Abstract
Photoinduced charge transport in lithium niobate for standard illumination, composition and temperature conditions occurs by means of small polaron hopping either on regular or defective lattice sites. Starting from Marcus-Holstein’s theory for polaron hopping frequency we draw a quantitative picture illustrating two underlying microscopic mechanisms besides experimental observations, namely direct trapping and migration-accelerated polaron trapping transport. Our observations will be referred to the typical outcomes of transient light induced absorption measurements, where the kinetics of a polaron population generated by a laser pulse then decaying towards deep trap sites is measured. Our results help to rationalize the observations beyond simple phenomenological models and may serve as a guide to design the material according to the desired specifications.
Highlights
Photoinduced charge transport in lithium niobate for standard illumination, composition and temperature conditions occurs by means of small polaron hopping either on regular or defective lattice sites
Schirmer and co-workers [9,10,11,12,13,14], it is nowadays accepted that charge transport in Lithium Niobate (LN) and related materials must be understood in terms of small polarons hopping among regular and/or defective sites
Spectroscopy ([1] and refs. therein) in which a polaron population is created in the material by a pulsed photo-excitation process and its decay towards deep trap centers is observed by means of time resolved absorption spectroscopy
Summary
Lithium Niobate (LN) stands out among other ferroelectric oxides for its large use in the realisation of acousto-optical, electro-optical and non-linear optical devices. Since its development in the ’60 s, this material has evidenced several light-induced effects that were recognized as a complex interplay between charge excitation and migration processes, such as photoconductivity, the bulk photovoltaic effect and photorefractivity The interest in those phenomena is timely because they bear a high interest for practical applications: in the field of nonlinear and ultra-fast optics the photorefractive effect is a drawback that limits the use of LN for high intensity multiphoton processes [1], while in photorefractive holography this effect is used to record high quality gratings, optical memories and demonstrate low-intensity all-optical interactions [2]. Its motion takes place by thermally assisted hopping transitions among different sites, until a deep trap is encountered; the polaron is stably trapped and ready to be photo-excited again [15]. Therein) in which a polaron population is created in the material by a pulsed photo-excitation process and its decay towards deep trap centers is observed by means of time resolved absorption spectroscopy. The effect of changing experimental constraints such as sample temperature and composition on the different hopping processes will be elucidated and some criteria will be given to establish a priori what is the regime one should expect on the basis of a given sample composition and temperature
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
