and lower noise level than previous demonstrations of mid-infrared diamond waveguides, resulting in a two orders of magnitude lower detectable concentration.

Nanoscale localization of the near-surface nitrogen vacancy center assisted by a silicon atomic force microscopy probe

The nitrogen vacancy (NV) center in diamond has wide applications in sensing, imaging and quantum information processing. One of the bases of these applications is to localize the NV center in diamond with high precision. In this work we demonstrate a method for nanoscale imaging and locating near-surface NV centers on diamond waveguides based on an atomic force microscopy (AFM) combined confocal system. The resulted lateral resolution for imaging the NV center is 31.6 nm and the precision of locating the NV center in diamond is 0.7 nm. Finally, the position of the NV center is indicated in AFM images of the diamond waveguide. These results provide a useful characterization tool for optimizing the diamond nanostructure for quantum information processing and quantum sensing.