CC BY
17LMI-I-29
Periodically poled crystals for nonlinear optical conversions and controlling of coherent light
V. Shur1, A. Akhmatkhanov1, A. Esin1, V. Pavelyev2
1Ural Federal University, Institute of Natural Sciences and Mathematics, Ekaterinburg, Russian Federation
2Samara University, Department of Nanoengineering, Samara, Russian Federation
We present the recent achievements in periodical poling in MgO doped single crystals of lithium niobate (LN), lithium tantalate (LT) and potassium titanyl phosphate (KTP) and the design and realization of various LN based diffraction optical elements (DOE) based on the experimental study of the domain structure evolution by the complementary high-resolution domain visualization methods [1].
The crystals with tailored periodically poled domain structures (PPLN and PPLT) produced with nano-scale period reproducibility have been used for Second Harmonic Generation (SHG) and Optical Parametric Oscillation (OPO) based on quasi-phase-matched nonlinear optical wavelength conversion. The wide range of wall velocities with two orders of magnitude difference was observed for switching in a uniform electric field [2,3]. The kinetic maps allowed analyzing the spatial distribution of the wall motion velocities and classifying the walls by velocity ranges. The distinguished slow, fast, and superfast domain walls in KTP and LN differed by their orientation [3,4]. The deep knowledge of the domain structure evolution at elevated temperatures and relaxation of the high bulk conductivity along the charged domain walls MgO:LN and MgO:LT allowed us to optimize the periodical poling technique and to produce high-fidelity domain patterns.
The fan-out periodical domain structures created in 3-mm-thick MgO:LN wafers allowed us to realize the widely tunable OPO generation with the signal wave from 2.5 to 4.5 p,m using the 1.053 p,m pump. The possibility of producing the elements with thickness up to 10 mm for highpower application has been discussed.The peridical domain struture with period of 40 p,m was created in KTP single crystals for OPO generation at 2.4 p,m using the 1.053 p,m pump. The abilities and perspectives of producing the elements with submicron periods has been discussed. The ferroelectric domains with opposite values of spontaneous polarization possess also the opposite values of the linear electrooptic effect, which allowed to demonstrate the electrical field controlled optical beam deflectors [5-7], diffusers [8], Fresnel zone plates [9] and Shack-Hartmann sensors [10]. The operation range of the created diffraction elements was limited by 200°C due to essential decrease of the threshold fields for ferroelectric domain switching. The possibility of continuous tuning of diffraction efficiency of the elements has been demonstrated. It was shown that the DOE response time is less than 0.1 p,s.
The following tunable diffraction elements have been produced: (1) the hexagonal zone plate with focus distance 150 mm and aperture 1.7 mm and (2) the 2D diffraction grating with period 20 p,m. The hexagonal zone plate has focused up to 25% of the laser light into a spot of 130 p,m in diameter. The 2D diffraction grating has allowed decreasing the zero-order diffraction maximum intensity by 80%. The transparency range of the DOEs was 320-1800 nm.
