- 著者
- Nozokido T. Ishino M. Kudo H. Bae J.
- 出版者
- American Institute of Physics
- 雑誌
- Review of scientific instruments (ISSN:00346748)
- 巻号頁・発行日
- vol.84, no.3, pp.036103, 2013-03
- 被引用文献数
- 7
Imaging of thermal radiation with a spatial resolution below the diffraction limit is demonstrated with a passive millimeter-wave microscope. This technique utilizes a sensitive radiometric receiver in combination with a scanning near-field microscope. Experiments were performed at 50 GHz (λ = 6 mm) with sample temperatures ranging from room temperature down to 160 K, and the performance was shown to be superior to that achieved with passive imaging systems in the infrared region. The images are affected by non-uniformities in the transmission of thermal radiation from the sample to the receiver via the near-field probe and the reflection of thermal radiation back to the receiver from the probe. The effects of these non-uniformities were successfully removed using a sample image acquired by active measurements using a vector network analyzer.
- 著者
- Uedono A. Shaoqiang C. Jongwon S. Ito K. Nakamori H. Honda N. Tomita S. Akimoto K. Kudo H. Ishibashi S.
- 出版者
- American Institute of Physics
- 雑誌
- Journal of applied physics (ISSN:00218979)
- 巻号頁・発行日
- vol.103, no.10, pp.104505, 2008-08
- 被引用文献数
- 22 27
A relationship between intra-4f transitions of Er and vacancy-type defects in Er-doped GaN was studied by using a monoenergetic positron beam. Doppler broadening spectra of the annihilation radiation were measured for Er-doped GaN grown by molecular beam epitaxy. A clear correlation between the defect concentration and the photoluminescence (PL) intensity was observed. The major defect species detected by positrons was identified as a Ga vacancy VGa, and its concentration increased with increasing Er concentration [Er]. For the sample with [Er]=3.3 at. %, the maximum integrated intensity of PL was observed. The VGa concentration was above 1018 cm−3 and additional vacancies such as divacancies started to be introduced at this Er concentration. For the sample with higher [Er], the PL intensity decreased, and the mean size of vacancies decreased due to an introduction of precipitates and/or metastable phases.
- 著者
- Courdurier M Noo F Defrise M Kudo H
- 出版者
- Institute of Physics
- 雑誌
- Inverse problems (ISSN:02665611)
- 巻号頁・発行日
- vol.24, no.6, pp.065001, 2008-12
- 被引用文献数
- 92 80
A case of incomplete tomographic data for a compactly supported attenuation function is studied. When the attenuation function is a priori known in a subregion, we show that a reduced set of measurements are enough to uniquely determine the attenuation function over all the space. Furthermore, we found stability estimates showing that reconstruction can be stable near the region where the attenuation is known. These estimates also suggest that reconstruction stability collapses quickly when approaching the set of points that is viewed under less than 180°. This paper may be seen as a continuation of the work 'Truncated Hilbert transform and image reconstruction from limited tomographic data' (Defrise et al 2006 Inverse Problems 22 1037). This continuation tackles new cases of incomplete data that could be of interest in applications of computed tomography.