Laser-based optical facility for determination of refractive index of liquids

Samedov, Farhad

doi:10.1016/j.optlastec.2004.10.005

Cited by 7 publications

(5 citation statements)

References 22 publications

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“…According to the working principles, most available methods could be roughly classified into three categories: geometrical optics, wave optics and near-field optics ͑nano-optics͒. The geometrical optics methods make use of the ray nature of the light and usually measure the refraction, 2 reflection, 3 and deflection 4,5 at the interface of the liquid sample and other reference media. As one of the most popular commercial refractometers, Abbé refractometer could reach 10 −4 RIU by using the total internal reflection phenomenon.…”

Section: Introductionmentioning

confidence: 99%

Optofluidic refractometer using resonant optical tunneling effect

et al. 2010

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This paper presents the design and analysis of a liquid refractive index sensor that utilizes a unique physical mechanism of resonant optical tunneling effect ͑ROTE͒. The sensor consists of two hemicylindrical prisms, two air gaps, and a microfluidic channel. All parts can be microfabricated using an optical resin NOA81. Theoretical study shows that this ROTE sensor has extremely sharp transmission peak and achieves a sensitivity of 760 nm/refractive index unit ͑RIU͒ and a detectivity of 85 000 RIU −1 . Although the sensitivity is smaller than that of a typical surface plasmon resonance ͑SPR͒ sensor ͑3200 nm/RIU͒ and is comparable to a 95% reflectivity Fabry-Pérot ͑FP͒ etalon ͑440 nm/RIU͒, the detectivity is 17 000 times larger than that of the SPR sensor and 85 times larger than that of the FP etalon. Such ROTE sensor could potentially achieve an ultrahigh sensitivity of 10 −9 RIU, two orders higher than the best results of current methods.

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Section: Introductionmentioning

confidence: 99%

Optofluidic refractometer using resonant optical tunneling effect

et al. 2010

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“…. For a given change in RI, a greater change in the position x of the projection of the exiting rays on the distant linear image sensor is obtained for greater m. Therefore, as an exit with m 4 is used, the obtained sensitivity of the measuring system is several times higher than that in the case of other cuvette devices [2][3][4][5][6][7][8].…”

Section: Evaluation Of the Dependence Of The Light Beam's Path On The...mentioning

confidence: 99%

“…Equation (2) shows that by choosing a suitable m the sensitivity of measurements can be increased several times compared to other optical systems using cuvettes as optical elements [2][3][4][5][6][7][8]. This provides the necessary conditions for compact design of the optical measuring device.…”

Section: Evaluation Of the Dependence Of The Light Beam's Path On The...mentioning

confidence: 99%

“…A rectangular cuvette was used and the path of the laser beam was calculated to measure the RI and the concentration of two-component solutions [4]. The same kind of cuvette was used in another optical system [5], where the plane containing the path of the laser beam was parallel to opposite walls of the rectangular cuvette.…”

Section: Introductionmentioning

confidence: 99%

“…The sensitivity of RI measurement, specified as the ratio of the change in the exiting beam deviation to the change of liquid RI, has been increased multiple times by recurring reflection and refraction of the beam on its way through the cylindrical boundary between the material of the cuvette and the liquid, as described in [1]. Unlike previous approaches for optical determination of the RI of liquids contained in cuvettes [2][3][4][5][6][7][8], the proposed approach allows the beam to cross the liquid four times or more. Two additional methods are used to enhance the quality of the measurement: a new method for detecting the position of the deviated beam projection by use of linear CMOS or CCD image sensors [10], and a new method for increasing the optical intensity of the beam exiting the cuvette [11].…”

Section: Introductionmentioning

confidence: 99%

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Determining the refractive index of liquids using a cylindrical cuvette

Vilitis

Shipkovs

Merkulov

2009

Meas. Sci. Technol.

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The refractive index of a liquid carries important information about its physical properties, including concentration and density, thus making it possible to determine and monitor the composition of the solution. This is important in fundamental research, chemical analysis and medical diagnostics, as well as in the processing and manufacturing of various substances. The authors have developed a compact and adaptable device of high sensitivity for measuring the refractive indices of both stationary liquids and continuous liquid flows. This device can be used in various technological processes requiring real-time analysis of flowing liquid substances, including aggressive compounds. The refractive index is determined by measuring the deviation of a laser beam passed through a cylindrical cuvette containing the test liquid. The magnitude of the deviation, which depends on the RI, is measured as the displacement of the transmitted beam's projection on a linear measuring element, such as a linear CMOS or CCD image sensor. In order to significantly improve the resolution and stability of RI measurements, an efficient solution has been developed, based on repeated reflection and refraction of the light beam travelling through the cylindrical cuvette with liquid. By this, deviation of the rays exiting the cuvette increases several times in respect to refractive index of the liquid. Additionally, a new method for detecting the position of the projected laser beam on a linear optical sensor is employed. Also, an increase in the intensity of the exiting rays has been achieved. By applying the techniques developed, it is possible to achieve high resolution and stability of refractive index measurements even when the distance between the image sensor and the cuvette is short. Hence, a basis for the construction of accurate and compact devices for determining the refractive indices of liquids is provided, suitable for a broad spectrum of applications.

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