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- Hashemi, Seyed Ehsan, 1986, et al.
(författare)
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Triggering of guiding and antiguiding effects in GaN-based VCSELs
- 2014
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 9001
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Konferensbidrag (refereegranskat)abstract
- We show numerically that many recently proposed GaN-based VCSEL cavities, with DBR mirrors deposited onto the current aperture, balance dangerously close to the border between the guided and antiguided regime. A guided cavity is often preferred because of its lower optical loss, but a strongly antiguided cavity offers built-in modal discrimination favoring single fundamental mode operation. We show that very small changes in the VCSEL structure are sufficient to strongly change the guiding character of the VCSEL cavity, and that thermal lensing caused by device self-heating under operation can dramatically reduce the optical loss but not the modal discrimination in the antiguided cavities.
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| 5. |
- Gierl, Christian, et al.
(författare)
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Tuneable VCSEL aiming for the application in interconnects and short haul systems
- 2011
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. - 9780819484963 ; 7959
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Widely tunable vertical cavity surface emitting lasers (VCSEL) are of high interest for optical communications, gas spectroscopy and fiber-Bragg-grating measurements. In this paper we present tunable VCSEL operating at wavelength around 850 nm and 1550 nm with tuning ranges up to 20 nm and 76 nm respectively. The first versions of VCSEL operating at 1550 nm with 76 nm tuning range and an output power of 1.3mW were not designed for high speed modulation, but for applications where only stable continious tuning is essential (e.g. gas sensing). The next step was the design of non tunable VCSEL showing high speed modulation frequencies of 10 GHz with side mode supression ratios beyond 50 dB. The latest version of these devices show record output powers of 6.7mW at 20 °C and 3mW at 80 °C. The emphasis of our present and future work lies on the combination of both technologies. The tunable VCSEL operating in the 850 nm-region reaches a modulation bandwidth of 5.5GHz with an output power of 0.8mW.
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| 10. |
- Bowers, L., et al.
(författare)
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Locked doors : a survey of patients, staff and visitors
- 2010
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Ingår i: Journal of Psychiatric and Mental Health Nursing. - : Wiley. - 1351-0126 .- 1365-2850. ; 17:10, s. 873-880
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Tidskriftsartikel (refereegranskat)abstract
- Locking the door of adult acute psychiatric wards has become increasingly common in the UK. There has been little investigation of its efficacy or acceptability in comparison to other containment methods. We surveyed the beliefs and attitudes of patients, staff and visitors to the practice of door locking in acute psychiatry. Wards that previously participated in a previous study were contacted and sent a questionnaire. A total of 1227 responses were obtained, with the highest number coming from staff, and the smallest from visitors. Analysis identified five factors (adverse effects, staff benefits, patient safety benefits, patient comforts and cold milieu). Patients were more negative about door locking than the staff, and more likely to express such negative judgments if they were residing in a locked ward. For staff, being on a locked ward was associated with more positive judgments about the practice. There were significant age, gender and ethnicity effects for staff only. Each group saw the issue of locked doors from their own perspective. Patients registered more anger, irritation and depression as a consequence of locked doors than staff or visitors thought they experienced. These differences were accentuated by the actual experience of the ward being locked.
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