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A laser Doppler velocimeter system for measuring groundwater velocity
Optics & Laser Technology
Abstracts
Multiplexed optical fibre interferometer and its application to temperature measurement
Growth and photorefractive properties of a-axis Ce doped strontium barium niobate (SBN) single-crystal fibres
Katsutoshi Hamano *, Ichirou Yamaguchi t
Yasuyuki Sugiyama, Shogo Yagi, Itaru Yokohama* and lwao Hatakeyama
*Faculty of Science, G a k u s h u i n University, t O p t i c a l Engineering L a b o r a t o r y , The Institute o f Physical a n d Chemical Research ( R I K E N ) , J a p a n
N T T Interdisciplinary Research Laboratories, tronics Laboratories, J a p a n
l l t h Meeting o n Lightwave Sensing Technology. J a p a n e s e Society o f Lightwave Sensing Technology, J a p a n Society o f Applied Physics
l l t h Meeting o n Lightwave Sensing Technology. Japanese Society o f Lightwave Sensing Technology, J a p a n Society o f Applied Physics
An interferometric sensor is proposed which is composed of a bundle of single-mode optical fibres and enables parallel measurements at several points. The optical fibres, each of which senses physical perturbations at separated points, are assembled at their exit ends. The interference pattern arising from superposition of light emanating from them is detected by a TV camera whose output is Fourier analysed by a computer. The phase change of the Fourier component gives the change in optical paths of each fibre and hence in such physical quantities as temperature, pressure and strain. Temperature measurement at two points on a plastic cylinder, whose end is heated periodically, is carried out. From the delay time of the temperature variation at these points, the thermal conductivity of the cylinder materials is derived.
Fibre type photorefractive crystals are attractive in that they provide strong optical field confinement which reduces the required light source power and a longer interaction length which allows high angular selectivity in holographic multiplex recording. We describe both the growth of cerium-doped strontium barium niobate (Ce: SBN60) singlecrystal fibres with the laser heated pedestal growth (LHPG) method and their photorefractive properties. Experimental data on the photorefractive sensitivity of the fibres grown along the a-axis (a-axis fibres) support the predicted superior sensitivity of a-axis fibres to c-axis fibres because the photorefractive effect in a-axis fibres can be based on the largest r33 of the SBN single crystals. In addition, a fine image reconstructed from a hologram stored in an a-axis fibre is demonstrated.
*Opto-elec-
Photorefractive reflection grating in BaTiO3 Toshihisa Yamashita, Tokuyuki Honda *, Hirokazu Matumoto *
Interferometric measurements of gravitational waves
Suzuki M o t o r C o r p o r a t i o n , *National Research L a b o r a t o r y of Metrology, J a p a n
Ken-ichi Ueda, Noboru Uehara Institute for Laser Science, University o f E l e c t r o - C o m m u n i cations, J a p a n l l t h Meeting o n Lightwave Sensing Technology. Japanese Society of Lightwave Sensing Technology, J a p a n Society o f Applied Physics Optical technologies related to the gravitational wave detection are reviewed. In spite of the huge energy, it is extremely difficult to detect the gravitational wave generated in super novae. In order to detect gravitational waves from a super galaxy group, the sensitivity should be higher than 10 -22. A large interferometer is a possible solution if we can develop the light source, mode cleaner optics, free-mass optical cavity, anti-vibration systems operating at their quantum or their optical limits. In this paper, we report the present status of the technological development of ultra-stabilized lasers, ultra-high quality optics, and high-power lasers for gravitational wave measurements.
R. Uma Maheswari, H. Kadono, T. Jaaskelainen D e p a r t m e n t o f Physics, University o f Joensuu, F i n l a n d 1 l th Meeting on Lightwave Sensing Technology. Japanese Society o f Lightwave Sensing Technology, J a p a n Society o f Applied Physics Recently, it has been reported that a Chinese tea dissolved in alcohol can produce very strong phase modulation. In this research work, we propose a self-aligning phase filter utilizing the phase modulation capability of Chinese tea. We have analysed the spatial resolution characteristics in order to investigate the origin behind the optical non-linearity of Chinese tea. A theoretical model has been presented based on the effects of thermal and density gradients. Our experimental results show clear evidence for the existence of density variation. Finally, some experimental evidence showing the wavelength-dependent nature of the phase modulation characteristic has been presented.
136
Two-beam coupling and self-pumped phase conjugation in BaTiO 3 are investigated in reflection-grating geometries. The power coupling constant is measured for two counterpropagating laser beams as a function of the beam angle. It is shown that the maximum coupling constant is as high as 16cm-L A self-pumped phase-conjugate mirror based on reflection gratings is fabricated in a ring geometry. The build-up time of the phase-conjugate wave is less than 0.1 s for 10 mW input power.
A laser Doppler velocimeter system for measuring groundwater velocity Fumiaki Hirano and Akira Saito Institute o f Technology, Shimizu C o r p o r a t i o n , J a p a n l l t h Meeting o n Lightwave Sensing Technology. Japanese Society of Lightwave Sensing Technology, J a p a n Society of Applied Physics
Nonlinear optical properties of Chinese tea extract
0030-3992/94/020136-02
l l t h Meeting on Lightwave Sensing Technology. J a p a n e s e Society o f Lightwave Sensing Technology, J a p a n Society of Applied Physics
This paper presents a technique for measuring groundwater velocities using a laser Doppler velocimeter (LDV). The LDV system has a rotating grating disc which functions both as a beam-splitter and as a frequency shifter for low velocities in order to determine the direction of velocity. The photon-counting method is used for processing the LDV signal. The LDV system is applied to sedimentation velocity measurement of 49.4 ILm polystyrene particles. It is confirmed that low speeds and the direction of velocity can be measured by the LDV system. Furthermore, the LDV system is proposed for low velocity measurements of groundwater in a borehole (groundwater laser Doppler velocimeter, GLDV). The GLDV system can be applied to groundwater velocity measurement in a borehole which is a minimum diameter of 66 mm and a maximum length of 200 m. The GLDV system has several sensors which can measure the direction, the temperature and the water pressure as well as velocities of groundwater, and two packers positioned at the upper and lower sides of a probe. The probe is fixed to arbitrary position by the packers.
@ 1994 B u t t e r w o r t h - H e i n e m a n n ktd Optics & Laser Technology Vol 26 No 2 1994
Abstracts
Multiplexed optical fibre interferometer and its application to temperature measurement
Growth and photorefractive properties of a-axis Ce doped strontium barium niobate (SBN) single-crystal fibres
Katsutoshi Hamano *, Ichirou Yamaguchi t
Yasuyuki Sugiyama, Shogo Yagi, Itaru Yokohama* and lwao Hatakeyama
*Faculty of Science, G a k u s h u i n University, t O p t i c a l Engineering L a b o r a t o r y , The Institute o f Physical a n d Chemical Research ( R I K E N ) , J a p a n
N T T Interdisciplinary Research Laboratories, tronics Laboratories, J a p a n
l l t h Meeting o n Lightwave Sensing Technology. J a p a n e s e Society o f Lightwave Sensing Technology, J a p a n Society o f Applied Physics
l l t h Meeting o n Lightwave Sensing Technology. Japanese Society o f Lightwave Sensing Technology, J a p a n Society o f Applied Physics
An interferometric sensor is proposed which is composed of a bundle of single-mode optical fibres and enables parallel measurements at several points. The optical fibres, each of which senses physical perturbations at separated points, are assembled at their exit ends. The interference pattern arising from superposition of light emanating from them is detected by a TV camera whose output is Fourier analysed by a computer. The phase change of the Fourier component gives the change in optical paths of each fibre and hence in such physical quantities as temperature, pressure and strain. Temperature measurement at two points on a plastic cylinder, whose end is heated periodically, is carried out. From the delay time of the temperature variation at these points, the thermal conductivity of the cylinder materials is derived.
Fibre type photorefractive crystals are attractive in that they provide strong optical field confinement which reduces the required light source power and a longer interaction length which allows high angular selectivity in holographic multiplex recording. We describe both the growth of cerium-doped strontium barium niobate (Ce: SBN60) singlecrystal fibres with the laser heated pedestal growth (LHPG) method and their photorefractive properties. Experimental data on the photorefractive sensitivity of the fibres grown along the a-axis (a-axis fibres) support the predicted superior sensitivity of a-axis fibres to c-axis fibres because the photorefractive effect in a-axis fibres can be based on the largest r33 of the SBN single crystals. In addition, a fine image reconstructed from a hologram stored in an a-axis fibre is demonstrated.
*Opto-elec-
Photorefractive reflection grating in BaTiO3 Toshihisa Yamashita, Tokuyuki Honda *, Hirokazu Matumoto *
Interferometric measurements of gravitational waves
Suzuki M o t o r C o r p o r a t i o n , *National Research L a b o r a t o r y of Metrology, J a p a n
Ken-ichi Ueda, Noboru Uehara Institute for Laser Science, University o f E l e c t r o - C o m m u n i cations, J a p a n l l t h Meeting o n Lightwave Sensing Technology. Japanese Society of Lightwave Sensing Technology, J a p a n Society o f Applied Physics Optical technologies related to the gravitational wave detection are reviewed. In spite of the huge energy, it is extremely difficult to detect the gravitational wave generated in super novae. In order to detect gravitational waves from a super galaxy group, the sensitivity should be higher than 10 -22. A large interferometer is a possible solution if we can develop the light source, mode cleaner optics, free-mass optical cavity, anti-vibration systems operating at their quantum or their optical limits. In this paper, we report the present status of the technological development of ultra-stabilized lasers, ultra-high quality optics, and high-power lasers for gravitational wave measurements.
R. Uma Maheswari, H. Kadono, T. Jaaskelainen D e p a r t m e n t o f Physics, University o f Joensuu, F i n l a n d 1 l th Meeting on Lightwave Sensing Technology. Japanese Society o f Lightwave Sensing Technology, J a p a n Society o f Applied Physics Recently, it has been reported that a Chinese tea dissolved in alcohol can produce very strong phase modulation. In this research work, we propose a self-aligning phase filter utilizing the phase modulation capability of Chinese tea. We have analysed the spatial resolution characteristics in order to investigate the origin behind the optical non-linearity of Chinese tea. A theoretical model has been presented based on the effects of thermal and density gradients. Our experimental results show clear evidence for the existence of density variation. Finally, some experimental evidence showing the wavelength-dependent nature of the phase modulation characteristic has been presented.
136
Two-beam coupling and self-pumped phase conjugation in BaTiO 3 are investigated in reflection-grating geometries. The power coupling constant is measured for two counterpropagating laser beams as a function of the beam angle. It is shown that the maximum coupling constant is as high as 16cm-L A self-pumped phase-conjugate mirror based on reflection gratings is fabricated in a ring geometry. The build-up time of the phase-conjugate wave is less than 0.1 s for 10 mW input power.
A laser Doppler velocimeter system for measuring groundwater velocity Fumiaki Hirano and Akira Saito Institute o f Technology, Shimizu C o r p o r a t i o n , J a p a n l l t h Meeting o n Lightwave Sensing Technology. Japanese Society of Lightwave Sensing Technology, J a p a n Society of Applied Physics
Nonlinear optical properties of Chinese tea extract
0030-3992/94/020136-02
l l t h Meeting on Lightwave Sensing Technology. J a p a n e s e Society o f Lightwave Sensing Technology, J a p a n Society of Applied Physics
This paper presents a technique for measuring groundwater velocities using a laser Doppler velocimeter (LDV). The LDV system has a rotating grating disc which functions both as a beam-splitter and as a frequency shifter for low velocities in order to determine the direction of velocity. The photon-counting method is used for processing the LDV signal. The LDV system is applied to sedimentation velocity measurement of 49.4 ILm polystyrene particles. It is confirmed that low speeds and the direction of velocity can be measured by the LDV system. Furthermore, the LDV system is proposed for low velocity measurements of groundwater in a borehole (groundwater laser Doppler velocimeter, GLDV). The GLDV system can be applied to groundwater velocity measurement in a borehole which is a minimum diameter of 66 mm and a maximum length of 200 m. The GLDV system has several sensors which can measure the direction, the temperature and the water pressure as well as velocities of groundwater, and two packers positioned at the upper and lower sides of a probe. The probe is fixed to arbitrary position by the packers.
@ 1994 B u t t e r w o r t h - H e i n e m a n n ktd Optics & Laser Technology Vol 26 No 2 1994