"Science" published!The Harbin Institute of Technology provides a new plan for high -purity overcoming hand -in -light sources

Recently, the team of Professor Song Qinghai, Shenzhen Campus of our school, has achieved important breakthroughs in the field of high -purity overcurrent, and uses the bound States in the Continuum (Bound States in The Continuum, BICS). , High -directional and high Q value round polarized light launch. On September 9th, the research results were published on "Science" on "Science" on "Science".

The super -integrated round polarization light source is an important part of the processing of classic optical and quantum optical information. The development of this field mainly depends on the progress of hand -based materials and hand -based optical cavity. The circular polarizing radiation realized in traditional methods generally has the characteristics of broadband and omnipotimbia, and at the same time, it has the disadvantages of large radiation angles and low circular polarization. Due to the traditional tradition Low -efficiency and energy waste caused by multi -polarizing and multi -directional radiation limits its actual application value. Although hand lasers with high circular polarization and directionality have previously reported reports, high -purity round polarization radiation can only be maintained within a certain power range, and the radiation bias has decreased sharply when the laser threshold is below the laser threshold. Therefore, there is no solution to achieve spontaneous radiation and laser of high circular polarization at the same time.

Researchers from the Shenzhen Campus and the National University of Australia used the physical characteristics of hand -based BICs to achieve high -efficiency and controllable high -purity round polarization radiation through the resonant surface.

High -purity circle polarization spontaneous radiation and laser on resonant super surface

The circular polarization of its radiation is close to 1

BICS has the polarization point of the overall number of over -top charters in momentum space, and theoretically has infinitely high Q values, so it is widely used in non -linear optics, laser and other fields. By introducing asymmetricity in the plane, the BICS mode will degenerate into the BICS mode, but it still has a high Q value. Interestingly, when introducing asymmetric in the introduction, BICS's polarizer will split into two polarizers with half -integer topological loads, and symmetrically distributed in momentum space. These two polarizers correspond to the polarization state of the left rotation and right rotation, respectively, and usually define these two points as C -point.

At point C, a certain round polarized light can be coupled to the nano structure, which produces a sharp electromagnetic field enhancement, and another kind of round polarization light and structure are completely decoupled, and the nano structure is perfectly known. This nature is widely known. However, it is rarely used in controlling the field of radiation. This is mainly because point C is usually a high -symmetrical point (GAMMA point) that can be banded from the optical crystal, which causes its Q value to be very low, and it is difficult to use to produce laser.

In order to achieve high -purity handicular radiation, it can be regulated to the strongest point of the local state density by regulating point C to the local state density. For example, if you move point C to the Gamma point, the Q value of the hand -standard BICS can also reach the maximum value. According to Fermi Golden, at this time, the radiation of a certain circular polarization is greatly enhanced, and the radiation of another round polarization is inhibited, and the Q value and spontaneous radiation rate will be quickly decreased as the angle increases, so therefore at the increase, so in this way Near Gamma Points can achieve high purity and directional circles.

The position of the control C in the momentum space is closely related to maximizing the inherent handling. In principle, it can be achieved by breaking the mirror symmetry inside and outside the surface at the same time. Therefore, in this study, the researchers introduced the asymmetric asymmetry outside the face while breaking the symmetry in the face, that is, the tilt of the structure. For each fixed asymmetry in the surface, there is a corresponding asymmetry outside the surface that can move the C point to the GAMMA point, and the asymmetry in the face is small, and the asymmetry inside and outside the surface is asymmetry. Maintaining linear relationships can easily achieve the maximum inherent hands.

In the experiment, the researchers prepared the super surface through the inclined reaction ion etching process, and gave it a characteristic of the circular polarization of 0.98, the far -field divergent angle of 1.06 degrees, and due to the circular polarization, the polarization of the circular polarization The light source is achieved by controlling the C -point C -point and the local state density in the power space, so hand radiation has nothing to do with the power of the pump, so it can realize the high purity, high Q value and high directional circular polarization from spontaneous radiation to laser. Light outlet.

"Compared with the traditional method, hand -sex BICS provides a new solution that can achieve the spectrum, far field and spinning angle momentum that controls spontaneous radiation and laser without self -spin injection." Professor Song Qinghai can be used. " According to the introduction, this method can improve the design of the current hand -made light source and promote its application in optical subsystems and quantum systems.

The first author of the paper was Zhang Xudong, a doctoral student in the Shenzhen Campus, and was completed by our school and the Australian National University. The first completion unit was our school. The corresponding author was Professor Song Qinghai of Shenzhen Campus and Professor Yuri Kieffshar, a National University of Australia. The study was supported by the National Natural Science Foundation of China, the Ministry of Science and Technology, the Shenzhen Science and Technology Commission, the Ministry of Technology and Industry and Information Technology of the Ministry of Technology and Industry and Industry, the Ministry of Technology and Information Technology, and the Pengcheng Laboratory, and the Extreme Optical Collaborative Innovation Center.

The thesis link:

https://www.science.org/doi/10.1126/sclence.abq7870

Wen, Picture | Zhang Xudong

Edit, typography | Liang Yingliang Wang Yifan

Review | Li Shoubin Song Ling

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