Terahertz Plasmonic Devices

Terahertz (THz) devices are designed to operate from 0.1-10 THz. The THz spectra have unique properties such as penetration through soft materials and reflecting from hard materials, which make THz technologies, a prime candidate for imaging. Plasmons are longitudinal charge oscillations in carrier rich materials. Plasmons can be generated over the channel of transistors inducing a voltage between the source-drain when conditions are satisfied. In this thesis, plasmonic devices operating in the THz region have been studied both theoretically and experimentally investigating GaN/AlGaN and Graphene based transistors. First, we report on a detailed study of dispersion properties of uniform grating gate THz plasmonic crystals, asymmetric dual grating gate plasmonic crystals and with symmetry-breaking defect-like cavities in order to understand the physics behind THz plasmons. For the first time, we defined the dispersion of plasmons in terms of effective plasmonic index. By adding an additional grating on top of the grating gate with a different periodicity, doubles the amount of absorption. Plasmons can be excited when polarization is perpendicular to the gate. We then showed focusing and exciting of THz plasmons polarization independent using circular grating lenses. Sub-micron THz ring resonators are presented showing THz guiding in plasmonic waveguides. So far, resonant sensing has been observed only at cryogenic temperatures since electron mobility is high enough at low temperatures to sustain resonant plasmonic excitation at the channel of the detector. Recently, graphene attracted the attention of the researchers because of its high mobility at room temperature. Room temperature detection has been attempted and achieved, however the detectors have very small responsivity with non-resonant behavior since the graphene is sandwiched and fabrication of such detectors in large scale is impossible with the methods used. Here, we present a resonant room temperature detection of THz with upside down free standing graphene FETs having more than a 400 quality factor, a record high number in the field which is up to 50 times higher than GaN detectors and hundreds of responsivity values with a maximum around 400 V/W which is record high for graphene (10,000 times higher than previously reported graphene detector)

Optical Switching Using Transition from Dipolar to Charge Transfer Plasmon Modes in Ge2Sb2Te5 Bridged Metallodielectric Dimers

Capacitive coupling and direct shuttling of charges in nanoscale plasmonic components across a dielectric spacer and through a conductive junction lead to excitation of significantly different dipolar and charge transfer plasmon (CTP) resonances, respectively. Here, we demonstrate the excitation of dipolar and CTP resonant modes in metallic nanodimers bridged by phase-change material (PCM) sections, material and electrical characteristics of which can be controlled by external stimuli. Ultrafast switching (in the range of a few nanoseconds) between amorphous and crystalline phases of the PCM section (here Ge2Sb2Te5 (GST)) allows for designing a tunable plasmonic switch for optical communication applications with significant modulation depth (up to 88%). Judiciously selecting the geometrical parameters and taking advantage of the electrical properties of the amorphous phase of the GST section we adjusted the extinction peak of the dipolar mode at the telecommunication band (?~1.55??m), which is considered as the OFF state. Changing the GST phase to crystalline via optical heating allows for direct transfer of charges through the junction between nanodisks and formation of a distinct CTP peak at longer wavelengths (?~1.85??m) far from the telecommunication wavelength, which constitutes the ON state

Tunable Room Temperature THz Sources Based on Nonlinear Mixing in a Hybrid Optical and THz Micro-Ring Resonator

We propose and systematically investigate a novel tunable, compact room temperature terahertz (THz) source based on difference frequency generation in a hybrid optical and THz micro-ring resonator. We describe detailed design steps of the source capable of generating THz wave in 0.5–10 THz with a tunability resolution of 0.05 THz by using high second order optical susceptibility (x(2)) in crystals and polymers. In order to enhance THz generation compared to bulk nonlinear material, we employ a nonlinear optical micro-ring resonator with high-Q resonant modes for infrared input waves. Another ring oscillator with the same outer radius underneath the nonlinear ring with an insulation of SiO2 layer supports the generated THz with resonant modes and out-couples them into a THz waveguide. The phase matching condition is satisfied by engineering both the optical and THz resonators with appropriate effective indices. We analytically estimate THz output power of the device by using practical values of susceptibility in available crystals and polymers. The proposed source can enable tunable, compact THz emitters, on-chip integrated spectrometers, inspire a broader use of THz sources and motivate many important potential THz applications in different fields

Bilateral Maxillary Sinus Osteoma

Osteomas are benign tumors characterized by proliferation of compact or spongy bone. The most common location is themandible, followed by the sinuses. These tumors grow slowly, are often asymptomatic, and are often discovered asincidental radiological findings. Osteomas are mostly seen in the frontal sinus, then in the ethmoid and maxillarysinuses, and very rarely in the sphenoid sinus.Symptoms occur when osteomas obstruct the opening of the sinus or strikeadjacent orbital or intracranial structures. A case of bilateral maxillary sinus is presented with the literature.<br style="font-variant-numeric: normal; font-variant-east-asian: normal; line-height: normal; text-align: -webkit-auto; text-size-adjust: auto;"

Deep Neck Infection Caused By Wisdom Tooth

Aım: Our study was presented to increase the awareness of deep neck infection caused by wisdom tooth. METHODSDeep neck infections are not rare and occur as a result of the several etiologies (tonsillitis, pharyngitis, foreign body ingestion,odontojenic infections). Deep neck infections are dramatically decreased today due to use of antibiotics as ıt is compared to preantibiotic era. 49 years old-male patient was consulted for Kütahya Health Science University, Dentistry faculty, oral andmaxillofacial department for deep neck abscess which can be caused by odontojenic origin. Patient was sistemicallyunremarkable. He had storyof abscess and pain related to lower left wisdom tooth region. He was smoker and had poor oralhygiene. Before the patient was referred our department, he was treated as inpatient basis at otolarnygology clinic. IV routewas opened and antibiotic (avitaz [piperasilin+tazobactam]) and paracerol were prescribed for the patient during the inpatientprocess. Patient was transferred for oral and maxillofacial department for the evaluation of causative left mesiangular impactedwisdom tooth. Surgical removal of wisdom tooth was performed and surgical region was closed primarily under the antibioticcovarage.Result: Patient was followed strictly after the removal of wisdom tooth. After two weeks following wisdom tooth extraction,neck swelling was resoluted.Conclusıon: Odontogenic infections are the most common causes of deep neck infections in adults. Not only early diagnosisbut also antimicrobial and surgical therapy need to treat deep neck infections of odontogenic origin. Early recognition ofinflamation’s focus is key for management of patient. Patient should be treated with experienced clinician trained in themanagement of airway problems. </p

Maxillary Sınus Mucocele

Paranasal sinus mucoceles are benign, slow-growing, locally enlarged masses filled with mucus and surrounded byepithelium. Chronic sinus inflammation, surgical operations and allergic diseases are mostly thought to cause theformation of paranasal sinus mucoceles.The formation of fibrotic bands between the anterior and posterior walls of thesinus and disrupting normal drainage has been expressed as the formation mechanism of maxillary sinusmucocele.Aggressive mucoceles can lead to destruction of the sinus wall. Giant maxillary sinus mucoceles leading tobone destruction are very rare in patients who have not had previous nasal or sinus surgery. Computed Tomography (CT)is an important diagnostic tool in determining the borders of the lesion and evaluating the characteristics of thepreoperative lesion. In this study, a case with a large maxillary mucocele that caused intraoral swelling is presented. Thecase was reviewed with its clinical features and radiological findings. </p

Bilateral Accessory Mental Foramen

Aim. Accessory mental foramen (AMF) is a not common anatomical variation. During the surgical procedures involving themandible such as implant surgery, periapical surgery, jaw surgeries, and periapical surgery and enucleation of pathologiesat the mental region, obvious attention should be given to prevent postoperative sequelae. Case Report.Orthopantomograph (OPG) is routinely taken to visualize the maxillofacial region at a dental clinic. OPG shows exactlyupper and lower jaw and teeth but superficially reveals some pathology or anatomic variation. It misses sometimes ananatomic landmark such as AMF. As the surgery is planned to a maxillofacial region, a detailed knowledge should beknown before going into surgery to not interfere with anatomic landmarks. A 52-year-old male patient was referred toKütahya Health Science University Dental Hospital, Turkey, to rehabilitate his bilateral partial edentulous lower jaw region.Implant surgery was planned in our patient. OPG was taken to evaluate the maxillofacial region but was unremarkable.Before the implant surgery, CBCT was obtained from our patient. CBCT and a three-dimensional reconstructed model ofthe male patient showed bilateral accessory mental foramen (AMF). Conclusion. Accessory mental foramen (AMF) carriesadditional innervation to the chin, mandibular anterior gingiva, and mental region. Reflection and protection of the AMFduring the surgery can prevent hemorrhage and neurosensory disturbance at the mental region and can improve quality oflife for the patient. CBCT has higher precision but also a higher price and radiation dose. Although anatomical variationsare uncommon, they can be found on digital panoramic radiographs but in limited percentage. </p

DEEP NECK INFECTION CAUSED BY WISDOM TOOTH

Our study was presented to increase the awareness of deep neck infection caused by wisdom tooth. Deep neck infections arenot rare and occur as a result of the several etiologies (tonsillitis, pharyngitis, foreign body ingestion, odontojenic infections).Patient was transferred for oral and maxillofacial department for the evaluation of causative left mesiangular impacted wisdomtooth. Surgical removal of wisdom tooth was performed and surgical region was closed primarily under the antibiotic covarage.Patient was followed strictly after the removal of wisdom tooth. After two weeks following wisdom tooth extraction, neck swelling was resoluted and patient returned to daily life. Odontogenic infections are the most common causes of deep neck infectionsin adults. Not only early diagnosis but also antimicrobial and surgical therapy need to treat deep neck infections of odontogenicorigin. Early recognition of inflamation’s focus is key for management of patient.Keywords: Abscess; Wisdom tooth; Neck&nbsp;</p

BILATERAL ACCESSORY MENTAL FORAMEN

ABSTRACTAim: Accessory mental foramen(AMF) is not a common anatomical variation. During the surgical proceduresinvolving mandible such as implant surgery at mental region, obvious attentionshould be given to prevent postoperative sequale.Case report: Orthopantomograph(OPG) is routinely taken to visualize the maxillofacial region at dentalclinic. OPG shows exactly upper,lower jaw and teeth, but superficially revealsome pathology or anatomic variation. It misses sometimes &nbsp;anatomic landmark such as AMF. As the surgeryis planned to maxillofacial region, a detailed knowledge should be known beforego into surgery to not interfere with anatomic landmark. 52 years old malepatient was referred to Kütahya Health Science University Dental Hospital,Turkey to rehabilitate his bilateral partial edentulous lower jaw region.Implant surgery was planned in our patient. OPG was taken to evaluate themaxillofacial region but is was unremarkable. Before the implant surgery, CBCTwas obtained from our patient. CBCT and a- three dimensional reconstructedmodel of male patient showed bilateral accessory mental foramen (AMF).Conclusion: CBCT should beprovided before the surgical procedures involving mandible. Accessory mentalforamen (AMF)&nbsp; carries additionalinnervation to chin, mandibular anterior gingiva and mental region. Reflectionand protection of the AMF during the surgery can prevent hemorrhage, neurosensorydisturbance at mental region and can improve quality of life for patient.&nbsp;</p

Ultrawide-bandwidth on-chip spectrometer design using band-pass filters

Here, we present the design and simulation of an ultrawide-bandwidth on-chip spectrometer that can be used in various applications, e.g. spectral tissue sensing. It covers 1200 nm wavelength range (400 nm-1600 nm) with 2 nm spectral resolution. The overall design size is only 3 × 3 cm2. The ultra-wide spectral range is made possible by using novel on-chip band-pass filters for the coarse wavelength division. The fine resolution is provided by the arrayed waveguide gratings. The band-pass filter is formed by using bend waveguides and adiabatic full-couplers. The additional loss caused by the band-pass filter is relatively small. The proposed spectrometer covers entire 400 nm-1600 nm range continuously with low crosstalk values. We envision that this design can be used in several different applications including food safety, agriculture, industrial inspection, optical imaging, and biomedical research