Photochromic effect in near-stoichiometric LiNbO3 and two-color holographic recording

Abstract

We have observed that newly developed near-stoichiometric LiNbO3 crystals have three different types of energy levels: ultraviolet (UV) absorption centers just above the valence band, metastable shallow electron traps slightly below the conduction band, and deep traps located about 1.9 eV below the conduction band. Irradiation with UV light induced a stable absorption band extending from λ ≈650 nm to the absorption edge, which is caused by the photoinduced charge transfer from UV-sensitive absorption centers to deep traps via the conduction band. The electron lifetimes at shallow and deep traps could be controlled by doping elements and concentrations. Based on these favorable energy states, nonvolatile two-color holographic recording has been carried out by use of 852 nm recording beams and UV gating light. Nonvolatile readout by a single 852 nm beam was demonstrated for several hours. It was found that two-color recording from the pre-exposed, colored state can also be an attractive way of achieving nonvolatile readout. In this article, we investigate the photochromic effect observed in near-stoichiometric LiNbO3 and its use in two-color holographic recording.

Photochromism‐induced light scattering and photoswithing in Er doped (K,Na)NbO3 transparent ceramics

“…The obtained E g value is about 2.98 eV. 28 The changes of Raman peak intensity also verifies the presence of color centers, as shown in the inset of Figure 4. These narrow absorption peaks are consistent with those of green and red emission spectra in Figure 3.…”

“…Under 407 nm laser irradiation, those excited electrons are captured by the defect energy levels, then forming color centers. 28 The changes of Raman peak intensity also verifies the presence of color centers, as shown in the inset of Figure 4. Finally, the incident light would be strongly scattered by the color centers, giving rise to an obvious decrease of the optical transmittance intensity.…”

Photochromism of vacancy-related defects in thermochemically reduced α-Al2O3:Mg single crystals

“…[1][2][3][4][5][6] In a previous communication, a reversible photochromic effect at low temperatures was reported in Mg doped ␣-Al 2 O 3 single crystals oxidized at elevated temperatures. In ionic crystals the photochromic effect is often related to photo-induced charge redistribution among ions or defects via the conduction band.…”

The photochromic effect of bismuth vanadate pigments: Investigations on the photochromic mechanism

“…In contrast to the latter, the term photochromism implies the reversibility of color change and has been observed for a variety of inorganic compounds (e.g., V 2 O 5 [1], MoO 3 [2], WO 3 [3,4], perovskites [5e7], PbMoO 4 [8], photochromic glasses [9,10]). Changes in optical properties due to illumination are desired for materials that find application in optical information storage [11,12], but the opposite is true in the case of pigments. BiVO 4 is one of the more common pigments that may exhibit photochromic effects depending on the method of preparation and after-treatment.…”