Micro Optical-Interference-Plate Featuring Highly Efficient Diamagnetic Rotation of Biogenic Crystals

Autor: Etsuhiro Muneyama, Takayuki Kimura, Hironori Asada, Kengo Kishimoto, Masakazu Iwasaka, Masahiro Inoue, Tomohito Sogame, Tsuyoshi Koyanagi
Rok vydání: 2018
Předmět:
Zdroj: IEEE Transactions on Magnetics. 54:1-4
ISSN: 1941-0069
0018-9464
DOI: 10.1109/tmag.2018.2833207
Popis: Optical interference, which enhances or reduces intensity of light propagating, is very important for many kinds of shape analysis methods. It will be available to detect a morphology change in micro- to nano-scale by using optical interference when we can obtain a new optical material from the animal kingdom. This paper focused on the light interference in biogenic guanine crystals which is derived from fish skin/scale. So far, it has been reported that two cross-stacked guanine crystals show stripe patterns which are produced by the optical interference between guanine crystals [1]. In this study, we have found that a very clear moire effect pattern is generated on a single guanine crystal plate combining with the mirror surface substrate. The observation system is consisted with telecentric lens and coaxial vertical illumination using blue LED. Guanine crystals in water are set on a mirror polishing Si substrate. Figure 1(a) shows the optical image of guanine crystal plates in water using our observation system. It can be clearly seen that homogeneous light and shade stripe patterns are observed on the plates when the surface of the guanine plates are parallel to the Si substrate reflecting that their very flat surface morphology. By contrast, when the guanine crystals in water are set on the substrates having the diffused reflection surface such as the black vinyl tape and Teflon plate, the light and shade stripe pattern is not observed on the single guanine crystal but observed on two crossstacked crystals as reported before (Fig.1(b)). These results suggest that moire pattern on the guanine crystal plate is perturbed or disappears when the substance or the defect which changes the reflective state of the light exists under the crystal plate. Next, we have investigated the response of guanine crystal to the magnetic field by using the moire pattern to determine that the guanine plate is parallel to the substrate. Furthermore, it makes possible to estimate the quite small angle between the guanine crystals and substrate surface from the pattern period of moire stripes measured by optical observation system. The time dependences of the ratio of guanine crystals oriented in the horizontal magnetic field direction are measured by changing the magnetic field amplitude as shown in Fig.2. The experimental procedure is as follows: First, the horizontal magnetic field of 500 mT is applied and guanine crystals are aligned as the long axis of the guanine plate is parallel to the field (step A). Next, the vertical magnetic field of 200 mT is applied in order to align guanine crystals as the long axis of guanine plate is orthogonal to the field and the moire pattern disappear (step B) [2]. From this state, the horizontal magnetic field which is orthogonal to the first horizontal filed is applied and moire patterns appear again (step C). As shown in the figure, the guanine crystal plates quickly oriented to the horizontal direction with the magnetic field of 350 mT or more. This suggests that the magnetic field operates moire pattern switching which is effective to obtain a reference signal. The dependence of orientation time of guanine crystal upon the angle between the long axis of guanine plate and horizontal magnetic field and the tilt angle dependence of reflection brightness from the guanine plate will also be presented.
Databáze: OpenAIRE
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