Faculty of Engineering

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Research Highlights

Vision control by refraction

Light plays a crucial role in allowing most living creatures to observe their surroundings. Our eyes detect the light reflected from objects, allowing us to perceive what is around us. Light allows us to navigate through, detect objects within, and learn from our environment. Light is a type of electromagnetic wave, but the wavelength-range of visible light is what allows it to be easily perceived and detected. Whether by human eye or other detection equipment, such as semiconductor-based technology, finer details can be observed under waves with a minute wavelength of between 400 and 800 nanometers (1 nm = 10-9m) compared to long-wavelength waves. 

The appearance of an object is largely determined by the refractive index of said object. When light hits an object, part of it is reflected while the rest is refracted. This phenomenon is governed by the refractive index. A glass bottle is as nearly as transparent as air, but still visible because it possesses a higher refractive index.

At KUAS, Dr. Imai is working on the development of materials with variable, controllable refractive indexes. Materials with variable refractive indexes have already been observed, but if a substance existed whose refractive index could be rapidly and easily changed by a large degree, it may lead to world-changing discoveries. This would eventually allow objects to change their appearance like a chameleon, or make objects appear three-dimensional without the use of goggles. Furthermore, measurement methods that employ light will become faster and more reliable.

Recently, Dr. Imai has investigated oxide crystals whose refractive index changes when a voltage is applied. These crystals responds much faster than the liquid crystals used for displays, and operate at a high frequency of around 1 GHz (109 Hz). However, their actual refractive index shift is too small to be detected by the human eye (around 10-4). This had led to oxide crystals being used in limited applications, such as optical modulators in communication devices.However, in one type of crystal called KTN (KTa1-xNbxO3), a refractive index that easily exceeds 10-3 has been observed. An index shift of this magnitude can visibly deflect laser light to an angle exceeding 10 degrees, and this shift has been confirmed at frequencies up to 1 MHz (106 Hz).

These crystals’ high-speed, wide-angle deflection capabilities have already led to the development and implementation of ultra-high-accuracy, high-speed thickness gauges and other miniaturized surveying systems. Dr. Imai will continue to pursue ways to improve upon these materials, thus realizing substantially larger index shifts and allowing for the creation of innovative optical devices and systems.


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