Investigation of photo-induced absorption in a Bi12TiO20 crystal

Abstract

A photorefractive Bi 12 TiO 20 (BTO) crystal is exposed with high intensity pulsed-laser beams 532 nm (the average intensity of the laser was 110 mW/cm 2 , the average intensity per pulse was 2 MW/cm 2 ), and the photo-induced dynamics of the absorption between 480 and 900 nm are studied and explained by two long-lived energy levels in the forbidden band. The relaxation times of the long-lived energy levels are experimentally found to be 10 4 and 10 5 s. The hysteresis character of the absorption coefficient is discussed.

Photoinduced absorption study of carrier dynamics in Ru-doped Bi12SiO20 crystals after nanosecond laser pulse excitation

“…11 The observed relaxation dynamics follows a double-exponential behavior, which the authors explained with two very long-lived ͑about 10 4 to 10 5 s͒ intermediate levels located in the forbidden band of BTO. For example, the above presented results are in good agreement with the recently published PIA data in BTO crystals, irradiated with a high intensity pulse laser of 532 nm.…”

“…For instance, Jones and Solymar 32 observed dark decay processes consisting of a rapid initial decay ͑attributed to the filling of shallow traps below the CB͒ followed by a slower "coasting" decay ͑associated with the recombination of charges to the deep traps͒. 6,[8][9][10][11][12] The situation in Ru-doped BSO can be expected to be even more complicated due to the interaction of several Ru-related centers in different valence states of the Ru-ion. Despite the known presence of more than one shallow trap, most models consider the existence of only one shallow trap for simplicity.…”

“…In inorganic PR crystals shallow levels are usually located a fraction of an electron volt away from the CB ͑or the VB͒ and act as acceptors where the excited charge carriers could be trapped and re-emitted by thermal excitation before being ͑re͒captured at deep traps. 11,12 Recently, it was demonstrated that ruthenium is attractive and promising as dopant, significantly improving both the response time and photoconductivity of different inorganic crystals such as Sr 0.61 Ba 0.39 Nb 2 O 6 ͑Ref. 6 The photoconductivity in sillenite crystals is assumed to be n-type and thus the light-induced absorption is associated with the filling of initially empty shallow traps with the electrons released by the action of light.…”

Influence of femtosecond pulsed laser irradiation on bismuth germanium oxide single crystal properties

“…Influences of laser irradiation, thermal treatment [22], and electron beam [23] on luminescence of Bi 12 GeO 20 are reported. Photo-induced absorption in Bi 12 TiO 20 was thoroughly studied in [29], whereas significant influence of doping and annealing on transmission and absorption of BGO were addressed in [16] and [19]. However, to the best of our knowledge, photo-induced increase in BGO transmission has not been reported so far.…”

Фотоиндуцированное Поглощение И Импульсна Запись Динамических Голограмм В Кристаллах Силиката Висмута

“…По своей энергетической структуре фоторефрактивные кристаллы относятся к широкозонным диэлектрикам, при этом существенное влияние оказывают примеси и структурные дефекты кристаллической решетки, приводящие к возникновению в запрещенной зоне донорных и акцепторных энергетических уровней [5,7]. Особенностью является одновременное существование как долгоживущих (секунды, часы), так и короткоживущих ловушек (микрои миллисекунды) [8][9][10][11][12][13]. Пе-реходы с уровня, лежащего в запрещенной зоне, в зону проводимости приводят к образованию подвижных носителей заряда, причем такие переходы возможны при использовании излучения с заметно большей длиной волны, чем для прямых межзонных переходов, позволяя работать с излучением в видимой и ближней ИК областях спектра [5,14].…”