Increasing the photon collection rate from a single NV center with a silver mirror

In the pursuit of realizing quantum optical networks, a large variety of different approaches have been studied to achieve a single photon source on-demand. The common goal for these approaches is to harvest all the emission from a quantum emitter into a single spatial optical mode while maintaining a high signal-to-noise ratio. In this work, we use a single nitrogen vacancy center in diamond as a quantum emitter operating at ambient conditions and we demonstrate an increased photon count rate up to a factor of 1.76 by placing a silver mirror fabricated on the end facet of an optical fiber near the emitter

Detection of Vital Anatomical Landmarks in Lower Posterior Premolars and First Molar Area (BuccallyPositioned)During Different Surgical Intervention Using Cone Beam Ct Scan

Background: The mental foramen (MF) is a very important structure; to avoid any trauma to mental nerve may be occur and in order to avoid that, its position, variation in anatomy and shapes should be clearly determined before any surgical procedure. Objective: To detect the exact position of MF and thickness of cortical plates in lower premolars and first molars among the Iraqi resident. Patients and Methods: For this prospective study, a total of 92 Iraqi adults patients (51 females, 41 males; age range 18-69 years). From October 2020 to February 2021, patients aged range from 25 to 65 years old.Five types of classification we used: Type 1, MF under the root of the lower first premolar. Type 2, MF between the root of mandibular first & second   premolar. Type 3, MF below the root of the mandibular second premolar. Type 4, MF between the root of lower second premolar & first molar. Type 5, MF below the root of the lower first molar. Bone thickness is measured in the horizontal direction on the both side lingually and buccally. Results: The most common situation of the MF was below the root of lower second premolar. Conclusion: Significant difference can be noted in the mean of the distance between MF and root apex in both gender, also significant difference in mean of bone thickness noted between both genders on both sides

Localization of the position of vital anatomical structures in the lateral wall of maxillary sinus during different surgical intervention using cone beam computed tomography

Background: Proper information about the anatomy of the maxillary sinus is required to avoid any unexpected complications that may arise due to the close relation between the maxillary sinus and posterior superior alveolar artery. Objective: To the current study used cone beam computed tomography CBCT imaging to assess the position of the posterior superior alveolar artery (PSAA) in relationship to the alveolar ridge and the flour of maxillary sinus. Patients and Methods: A number of 95 Iraqi patients participated in this prospective study (53 females, 42 males; age range 20-49 years). From January 2021 to February 2022, attended a 2nd specialised dentistry institution in Baquba city for CBCT scanning for numerous diagnostic and management purposes. Results: According to our study, we detected the presences of artery in (83.68%) of the sample. females showed higher PSAA prevalence than men on both sides, and the difference was significant overall, Also, the existence of artery for each side and total in the intramembranous locating in females is greater than that in males, which may demonstrate that the probability of Bleeding and other side effects is higher in males, since the existence of artery in the intramembranous area in females will reduce the likelihood of traumatic injury throughout any surgical treatment. Conclusion: This research used CBCT to determine the precise location of PSAA in the Iraqi population. This data could assist in decreasing the likelihood of hemorrhage as well as other complications which may happen throughout any surgical treatment, such as dental implant placement, ridge expansion.As well as other surgical interventions in this region

Entwicklung und Charakterisierung eines durchstimmbaren Diodenlaser basierten Hochleistungs MOPA System

The aim of this work is to develop and characterize widely tunable high power diode lasers emitting at 976 nm, to serve in non-linear frequency conversion applications. In particular, to serve as pump sources in infrared upconversion detection systems. This is realized by a master oscillator power amplifier (MOPA) configuration, where the MO provides the wavelength stabilization and tuning, while the PA ensures power amplification to the watt level. In this thesis, two approaches of developing tunable laser sources are investigated. The first concept utilizes tunable multi-arm distributed Bragg reflector ridge waveguide (DBR-RW) lasers, while the second employ widely tunable sampled-grating (SG) lasers. In the first approach, three types of monolithic multi-arm lasers are developed: two-arm (Y-branch), four-arm and six-arm DBR-RW lasers. Among the main findings of this work, is that the performance of these lasers is strongly influenced by the intersection point between the individual arms, and is less affected by the bend structure. This is shown in a comparison between three Y-branch lasers with different S-bend (Sinus, Co-sinus and single bend) structures. The performance of these lasers varies only slightly. However, they provide reduced output power and beam quality in comparison to DBR-RW reference lasers. This deterioration is explained by the intersection point between the two laser arms. This is confirmed by passive RW simulations which show that the studied S-bend structures (alone), do not influence the beam quality. Higher order modes are first supported when combining two bend structures, in particular at the intersection point which causes the worse beam quality. Based on the findings of the Y-branch lasers, four-arm lasers with different common sections and arm curvatures are developed and characterized. The first laser have a single intersection point between all four arms, while the second laser have two separate intersection points. The latter structure provides comparable performance from all four arms. The laser with a single intersection point however, shows reduced output power and beam quality for the outer arms in comparison to the inner. This study confirms once again that the laser performance is strongly dependent on the common section and in addition, is less influenced by the arm curvature. This is seen in the comparable performance of the laser with two intersection points, which have stronger curvature for the outer arms in comparison to the inner. This is further approved by results from a six-arm laser that have three individual intersection points. This laser shows less deviation in performance between the six arms, despite the three different curvatures of the outer, middle and the inner arms. Thermal wavelength tuning of the developed laser sources is obtained by resistor based micro-heaters embedded on top of the grating sections. The characterization of these heaters demonstrate that up to 7.5 nm of tuning can be achieved from each arm of a Y-branch DBR laser. This indicates that a combined tuning of N × 7.5 nm can be obtained from a laser with N arms. This could be achieved by spectrally distancing the gratings of the each arm by 7.5 nm, and is set by the number of arms and ultimately limited by the available gain bandwidth. The second approach uses SG structures to obtain wide wavelength tuning from a single laser cavity. In this work, numerical tools and design approach are provided to obtain single mode operation over a desired wavelength tuning range. Design parameters such as grating length, period and coupling coefficients are discussed in regards to optimizing the tuning performance. Different vertical structures that can support such gratings are fabricated and characterized, among which a double quantum well (DQW) based structure, with a 1st order grating and a wide n-cladding layer is proposed. This structure provides coupling coefficients of about 250 cm-1, with a narrow far field angle of 24° at full width at half maximum. While InP based SG lasers are well established, a milestone of this work is the first time demonstration of fully functional GaAs based SG-lasers. These devices consist of four sections: a gain section, a phase section, a front and a back SG. They emits up to 70 mW of output powers, have a spectral linewidth less than 17 pm with diffraction limited beam quality. They provide up to 21 nm of discrete wavelength tuning when operating a single SG heater, with a SG mode spacing of about 2.3 nm. By operating both SG heaters, 23.5 nm of quasi-continuous tuning is obtained with a mode spacing of about 115 pm. To increase the output power of the tunable light sources, MOPA systems are developed which utilize tapered power amplifier (TPA) structures. Among the main results of this work, is the development of a hybrid MOPA system, constructed on a compact 25 mm × 25 mm conduction cooled package (CCP). This system provides an output power of 5.5 W from a nearly diffraction limited beam with M2 (1/e2) = 2.2 along the slow axis. A combined 9.7 nm of wavelength tuning is obtained from the two laser arms. Over this tuning range, a power variation less than 0.5% is observed, while a spectral linewidth small than 17 nm is maintained. Another main result is the development of a watt level SG-based MOPA system, providing narrow spectral linewidth below 17 pm together with M2 (1/e2) = 1.6 along the slow axis. More than 23 nm of quasi-continuous wavelength tuning is achieved, with a power variation between 0.5 and 1.0 W.Das Ziel der vorliegenden Dissertation ist die Entwicklung und Charakterisierung von weit abstimmbaren Diodenlaser-basierten Hochleistungslichtquellen bei einer Emissionswellenlänge von 976 nm. Ein mögliches Anwendungsgebiet dieser Laser ist der Einsatz als Pumplichtquelle für die nichtlineare Frequenzkonversion, unter anderem die Upconversion von infrarotem Licht in den sichtbaren Spektralbereich zu ermöglichen. Grundkonzept dieser Lichtquellen ist eine Master Oscillator Power Amplifier (MOPA) Konfiguration. Der MO realisiert die Wellenlängenstabilisierung und -abstimmung, während der PA die Leistungsverstärkung auf Wattniveau realisiert. In dieser Arbeit werden zwei Ansätze zur Entwicklung von weit abstimmbaren Laserquellen untersucht. Das erste Konzept verwendet thermisch abstimmbare Bragg-Spiegel Rippenwellenleiter-Laser (DBR-RW-Laser) mit mehreren über Y-Koppler kombinierten Armen. Das zweite Konzept basiert auf einem Sampled-Grating (SG)-Laser, um eine weite Wellenlängenabstimmbarkeit zu erreichen. Im ersten Ansatz werden drei verschiedene Typen von monolithischen Mehrarmlasern mit einander verglichen: Zweiarmige Y-Laser bilden die einfachste Lösung. Dazu kommen vierarmige und sechsarmige DBR-RW-Laser, die benutzt werden, um den Einfluss unterschiedlicher Krümmungen der Rippenwellenleiter und den Einfluss der Y-Koppler zu untersuchen. Zu den wichtigsten Ergebnissen dieser Arbeit gehört, dass die Leistung der untersuchten Laser wesentlich von der Form der Kopplungssektion zwischen den einzelnen Armen und weniger von der Biegestruktur beeinflusst wird. Dies wird durch einen experimentellen Vergleich zwischen drei Y-Lasern mit unterschiedlichen S-Biegestrukturen (Sinus, Cosinus und einfache Biegung) gezeigt. Diese Laser erreichen nur geringfügig unterschiedliche Ausgangsleistungen. Allerdings, verschlechtert sich die Strahlqualität und die Ausgangsleistung im Vergleich zu DBR-RW-Referenzlasern deutlich. Diese Verschlechterung kann durch Verluste in der Kopplungssektion zwischen den zwei Laserarmen erklärt werden. Durchgeführte Rechnungen basierend auf einer Simulation für passive Rippenwellenleiter bestätigten dies. Der Einfluss der untersuchten S-Biegestrukturen auf die Strahlqualität ist nur schwach. Räumliche Moden höherer Ordnung, die die Strahlqualität verschlechtern, treten dann auf, wenn zwei Biegestrukturen symmetrisch miteinander kombiniert werden. Basierend auf diesen Erkenntnissen wurden vierarmige Laserquellen mit zwei verschiedenen Kopplungssektionen und unterschiedlichen Krümmungsradien prozessiert und ihre elektro-optische, spektralen und Strahleigenschaften miteinander verglichen. Das erste Layout verfügt über einen einzigen Kopplungspunkt an dem sich alle vier Arme treffen, während das andere Design zwei getrennte Kopplungspunkte besitzt. Für letzteren erreichen alle vier Arme eine vergleichbare Leistung, während der Laser mit einem einzigen Kopplungspunkt eine verringerte Ausgangsleistung und Strahlqualität für die äußeren Laserarme im Vergleich zu den inneren Armen zeigt. Diese Untersuchung zeigt erneut, dass die Laserleistung primär von der Art der Kopplung abhängt und weniger von der Biegestruktur. Dies bestätigen Messungen für die Lichtquellen mit zwei getrennten Kopplungspunkten. Trotz unterschiedlicher Krümmungsradien wird für alle Arme die gleiche Ausgangsleistung erreicht. Weitere Untersuchungen an den sechsarmigen Lasern mit getrennten Kopplungspunkten zeigten dieses Ergebnis. Trotz der drei unterschiedlichen Krümmungsradien der äußeren, mittleren und inneren Arme, sind nur geringere Unterschiede in der Laserleistung der sechs Arme festzustellen. Die spektrale Abstimmung der Laser wird über resistive Mikroheizer realisiert, die oberhalb der DBR-Gitter in die Gittersektionen eingebettet sind. Durch Betreiben der Heizelemente ist eine Durchstimmung von bis zu 7,5 nm pro Arm erreicht worden. Für einen Laser mit N Armen ergibt sich damit, wenn der Abstand der prozessierten Gitterwellenlängen 7,5 nm beträgt, eine Abstimmung von N × 7,5 nm. Die Gesamtabstimmbarkeit ist dann durch die Anzahl der Arme bestimmt und durch die Verstärkungs-bandbreite limitiert. Beim zweiten Ansatz wird ein SG-Laser untersucht, der eine große Wellenlängenabstimmung eines einzelnen Lasers ermöglicht. Voraussetzung für das Design dieser Laser mit dem gewünschten abstimmbaren Wellenlängenbereich waren umfangreiche numerische Simulationen. Die verschiedenen Designparameter (Gitterlänge, Periode und Kopplungskoeffizient) werden im Hinblick auf die Optimierung der Laserleistung und der Durchstimmung diskutiert. Geeignete vertikale Schichtstrukturen, die die erforderlichen Gitterstrukturen ermöglichen, wurden hergestellt und charakterisiert. Favorisiert wurde dabei eine Schichtstruktur mit doppelten Quantengraben sowie einem Gitter erster Ordnung und einer breiten n-Mantelschicht. Diese Struktur liefert die notwendigen Kopplungskoeffizient von ungefähr 250 cm-1 zusammen mit einem geringen vertikalen Fernfeldwinkel von 24° (Halbwertsbreite). SG-Laser wurden bisher nur auf InP Basis realisiert. Erstmalig konnte im Rahmen dieser Arbeit funktionsfähige GaAs-basierte SG-Laserquellen demonstriert werden. Die entwickelten Laser bestehen aus vier Abschnitten: einer Gewinn-, einer Phasen-, einer vorderen und einer hinteren SG Sektion. Diese liefern Ausgangsleistungen von bis zu 70 mW und haben eine spektrale Linienbreite kleiner als 17 pm mit nahezu beugungsbegrenzter Strahlqualität. Auch hier erfolgt die Abstimmung mittels oberhalb der Gitter implementierter Heizer. Es konnte bei Betrieb eines einzelnen SG-Heizelementes eine diskrete Wellenlängenabstimmung von bis zu 21 nm erzielt werden. Der SG-Modenabstand ist hierbei etwa 2,3 nm. Bei Verwendung beider SG Heizelemente wird eine quasi-kontinuierliche Abstimmung über 23,5 nm möglich, mit einem Modenabstand von 115 pm. Um die Ausgangsleistung der abstimmbaren Lichtquellen zu erhöhen, wurden MOPA-Systeme entwickelt, bei denen Trapez-Verstärker verwendet wurden. Eines der Hauptergebnisse dieser Arbeit ist ein hybrides Y-Laser-basiertes MOPA-System auf einer Grundfläche von nur 25 mm × 25 mm auf einer Conduction Cooled Package (CCP) aufgebaut. Das MOPA-System liefert eine Ausgangsleistung von 5,5 W mit einer nahezu beugungsbegrenzten Strahlqualität mit einer Beugungsmaßzahl M2 (1/e2) = 2,2 in der lateralen Achse. Der MOPA kann entsprechend der spektralen Eigenschaften des MO über 9,7 nm abgestimmt werden. Über den gesamten Abstimmbereich ist die Leistungsvariation kleiner als 0,5\%, mit einer spektralen Breite von kleiner als 17 pm. Ein weiteres MOPA-System wurde auf Basis von SG-Lasern entwickelt. Mit diesen können Leistungen im Wattniveau bei einer Strahlqualität von M2 (1/e2) = 1,6 in der lateralen Achse erreicht werden. Wie auch der verwendete MO, lässt sich der MOPA spektral über 23 nm abstimmen bei einer spektralen Breite von unter 17 pm. Hier variiert die Ausgangsleistung über den Abstimmbereich zwischen 0,5 und 1,0 W.EC/H2020/642661/EU/Infrared sensing made visible: Combining infrared light sources and upconversion sensors for improved sensitivity in medical applications and gas analysis/Mid-TEC

Development and Characterisation of a Diode Laser Based Tunable High-Power MOPA System

The aim of this work is to develop and characterize widely tunable high power diode lasers emitting at 976 nm, to serve in non-linear frequency conversion applications. In particular, to serve as pump sources in infrared upconversion detection systems. This is realized by a master oscillator power amplifier (MOPA) configuration, where the MO provides the wavelength stabilization and tuning, while the PA ensures power amplification to the watt level. In this thesis, two approaches of developing tunable laser sources are investigated. The first concept utilizes tunable multi-arm distributed Bragg reflector ridge waveguide (DBR-RW) lasers, while the second employ widely tunable sampled-grating (SG) lasers. In the first approach, three types of monolithic multi-arm lasers are developed: two-arm (Y-branch), four-arm and six-arm DBR-RW lasers. Among the main findings of this work, is that the performance of these lasers is strongly influenced by the intersection point between the individual arms, and is less affected by the bend structure. This is shown in a comparison between three Y-branch lasers with different S-bend (Sinus, Co-sinus and single bend) structures. The performance of these lasers varies only slightly. However, they provide reduced output power and beam quality in comparison to DBR-RW reference lasers. This deterioration is explained by the intersection point between the two laser arms. This is confirmed by passive RW simulations which show that the studied S-bend structures (alone), do not influence the beam quality. Higher order modes are first supported when combining two bend structures, in particular at the intersection point which causes the worse beam quality. Based on the findings of the Y-branch lasers, four-arm lasers with different common sections and arm curvatures are developed and characterized. The first laser have a single intersection point between all four arms, while the second laser have two separate intersection points. The latter structure provides comparable performance from all four arms. The laser with a single intersection point however, shows reduced output power and beam quality for the outer arms in comparison to the inner. This study confirms once again that the laser performance is strongly dependent on the common section and in addition, is less influenced by the arm curvature. This is seen in the comparable performance of the laser with two intersection points, which have stronger curvature for the outer arms in comparison to the inner. This is further approved by results from a six-arm laser that have three individual intersection points. This laser shows less deviation in performance between the six arms, despite the three different curvatures of the outer, middle and the inner arms. Thermal wavelength tuning of the developed laser sources is obtained by resistor based micro-heaters embedded on top of the grating sections. The characterization of these heaters demonstrate that up to 7.5 nm of tuning can be achieved from each arm of a Y-branch DBR laser. This indicates that a combined tuning of N × 7.5 nm can be obtained from a laser with N arms. This could be achieved by spectrally distancing the gratings of the each arm by 7.5 nm, and is set by the number of arms and ultimately limited by the available gain bandwidth. The second approach uses SG structures to obtain wide wavelength tuning from a single laser cavity. In this work, numerical tools and design approach are provided to obtain single mode operation over a desired wavelength tuning range. Design parameters such as grating length, period and coupling coefficients are discussed in regards to optimizing the tuning performance. Different vertical structures that can support such gratings are fabricated and characterized, among which a double quantum well (DQW) based structure, with a 1st order grating and a wide n-cladding layer is proposed. This structure provides coupling coefficients of about 250 cm-1, with a narrow far field angle of 24° at full width at half maximum. While InP based SG lasers are well established, a milestone of this work is the first time demonstration of fully functional GaAs based SG-lasers. These devices consist of four sections: a gain section, a phase section, a front and a back SG. They emits up to 70 mW of output powers, have a spectral linewidth less than 17 pm with diffraction limited beam quality. They provide up to 21 nm of discrete wavelength tuning when operating a single SG heater, with a SG mode spacing of about 2.3 nm. By operating both SG heaters, 23.5 nm of quasi-continuous tuning is obtained with a mode spacing of about 115 pm. To increase the output power of the tunable light sources, MOPA systems are developed which utilize tapered power amplifier (TPA) structures. Among the main results of this work, is the development of a hybrid MOPA system, constructed on a compact 25 mm × 25 mm conduction cooled package (CCP). This system provides an output power of 5.5 W from a nearly diffraction limited beam with M2 (1/e2) = 2.2 along the slow axis. A combined 9.7 nm of wavelength tuning is obtained from the two laser arms. Over this tuning range, a power variation less than 0.5% is observed, while a spectral linewidth small than 17 nm is maintained. Another main result is the development of a watt level SG-based MOPA system, providing narrow spectral linewidth below 17 pm together with M2 (1/e2) = 1.6 along the slow axis. More than 23 nm of quasi-continuous wavelength tuning is achieved, with a power variation between 0.5 and 1.0 W