- 著者
- Sakurai Yoko Kakushima Kuniyuki Ohmori Kenji Yamada Keisaku Iwai Hiroshi Shiraishi Kenji Nomura Shintaro
- 出版者
- Optical Society of America
- 雑誌
- Optics Express (ISSN:10944087)
- 巻号頁・発行日
- vol.22, no.2, pp.1997-2006, 2014-01
- 被引用文献数
- 3
Low-temperature photoluminescence (PL) spectra of electron-hole systems in Si nanowires (NWs) prepared by thermal oxidization of Si fin structures were studied. Mapping of PL reveals that NWs with uniform width are formed over a large area. Annealing temperature dependence of PL peak intensities was maximized at 400 °C for each NW type, which are consistent with previous reports. Our results confirmed that the micro-PL demonstrated here is one of the important methods for characterizations of
- 著者
- Nomura Shintaro Iitaka Toshiaki
- 出版者
- American Physical Society
- 雑誌
- Physical review E (ISSN:15393755)
- 巻号頁・発行日
- vol.76, no.3, pp.037701, 2007-09
A linear scale method for calculating electronic properties of large and complex systems is introducedwithin a local density approximation. The method is based on the Chebyshev polynomialexpansion and the time-dependent method, which is tested on the calculation of the electronicstructure of a model n-type GaAs quantum dot.
- 著者
- Akiyama Suguru Nomura Shintaro
- 出版者
- Optical Society of America
- 雑誌
- Optics Express (ISSN:10944087)
- 巻号頁・発行日
- vol.20, no.20, pp.21847-21859, 2012-09
- 被引用文献数
- 4
We investigated the dynamic response of a cascaded-ring-resonator-loaded Mach–Zehnder modulator (CRR-MZM), in which a number of cascaded ring resonators (RRs) are loaded in the interferometer as phase modulators. The analytical form is derived for the small-signal response of CRR-MZM using temporal-coupled-mode (TCM) theory, and its validity is confirmed by numerical calculations. It is revealed that the bandwidth of the CRR-MZM is maximized by setting proper delays in driving signals between neighboring RRs; the optimized delay is twice the photon lifetime of each RR. The calculated performances of CRR-MZMs are compared with those of standard modulators based on a single-ring-resonator (SRR) without interferometer, in terms of the modulation depth and bandwidth. For a given degree of the refractive index change in a waveguide, CRR-MZM can provide a larger modulation depth than a SRR-type modulator in frequency ranges exceeding 25 GHz.
- 著者
- Akiyama Suguru Kurahashi Teruo Morito Ken Yamamoto Tsuyoshi Usuki Tatsuya Nomura Shintaro
- 出版者
- Optical Society of America
- 雑誌
- Optics Express (ISSN:10944087)
- 巻号頁・発行日
- vol.20, no.15, pp.16321-16338, 2012-07
- 被引用文献数
- 14 2
A cascaded-ring-resonator-loaded Mach–Zehnder modulator (CRR-MZM) is presented in which a number of cascaded ring resonators (RRs) are loaded in the interferometer as phase modulators. The ability of the design to provide enhanced modulation efficiency at a wide optical bandwidth is demonstrated in comparison with a conventional single-RR-type modulator without an interferometer. The optimization of RRs for the CRR-MZM is investigated experimentally by measuring the transmission spectra in both intensity and group delay of RRs having various structural parameters. Using the optimized parameters, we fabricated a CRR-MZM with 10 cascaded RRs loaded on each arm of the interferometer on a silicon-on-insulate substrate. The RRs had pin-diodes along the waveguides, which were operated with forward bias voltage. Its modulation efficiency was enhanced by a factor of 4.4 at the expense of additional loss of less than 3.5 dB compared with a standard non-resonant MZM. 10 Gb/s-operations of CRR-MZM were successfully demonstrated using pre-emphasized RF signals with amplitude of 1.5 Vpp in a wavelength range of 2 nm.