Rajesh Ganesan^1,2, David. R. McKenzie¹, Marcela MM Bilek¹, Christos Pernagidis^2
1The University of Sydney, Sydney, Australia
²Avaluxe International GmbH, Fürth, Germany
We report a significant technical advance in deposition processes for high-performance optical materials using reactive high-power impulse magnetron sputtering (R-HiPIMS) with RF-superimposed pulse excitation. This approach enables the controlled growth of tantalum nitride (TaN), niobium pentoxide (Nb_₂O₅), tantalum pentoxide (Ta_₂O₅), and hafnium oxide (HfO_₂) on fused silica, BK7, and polycarbonate substrates to engineer optical responses with precise spectral selectivity. These materials are selected for their high refractive indices, wide bandgaps, and superior laser power handling, which are essential for advanced photonic and laser systems.
We drive plasma processes via an RF-superimposed HiPIMS architecture directly into the negative differential resistance (NDR) region of the VI characteristics, without the broad kick pulses typically required for ignition. This rapid transition stabilises the plasma in a highly ionised state with strong ion flux control and enhanced energy coupling to the growing film. The resulting deposition environment increases adatom mobility, promotes dense packing, and suppresses defect formation while maintaining consistent stoichiometry even under reactive conditions.
Films produced by this method exhibit high density, ultralow surface roughness, elevated refractive index, and markedly reduced absorption losses. Mechanical adhesion and environmental durability are significantly improved relative to coatings produced by conventional magnetron sputtering. These properties translate into higher laser damage thresholds and improved long-term optical stability, which are critical for components exposed to extreme photon flux or variable environmental loads.
The demonstrated performance establishes RF-superimposed HiPIMS as a powerful platform for next-generation optical and photonic coatings. Through its process expertise and industrial consultancy capabilities, Avaluxe Coating Technologies now successfully implements and optimises these advanced thin-film processes directly at customer sites for partners seeking robust, high-precision coatings tailored to their specific laser, sensing, and imaging applications.