All-fiber laser wavelength measurement system based on two quadrature Faraday rotation devices

We demonstrate a method of displacement measurement based on Nd:YAG laser with birefringence external cavity. The measurement system is composed of Nd:YAG laser, a wave plate with phase retardation of 450 and an external feedback mirror. Due to the birefringence effect, the external cavity modulates the laser output intensities in the two orthogonal directions with a phase difference of 900, which is two times to that of the wave plate. Both the in-quadrature laser intensities vary one period, when the external cavity length changes λ/2. These two channel laser intensities with phase difference of 900 can be subdivided to λ/8 after 4-fold evaluation. The movement direction of external mirror can be distinguished by the lead or lag between these two channel signals. Our method can improve the resolution of displacement measurement 4 times that of conventional optical feedback, and reach 133nm for a laser wavelength of 1.064µm.

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Analysis of temperature dependence for a ratiometric wavelength measurement system using SMS fiber structure based edge filters

Optics Communications ◽

10.1016/j.optcom.2009.11.020 ◽

2010 ◽

Vol 283 (7) ◽

pp. 1291-1295 ◽

Cited By ~ 3

Author(s):

A.M. Hatta ◽

Y. Semenova ◽

G. Rajan ◽

P. Wang ◽

J. Zheng ◽

...

Keyword(s):

Temperature Dependence ◽

Measurement System ◽

Fiber Structure ◽

Wavelength Measurement

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Study on Continuous Monitoring Glucose Concentration with Terbium Gallium Garnet Crystal

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.317-319.53 ◽

2011 ◽

Vol 317-319 ◽

pp. 53-57

Author(s):

Dong Ming Li ◽

Shu Hai Jia ◽

Ji Wang

Keyword(s):

Correlation Coefficient ◽

Faraday Rotation ◽

Glucose Concentration ◽

Continuous Monitoring ◽

Closed Loop ◽

Laser Wavelength ◽

Garnet Crystal ◽

Closed Loop System ◽

Glucose Levels ◽

Measurement Results

In a continuing effort to develop a noninvasive means of monitoring glucose levels using many methods. In this paper a laser, closed-loop, system was designed and a model was developed to extract the glucose concentration information by Faraday rotation with Terbium Gallium Garnet Crystal(TGG Tb3Ga5O12). The system was tested using various concentrations of glucose. The results show that for a static, non-moving sample, glucose can be predicted. For the physiologic range (0-16mmol/l) for either laser wavelength (523nm or 632.8nm), the Correlation coefficient value (R2) are 09977and 0.9995 respectively. The measurement results of 24 hours show the system with good stability, which error is less than 0.05%.

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