On February 2, Professor Nozomu Nishizawa and Professor Hiroo Sokata of the Institute for Future Industrial Technology, Tokyo Institute of Technology, Science and Technology Innovation Research Institute, and others introduced spin light-emitting diodes (spin LEDs) that emit pure circular polarization at room temperature to the world. Announced that it was created ahead of the others.
Among the various types of light used in various fields such as science, engineering, and medicine in recent years, circularly polarized light has attracted particular attention.Light that travels while the vibration surface (polarizing surface) of the light wave rotates spirally to the right or left, and is often used in the selection of optically active substances, especially in the field of synthetic chemical industry.
In the realization of room temperature circular polarization, the biggest challenges are the development of the principle to align all the directions of the rotation axes of the electrons that control the rotation direction of the spiral of circular polarization, and the non-magnetism that occurs by joining the semiconductor and magnetic metal in the element. It has been considered to be the development of a manufacturing method that eliminates the production of substances.This time, the research group succeeded in suppressing the chemical change at the junction surface even when a large current is flowing, by using the "crystalline alumina intermediate layer" originally developed by Sokata Laboratory.As a result, we were able to discover the phenomenon in which circularly polarized light is amplified by light emission under a large current.
As a result, we were the first in the world to create a spin LED that emits pure circularly polarized light at room temperature.This diode, which uses crystalline alumina for the intermediate layer, emits "unpolarized light" without polarized light, which is close to natural light when the current is small, but when the current is increased and the emission intensity is increased, it is circularly polarized light. The purity of the light increases rapidly and reaches pure circularly polarized light.From this property, it is presumed that the strong emission itself generated in the diode has the effect of amplifying circularly polarized light.
At present, the crystalline alumina intermediate layer in the device has a durability of only about one week under a large current energization state.In the future, the company aims to further improve its quality and realize an ultra-compact laser that emits circularly polarized light.In the process, the principle of amplifying circularly polarized light that was found this time may be clarified.In addition, it is expected to be applied to detailed observation of life activities, which was difficult until now, and encrypted communication using circularly polarized light.
