Science and Technology Daily, Beijing, April 12 Recently, researchers at the Massachusetts Institute of Technology (MIT) have developed a new generation of ultra-sensitive magnetic field detectors using radon in artificial diamonds, which is nearly a thousand times more efficient than previous generation detectors . This will bring miniaturized battery charging equipment to the medical field, material imaging, smuggling inspections and even geological exploration. Related papers were published in the recently published "Nature & Physics" magazine.
According to the report of the physicists' organization network, pure diamonds are lattice structures composed entirely of carbon atoms and do not interact with magnetic fields. The rhodium in synthetic diamonds is called a nitrogen lattice vacancy. It is a nitrogen vacancy formed by a nitrogen atom in the crystal lattice replacing a carbon atom. The electrons in the vacancy can interact with the magnetic field and are extremely sensitive to the magnetic field. The diamond chip contains trillions of nitrogen vacancies, and each vacancy can perform magnetic field testing. Scientists hope to build a highly efficient and portable magnetometer based on this, the problem is how to gather all the tests. A nitrogen vacancy is detected by laser irradiation, which absorbs photons and then emits light. The intensity of the re-emitted light carries the information of the state of the vacancy magnetic field.
To make accurate measurements with this chip, it is necessary to collect as many photons as possible. The paper's first author, graduate student Hannah Clevinson, said that in previous experiments, the nitrogen vacancies on the chip surface were usually directly excited by lasers. “This will only absorb a small part of the light. Most of the light passes through the diamond. We add a facet to the diamond so that the laser is coupled together in the diamond and all incident light can be absorbed and utilized.â€
The researchers calculated the angle at which the laser entered the crystal so that the laser energy reflected from each facet, like a billiard ball on a pool table, tirelessly bounced round the face of the crystal until all of its energy was absorbed. "The total path that we pass adds up to nearly 1 meter," said Dirk Ingrid, an associate professor of electrical and computer science at the MIT Jamison Vocational Training Center. "It's like you wrap a 1-meter-long diamond sensor within a few millimeters. "So, the pump laser energy efficiency of the chip is nearly a thousand times that of the past. "We can use almost any pump light to detect almost all nitrogen vacancies."
When a photon hits one of the nitrogen vacancies, it hits a higher energy state. When the electron returns to its original energy state, it releases additional energy like other photons. A magnetic field will bombard the electron's magnetic direction (or spin direction) and increase its energy difference between the two energy states. The stronger the magnetic field, the more electron spins will be struck, changing the brightness of the empty light.
Due to the geometry of the nitrogen lattice vacancies, the re-emitted photons exit at four angles. A lens on each side can collect 20% of the emitted light and collect them on a photodetector, enough to produce a reliable detection.
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