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Changhe Zhou
OPTICAL MEASUREMENT TECHNIQUES USING DAMMANN GRATINGS

Optical measurement techniques using Dammann gratings and deep-etched gratings are reported. Dammann grating is a digital binary-phase diffractive optical element that can produce multiple equal intensitites in different diffractive orders. Three-dimensional objects can be measured using a Dammann grating when its surface deforms the lattice of the illumination array that is produced by a Dammann grating. A structure of three Dammann gratings can be used to characterize the ultrashort femtosecond laser pulse where one grating is used to split the ultrashort femtosecond laser pulse while the other two are used to collimate the split pulses and one of the two’s is moved along the optical axis relatively to give the controllable delay between the two split pulses. Experimental results demonstrated the effectiveness of Dammann SHG FROG (second- harmonic generation frequency-resolved optical gating) apparatus. It will also be reported that a phase-shifting measurement technique can be constructed by using three deep-etched fused silica gratings when one of the gratings is moved vertically to generate the required shifted phase between two split beams. Generally speaking, novel measurement techniques can be invented by using new diffractive optical elements.

Jianjun Ma , Yasser Chiniforooshan, Huacai Chen, Jiahua Chen, Wojtek J. Bock and Andrea Cusano
DRAMATIC IMPACT OF END-FACE-TIR AND MODE MIXING ON SIGNAL COLLECTION OF A FIBER-OPTIC EVANESCENT WAVE SENSING PLATFORM

In this paper, for the first time, we report that for a specific fiber-optic evanescent wave (EW) sensing architecture we proposed before, the total internal reflection of fluorescent signal power occurred at the fiber end face will experience enormous mode mixing when encountering roughened end face. As a result, 94% of the overall detectable power will be contributed by this effect. For a smooth fiber end face, this figure becomes mere 52%. We will interpret the mechanism behind these unusual phenomena and its significance for the performance enhancement of fiber-optic EW sensor.

Uwe Brand, Lutz Doering, Vladimir Nesterov, Febo Menelao
MICRO- AND NANOFORCE METROLOGY AT PTB


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