The work presents a study of CPT-based atomic clocks with miniature rubidium vapour cells fabricated by direct optical bonding (DOB). This MEMS-compatible technology was for the first time used for making cells containing alkali-metal vapour. One of its important advantages is relatively low temperature (e.g. room temperature) required for cell assembly. The work discusses results of spectral measurements of DOB-fabricated cells with a volume of less than 1 cm3 , which provided stability of CPT-based atomic clocks better than 5·10–11 at 1 second and 5·10–12 at 24 hours. The obtained results suggest a significant potential of DOB for fabrication of alkali-metal vapour cells for broader application and cost reduction of atomic clocks.
The overview of different types of reflectometers is given. The theoretical calculation of factors, such as instability of internal reference clocks and resolution of time interval measurement device, influencing on resolution and uncertainty of signal delay (which can be calculated into length) is given. One of the ways to decrease uncertainty type A of distance measurements is suggested scheme of pulse reflectometer with multistop event timer. Due to ability of measurement averaging it is possible to reduce resolution less then 0.1 mm. In the work principle of operation of the proposed reflectometer and functional scheme are given. The impact of such factors as chromatic and polarization mode dispersion, timer trigger error, temperature fluctuations are considered. The requirements to laser module due to dispersion characteristics of measured fiber are given. The temperature variation affects mostly on signal delay in photodetector and other electronics. It also changes the delay of optical pulse in fiber coil, which is used for dead zone riddance. The results of theoretical error limits calculations for such reflectometers are presented. The results of experimental studies of reflectometer are presented. It is shown that the proposed scheme of the optical time domain reflectometer and technical solutions make possible the signal propagation delays measurements with an resolution better than 5 ps and combined uncertainty less than 100 ps.
The holographic disk reading device for recovery of CGFH is described. Principle of its work is shown. Analyzed approaches for developing algorithms, used in this device: guidance and decoding. Listed results of experimental researches.
Holographic memory systems provide such advantages as long data storage term, high data density and do not need a power supply. Instead of recording interference pattern, it is proposed to record computer generated 1D Fourier holograms (CGFH). High information density is reached by multiplexing 1D Fourier Holograms. In this work factors, which impact the quality of recorded CGFH are analyzed in mathematical modelling and experimental researches.
Holographic memory systems provide such advantages as long data storage term, high data density and do not need a power supply. But traditional holographic systems require vibration isolation and are rather complicated. So computer generation of Fourier holograms (CGFH) is proposed. Instead of recording interference pattern, it is calculated on computer. High information density is reached in new method by multiplexing 1D Fourier Holograms. Optical equivalent of the 1D Fourier holograms computer synthesis is listed. Different spatial light modulators are analyzed for displaying CGFH. System for hologram recording is described. Results of recovering information CGFH are also listed.
Computer holographic synthesis allows to significantly simplify the recording scheme of microholograms in holographic memory system as the classic high precision holographic setup based on two-beam interference is removed by simple scale reduction projection scheme. Application of computer generated 1D-Fourier holograms provides the possibility of selective reconstruction of the multiplexed holograms with different orientation of data lines by corresponding rotation of anamorphic objective (cylindrical lens), used in the read-out systems. Two configurations of read-out optical scheme were investigated by our team: full-page scheme and line-by-line scheme. In the present article we report the specificities of these schemes and consider their advantages and disadvantages. The results of experimental modeling of both read-out configurations are also presented.
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