Atoms store 2D images in record time

Physicists in Israel have shown that 2D images of light can be projected into atomic gas, stored there and recovered in time to 9 9s later. Although this is not the first time this has been done, recovery time is a thousand times longer than the old record, and researchers are still developing the technique to extend the recovery time.

Normally if a ' probe ' laser beam is projected onto the atomic gas with the right frequency to cause the atom to jump to a higher energy level, the light will be absorbed by atoms and then transmitted. Radiate back in different directions when the atoms return to the main state. If a ' pump ' (pump) laser is set to correspond to another excited energy state and is projected on atoms at the same time, the ' probing ' laser beam will cross the atomic cloud without hindered - an effect called electromagnetically - induced transparency (EIT).

In 2001, researchers found that if the ' pump ' laser beam was switched off immediately while the ' probe ' laser beam was still in the atomic gas, the ' probe ' laser beam could retained there until the ' pump ' laser beam is turned on again.

Currently, Nir Davidson and colleagues from Weizmann University of Science and Israel Technion University have shown that the EIT effect can be used to store and restore 2D images.

Figure 1 .Nir Davidson and colleagues at Weizman Institute of Science and Technion - Israel Institute of Technology show that images '2', '6' and '9' appear first (left column) and later (right column) when they save Keep them in atomic gas.For '2' images, they show how images are weakened in atomic gas (the middle column) simply due to the scattering nature of the environment.The blurring of images, as a result of atomic diffusion, can be reduced using 'phase shifting' techniques.

The team began with dividing light from laser diodes into two beams - the ' probe ' beam and the ' pump ' beam - polarizing 900 from each other and then projecting them onto a cell consisting of the rubidium atoms - 87 evaporated at room temperature. However the path of the ' probe ' laser beam is blocked by a 2D mask (2D mask) that prints their images onto atoms by limiting excited atoms to energetic states. higher volume.

Just when the ' probe ' beam started to leave the atomic gas, the ' pump ' beam was turned off and turned on again after a while. They then directed any light released from the gas into the CCD camera after filtering the ' pump ' laser light using polarized glasses.

Experiments with 2D masks with numbers '2', '6' and '9', Davidson and his colleagues discovered that they could store images in atomic gas up to 9 μs and receive credits camera signal - 103 times more powerful than the US research group presented earlier this year when using another technique. They say this is the longest retention time before the diffusion of atoms will make the image unreadable.

To overcome this limit, the team tried to apply a technique in semiconductor manufacturing called phase shift printing that is often used to etch acid properties with high resolution without any what distribution of refraction . In image retention, the phase transition between different parts of the image causes properties that are directly related to the image to be mutually suppressed so that the image is ' immune ' to the atomic diffusion.

Figure 2. Save images of 3 lines with 340 nm width in time up to 30 μs.The left-hand side is the test result (left column) and the theoretical calculation result (right column) when the image is projected to the element (cell) with no phase change.On the right hand side is the image received with better resolution when phase shift π for 2 external lines.This effect is an atomic equivalent compared to the printing of phase shift in the semiconductor industry.

Using this phase shift technique, Davidson and colleagues can store images of 3 lines of 340 μm width and can reproduce them after they recover them on 30 30s camera afterwards.

Currently the Israeli team is trying to change the field of the ' probe ' laser beam from bell-shaped ' Gaussian ' curves to a more complex form to be able to represent 3D information - a close form. like a movie.

According to the researchers, the system will have enough capacity to be used as a memory device for photon states used in quantum computation.

Damap