Local domain inversion in MgO-doped lithium niobate by pyroelectric field-assisted femtosecond laser lithography

Abstract

We explore a physical approach to invert ferroelectric domains in the volume of MgO-doped lithium niobate crystals without any external electric field. Permanent defect structures are created by focused infrared femtosecond laser pulses below the material surface along the polar axis followed by a thermal treatment. This procedure leads to an inversion of ferroelectric domains beneath and above the laser-induced filaments up to the surfaces of the crystal. All domain walls are straight and up to 800 μm long. We measure the domain width in dependence on the length of the filaments and the writing energy. The smallest achieved domain width and the domain spacing is 1 μm. We propose a model taking into account the temperature dependence of the pyroelectric field and thermally activated bulk charges to explain the mechanism of domain inversion. Our findings pave the way to all-optical printing of arbitrary ferroelectric domain structures for nonlinear photonic applications.

Localized Ferroelectric Domains via Laser Poling in Monodomain Calcium Barium Niobate Crystal

“…Similarly, in our earlier work with lithium niobate, we were able to create high quality ferroelectric domains by starting their formation on the crystal surface. [29] It seems that similar anchoring on laser damaged regions (filaments) accompanied formation of ferroelectric domains inside lithium niobate crystal as reported in Imbrock, et al [20] While there is no systematic studies of the role of anchoring on domain formation and their stability available as yet, we think that the same mechanism contributes toward the optical induction of macroscopic domains in multi-domain ferroelectrics, demonstrated in our works so far. It is well known that domain walls may trap electric charges.…”

“…[12] In the latter situation, which is actually practically more relevant, domains form or/and switch in special conditions under external stimuli such as mechanical stress, [13] thermal processing, [14] temperature gradient, [15] electron, [16] or ion beam [17] and/or external or internal electric fields. [18][19][20] In fact, the use of electric field for domain formation and patterning is nowadays a method of choice. [18,21] In it, the ferroelectric crystal is placed between electrodes connected to high voltage power supply.…”

“…When illuminated by tightly focused laser beam, these charged wall regions contribute toward polarization reversal in a manner similar to that observed in laser filaments in LiNbO 3 . [ 20 ] However, it is not apparent what kind of anchoring centers could exist in monodomain ferroelectrics. Therefore, it is not obvious if nondestructive, controllable spontaneous polarization reversal inside the bulk of single domain crystals can be optically realized.…”

Improvement on Thermal Stability of Nano-Domains in Lithium Niobate Thin Films

“…This breaks the balance between the depolarization field, E d , and the screening field, E sceen . Therefore, the thermally actived bulk charges, such as protons in lithium niobate may drift in bulk, or the surface charges may accumulated on the surface, to compensate for this field imbalance [28,29]. This will result in a space charge field, E sc , in lithium niobate with its direction antiparallel to the spontaneous polarization, P s .…”

Engineering optical anisotropy in nonlinear crystals with ultrafast light

“…Importantly, the ability to control the orientation of nanogratings with the pulse polarization allows one to vary the spatial orientation and strength of the induced form-birefringence. In view of the recent advances in 3D femtosecond laser modification of linear and nonlinear crystals, [33][34][35][36][37][38] LiNbO 3 with tailored optical properties and incorporated microphotonic components becomes a reality. The very possibility of making such a unique device opens up unprecedented opportunities in the design of optical circuits for signal guiding and processing, frequency conversion, and beam shaping.…”