Pyroelectrically induced photorefractive damage in magnesium-doped lithium niobate crystals

Abstract

Beam distortion due to photorefraction limits the usability of lithium niobate (LiNbO3) crystals for frequency conversion applications. To prevent beam distortion in LiNbO3, 5 mol.% magnesium-doped LiNbO3 (MgO:LN) is usually used. However, we show that strong beam distortion of green laser light can occur within seconds in MgO:LN, starting at light intensity levels in the 100 mW/cm2 regime, if the crystal is heated by several degrees Celsius during or before illumination. Beam distortion does not occur in undoped congruent LiNbO3 (CLN) under the same conditions. We show that the pyroelectric effect together with an elevated photoconductivity compared to that of CLN causes this beam distortion and that this effect also influences frequency conversion experiments in the infrared even if no external heating is applied

CW frequency doubling of 1029nm radiation using single pass bulk and waveguide PPLN crystals

“…This behavior has already been reported in Ref. [15][16][17][18][19][20][21][22][23] and may be related to inhomogeneities of the waveguide which prevent the destructive interference of the SH power. In case of crystal C, a strong asymmetry is observed between upper and lower lobes.…”

“…Although our crystals are doped with 5% MgO in order to prevent from photorefractive effect, Ref. [18] shows that for temperatures around 50 1C, similar to our QPM temperature, the green light generated in the guide can induce a pyroelectrically photorefractive damage that leads to a refractive index inhomogeneities which causes light scattering. This effect is shown to persist several days, even when the crystal being stored in the dark.…”

“…In case of crystal C, a strong asymmetry is observed between upper and lower lobes. This effect can be attributed to inhomogeneities of the polling period or index of the guide [17][18][19][20][21][22][23][24].…”

Apodization of chirped quasi-phasematching devices

“…Often, Dz ≈ 0.5 by design, due to QPM fabrication limitations [30], minimization of photorefractive effects [31][32][33], and also in order to maximize the amplitude of the first Fourier order (m 1) in Eq. (3), but we consider more general cases here.…”

Diffraction-Limited High-Power Single-Cycle Terahertz Pulse Generation in Prism-Cut LiNbO3for Precise Terahertz Applications

“…In last decade, optical rectification in second-order nonlinear optical crystals, such as ZnTe, GaSe, and DAST, has been emerging as an efficient alternative method for generating more intense single-cycle THz pulses. However, the magnitude of the THz pulse energy is often limited by several factors, such as absorption, phonon resonances, and photorefractive damages in nonlinear crystals [11,12]. In addition, the group velocity of the ultrashort optical excitation pulses has to be well-matched to the phase velocity of the newly generated THz pulses in the nonlinear medium for efficient frequency conversion [13].…”