A study of 222Rn concentration of salty underground water and spring water in Jeju,Korea

Journal of Radioanalytical and Nuclear Chemistry - The efficiency transfer procedure from a geometry where a volume source was placed directly on the endcap of a germanium detector to three...     

Transmittance Characteristics of Buckled Fabry--Perot Tunable Filter with Membrane Structure

A wavelength tunable thermo-optic filter has been designed and fabricated for 1550 nm transmission. It has a Fabry--Perot resonator at the center with two sets of distributed Bragg reflector mirrors at both ends. The filter is fabricated as a free-standing membrane of alternating poly-Si and SiO₂ films surrounded by a thick silicon frame. The membrane is buckled due to the residual stress. Because of the buckling effect, high tuning efficiency of more than 0.17 nm/°C is observed. When the filter has a buckled surface, the incident light normal to the filter should have a range of non-zero angle of incidence to the membrane, which is dependent on the degree of buckling that depends again on the temperature. The transmittance calculations which integrate each incoming ray from a different incident angle show good qualitative agreement with the temperature dependence of the center wavelength and bandwidth.