{'fraction_non_alphanumeric': 0.03507795100222717, 'fraction_numerical': 0.021158129175946547, 'mean_word_length': 5.217993079584775, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Linear and Nonlinear Optical Properties of Iridium Nanoparticles by Atomic Layer deposition

: Nonlinear optical phenomena enable novel photonic and optoelectronic applications. Especially metallic nanoparticles and thin films with nonlinear optical properties offer the potential for micro-optical system integration. For this purpose, new nonlinear materials need to be continuously identified, investigated, and utilized for nonlinear optical applications. While noble metal nanoparticles, nanostructures, and thin films of Ag and Au were widely studied, iridium (Ir) nanoparticles and ultra-thin films have not been investigated yet. Here, we present a combined theoretical and experimental study on the linear and nonlinear optical properties of Ir nanoparticles deposited by atomic layer deposition (ALD). Linear optical constants, i.e., the effective refractive index n and extinction coefficient k, were evaluated at different growth stages of nanoparticle formation. Both linear and nonlinear optical properties of these Ir ALD coatings were calculated theoretically using Bruggeman and Maxwell-Garnett theories. The third-order susceptibility of Ir nanoparticle samples was experimentally investigated using the Z-scan technique. Exemplary, for an Ir ALD coating with 45 cycles resulting in small Ir nanoparticles, the experimentally determined nonlinear third-order susceptibility is about χ Ir(3) = (2.4 – i2.1) x 10 -17 m²/V² at the fundamental wavelength of 700 nm. By using the nonlinear Maxwell-Garnett theory with Miller's rule, this nonlinear susceptibility is calculated (3.55 + i15.70) x 10 -11 m²/V² and for nonlinear Bruggeman theory it results in (1.06 + i2.08) x 10 -14 m²/V² at 233 nm. The strong increase is due to the proximity to the Mie resonance of Ir nanoparticles.