arXiv subjects

J. P. Hadden

Publications and source records attributed to J. P. Hadden.

12 recordsLinked to original sources

arXiv2025

Tracking the creation of single photon emitters in AlN by implantation and annealing

In this study, we inspect and analyze the effect of Al implantation into AlN by conducting confocal microscopy on the ion implanted regions, before and after implantation, followed by an annealing step. The independent effect of annealing is studied in an unimplanted control region, which showed that annealing alone does not produce new emitters. We observed that point-like emitters are created in the implanted regions after annealing by tracking individual locations in a lithographically patterned sample. The newly created quantum emitters show anti-bunching under ambient conditions and are spectrally similar to the previously discovered emitters in as-grown AlN.

physics.app-ph↗

arXiv2023

Polarization study of single color centers in aluminum nitride

Color centers in wide-bandgap semiconductors are a promising class of solid-state quantum light source, many of which operate at room temperature. We examine a family of color centers in aluminum nitride, which emits close to 620 nm. We present a technique to rapidly map an ensemble of these single photon emitters, identifying all emitters, not just those with absorption dipole parallel to the laser polarization. We demonstrate a fast technique to determine their absorption polarization orientation in the c-plane, finding they are uniformly distributed in orientation, in contrast to many other emitters in crystalline materials.

physics.app-ph↗

arXiv2022

Design of free-space couplers for suspended triangular nano-beam waveguides

Photonic waveguides with triangular cross section are being investigated for material systems such as diamond, glasses and gallium nitride, which lack easy options to create conventional rectangular nanophotonic waveguides. The design rules for optical elements in these triangular waveguides, such as couplers and gratings, are not well established. Here we present simulations of elements designed to couple light into, and out of, triangular waveguides from the vertical direction, which can be implemented with current angled-etch fabrication technology. The devices demonstrate coupling efficiencies approaching \unit{50}{\%} for light focused from a high numerical aperture objective. The implementation of such couplers will enable fast and efficient testing of closely spaced integrated circuit components.

physics.optics↗

arXiv2022

Enhanced light collection from a gallium nitride color center using a near index-matched solid immersion lens

Among the wide-bandgap compound semiconductors, gallium nitride is the most widely available material due to its prevalence in the solid state lighting and high-speed/high-power electronics industries. It is now known that GaN is one of only a handful of materials to host color centers that emit quantum light at room temperature. In this paper, we report on a bright color center in a semi-polar gallium nitride substrate, emitting at room temperature in the near-infrared. We show that a hemispherical solid immersion lens, near index matched to the semiconductor, can be used to enhance the photon collection efficiency by a factor of $4.3\pm0.1$, whilst improving the lateral resolution by a factor equal to the refractive index of the lens.

physics.optics↗

arXiv2020

Quantum micro-nano devices fabricated in diamond by femtosecond laser and ion irradiation

Diamond has attracted great interest as a quantum technology platform thanks to its optically active nitrogen vacancy center (NV). The NV's ground state spin can be read out optically exhibiting long spin coherence times of about 1 ms even at ambient temperatures. In addition, the energy levels of the NV are sensitive to external fields. These properties make NVs attractive as a scalable platform for efficient nanoscale resolution sensing based on electron spins and for quantum information systems. Diamond photonics enhances optical interaction with NVs, beneficial for both quantum sensing and information. Diamond is also compelling for microfluidic applications due to its outstanding biocompatibility, with sensing functionality provided by NVs. However, it remains a significant challenge to fabricate photonics, NVs and microfluidics in diamond. In this Report, an overview is provided of ion irradiation and femtosecond laser writing, two promising fabrication methods for diamond based quantum technological devices. The unique capabilities of both techniques are described, and the most important fabrication results of color center, optical waveguide and microfluidics in diamond are reported, with an emphasis on integrated devices aiming towards high performance quantum sensors and quantum information systems of tomorrow

physics.optics↗

arXiv2018

Integrated waveguides and deterministically positioned nitrogen vacancy centers in diamond created by femtosecond laser writing

Diamond's nitrogen vacancy (NV) center is an optically active defect with long spin coherence times, showing great potential for both efficient nanoscale magnetometry and quantum information processing schemes. Recently, both the formation of buried 3D optical waveguides and high quality single NVs in diamond were demonstrated using the versatile femtosecond laser-writing technique. However, until now, combining these technologies has been an outstanding challenge. In this work, we fabricate laser written photonic waveguides in quantum grade diamond which are aligned to within micron resolution to single laser-written NVs, enabling an integrated platform providing deterministically positioned waveguide-coupled NVs. This fabrication technology opens the way towards on-chip optical routing of single photons between NVs and optically integrated spin-based sensing.

quant-ph↗

arXiv2018

Polarized micro-Raman studies of femtosecond laser written stress-induced optical waveguides in diamond

Understanding the physical mechanisms of the refractive index modulation induced by femtosecond laser writing is crucial for tailoring the properties of the resulting optical waveguides. In this work we apply polarized Raman spectroscopy to study the origin of stress-induced waveguides in diamond, produced by femtosecond laser writing. The change in the refractive index induced by the femtosecond laser in the crystal is derived from the measured stress in the waveguides. The results help to explain the waveguide polarization sensitive guiding mechanism, as well as providing a technique for their optimization.

physics.optics↗

arXiv2016

Diamond photonics platform enabled by femtosecond laser writing

We demonstrate the first buried optical waveguides in diamond using focused femtosecond laser pulses. The properties of nitrogen vacancy centers are preserved in the waveguides, making them promising for diamond-based magnetometers or quantum information systems.

physics.optics↗

arXiv2016

Single-crystal diamond low-dissipation cavity optomechanics

Single-crystal diamond cavity optomechanical devices are a promising example of a hybrid quantum system: by coupling mechanical resonances to both light and electron spins, they can enable new ways for photons to control solid state qubits. However, realizing cavity optomechanical devices from high quality diamond chips has been an outstanding challenge. Here we demonstrate single-crystal diamond cavity optomechanical devices that can enable photon-phonon-spin coupling. Cavity optomechanical coupling to $2\,\text{GHz}$ frequency ($f_\text{m}$) mechanical resonances is observed. In room temperature ambient conditions, these resonances have a record combination of low dissipation (mechanical quality factor, $Q_\text{m} > 9000$) and high frequency, with $Q_\text{m}\cdot f_\text{m} \sim 1.9\times10^{13}$ sufficient for room temperature single phonon coherence. The system exhibits high optical quality factor ($Q_\text{o} > 10^4$) resonances at infrared and visible wavelengths, is nearly sideband resolved, and exhibits optomechanical cooperativity $C\sim 3$. The devices' potential for optomechanical control of diamond electron spins is demonstrated through radiation pressure excitation of mechanical self-oscillations whose 31 pm amplitude is predicted to provide 0.6 MHz coupling rates to diamond nitrogen vacancy center ground state transitions (6 Hz / phonon), and $\sim10^5$ stronger coupling rates to excited state transitions.

quant-ph↗

arXiv2013

On Chip Manipulation of Single Photons from a Diamond Defect

Operating reconfigurable quantum circuits with single photon sources is a key goal of photonic quantum information science and technology. We use an integrated waveguide device comprising of directional couplers and a reconfigurable thermal phase controller to manipulate single photons emitted from a chromium related colour centre in diamond. Observation of both a wave-like interference pattern and particle-like sub-Poissionian autocorrelation functions demonstrates coherent manipulation of single photons emitted from the chromium related centre and verifies wave particle duality.

quant-ph↗

arXiv2011

Nano-fabricated solid immersion lenses registered to single emitters in diamond

We describe a technique for fabricating micro- and nano-structures incorporating fluorescent defects in diamond with a positional accuracy in the hundreds of nanometers. Using confocal fluorescence microscopy and focused ion beam (FIB) etching we first locate a suitable defect with respect to registration marks on the diamond surface and then etch a structure using these coordinates. We demonstrate the technique here by etching an 8 micron diameter hemisphere positioned such that a single negatively charged nitrogen-vacancy defect lies at its origin. This type of structure increases the photon collection efficiency by removing refraction and aberration losses at the diamond-air interface. We make a direct comparison of the fluorescence photon count rate before and after fabrication and observe an 8-fold increase due to the presence of the hemisphere.

quant-ph↗

arXiv2010

Strongly enhanced photon collection from diamond defect centres under micro-fabricated integrated solid immersion lenses

The efficiency of collecting photons from optically active defect centres in bulk diamond is greatly reduced by refraction and reflection at the diamond-air interface. We report on the fabrication and measurement of a geometrical solution to the problem; integrated solid immersion lenses (SILs) etched directly into the surface of diamond. An increase of a factor of 10 was observed in the saturated count-rate from a single negatively charged nitrogen-vacancy (NV-) within a 5um diameter SIL compared with NV-s under a planar surface in the same crystal. A factor of 3 reduction in background emission was also observed due to the reduced excitation volume with a SIL present. Such a system is potentially scalable and easily adaptable to other defect centres in bulk diamond.

quant-ph↗