Light-induced absorption changes in reduced lithium niobate

Jermann, F.; Simon, Maria Cristina Pais; Bower, R.W.; Krätzig, E.; Schirmer, O. F.

doi:10.1080/00150199508228312

Cited by 43 publications

(50 citation statements)

References 9 publications

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“…Table II. Such a drastic spectral dependence of b 0 is in accordance with the data 24 on the light-induced changes of the polaron/bipolaron absorption in the reduced LiNbO 3 crystals.…”

Section: Discussionsupporting

confidence: 77%

“…24. Note that this finding is in contrast to the other mechanisms of NLA in LiNbO 3 reported in Refs.…”

Section: Discussioncontrasting

confidence: 55%

“…The latter term is used in accordance with the definition given previously. 24 At room temperature, almost all of these polarons are paired forming the bipolarons in equilibrium. Bipolarons can be broken into single polarons again by illumination within visible range.…”

Section: Discussionmentioning

confidence: 99%

“…The broad absorption band near 500 nm has been attributed to the presence of bipolarons and a narrower band at 760 nm (a short-wavelength tail is extended down to 600 nm) has been assigned to the formation of single polarons under illumination with proper wavelength. 3,7,24 Therefore, the existence of such a dissociation-annihilation process in cw illuminated crystals is expected to manifest itself in the optical absorption change dependent on the wavelength of pump laser beam.…”

Section: Discussionmentioning

confidence: 99%

“…Combined solution of equations, describing the dissociation-annihilation process and optical absorption, gives the following dependence 24 of the light-induced absorption changes jDaj on I 0…”

Section: Discussionmentioning

confidence: 99%

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Z-scan study of nonlinear absorption in reduced LiNbO3 crystals

Кострицкий

Aillerie

2012

Journal of Applied Physics

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Bipolaron recombination in conjugated polymers J. Chem. Phys. 135, 074902 (2011) Correlation effects on the dynamics of bipolarons in nondegenerate conjugated polymers J. Chem. Phys. 130, 234908 (2009) Acidification of three-dimensional emeraldine polymers: Search for minimum energy paths from base to salt J. Chem. Phys. 128, 234903 (2008) Transformation of polarons to bipolarons in disordered matter Appl. Phys. Lett. 92, 222108 (2008) A suitable model for emeraldine salt J. Chem. Phys. 128, 174706 (2008) Additional information on J. Appl. Phys. The nonlinear absorption (NLA) was studied by open-aperture Z-scan experiments in the chemically reduced nominally pure LiNbO 3 crystals at cw-illumination with the red (644 nm) and green (514.5 nm) laser beams. The magnitude of the measured NLA is considerably different from the reported Z-scan results obtained in as-grown LiNbO 3 . The positive sign of NLA obtained with the red light has been related to the generation of the small bound polarons absorbing in red and near-IR ranges. Application of green light results in the light-induced transparency, i.e., the Z-scan traces show negative sign of NLA. Intensity dependence of Z-scan traces allows for conclusion that the photo-induced dissociation of small Nb Li 4þ :Nb Nb 4þ bipolarons and sequent generation of small polarons gives the dominating contribution to the nonlinear optical absorption in reduced crystals with a large bipolarons concentration. V C 2012 American Institute of Physics.

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“…Table II. Such a drastic spectral dependence of b 0 is in accordance with the data 24 on the light-induced changes of the polaron/bipolaron absorption in the reduced LiNbO 3 crystals.…”

Section: Discussionsupporting

confidence: 77%

“…24. Note that this finding is in contrast to the other mechanisms of NLA in LiNbO 3 reported in Refs.…”

Section: Discussioncontrasting

confidence: 55%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 3 more Smart Citations

Z-scan study of nonlinear absorption in reduced LiNbO3 crystals

Кострицкий

Aillerie

2012

Journal of Applied Physics

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Investigation of Small Polarons in Reduced Iron-Doped Lithium-Niobate Crystals by Non-Steady-State Photocurrent Techniques

Peithmann

Korneev

Flaspöhler

et al. 2000

phys. stat. sol. (a)

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Photorefractive iron-doped lithium-niobate crystals (LiNbO 3 : Fe) are of special interest for applications in the fields of optical communication techniques and holographic data storage. Recently, considerable attention has been concentrated on a shallow photorefractive center in LiNbO 3 : Fe, which enables non-volatile storage of holograms by two-color processes [1 to 4]. This center is attributed to the intrinsic Nb 4a5 Li antisite defect (Nb 4a5 on Li site) [5,6]. The center with a trapped electron (Nb 4 Li ) forms a`small polaron'. Because of the short lifetime of these small polarons at room temperature, high light intensities (above 10 kWm À2 ) are required to generate them [1,3].Thermally reduced LiNbO 3 :Fe is of special interest for practical applications, because reduction enlarges the photoconductivity, which makes photorefractive processes faster. However, lifetime and influence of the small polarons grow upon reduction. In this contribution we employ the technique of non-steady-state photocurrents (photo-EMF) to investigate a reduced iron-doped LiNbO 3 crystal. A recent publication shows that this approach is promising for getting more information about shallow centers [7]. Here we check with temperature dependent measurements whether the photo-EMF and light-induced absorption changes li are governed by the same type of defect.An iron-doped LiNbO 3 crystal (iron content c Fe 7 Â 10 24 m À3 , size b Â c 4X61 Â 5X31 mm 2 , thickness d 2X21 mm) is reduced by thermal annealing (1000 C, 2 h, vacuum). The absorption coefficient for ordinarily polarized light of the wavelength l 532 nm is 2350 m À1 . Non-steadystate photocurrents are generated in the sample by illumination with two interfering light beams (fringe spacing of the interference pattern L 0X6 mm) of a frequency-doubled Nd : YAG laser (wavelength l 532 nm, incident light intensity I 2 kWm À2 ) [8,9]. The phase of one of the beams is periodically modulated, and an oscillating light intensity pattern is created. This yields an ac current signal which is directly detected by a lock-in amplifier. The crystal is mounted on a temperature-controlled stage which enables adjustment of the temperature in the range from 300 to 375 K. Measurements of the non-steady-state photocurrents I W are carried out for various temperatures T and modulation frequencies W 2%f. The dependence of I W on the frequency W can be described by [10,11] where ( EMF is the lifetime of the charge carriers in shallow traps and ( M is the Maxwell time, which is given by ( M 0 a' ph with the photoconductivity ' ph , the dielectric constant , and the permittivity of free space 0 . Measurements of the light-induced absorption li are carried out using green pump light of an argon-ion laser (wavelength l 514 nm, intensity up to 30 kWm À2 ). Absorption changes are monitored by means of different weak laser beams (wavelengths 633, 670, 785, and 1064 nm, ordinarily polarized). The pump light illuminates the sample shorter than one second to prevent light-induced heating. After switching off...

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Decay time of polaron photoluminescence in congruent lithium niobate

Harhira¹,

Guilbert

Bourson

et al. 2007

Phys. Status Solidi (c)

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The intensity, the peak wavelength and the decay time of polaron photoluminescence in congruent lithium niobate are measured versus temperature from 77 K to 290 K. The radiative relaxation shows quasi athermal behaviour (τ R ≈ 9 µs) whereas the nonradiative relaxation follows arrhenius law with activation energy of 220 meV. The crossing point between radiative and nonradiative lifetimes is about 210 K.1 Introduction Lithium niobate (LiNbO 3 , LN) is of great interest for optical applications owing to its large electro-optic and non linear optical coefficients. Several physical properties involved in device operation are sensitive to the concentration of point defects and to the chemical reduction degree of the material. In particular the defect structure of LiNbO 3 is attributed to the presence of Nb in the lithium site (so called niobium antisite). Niobium antisite defects Nb Li 5+ are able to trap an electron on an energy level below the conduction band, giving a small bound polaron Nb Li 4+ [1]. This defect plays a major role in light-induced phenomena (photoconductivity, light-induced absorption, photorefractive effect [2][3][4]. Previous studies show that excitation of congruent lithium niobate in the visible range always gives a photoluminescence (PL) band in the near infrared, which is attributed to polaron defects [5]. Recently the PL efficiency of congruent LN has been measured versus temperature under continuous wave excitation at 355 nm [6]. The main aim of the present work is to study the PL decay after short pulse excitation and to measure the relaxation time versus temperature.

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Light-induced absorption changes in reduced lithium niobate

Cited by 43 publications

References 9 publications

Z-scan study of nonlinear absorption in reduced LiNbO3 crystals

Z-scan study of nonlinear absorption in reduced LiNbO3 crystals

Investigation of Small Polarons in Reduced Iron-Doped Lithium-Niobate Crystals by Non-Steady-State Photocurrent Techniques

Decay time of polaron photoluminescence in congruent lithium niobate

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