Methods for controlling of the laser-induced absorption in a BTO crystal by using of cw-laser radiation

Abstract

A photorefractive BTO crystal is exposed with cw-laser beams (430 mW/cm 2 at 514 nm), and the photoinduced absorption between 480 and 900 nm is studied. A method of controlling this absorption by low intensity laser radiation of "green" and "red" wavelengths is demonstrated. The physical mechanism can be explained by the redistribution of electrons on the long-lived energy levels into the forbidden band. Dynamical characteristics of the redistribution are estimated.

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

“…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.…”

“…Sillenite Bi 12 M͑M=Si,Ge,Ti͒O 20 type crystals are reversible photorefractive ͑PR͒ and photochromic materials, which are finding a wide range of applications in real-time holography, coherent light amplification, optical information processing, optical interconnection and communication, dynamic holographic interferometry, etc. 1,2 The sillenites are known to posses a complicated structure of the energy levels, with a large number of photoactive centers in the band gap, which can act as traps for charge carriers and be involved in the charge transport mechanism.…”

“…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.…”

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].…”

Photoinduced absorption in bismuth titanate crystals on nano- and picosecond excitation

“…The induced absorption when photorefractive crystals of bismuth titanate were exposed to continuous laser radiation at a wavelength of 514 nm was analyzed in [10], and also the dynamic characteristics of photoin duced processes were determined. The works devoted to studies of the induced absorption on pulsed excita tion are few in number.…”