Optical information storage and recovery

Alexander I. Ryskin, Aleksandr S. Shcheulin, B. Koziarska +5 more

We demonstrate that semiconducting CdF2 crystals doped with indium is an efficient medium for optical storage of information in static and dynamic regimes. A metastable phototransformation of 1018 cm−3 In centers from a localized deep state to a hydrogenlike shallow state leads to a change of the refractive index Δn of about 10−4 for the probe beam at the wavelength of 500 nm. The diffraction efficiency is temperature dependent due to spontaneous decay of the grating caused by thermal recovery of the In impurity from the metastable hydrogenic state to the localized ground state.

Hongtao Wang, Haoran Zhang, Xiaoyan Zhou +8 more

P. J. van Heerden

Seiji Armstrong

Hai-Hua Wang, Aijun Li, Jin-Yue Gao

Atomic coherence is the interaction process between light and atoms, that is one or more coherent fields couple the different atomic states and cause the quantum interference between the different transition channels. Atomic coherence has led to many interesting and unexpected consequences, such as the Hanle effects, electromagnetically induced transparency (EIT), coherence population trapping (CPT), stimulated Raman adiabatic passage (STIRAP), spontaneous emission control, resonant enhancement of optical nonlinearity, slow and superluminal light propagation, quantum light storage, etc. In which, light storage based on atomic coherence plays an important role in the coherent control of light pulse information. In this chapter, we present some previous works on atomic coherence and optical storage. Firstly, we present the storage and recovery of light pulse based on F-STIRAP, which is fundamentally different from the conventional EIT-based process. Secondly, we present the applications of light storage based on EIT in a Pr3+:Y2SiO5 crystal, which includes the erasure of stored optical information, all-optical routing by light storage, and the coherent control of double light pulses. At last, we propose theoretically and demonstrate experimentally a method to control the atomic coherence by a STIRAP or F-STIRAP process.

Lukas Langer, S. V. Poltavtsev, I. A. Yugova +6 more

The possibility to store optical information is important for classical and quantum communication. Atoms or ions as well as color centers in crystals offer suitable two-level systems for absorbing incoming photons. To obtain a reliable transfer of coherence, strong enough light-matter interaction is required, which may enforce use of ensembles of absorbers, but has the disadvantage of unavoidable inhomogeneities leading to fast dephasing. This obstacle can be overcome by echo techniques that allow recovery of the information as long as the coherence is preserved. Albeit semiconductor quantum structures appear appealing for information storage due to the large oscillator strength of optical transitions, inhomogeneity typically is even more pronounced for them and most importantly the optical coherence is limited to nanoseconds or shorter. Here we show that by transferring the information to electron spins the storage times for the optical coherence can be extended by orders of magnitude up to the spin relaxation time. From the spin reservoir it can be retrieved on purpose by inducing a stimulated photon echo. We demonstrate this for an n-doped CdTe/(Cd,Mg)Te quantum well for which the storage time thereby could be increased by more than three orders of magnitude from the picosecond-range up to tens of nanoseconds.