Substantial developments have been achieved in the synthesis of chemical vapour deposition (CVD) diamond in recent years, providing engineers and designers with access to a large range of new diamond materials. CVD diamond has a number of outstanding material properties that can enable exceptional performance in applications as diverse as medical diagnostics, water treatment, radiation detection, high power electronics, consumer audio, magnetometry and novel lasers. Often the material is synthesized in planar form; however, non-planar geometries are also possible and enable a number of key applications. This paper reviews the material properties and characteristics of single crystal and polycrystalline CVD diamond, and how these can be utilized, focusing particularly on optics, electronics and electrochemistry. It also summarizes how CVD diamond can be tailored for specific applications, on the basis of the ability to synthesize a consistent and engineered high performance product.

In order to improve the performance of existing technologies based on single crystal diamond grown by chemical vapour deposition (CVD), and to open up new technologies in fields such as quantum computing or solid state and semiconductor disc lasers, control over surface and bulk crystalline quality is of great importance. Inductively coupled plasma (ICP) etching using an Ar/Cl gas mixture is demonstrated to remove sub-surface damage of mechanically processed surfaces, whilst maintaining macroscopic planarity and low roughness on a microscopic scale. Dislocations in high quality single crystal CVD diamond are shown to be reduced by using substrates with a combination of low surface damage and low densities of extended defects. Substrates engineered such that only a minority of defects intersect the epitaxial surface are also shown to lead to a reduction in dislocation density. Anisotropy in the birefringence of single crystal CVD diamond due to the preferential direction of dislocation propagation is reported. Ultra low birefringence plates (< 10 -5 ) are now available for intra-cavity heat spreaders in solid state disc lasers, and the application is no longer limited by depolarisation losses. Birefringence of less than 5×10 -7 along a direction perpendicular to the CVD growth direction has been demonstrated in exceptionally high quality samples. † Corresponding author 2 of 25 1.

Defects causing colour in nitrogen-doped chemical vapour-deposited (CVD) diamond can adversely affect the exceptional optical, electronic and spintronic properties of the material. Several techniques were used to study these defects, namely optical absorption spectroscopy, thermoluminescence (TL) and electron paramagnetic resonance (EPR). From our studies, the defects causing colour in nitrogen-doped CVD diamond are clearly not the same as those causing similar colour in natural diamonds. The brown colour arises due to a featureless absorption profile that decreases in intensity with increasing wavelength, and a broad feature at 360 nm (3.49 eV) that scales in intensity with it. Another prominent absorption band, centred at 520 nm (2.39 eV), is ascribed to the neutral nitrogen-vacancy-hydrogen defect. The defects responsible for the brown colour possess acceptor states that are 1.5 eV from the valence band (VB) edge. The brown colour is removed by heat treatment at 1600 ° C, whereupon new defects possessing shallow (<1 eV) trap states are generated.

In this paper, we analyse the prospects for using nitrogen-vacancy centre (NV) containing diamond as a laser gain material by measuring its key laser related parameters. Synthetic chemical vapour deposition grown diamond samples with an NV concentration of ~1 ppm have been selected because of their relatively high NV concentration and low background absorption in comparison to other samples available to us. For the samples measured, the luminescence lifetimes of the NV- and NV0 centres were measured to be 8±1 ns and 20±1 ns respectively. The respective peak stimulated emission cross-sections were (3.6±0.1)×10-17 cm2 and (1.7±0.1)×10-17 cm2. These measurements were combined with absorption measurements to calculate the gain spectra for NV- and NV0 for differing inversion levels. Such calculations indicate that gains approaching those required for laser operation may be possible with one of the samples tested and for the NV- centre

CommuniCationbeen investigated. [33][34][35][36][37][38] Pulsed laser sequences [33][34][35][36][37] were used to measure Rabi oscillations between different spin ground states, and scanning probe techniques [37] were used to achieve nanoscale resolution. For many practical applications, however, wide field imaging and a simple experimental procedure are beneficial. To accomplish this, we opt for continuous wave laser excitation [35,38] to measure the spin populations of NVs in the presence of microwave fields using a conventional inverted microscope. In this way, we demonstrate wide-field imaging of microwave fields over a 200 × 200 μm 2 area with submicrometer spatial resolution, and spectral analysis of the microwave field with a resolution bandwidth of 460 kHz (i.e., the linewidth of NV). Minimum detectable microwave power of tens of nanowatts and a large dynamic range of over 33 dB in microwave power is obtained. Importantly, by using a bias magnetic field we could control the microwave frequency that NV centers are sensitive to-via Zeeman effect-over a frequency range of 170 MHz (potentially up to 100 GHz (ref.[35])). In addition, we demonstrate a high frequency sensitivity of 2.5 kHz Hz −1/2 for a single frequency-modulated microwave signal detection.A schematic of our apparatus is depicted in Figure 1a (see Figure S1 in the Supporting Information for the detailed experimental setup). A diamond chip containing a thin layer of NV centers with NV density of 3-4 ppm and linewidth of 460 kHz (see the Experimental Section for detail) contributes to spatial and spectral resolutions and signal-to-noise ratio. This diamond chip is closely placed on top of a microwave circuit under investigation, allowing near field imaging of microwave fields. An inverted optical microscope is used to deliver green (532nm) laser probe light and NV fluorescence (600-750 nm) is collected through the same objective. The collected light is filtered and focused onto an electron-multiplying charge coupled device (EM-CCD) for imaging. An electromagnet is used to provide a bias DC magnetic field B 0 that controls the frequency splitting ν 0 between the NV's spin 0 ground state |0> g and the spin -1 ground state |- − is the gyromagnetic ratio. For simplicity, in this work we align B 0 with one of possible NV orientations and focus on states |-1> g and |0> g , only. The spectral analysis of an unknown microwave field is accomplished by scanning ν 0 over a wide frequency range, by sweeping a voltage applied to the electromagnet, while monitoring the NV fluorescence intensity. As illustrated in Figure 1b, when the microwave frequency f RF is resonant with ν 0 , the NV is driven from |0> g to |-1> g by the microwave magnetic field with polarization perpendicular Spatial and spectral analysis of electromagnetic fields [1] at microwave frequencies is crucial for many applications, spanning a wide range of disciplines. Examples include the study of quantum electromagnetic metamaterials, [2,3] nanomaterials, [4] magnonics, [5][6][7] integrated cir...

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Microwave assisted chemical vapour deposited bulk diamond products have been used in a range of high power laser systems, due to low absorption across a range of wavelengths and exceptional thermal properties. However the application of polycrystalline products has frequently been limited to applications at longer wavelengths or thermal uses outside of the optical path due to the birefringence and scatter that are intrinsic properties of the polycrystalline materials. However, there are some solid state structures, including thin disc gain modules and amplifiers, that will gain significantly in terms of potential output powers if diamond could be used as a heat spreader in the optical path as well as a heat spreader on the rear surface of the disk. Therefore single crystal grades of diamond have been developed that overcome the limitations of the polycrystalline material, with low absorption, low scatter and low birefringence grades for demanding optical applications. We will present new data, characterising the performance of these materials across infra-red and visible wavelengths with absorption coefficient measured by laser calorimetry at a range of wavelengths from 1064 nm to 452 nm.