Interdigitated diamond photoconductive antennas (IPCAs) with buried pin-type graphitized electrodes have been produced and tested. Each electrode was an array of interconnected parallel pins, which were formed inside N-doped HPHT diamond by 3D laser writing with fs or ns pulses due to local diamond-graphite phase transition. IPCAs differed in the pin period, which varied from 50 to 300 µm, whereas an interelectrode distance was the same (300 µm) in all cases. Increase in the pin period caused decrease in the IPCA efficiency due to transformation of the electric field between the electrodes. Influence of the pin period was clarified via the computer modeling included electrostatic and electrodynamic solutions. Optimization of the electrode parameters has made possible to increase the maximum fluence of THz pulse up to 0.5 µJ/cm2 at the electric field strength 60 kV/cm inside diamond.

Multipulse laser irradiation can form optically isolated and negatively charged nitrogen vacancy centers (NV-) in diamonds with low nitrogen concentrations of (similar to 1 ppb). Due to its potentially low destructive nature, this technique is of current interest. This study reports on the optical and spin properties of single NV centers produced using the third harmonic (266 nm) of a 120-fs Ti:sapphire laser. Time-resolved photon counting measurements and optically detected magnetic resonance spectroscopy were employed to examine the kinetics of dipole-allowed optical transitions in laser-induced NV centers at room temperature. These methods were also used to measure their absorptive and emissive properties, and to evaluate the decoherence dynamics of their electron spin states.

A combined laser-AFM-Raman setup is applied to study nanoscale surface modifications in DLC (a-C:H) films caused by multipulse laser irradiation at low (sub-threshold) fuences. The beam of a pulsed Nd:YAG laser (wavelength lambda = 532 nm, pulse duration tau = 7 ns, pulse repetition rate f = 1-2.5 kHz) is introduced into the optical path of an atomic force microscope (AFM), matched with that of a Raman confocal microscope. Three laser-induced processes that determine nanoscale surface modifications are found to occur in laser spots: (i) annealing - resulting in subnanometer surface deepening at the spot edges, (ii) graphitization - leading to surface swelling of 5-10 nm height, and (iii) nanoablation (oxidation) - resulting in formation of microcraters of few nm to hundred nm depth in the spot center. Raman spectra confirm the surface graphitization in the spots during formation of nm-height hillocks and microcraters, evidencing a decrease of the graphitized layer thickness at lower fluences. The nanoablation rates of 4 x 10(-5)-4 x 10(-3) nm/pulse are determined for multipulse irradiation of a-C:H films at the fluences of E = 0.045-0.1 J/cm(2). The extremely low rates of laser ablation of the DLC surface are characteristic of pulsed laser-assisted oxidation with the activation energy of similar to 6.3 kcal/mol estimated from the Arrhenius plot of the ablation rate-on-fluence dependence.

Laser-induced defect formation during nanoablation of low nitrogen (<5 ppb) synthetic diamond has been investigated. The multipulse generation of single negatively charged nitrogen vacancy centers (NV-) in diamond is reported for the first time. The different doses of third harmonic pulses of an ultrafast Ti:Sapphire laser (120 fs, 266 nm) with an energy far below the graphitization threshold resulted in NV- centers located close to the irradiated surface (<10 mu m). Photoluminescence spectroscopy, scanning confocal mapping, time-resolved photon counting measurements, and optically detected magnetic resonance were used to identify the emitting centers produced during laser irradiation and to prove their singleness. In situ control of single NV- laser generation was demonstrated.

A comparative study of optical breakdown in several CVD and HPHT single crystals has been performed with IR femtosecond pulses, which are widely used for diamond bulk processing. The breakdown thresholds for the diamond surface and bulk are measured and then compared with the morphology of the laser-modified regions formed during the breakdown process. The highest level of the bulk breakdown threshold is found to be typical for the HPHT crystals, whereas for the CVD crystals breakdown threshold varies greatly. It is assumed that certain defects assembled in microbunches of various sizes may decrease considerably the diamond breakdown threshold. The nature of these defects and the mechanism of the threshold reduction are under study.

The morphology and crystal structure of Au nanoparticles obtained by irradiating a solution of hydrochloroauric acid HAuCl4 with laser pulses have been investigated by transmission electron microscopy, electron diffraction, and electron tomography. Along with round and shapeless particles, characterized by a cubic structure with twins, there are flat particles with trigonal morphology. They have a layered microstructure, with alternation of face-centered cubic and close-packed hexagonal crystal structures of layers oriented parallel to the base prism planes.

Diamond-based X-ray luminescent composites are robust materials to be used in synchrotrons and free-electron lasers to detect and visualize high-intensity X-ray beams. Such composites consist of luminescent rare-earth (RE) particles embedded into an X-ray transparent diamond matrix. In this work, polycrystalline diamond composites with embedded particles of EuF 3 , SrF 2 :Eu and YAG:Ce were grown by microwave plasma CVD using diamond seeds with an average particle size difference of two orders of magnitude: from 5 nm up to 500 nm, with positive and negative zeta potentials. The structure, phase composition, and luminescent characteristics of the resulting composite films were investigated and analyzed. We found that various particle types can be better-suited for different composites, and the exact seeding should be selected on the case-by-case basis. The direct comparison of various diamond-based composites, grown in the identical CVD conditions but with various luminescent powders, show that YAG:Ce particles in diamond allow achieving a brighter photoluminescence (PL) in comparison to Eu-based fluorides. However, the set of fluoride powders doped with Eu 3 + ions allow obtaining unusually narrow (FWHM = 0.9 nm) and intensive line near 611 nm in PL spectra, which might be better-suited for detection and characterization applications rather than a broad peak of Ce with FWHM approximate to 120 nm.

Numerical modeling of the propagation of high-power femtosecond laser beams in a diamond crystal in the self-focusing mode is carried out. The wavelength of the modeled beams is varied in a wide range (400 nm, 532 nm, 800 nm, and 1064 nm), which covers the most common ultrashort laser systems. For all the wavelengths analyzed, a limitation in the growth of laser energy density inside the diamond crystal with increasing pulse energy is found. This effect has a certain similarity to the effect of optical limitation in laser filaments, but manifests itself outside the filament formation zone and is capable of equalizing the laser energy density, as well as the electron density, inside the extensive pre-focal region.

The work studies the effect of nitrogen additions on the secondary nucleation (nucleation) of diamond during its synthesis by chemical vapor deposition (CVD). A series of polycrystalline diamond (PCD) films 2 μm thick were grown on silicon substrates in methane-hydrogen-nitrogen gas mixtures with different nitrogen concentrations (0–1%). The structure and roughness of the grown films were studied using scanning electron microscopy (SEM) and optical profilometry. It has been shown that small additions of nitrogen play a key role in the processes of secondary nucleation of diamond, having a significant impact on the morphology of films. The comparison of the characteristics of grown PCD allowed us to find the optimal nitrogen concentration [N2] ≈ 0.2% for the formation of nanocrystalline diamond (NCD) films with low surface roughness and increased growth rate. The results obtained are expected to be used to optimize the parameters of CVD synthesis of PCD films for use as protective or friction-reducing layers, as well as for the manufacture of superhard cutting tools.

Irradiation of carbon-containing liquids by ultrashort laser pulses makes it possible to synthesize linear carbon chains (polyynes), which are of great practical interest for optics and electronics. To obtain homogeneous suspensions of polyynes, it is important to study the stability of synthesized structures and search for efficient methods of separating polyynes from laser processing byproducts. In this study polyynes were synthesized using irradiation of graphite suspensions in ethanol by a picosecond laser source (τ = 10 ps, f = 10 kHz, λ = 1064 nm). The processed suspensions contained polyynes of different length (C8H2–C16H2) and some other carbon components. The stability of polyynes was investigated, and a systematic comparison of the results of separating polyynes from other components of irradiated suspensions using filtering, sedimentation, and centrifugation was performed. The optical properties of synthesized polyynes were investigated by optical spectroscopy. The laser processing byproducts were studied using transmission electron microscopy.

Cavitation has a significant impact on pulsed laser ablation of liquids. At high repetition rates of laser pulses, it tends to hinder laser breakdown and associated processes. Here, we report on the particular case of the cavitation process occurring only at the elevated pulse repetition rate — the formation of a laser trapped bubble. The effect was observed in liquid hydrocarbons (n-hexane and ethanol) and water. The cavitation bubbles generated by picosecond pulses were captured in the caustic beam in front of the laser focus and stay there for a long time (several seconds). After growing up to ∼ 100μm in size, such a bubble completely blocks the laser radiation and stops all processes in the laser waist. The scenario of laser trapped bubble formation is investigated, the effects of pulse energy and pulse repetition rate are analyzed, and a possible mechanism for the observed effect is proposed. The special importance of laser trapped bubbles for the optimization of laser synthesis of new materials, particularly the linear carbon chains in hydrocarbons, is demonstrated.

Abstract—The effect of preliminarily implantation of chromium, titanium, molybdenum, niobium, and zirconium ions on the structure and wear resistance of cutting plates made of a WC–3

A possibility of laser printing of graphene nanoribbon pixels while preserving the integrity of the structure and shape on the silicon substrate in accordance with the irradiated laser spot is demonstrated. To provide the transfer, a target consisting of a transparent sapphire plate and an absorbing thin titanium film (500 nm thick) coated with a film consisting of graphene nanoribbons is irradiated with a KrF excimer laser (λ=248 nm, τ=20 ns). Optimal conditions for laser irradiation are determined and a technique is developed for transferring a carbon nanomaterial from a growth nickel surface to a titanium film aimed at creating stronger bonds between the nanoribbons. Raman spectroscopy confirms the preservation of structural features of the synthesized atomically precise 7-atoms-wide graphene nanoribbons with an armchair edge during laser transfer.

It is recommended to use high-speed milling to maintain an effective material removal rate and the required cutting-edge geometry. However, on the other hand, high speed increases wear, so the surface of the cutters is modified by deposition functional coatings. The wear of end mills made of CTS12D and H10F tungsten carbides during the high-speed processing of aluminum A97075 (B95T1) was compared. To increase the durability of the tools, well-proven technologies for deposition diamond-like and polycrystalline diamond coatings in microwave plasma with different film structures, which were determined by the coating growth conditions, were used. The milling cutter corner was mostly worn out, but the nature of the wear had its characteristics. It was revealed that at a forced cutting mode of about 1000 m/min, cutters made of CTS12D alloy with a nanocrystalline diamond coating with a “cauliflower” structure and with a diamond-like film showed 10% higher resistance. The primary wear mechanism was adhesive. Images of worn cutting edges were obtained using a 3D optical digital image processing system.

Conductive graphitized grooves on the dielectric surface of diamond have been created by KrF excimer laser radiation. The advantages of such a circuit board in high-field applications is rather limited because the crystal surface has a relatively low electrical breakdown threshold. To increase the electrical strength, a method of encapsulating surface conductive graphitized structures by chemical vapor deposition of an epitaxial diamond layer has been proposed and realized. The quality of the growth diamond is proved by Raman spectroscopy. A comparative study of the electrical resistivity of graphitized wires and the breakdown fields between them before and after diamond growth was carried out. The proposed technique is crucial for diamond-based high-field electro-optical devices, such as THz photoconductive emitters.

The paper reports a possibility of using high-power femtosecond laser pulses for imaging and subsequent study (by means of optical microscopy) of small-scale structural inhomogeneities in synthetic diamond single crystals. The irradiation of diamond by laser pulses in the intense self-focusing mode creates conditions for multiple optical microscopic breakdowns, whose distribution in the diamond bulk reflects spatial oscillations of local breakdown threshold. The breakdown-produced sp2 inclusions form ordered stripe microstructures with a characteristic period of several microns. It is shown that spatial oscillations of breakdown threshold correlate with changes in the local concentration of impurity–vacancy defects NV and SiV.

Diamond is a promising material for terahertz applications. In this work, we use a non-invasive optical pump–terahertz probe method to experimentally study the photoinduced carrier dynamics in doped diamond monocrystals and a new diamond-silicon composite. The chemical vapor deposited diamond substrate with embedded silicon microparticles showed two photoinduced carrier lifetimes (short lifetime on the order of 4 ps and long lifetime on the order of 200 ps). The short lifetime is several times less than in boron-doped diamonds and nitrogen-doped diamonds which were grown using a high temperature–high pressure technique. The observed phenomenon is explained by the transport of photoexcited carriers across the silicon–diamond interface, resulting in dual relaxation dynamics. The observed phenomenon could be used for ultrafast flexible terahertz modulation.

The chemical vapor deposition synthesis of periodic structures in the form of single-crystal diamond–SiO2 nanosphere composites, which exhibit the properties of photonic crystals in the visible spectral range, are reported.