Diamond is one of the most promising materials for high power and extreme conditions electronics. For this to become a reality, incorporation of active dopants needs to be understood. In this article we demonstrate how cathodoluminescence spectroscopy can be used to quantify and spatially map the boron concentration in diamond. We achieve this by probing exciton dynamics outside the steady state using ultrafast electron pulses and time-resolved spectroscopy. The capture lifetime of free excitons by boron allows us to measure the impurity concentration directly, and is selectively sensitive to electrically active dopants. In addition, we update the value of the Auger lifetime of boron-bound excitons in diamond to 185±2 ps. We study different regimes of free and bound excitons dynamics by characterizing different growth sectors of the crystal, with boron concentration varying between 2.8⋅1016 and 4.7⋅1017cm−3. At higher doping levels, a regime of free-exciton-diffusion-limited relaxation is reached. Overall, this study provides new prospects for the characterization of doping in diamond, by allowing to study impurities incorporation and activation at the microscale and the impact of crystalline defects on the electrical properties, non-destructively and in a self-consistent way.

• Review of the state of the art on reactive ion etching of single crystal diamond • In-depth analysis of diamond ICP RIE process parameters • Quantitative analysis of reported etch rates, selectivity and etch depths • Comprehensive catalog of diamond ICP RIE recipes providing selection guidelines

We report on the design, fabrication and optical performance of gain mirrors in single crystal diamond substrates for vertical external cavity surface emitting lasers (VECSELs). VECSELs have gained attention recently due to their potential for high emission power in single mode with low beam divergence, yet their maximum output power remains typically limited due to thermal roll-over resulting from insufficient heat dissipation. In order to increase the heat transfer, we exploit the excellent thermal conductivity of single crystal diamond, which is assembled in direct contact with the active structure. The optical cavity is hereby defined by an output coupler and a high reflection grating structure etched into the diamond surface. We here present the design and microfabrication of a diffraction grating that was optimized to reflect light into the 0th order, therefore combining the role of a gain mirror and a heatsink at the same time. Our process involved metal mask deposition onto the diamond surface, e-beam lithography and reactive ion etching. Characterization showed reflection above 95% at a center wavelength of 1550 nm, potentially allowing the integration of the diamond mirror into a vertical external cavity surface emitting laser.

Wireless energy transmission is blooming thanks to the recent advances in high- power lasers, in which case such transmission is referred to as Laser Power Beaming (LPB). Here, we discuss the use of diamond-based VECSELs for LPB, detailing all of the advantages and the key role of diamond in these structures. Some applications, from the most accessible to the most advanced, will also be presented.

Optically-pumped vertical external cavity surface emitting lasers (VECSELs) based on flip-chip gain mirrors emitting at the 1.55-μm wavelength range are reported. The gain mirrors employ wafer-fused InAlGaAs/InP quantum well heterostructures and GaAs/AlAs distributed Bragg reflectors, which were incorporated in a linear and a V-cavity configurations. A maximum output power of 3.65 W was achieved for a heatsink temperature of 11°C and employing a 2.2% output coupler. The laser exhibited circular beam profiles for the full emission power range. The demonstration represents more than 10-fold increase of the output power compared to state-of-the-art flip-chip VECSELs previously demonstrated at the 1.55-μm wavelength range, and opens a new perspective for developing practical VECSEL-based laser system for applications such as LIDAR, spectroscopy, communications and distributed sensing.

Optically-pumped vertical external cavity surface emitting lasers (VECSELs) based on flip-chip gain mirrors emitting at the 1.55-mu m wavelength range are reported. The gain mirrors employ wafer-fused InAlGaAs/InP quantum well heterostructures and GaAs/AlAs distributed Bragg reflectors, which were incorporated in a linear and a V-cavity configurations. A maximum output power of 3.65 W was achieved for a heatsink temperature of 11 degrees C and employing a 2.2% output coupler. The laser exhibited circular beam profiles for the full emission power range. The demonstration represents more than 10-fold increase of the output power compared to state-of-the-art flip-chip VECSELs previously demonstrated at the 1.55-mu m wavelength range, and opens a new perspective for developing practical VECSEL-based laser system for applications such as LIDAR, spectroscopy, communications and distributed sensing.

Optically pumped vertical external cavity surface emitting lasers (VECSELs) based on flip-chip gain mirrors emitting at the 1.55 mu m wavelength range are reported. The gain mirrors employ wafer-fused InAlGaAs/InP quantum well heterostructures and GaAs/AlAs distributed Bragg reflectors fixed on a diamond heat-sink substrate in a flip-chip geometry, incorporated in a V-cavity configuration. A maximum output power of 3.65 W was achieved for a heatsink temperature of 11 degrees C and employing a 2.2% output coupler. The laser exhibited circular beam profiles for the full emission power range. This demonstration represents more than five-fold increase of the output power compared to the state-of-the-art flip-chip VECSELs previously reported at the 1.55 mu m wavelength range. It opens new perspectives for developing practical VECSEL-based laser systems operating at a wavelength range widely used in many applications.

The outstanding material properties of single crystal diamond have been at the origin of the long-standing interest in its exploitation for engineering of high-performance micro- and nanosystems. In particular, the extreme mechanical hardness, the highest elastic modulus of any bulk material, low density, and the promise for low friction have spurred interest most notably for micro-mechanical and MEMS applications. While reactive ion etching of diamond has been reported previously, precision structuring of freestanding micro-mechanical components in single crystal diamond by deep reactive ion etching has hitherto remained elusive, related to limitations in the etch processes, such as the need of thick hard masks, micromasking effects, and limited etch rates. In this work, we report on an optimized reactive ion etching process of single crystal diamond overcoming several of these shortcomings at the same time, and present a robust and reliable method to produce fully released micro-mechanical components in single crystal diamond. Using an optimized Al/SiO 2 hard mask and a high-intensity oxygen plasma etch process, we obtain etch rates exceeding 30 µm/h and hard mask selectivity better than 1:50. We demonstrate fully freestanding micro-mechanical components for mechanical watches made of pure single crystal diamond. The components with a thickness of 150 µm are defined by lithography and deep reactive ion etching, and exhibit sidewall angles of 82°–93° with surface roughness better than 200 nm rms, demonstrating the potential of this powerful technique for precision microstructuring of single crystal diamond.

A system of two site-controlled semiconductor quantum dots (QDs) is deterministically integrated with a photonic crystal membrane nano-cavity. The two QDs are identified via their reproducible emission spectral features, and their coupling to the fundamental cavity mode is established by emission co-polarization and cavity feeding features. A theoretical model accounting for phonon interaction and pure dephasing reproduces the observed results and permits extraction of the light-matter coupling constant for this system. The demonstrated approach offers a platform for scaling up the integration of QD systems and nano-photonic elements for integrated quantum photonics applications.

We demonstrate the fabrication of arrayed, site-controlled pyramidal InGaAs/GaAs quantum dots (QDs) grown by metalorganic vapor phase epitaxy with tailored emission energy and periods as small as 200 nm, suitable for the integration with compact photonic structures. The observed variation of the QD emission energy with the geometric parameters of the array is attributed to adatom and precursor diffusion mechanisms during epitaxial growth. By adjusting the pattern geometry, the emission energy can be tuned over a wide range of ∼80 meV around 1.4 eV, with inhomogeneous broadening <10 meV. Single photon emission of isolated QDs with gX,X(2)(0)=0.11 is demonstrated, which attests to the suitability of these QDs for nanophotonic applications.

We fabricated and studied a system comprising four site-controlled semiconductor quantum dots (QDs) embedded in a linear photonic crystal membrane cavity. The excellent position control and small spectral broadening permit coupling of the emission of all four QDs to the same photonic cavity modes. This is corroborated by co-polarization of the QD and cavity emission lines, as well as reduction in decay time, both with characteristic dependence on QD-cavity energy detuning. Scaling up to larger QD systems is discussed.

We demonstrate the self-formation of hexagonal nanotemplates on GaAs (111)B substrates patterned with arrays of inverted tetrahedral pyramids during metal-organic vapor phase epitaxy and its role in producing high-symmetry, site-controlled quantum dots (QDs). By combining atomic force microscopy measurements on progressively thicker GaAs epitaxial layers with kinetic Monte Carlo growth simulations, we demonstrate self-maintained symmetry elevation of the QD formation sites from three-fold to six-fold symmetry. This symmetry elevation stems from adatom fluxes directed towards the high-curvature sites of the template, resulting in the formation of a fully three-dimensional hexagonal template after the deposition of relatively thin GaAs layers. We identified the growth conditions for consistently achieving a hexagonal pyramid bottom, which are useful for producing high-symmetry QDs for efficient generation of entangled photons.

Using site-controlled semiconductor quantum dots (QDs) free of multiexcitonic continuum states, integrated with photonic crystal membrane cavities, we clarify the effects of pure dephasing and phonon scattering on exciton-cavity coupling in the weak-coupling regime. In particular, the observed QD-cavity copolarization and cavity mode feeding versus QD-cavity detuning are explained quantitatively by a model of a two-level system embedded in a solid-state environment.

Two site-controlled quantum dots (QDs) were integrated in a photonic crystal molecule (PCM) formed by L3 nanocavities. A statistical analysis of the coupled cavity modes demonstrated the formation of bonding and anti-bonding delocalized PCM states. Excitonic transitions belonging to each QD were identified by scanning micro-photoluminescence spectroscopy. Co-polarization of the QDs photoluminescence with the coupled cavity modes provides evidence for the simultaneous coupling of two spatially separated QDs to the same PCM mode.

We describe the fabrication, epitaxial growth and photoluminescence (PL) spectra of systems of site-controlled pyramidal quantum dots (QDs) integrated with photonic crystal (PhC) membrane cavities. The spectra of the individual QDs are characterized by scanning micro-PL spectroscopy, and the cavity modes are identified by polarization-resolved PL measurements and modeling. Weak coupling of systems incorporating up to four identifiable QDs with single modes of the PhC cavities is demonstrated.

Exciton and cavity mode (CM) dynamics in site-controlled pyramidal quantum dots (QDs), integrated with linear photonic crystal membrane cavities, are investigated for a range of temperatures and photo-excitation power levels. The absence of spurious multi-excitonic effects, normally observed in similar structures based on self-assembled QDs, permits the observation of effects intrinsic to two-level systems embedded in a solid state matrix and interacting with optical cavity modes. The coupled exciton and CM dynamics follow the same trend, indicating that the CM is fed only by the exciton transition. The Purcell reduction of the QD and CM decay times is reproduced well by a theoretical model that includes exciton linewidth broadening and temperature dependent non-radiative processes, from which we extract a Purcell factor of 17 ± 5. For excitation powers above QD saturation, we show the influence of quantum wire barrier states at short delay time, and demonstrate the absence of multiexcitonic background emission.

The fabrication and characterization of site-controlled InGaAs/GaAs quantum dots (QDs) made by MOVPE using triethylgallium (TEGa) on patterned {111}B GaAs substrates are reported. Results are compared to more traditional pyramidal QD structures grown employing trimethylgallium (TMGa). Several potential advantages of the use of TEGa are demonstrated, including more reproducible achievement of QD transitions with narrow (<100µeV) linewidths and better spectral uniformity across patterned substrates. These features are important for QD integration in optical cavities, which require both site and spectral stringent control.

We report on the effects of optical disorder on breaking the symmetry of the cavity modes of H3 photonic crystal cavities incorporating site-controlled pyramidal quantum dots (QDs) as the internal light source. The high in-plane symmetry of the polarization states of the pyramidal QDs simplifies the analysis of the polarization states of the H3 cavities. It is shown that the optical disorder induced by fabrication imperfections lifts the degeneracy of the two quadrupole cavity modes and tilts the elongation axes of the cavity mode patterns with respect to the ideal, hexagonal symmetry case. These results are useful for designing QD-cavity structures for polarization-entangled photon sources and few-QD lasers.

A new design of vertical external cavity surface emitting laser (VECSEL) with diamond-based high contrast gratings is proposed. The self-consistent model of laser operation has been calibrated based on experimental results and used to optimize the new proposed device and to perform comparative thermal and optical analysis of conventional and double-diamond high-contrast-grating VECSELs. The proposed design considerably reduces the dimensions and complexity of the device and provides up to 80% increase of the maximum emitted power as compared with the conventional design.