Photon emitters in hexagonal boron nitride: creating, enhancing, and controlling optically active colour centres

In this thesis, I study photon emitters in hBN to create and control optically active colour centres. In addition, enhancing the coupling efficiency of a quantum emitter into an objective lens is studied. I present a step-by-step method for designing a bullseye Bragg grating structure to enhance the collection efficiency and increase the Purcell factor. In my design, I explore the coupling condition between the dipole and the cavity and show that the collection efficiency remains high because of exploiting a gold layer as a reflector layer. I calculate the coupling efficiency between the dipole and the cavity. I apply apodization to the grating in the bullseye structure to achieve higher collection efficiency. I investigate different approaches, including treatment, local strain using nanostubs, annealing and ion irradiation to generate defect centres in hBN. I use a combination of strain and plasma/annealing treatment to generate reproducible defect centres in hBN. I discovered that consecutive annealings at medium temperature on a single flake could create ensembles of defects, while single annealing at high temperatures could create narrower linewidth defects, that some of them showed power saturation behaviours. I investigate fluence and ion energy for Kr+ irradiated sample. My studies show that the fluence of 10^12 cm^-2 with an ion energy of 150-200 eV can create single defect-like emitters. Subsequent annealing on these samples showed one sign of a narrow linewidth emitter in the highest energy sample. Moreover, we investigate the electron spin properties of VB- centres in ensembles of defects in a C-implanted hBN sample. We report that the dephasing time of the Rabi oscillation and Ramsey interferometry at 90 mT are around 30 ns and 3 ns, respectively. We apply the spin-echo sequence to the VB- centres and achieve a spin-echo coherence time of 100 ns at 90 mT

Lateral Growth of Three-Dimensional Turbidity Current for Supercritical Initial Conditions

The aim of this paper is to investigate the lateral growth of an unsteady turbulent inclined turbidity current. To do so, the Buckingham Π theorem together with a dimensional analysis are implemented to derive two appropriate relations, one of which relates the current width to the current length and the other one expresses the current width in terms of time. The coefficients of the two relations are determined experimentally. Based on the results obtained, three different regimes namely, inertia-viscous as the first regime, buoyancy-viscous, and gravity-viscous as the second and third regimes are distinguished within the current. The experimental results indicate that the lateral growth rate in the first regime is less than that in the second one. Based on the results obtained, the lateral growth in some particular regions is independent of slope, concentration, and volumetric flow rate variations

Schema modes in cluster B personality disorders

Summary Aim: The present study aimed to investigate the role of schema modes in cluster B personality disorders. Materials and methods: The participants were 220 individuals -38 men and 137 women -selected from psychiatric and psychological clinics in Tabriz, Iran. Among the participants, 153 individuals were diagnosed with cluster B personality disorder (44 with borderline disorder, 16 with antisocial disorder, 56 with histrionic disorder and 37 with narcissistic personality disorder). The remaining 67 participants had no personality disorder. The diagnosis was based on the Structured Clinical Interview for DSM-IV Axis II disorders (SCID-II). All participants (with or without personality disorder) were assessed with Millon Clinical Multiaxial Inventory-III (MC-MI-III) and Schema Mode Inventory (SMI). Results: Vulnerable, angry and impulsive child modes are predictors of borderline personality disorder, and angry child, self-soother and healthy adult modes are predictors of antisocial personality disorder. The impulsive and happy child, the attack-bully and healthy adult schema modes predict histrionic personality disorder. Finally, the angry child, happy child, self-soother and self-aggrandizer schema modes could predict narcissistic personality disorder. Conclusions: Special schema modes have a role in explaining cluster B personality disorders, and yet these disorders may overlap with regard to some dimensions, especially in terms of cognitions and beliefs. This can be interpreted as a lack of specificity in categorical classification systems such as the DSM. personality disorder/cluster B/schema modes/cognitive theory of personality disorde

Bullseye dielectric cavities for photon collection from a surface-mounted quantum-light-emitter

Coupling light from a point source to a propagating mode is an important problem in nano-photonics and is essential for many applications in quantum optics. Circular "bullseye" cavities, consisting of concentric rings of alternating refractive index, are a promising technology that can achieve near-unity coupling into a first lens. Here we design a bullseye structure suitable for enhancing the emission from dye molecules, 2D materials and nano-diamonds positioned on the surface of these cavities. A periodic design of cavity, meeting the Bragg scattering condition, achieves a Purcell factor of 22.5 and collection efficiency of 80 %. We also tackle the more challenging task of designing a cavity for coupling to a low numerical aperture fibre in the near field. Using an iterative procedure, we show that apodized (non-periodic) rings can achieve a collection efficiency that exceeds the periodic Bragg cavity.Comment: 9 pages, 6 figure

Room-Temperature Quantum Emitter in Aluminum Nitride

A device that is able to produce single photons is a fundamental building block for a number of quantum technologies. Significant progress has been made in engineering quantum emission in the solid state, for instance, using semiconductor quantum dots as well as defect sites in bulk and two-dimensional materials. Here we report the discovery of a room-temperature quantum emitter embedded deep within the band gap of aluminum nitride. Using spectral, polarization, and photon-counting time-resolved measurements we demonstrate bright ($>10^5$ counts per second), pure ($g^{(2)}(0) < 0.2$), and polarized room-temperature quantum light emission from color centers in this commercially important semiconductor

Room-temperature quantum emitter in aluminum nitride

A device that is able to produce single photons is a 5 fundamental building block for a number of quantum technologies. 6 Significant progress has been made in engineering quantum emission in 7 the solid state, for instance, using semiconductor quantum dots as well 8 as defect sites in bulk and two-dimensional materials. Here we report 9 the discovery of a room-temperature quantum emitter embedded deep 10 within the band gap of aluminum nitride (AlN). Using spectral, 11 polarization, and photon-counting time-resolved measurements we 12 demonstrate bright (>105 counts s−1), pure (g2(0) < 0.2), and polarized 13 room-temperature quantum light emission from color centers in this 14 commercially important semiconductor

BPR implementation process: an analysis of key success and failure factors

This paper investigates the effects of different factors influencing on the successful implementation of the business process re-engineering (BPR) in Iran. The study selects 386 experts randomly and using some statistical tests examines the effects of four groups of factors including strategic, organizational, methodologic and technological & educational issues on the success of the BPR implementation in Iran. The study designs a questionnaire in Likert scale and distributes it among some experts where Cronbach alpha was calculated as 0.71. The implementation of Pearson correlation ratio has confirmed that technological and educational factors marinated the highest effects (r = 0.523, Sig. = 0.000) followed by strategic (r = 0.505, Sig. = 0.000), organizational (r = 0.352, Sig. = 0.000) and methodologic issues (r = 0.267, Sig. = 0.000). In addition, the implementation of Stepwise regression has confirmed that technological & educational, strategic and methodologic factors influence on BPR in Iran

Bulbourethral Sling in Men with Stress Urinary Incontinence

Objective: This study evaluated  the efficacy and safety of  the bulbourethral sling in male urinary incontinence. Materials and methods: This case series was conducted in  Imam Khomeini hospital-Tehran , between April 2001 to December 2006. Bulbourethral sling was implanted in 7  patients with stress urinary incontinence after prostate surgery. The patients were monitored and evaluated in a prospective manner. The average follow up period was 24 months. Treatment was considered to be successful if the patient stopped wearing any kind of pad and improved if the patient  was wearing only one pad daily. Results: Five patients were completely dry. One patient weared one pad daily and the last patient suffered from treatment failure. All patients who were completely dry or had improvement were satisfied and presented no obstructive or irritative urinary symptoms. Urethral erosion was not reported. The overall success rate was 85%. Conclusion: The bulbourethral sling in men has satisfying results to treat urinary incontinence