A Two‐Dimensional KTiOPO₄ Photonic Crystal Grown Using a Macroporous Silicon Template

Abstract

Photonic crystals (PCs) are an ideal framework to control optical nonlinear interactions. Since 1995, it has been shown that within a PC one may enhance, [1][2][3] phase match, [4,5] or hold a non-vanishing second-order interaction even if the material is centrosymmetric. [6] More recently, it has been pointed out that the structuring of the dielectric together with modulation of the second-order nonlinear susceptibility may lead to a backward parametric oscillation, [7] a nonlinear effect predicted many years ago that has not yet been observed. All such control over the nonlinear interaction is possible in 1D, 2D, or 3D PCs. Among them, 2D photonic structures are, perhaps, the most interesting, because such structures could, in principle, be easier to integrate into optoelectronic devices meant for light amplification, light generation at other frequencies, optical-data processing, or any kind of sensing. [8][9][10][11] The fabrication of 2D PCs using top-down procedures such as electron-beam lithography has been applied successfully in several kinds of semiconductors. [12][13][14] Unfortunately, patterning of inorganic crystals applying, for instance, focused-ionbeam bombardment and subsequent reactive-ion etching is limited to small depth/diameter ratios. [15] Developing procedures that would be more efficient in patterning inorganic crystals is very interesting for the fabrication of new light modulators that could take full advantage of the nonlinear optic and electro-optic coefficients of such materials. [16] On the other hand, neither the viability nor cost-effectiveness of integrating some very expensive nonlinear semiconductors in silicon-based devices have been clearly demonstrated. There are alternative routes to pattern inorganic nonlinear optical materials, such as KTiOPO 4 (KTP) or LiNbO 3 routes based on a periodical poling followed by a selective domain etching.[17]Although periodical poling has been applied with different degrees of success to obtain 1D arrays with a sub-micrometer period in some nonlinear materials, [18] it is still difficult to accurately control the size of small domains. Moreover, after poling one ends up with a stand-alone sample that would, certainly, be difficult to embed in any silicon-based device. We present here a completely novel combination of both topdown and bottom-up approaches to grow 2D PCs of KTP. These crystals are grown in ordered macroporous silicon templates. An additional benefit of such an approach is that, while being simple, the silicon matrix and the structured nonlinear material, which would eventually be used to modulate or generate light, forms an integral unit. To fabricate such a hybrid structure, an ordered silicon matrix of air holes and a KTP substrate were kept closely bound in a growth solution of KTP. We observed that KTP columns grew inside the air holes of the silicon matrix following the crystalline orientation of the substrate. Finally, the potential of the 2D array of KTP columns to control the nonlinear interaction was demonstrated by ...

Electronic structure of KTiOAsO4: A comparative study by the full potential linearized augmented plane wave method, X-ray emission spectroscopy and X-ray photoelectron spectroscopy

“…It is noteworthy to mention also that, KTA reveals higher electrooptic and nonlinear values 30% and 60% (for SHG under pumping at = 1.32 m), respectively, and lower absorption in the spectral region ranging from 3 to 5 m as compared with those of potassium titanyl phosphate, KTiOPO 4 (KTP) [3,[7][8][9]. Two-dimensional KTP-family crystals grown in ordered macroporous silicon templates reveal unique photonic properties [10].…”

Investigation of the Linear and Nonlinear Optical Susceptibilities of KTiOPO4 Single Crystals: Theory and Experiment

“…7 Zhang et al 8 studied the ion exchange in KTP crystals irradiated by copper and hydrogen ions. Pena et al 9 studied a two-dimensional KTP photonic crystal grown using a macroporous silicon template. One of the most important applications is a laser system for medical surgery that uses KTP for generating blue light.…”

New approaches for the fabrication of photonic structures of nonlinear optical materials

“…We present here the advances we developed recently in a completely new procedure that combines topdown and bottom-up approaches to fabricate 2D and 3D PCs of nonlinear dielectric materials, and that for the moment has been tested on KTP [16]. These crystals are grown on the surface of a KTP substrate, which gives to the photonic structure the requested crystallographic orientation, within the pores of a silicon macroporous template that gives the final shape to the photonic structure.…”