Non-steady-state photoelectromotive force in crystals with long photocarrier lifetimes

Соколов, И. А.; Степанов, С. И.

doi:10.1364/josab.10.001483

Cited by 79 publications

(32 citation statements)

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“…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 ).…”

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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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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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“…exp(i t) , (9.25) which is very similar to the expression obtained in [121] if we make the assumption that d 1. It is necessary to note that the existence of an alternating homogeneous current does not mean automatically that there is a homogeneous oscillating electric field in the crystal.…”

Section: Spatial Rectificationsupporting

confidence: 66%

“…This technique allows one to measure the speed of propagation of the grating of the photoexcited free carriers and to prove the existence of high-frequency SCW. In [121], the resonance was detected by measuring the current in the outside circuit when the crystal (BSO) was illuminated by an alternating interference pattern and the external DC fields (4-10 kV/cm) were applied, and in [107,108] a similar resonance was revealed when the crystal was illuminated by an alternating interference pattern and an AC field was applied. The measurements of the dependencies of the resonance frequency on external field and on wave number agree with the dispersion law described by (28).…”

Section: High-frequency Branch Of Scwmentioning

confidence: 99%

Space-Charge Waves in Sillenites: Rectification and Second-Harmonic Generation

Петров

Bryksin

Photorefractive Materials and Their Applications 2

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This paper consists of two parts. The first contains a short review of the main characteristics and holographic phenomena typical of sillenites, and the second part is devoted to new phenomena associated with space-charge waves, namely to second-harmonic generation and rectification of these waves. Major Characteristics of Sillenites as Holographic Materials General Properties of SillenitesSillenites are reversible holographic materials, efficient photoconductors. They exhibit a strong electrooptic effect, excellent piezoelectric properties, and a relatively high Faraday effect. Owing to these features, sillenites find wide application in dynamic holography and interferometry, optical information processing, optical sensors of electric and magnetic fields, and piezoelectric devices. As reversible holographic materials, sillenites offer numerous advantages (a fast enough response time of 1-10

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“…18,19 In these experiments the displacement current is believed to be negligible compared with the charge transport across the crystal and through the external circuit. The entire crystal is illuminated, so indeed the high photoconductivity of these materials facilitates charge transport from the crystal bulk to the electrodes.…”

Section: Resultsmentioning

confidence: 99%

Optical and electrical Barkhausen noise induced by recording ferroelectric domain holograms

et al. 1995

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Ferroelectric domain gratings with periods of the order of an optical wavelength are induced in strontium barium niobate by photorefractive space-charge fields. We measure the Barkhausen noise in current and diffraction efficiency while optically recording domain gratings and show that the two are strongly correlated in time. Significant random depolarization occurs under high-intensity illumination. We deduce the kinetics of the domain inversion process from the shape of the current transients.

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Non-steady-state photoelectromotive force in crystals with long photocarrier lifetimes

Cited by 79 publications

References 5 publications

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

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

Space-Charge Waves in Sillenites: Rectification and Second-Harmonic Generation

Optical and electrical Barkhausen noise induced by recording ferroelectric domain holograms

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