Investigating the influence of ITO thin film thickness on the optical Kerr nonlinearity using ultrashort laser pulses
Fatma Abdel Samad, Alaa Mahmoud, Mohamed Sh. Abdel-wahab, Wael Z. Tawfik, Rozalina Zakaria, S. Venugopal Rao, Tarek Mohamed
Abstract
In this paper, we present results from the measurements of the optical Kerr nonlinearity of indium tin oxide (ITO) thin films of different thicknesses using the femtosecond (fs) Z-scan technique. ITO thin films were prepared by radio frequency magnetron sputtering on a glass substrate at room temperature. The coated ITO thin films were subsequently characterized by UV–visible absorption spectroscopy, x-ray diffraction, and scanning electron microscopy. Using <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>∼</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>100</mml:mn> </mml:mrow> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">f</mml:mi> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> </mml:math> pulses at 80 MHz repetition rate, the optical Kerr nonlinearity in ITO with different thicknesses was investigated at different excitation wavelengths and incident pulse energies. The optical Kerr nonlinearity was found to be dependent on excitation wavelength, incident power, and ITO thickness, with a maximum value of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>∼</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>9</mml:mn> </mml:mrow> </mml:mrow> <mml:mo>×</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>1</mml:mn> </mml:mrow> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>0</mml:mn> </mml:mrow> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>−</mml:mo> <mml:mn>12</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">c</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:mrow> <mml:mn>2</mml:mn> </mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>/</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">W</mml:mi> </mml:mrow> </mml:mrow> </mml:math> at a wavelength of 820 nm, power of 1 W, and 170 nm ITO thickness. These results suggest that Kerr nonlinearity in ITO can be tailored by varying the film thickness, which would be ideal for ultrafast all-optical switching in future optoelectronic devices.