Refractive Index Of Magnetic Fluid Research Articles

Highly sensitive magnetic field sensor based on microfiber coupler with magnetic fluid

A kind of magnetic field sensor using a microfiber coupler (MFC) surrounded with magnetic fluid (MF) is proposed and experimentally demonstrated. As the MFC is strongly sensitive to the surrounding refractive index (RI) and MF's RI is sensitive to magnetic field, the magnetic field sensing function of the proposed structure is realized. Interrogation of magnetic field strength is achieved by measuring the dip wavelength shift and transmission loss change of the transmission spectrum. The experimental results show that the sensitivity of the sensor is wavelength-dependent. The maximum sensitivity of 191.8 pm/Oe is achieved at wavelength of around 1537 nm in this work. In addition, a sensitivity of −0.037 dB/Oe is achieved by monitoring variation of the fringe visibility. These suggest the potential applications of the proposed structure in tunable all-in-fiber photonic devices such as magneto-optical modulator, filter, and sensing.

Research on temperature and magnetic field sensing characteristics of photonic crystal fiber filled with magnetic fluid

In this study, the photonic crystal fiber (PCF) air holes were filled with a kind of new functional material—magnetic fluid (MF) is presented. According to the sensitive characteristics of MF's refractive index versus temperature and magnetic field, the loss characteristic of the PCF filled with MF caused by temperature/magnetic field were analyzed theoretically by finite element method. It could be concluded that when the surrounding temperature rises from 37.5 to 80°C, the PCF loss sensitivity is about −0.167 dB/°C; when the external magnetic field rises from 20 to 300 Oe, the PCF loss sensitivity is about 0.042 dB/Oe. Besides, experiment was also carried out to verify the aforementioned results. With the same external condition, the loss sensitivity of temperature is about −0.167 dB/°C and loss sensitivity of magnetic field is about 0.046 dB/Oe. The results indicated that theoretical calculation basically agrees with the experimental verification, by which a new method and new thought for temperature and magnetic field measurement is provided. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:831–834, 2014

Magnetic field sensing based on capillary filled with magnetic fluids

A kind of magnetic field sensing system based on capillary tube filled with magnetic fluids is developed in this work. The analytical expressions for the sensing system are derived in detail. The sensitivity and other sensing properties of the system are investigated numerically and experimentally. The focal line position of the emergent light after the capillary is related with the strength of the externally applied magnetic fields and recorded and judged by the CCD to sense the magnetic field indirectly. The sensing mechanism is analyzed and ascribed to the magnetically tunable refractive index of magnetic fluids. This kind of sensing unit has the advantages of miniaturization of device, easy operation, and lower dosage of sensing media.

Magnetic field sensing based on V-shaped groove filled with magnetic fluids

A magnetic field sensing system based on V-shaped groove filled with magnetic fluids is developed in this work. The propagation direction of the emergent light after the V-shaped groove (or the position of the emergent light on the detecting plane) is related to the strength of the externally applied magnetic field. The analytical expressions for the sensing system are derived in detail. The sensitivity and other sensing properties of the sensing system are investigated numerically and experimentally. The sensing mechanism is analyzed and ascribed to the magnetically tunable refractive index of magnetic fluids.

Novel optical devices based on the tunable refractive index of magnetic fluid and their characteristics

As a new type of functional material, magnetic fluid (MF) is a stable colloid of magnetic nanoparticles, dressed with surfactant and dispersed in the carrier liquid uniformly. The MF has many unique optical properties, and the most important one is its tunable refractive index property. This paper summarizes the properties of the MF refractive index and the related optical devices. The refractive index can be easily controlled by external magnetic field, temperature, and so on. But the tunable refractive index of MF has a relaxation effect. As a result, the response time is more than milliseconds and the MF is only suitable for low speed environment. Compared with the traditional optical devices, the magnetic fluid based optical devices have the tuning ability. Compared with the tunable optical devices (the electro-optic devices (LiNbO3) of more than 10GHz modulation speed, acoustic–optic devices (Ge) of more than 20MHz modulation speed), the speed of the magnetic fluid based optical devices is low. Now there are many applications of magnetic fluid based on the refractive index in the field of optical information communication and sensing technology, such as tunable beam splitter, optical-fiber modulator, tunable optical gratings, tunable optical filter, optical logic device, tunable interferometer, and electromagnetic sensor. With the development of the research and application of magnetic fluid,a new method, structure and material to improve the response time can be found, which will play an important role in the fields of optical information communication and sensing technology.

Simultaneous identification of the low-field-induced tiny variation of complex refractive index for anisotropic and opaque magnetic-fluid thin film by a stable heterodyne Mach-Zehnder interferometer

We use a heterodyne Mach-Zehnder interferometer to simultaneously and simply measure the complex refractive index by only normal incidence on the specimen, instead of using a complicated measurement procedure or instrument that only measures the real or imaginary part of the complex refractive index. To study the tiny variation of the complex refractive index, the small complex refractive-index variation of a rare-concentration magnetic-fluid thin film, due to a weak field of less than 200 Oe, was processed by this interferometer. We also present the wavelength trend of the complex refractive index of magnetic fluids to verify the appearance of the slight change in a small wavelength range.

磁场作用下磁性液体折射率的测量

An optical alignment-free and highly accurate method is employed to measure the magnetic field-dependent refractive index of magnetic fluid (MF) in bulk. The measured refractive index decreases significantly with the increasing magnetic strength and then tends to saturate in the high intensity range. By applying a tunable magnetic field ranging between 0 and 1661 Oe, the maximum shift of the refractive index of MF in bulk is found to be 0.0231.

Origin and applications of magnetically tunable refractive indexof magnetic fluid films

When an external field was applied, the refractive index of the magnetic fluid film was observed to be modulated as the field exceeded a critical strength. We found that the stronger the magnetic field, the higher the refractive index. By taking both the formation of the columns and the variation in the concentration of the liquid phase in magnetic fluid films under external magnetic fields into account, the refractive index was calculated and compared with experimental data. When we did this, we noticed a consistency that implies that the phase separation leads to the variation in the refractive index of the magnetic fluid film as the magnetic field strength is changed. With such a property as a tunable refractive index, the feasibility of using a magnetic fluid in a tunable optical device is worthy of investigation.

Tunable refractive index of magnetic fluids and its applications

Magnetic fluid is a type of colloid consisting of magnetic nano-particles dispersed in a liquid carrier with the aid of surfactants and Brownian motion. Thus, the optical properties of magnetic fluids can be manipulated through careful selection of magnetic particles and carriers. In this work, we give an example by designing a refractive index around 1.465 at 1.557 μm wavelength with magnetic fluids composed of various carriers and particles, that could play an important role in optical fiber communication. In addition, we also show how to achieve a desired flexibility in the tunable refractive index with externally varying fields by adopting suitable magnetic fluid films. These results reveal the feasibility of developing index-match or index-tunable devices using magnetic fluids. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)