Channel Waveguides in Lithium Niobate and Lithium Tantalate

Abstract

Low-loss photonic waveguides in lithium niobate offer versatile functionality as nonlinear frequency converters, switches, and modulators for integrated optics. Combining the flexibility of laser processing with liquid phase epitaxy we have fabricated and characterized lithium niobate channel waveguides on lithium niobate and lithium tantalate. We used liquid phase epitaxy with K2O flux on laser-machined lithium niobate and lithium tantalate substrates. The laser-driven rapid-prototyping technique can be programmed to give machined features of various sizes, and liquid phase epitaxy produces high quality single-crystal, lithium niobate channels. The surface roughness of the lithium niobate channels on a lithium tantalate substrate was measured to be 90 nm. The lithium niobate channel waveguides exhibit propagation losses of 0.26 ± 0.04 dB/mm at a wavelength of 633 nm. Second harmonic generation at 980 nm was demonstrated using the channel waveguides, indicating that these waveguides retain their nonlinear optical properties.

Efficient Optimization of High‐Quality Epitaxial Lithium Niobate Thin Films by Chemical Beam Vapor Deposition: Impact of Cationic Stoichiometry

“…Therefore, extreme limits must be achieved in the control of the required amounts for Nb and Li elements in the deposition technique. As a consequence, if epitaxial LNO thin films have been grown by different techniques ( [ 13 ] and references therein]), including Liquid phase Epitaxy (LPE), [ 20 ] sputtering, [ 21 ] Chemical Vapor Deposition (CVD), [ 22,23 ] Pulse Laser Deposition (PLD), [ 24 ] Molecular Beam Epitaxy (MBE), [ 25 ] sol‐gel, [ 26 ] and atomic layer deposition (ALD), [ 27 ] a fabrication approach that allows a precise tuning of the Li and Nb elements, yielding films of high epitaxial quality, is of particular interest for an actual industrial implementation of the LNO films through a potentially appealing technique.…”

Lithium tantalate photonic integrated circuits for volume manufacturing

“…However, the commercial use of LTOI in wireless applications, owing to its suitable acoustic properties, combined with the above optical properties, makes it an ideal platform for scalable manufactured electro-optical PICs, although such a use has never been demonstrated or pursued. Although free-standing ‘whispering gallery’ mode resonators have been fabricated from LiTaO 3 single crystals 26 , as a result of femtosecond laser direct writing 27 or focused ion beam milling 28 , scalable manufactured PICs have remained an outstanding challenge.…”

Epitaxy of LiNbO3: Historical Challenges and Recent Success

“…Consequently, Yamada et al [23] later utilized a Li 2 O-B 2 O 3 flux system to grow comparatively high-quality films with XRD rocking curves of 11.4 arcseconds, as shown in Figure 3, but this time without any detectable impurity inclusions and, therefore, lower optical losses of <1 dB/cm at 458 nm. Efforts toward the LPE epitaxy of LN continue and have looked at alternative growth parameters, such as using K 2 O fluxes [24], doping [25], and even using LPE to grow LN waveguides in laser cut channels [26] and continue as one of the lowest optical loss sources for single crystal epitaxial LN [23].…”

“…Of particular interest are the elimination of rotational domains, as this has been shown to strongly effect optical quality [15,16]. There are various epitaxial methods that have successfully grown LN, including liquid phase epitaxy (LPE) [17][18][19][20][21][22][23][24][25][26], sputtering [12,14,[27][28][29][30][31][32][33][34][35][36][37][38][39][40], chemical vapor deposition (CVD) [41][42][43][44][45][46][47][48][49][50], pulsed laser deposition (PLD) [13,[51][52][53][54][55][56][57][58][59][60]…”