We report the observation of optically pumped lasing in ZnO at room temperature. Thin films of ZnO were grown by plasma-enhanced molecular beam epitaxy on (0001) sapphire substrates. Laser cavities formed by cleaving were found to lase at a threshold excitation intensity of 240 kW cm−2. We believe these results demonstrate the high quality of ZnO epilayers grown by molecular beam epitaxy while clearly demonstrating the viability of ZnO based light emitting devices.

Optically pumped lasing of ZnO at room temperature

A review of quartz optically stimulated luminescence characteristics and their relevance in single-aliquot regeneration dating protocols

Distinguishing quartz and feldspar in single grain luminescence measurements

Mossbauer spectra measured by the Opportunity rover revealed four mineralogical components in Meridiani Planum at Eagle crater: jarosite- and hematite-rich outcrop, hematite-rich soil, olivine-bearing basaltic soil, and a pyroxene-bearing basaltic rock (Bounce rock). Spherules, interpreted to be concretions, are hematite-rich and dispersed throughout the outcrop. Hematitic soils both within and outside Eagle crater are dominated by spherules and their fragments. Olivine-bearing basaltic soil is present throughout the region. Bounce rock is probably an impact erratic. Because jarosite is a hydroxide sulfate mineral, its presence at Meridiani Planum is mineralogical evidence for aqueous processes on Mars, probably under acid-sulfate conditions.

https://science.sciencemag.org/content/sci/306/5702/1740.full.pdf

Jarosite and hematite at Meridiani Planum from Opportunity's Mössbauer spectrometer

Optically Stimulated Luminescence (OSL) dosimetry is attractive to the health physics and dosimetry community due to its all-optical character, fast data acquisition and the avoidance of heating the detector. Until recently there was no luminescent material sensitive enough to radiation, and at the same time suitable for stimulation with visible light, for use in this application. However, anion-deficient aluminum oxide doped with carbon (Al2O3:C) appears to be not only an extremely sensitive thermoluminescence (TL) material, but is also well-suited to OSL applications. Several OSL readout protocols have been suggested, including cw-OSL, pulsed OSL (POSL), and 'delayed' OSL (DOSL). The paper discusses the physical mechanisms that give rise to the OSL signals and the dependence of these signals upon absorbed dose. Example applications of the use of OSL from Al2O3:C in environmental radiation and ultraviolet-B dosimetry are discussed.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Optically stimulated luminescence dosimetry

The 14th International Conference on Solid State Dosimetry (SSD14)

Radiophotoluminescence from Ag-doped alkali-phosphate glass in real time, during irradiation with a LINAC x-ray beam: A comparison of simulations and experiment

Dipole-relaxation parameters for Ce3+-Fint

Deep level characterization of ZnSe grown using the seeded physical vapor transport (SPVT) technique is presented for the first time. Deep level characterization of ZnSe grown by the high pressure Bridgman technique is also presented primarily for the purpose of comparison. Thermally stimulated current (TSC) measurements reveal several hole trapping levels in the SPVT samples. TSC from the Bridgman samples, however, reveals a complex structure of overlapping peaks which we were unable to resolve. Thermoluminescence (TL) measurements on Bridgman samples indicate that the primary radiative recombination center is the Cured center (Ev + 0.71 eV). No TL was observed from the SPVT samples despite the fact that TSC and photoluminescence (PL) reveal the presence of both the Cured and Cugreen (Ev + 0.33 eV) centers in both types of sample. We present a model which describes the role of these centers in both SPVT and Bridgman samples and which explains the lack of TL from the SPVT specimens.



Tiefe Storstellen von ZnSe, das mit Hilfe des seeded physical vapor transports (SPVT) hergestellt wurde, werden hier zum ersten Mal prasentiert. Zum Vergleich werden auserdem Resultate von Messungen an ZnSe, das mit dem herkommlichen Hochdruck-Bridgman-Verfahren produziert wurde, angegeben. Thermisch-stimulierte Strommessungen (TSC) lassen darauf schliesen, das mehrere Locherhaftstellen in den SPVT-Proben vorhanden sind. Andererseits zeigen TSC-Messungen an den Bridgman-Proben, das eine komplizierte Struktur von uberlappenden Peaks, die wir nicht auflosen konnten, vorliegt. Thermo-Lumineszenz(TL)-Messungen deuten darauf hin, das das Cured-Zentrum (Ev + 0,71 eV) das primare Strahlungsrekombinationszentrum ist. An den SPVT-Proben wurde keine TL beobachtet, obwohl TSC und Photolumineszenz die Anwesenheit von sowohl Cured- als auch Cugreen(Ev + 0,33 eV)-Zentren in beiden Probentypen zeigen. Ein Modell mit diesen Farbenzentren wird prasentiert, das deren Rolle in SPVT- und in Bridgman-Proben beschreibt und das Fehlen von TL in den SPVT-Proben erklart.

Deep level characterization of seeded physical vapor transport grown ZnSe

Purpose: Recent development of wide‐beam multidetector CT and conebeam CT demands alternative methodology to CTDI. In this study, the Optically Stimulated Luminescence(OSL) technique was evaluated for CTquality assurance and dose optimization.Method and Materials:CT scans were performed on 38‐mm2 thin Luxel™ Al 2 O 3 : C dosimeters oriented in axial plane of a GE LightSpeed Ultra and at the center of a CT body dosimetry phantom. A 5‐mm beam collimation was selected to determine the energy response of the OSLdetector at 80, 120, and 140 kVp stations. mA response of the OSLdetector was evaluated from 60 to 350 mA. Helical scans of varying length coverage were also performed with the detector placed at the isocenter. The exposed OSL discs were measured using a Riso TL/OSL‐DA‐15 reader. Each OSL measurement was followed by a standard beta source irradiation and subsequent OSL measurement to normalize for the differing mass of the disks. The normalized OSL signal reading was used in the data analysis. Results: Good mA linearity was observed at all 3 kVp stations. There are discontinuities seen at ∼ 250 mA and it is known to be caused by tube focal spot change. The 120 and 140 kVp data show good correlation with ionization chamber reading. For 80 kVp, OSL signals to ion chamber readings are all higher, particularly at low mA range, indicating higher sensitivity of the OSLdetector over the ion chamber. The helical scans show an increased OSL signal with scan length and a leveling of the signal at large scan coverage. Conclusion: The OSLdetectors are of small size and responded well to CT exposure. It provides a practical technique for quantifying the dose at any location of a phantom for quality assurance and hence exhibits a potential for estimating patient organ dose.

Stephen W.S. McKeever

Papers

The 14th International Conference on Solid State Dosimetry (SSD14)

Radiophotoluminescence from Ag-doped alkali-phosphate glass in real time, during irradiation with a LINAC x-ray beam: A comparison of simulations and experiment

Dipole-relaxation parameters for Ce3+-Fint

Deep level characterization of seeded physical vapor transport grown ZnSe

TU‐E‐330D‐03: Evaluation of An OSL Dosimetry System for CT Quality Assurance and Dose Optimization