With the excitation of a 978 nm laser, the upconversion (UC) emissions of the YVO4: Er3+, Yb3+, Cr3+ nanoparticles include three emission bands located at 524, 552 and 658 nm, respectively. The UC emission characterization confirms that the UC emission of the YVO4: Er3+, Yb3+ nanoparticles can be modulated by the doping of the Cr3+ ions, the increase of the incident laser power and the change of the laser pulse-width. With the doping of the Cr3+ ions, the two green emissions decrease because of the energy transfer from the Er3+ states H211/2 and S3/24 to the Cr3+ ions. With the increase of the incident laser power, the two green emissions increase due to the decrease of the transfer rate of the energy transfer path to the state F9/24 of the Er3+ ions. With the increase of the incident laser pulse-width from 0.2 to 6 ms the intensity ratio of the emission at 524 nm to the emission at 658 nm increases from 0.063 to 0.19, which is due to the number accumulation at the state H211/2 due to the small transfer rate from the Er3+ state H211/2 to the Cr3+ ions. The experimental results confirm that the concentration of the Cr3+ ions has less effect on the average life-time of the UC emissions at 524, 552, and 658 nm.
1-D photonic crystals with defects such as (L1H1)mLCH2(L2H2)n are investigated. The bandgap edge transmission peak is narrowed when the couple layer LC and the cover layer H2(L2H2)n are added to the photonic crystal (L1H1)m. Three different structures are studied. Structure A is not suitable for the tunable filter, which has two discrete tuning regions. Structures B and C provide good optical tuning methods: large dynamic range (>150 nm), narrow bandwidth [full-width at half maximum (FWHM) is about 2 nm], and good tuning linearity. These structures can be easily fabricated by the surface micromachined technique.
Polyimide has been an important sacrificial layer material in the MEMS switch. Polyimide can be spun and photographied on silicon substrate. NaOH liquid can etch and develop polyimide. Then it needs to cure. After MEMS switch are manufactured, polyimide must be removed. The different cure temperature and time impacts the character of polyimide. The experiment result shows that it is easy to remove and can be lithographed. So it is suitable for microwave device. In this paper, refers that polyimide can be etched by NaOH, O2 and CF4.
Photonic crystal with defects such as (L1H1)m LCH2(L2H2)n is investigated in this paper. The band gap edge transmission peak is narrowed when the couple-layer LC and the cover layer H2(L2H2)n are added to the photonic crystal (L1H1)m.
Two different structures were studied in thip paper. Structure A is not suitable for the tunable filter, which has two discrete tuning regions. Structure B provides a good optical tuning method: large dynamic range (>150 nm), narrow bandwidth (FWHM is about 2 nm) and good tuning linearity. This kind of structure can be fabricated by the surface micromachined technique easily.
In this paper we demonstrated a micromechanical optical modulator fabricated by surface micromechanical techniques. This modulator is optimized for a wavelength of 1.3 micrometers and intended for a fiber-to-the-home system. The modulation voltage is between 10 - 30 V, and at this modulation voltage modulator can work stably for long time in a wide frequency range.
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