INSTITUTE OF APPLIED PHYSICS - Ion beam enhanced etching

Ion beam enhanced etching

Micro- and Nano structuring of crystalline materials

LiNbO3 1
Fabrication process for the structuring of crystalline material.(rights: IAP)

Crystalline materials have a wide spectrum of applications. Micro optical elements made of these can be used as laser materials or for the creation of nonlinear and electro optical switching devices. On the other side their high durability against standard structuring techniques makes the creation of such micro- and nano optical elements a very challenging task.
Because of its outstanding optical properties, like high nonlinearity and high electro optical coefficients, lithium niobate is a material of high interest in the field of integrated optics for the last decades.
In cooperation with the Institute of Solid State Physics (Uni Jena) a structuring process was developed in our group, which allows the fabrication of three dimensional photonic elements in bulk lithium niobate with a structure size below 1 µm. First step of the process is the application of a masking structure on the lithium niobate surface, by means of sputtering, electron beam lithography and different etching techniques. In the second step the mask plated substrate is irradiated by high energy ions (e.g. helium, argon) in order to damage the crystal structure in the non-masked regions. After removing the mask the damaged domains can be etched away in a wet chemical etching bath (diluted hydrofluoric acid).
By controlling the irradiation parameters like ion species, ion energy and ion fluence and the mask geometry and the mask material the shape of the elements can be predicted.
Using this structuring technique the creation of many kinds of optical elements in lithium niobate is possible and multiple applications can be realized.

LiNbO3 2
Several optical elements fabricated in lithium niobate. (rights: IAP)