Researchers at Jilin University (Changchun, China) and the Chinese Ministry of Education (Beijing, China) are not only using electromagnetically induced transparency (EIT) to drastically slow a signal light pulse within a crystal to store it; they are speeding it up again using a phenomenon that optically splits the pulse into two pulses, each propagating in a different, adjustable direction. The phenomenon could have practical application in all-optical or quantum-information networks. In addition, the crystalline host is easier to work with than the atomic gases often used for EIT.
A signal pulse from a dye laser emitting at 606 nm enters the crystal, which is 0.05% praseodymium-doped yttrium orthosilicate held at 3.5 K. Another pulse, slightly wavelength-shifted, slows the signal pulse. After a storage time of 10 µs, two trigger pulses coming from other directions get the signal pulse back up to speed, but the phase matching between the pulses also creates two signal pulses from one. Changing the intensity of the trigger pulses changes the output-signal pulse directions; such manipulation can potentially allow information to be controllably distributed between different light channels. Contact Hai-Hua Wang at [email protected].