Application of Electron Spin to create Maser

Most lasers operate at infrared and visible wavelengths, but the first laser, built in 1954, is actually a maser - using microwaves. On September 15 in Physical Review Letters 97.116601, Dutch scientists came up with a new design of maser, using the spin properties of electrons.

If successful, it will potentially reduce the current types of maser to microelectronic size, and will be a new application of the " spintronics " industry, a nascent industry, developed to improve systems. Current electronic systems using spin electrons instead of electrons (electrons charge).

Today's electronic devices use electrical charge to encode binary information - "on" and "off" states, converted into numbers 0 and 1 like the computer's encryption system. . Spintronics, which is a component system that uses other properties of electrons, in particular involves magnetism - the arrangement of " up " or " down " spins, under the influence of a magnetic field.

There have been a few devices using electronic spin properties that have been put to use, but are still limited, and most "just stop on the proposed models" Steven Watts, of the University of Groningen, Ha Lan said. "Microwave microwave amplification systems, also known as maser, are small in size that need to be targeted," he said. But the maser is a self-sustaining device, which is often used in large systems or needs to be cooled to the helium liquid temperature.

In a conventional laser, energy flows into the atoms of a gas or solid, to stimulate them to a higher energy state. Atoms release photons when they jump back to the ground state, and these photons can affect excited atoms and release photons. The whole system can become a self-excited light generator - or a laser - when and only if there is enough energy to reach a state called "population inversion", there are many atoms are in the excited state rather than in the ground state.

Watts and colleagues at Groninger University, Bart van Wees, proposed a maser using a sandwich model (with three layers like sandwiches), with a ferromagnetic material like Fe above, an object whether magnetic is like aluminum below, and an insulating layer in the middle. Putting a magnetic field down below this clamp will create two energy states of the electron: the ground state for the spins pointing down and an excited state for the spins pointing up. Electrons can be excited to a higher energy level, a spin-up state by infusing a radiation of microwave radiation.

But the incoming microwaves are not enough to synthesize excited electrons to achieve the state density inversion needed for active maser. So the researchers added the population of excited electrons with a "spin current" , from the ferromagnetic layer to the dominant magnetic layer - where the spin current will be the current of electrons with a spin direction. -up. The team calculated with this support, the paramagnetic layer would contain enough excited electrons to activate the maser immediately, and the sandwich would release a strong stimulating radiation in a combination of microwaves.

" This maser is very interesting on a physical point of view, " said Stuart Wolf of the University of Virginia, but he said it is unclear how the application of this maser will be popular. Watts agrees that spin maser is just a primitive form, but he also hopes to move on to making small excited maser for use in future microelectronic devices, like microwaves have been used. used in many electromagnetic devices, and most commonly mobile phones.

Bunhia