This study presents a structuration approach to reach a high luminous transmittance (Tlum) and solar modulation efficiency (ΔTsol) of thermochromic vanadium dioxide (VO2) thin films. Before starting optical simulations, we confirm that the optical properties of monoclinic VO2 continuous films deposited by reactive magnetron sputtering show a good correspondence with numerical results. Then, calculations on ordered VO2 nanostripes demonstrate an enhanced transmittance due to the presence of vertical openings, leading to a variety of photonic effects. A series of optimizations by varying the column width, period, and film thickness establishes that 20 nm wide and 10 nm separated nanostripes have a ΔTsol of 14.2% and a Tlum of 47.6% for a film thickness of 250 nm. In comparison to a dense film without nanostructuring, the film transparency (related to Tlum) is significantly enhanced, while ΔTsol remains unchanged. Furthermore, this also translates into a favorable, less opaque color, so the geometry could be useful for various thermochromic applications, such as smart windows.

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We present an experimental setup capable of quantitative examination of acoustic whistlers in tubes of varying lengths and diameters. It is simple enough to be used as an undergraduate lab or classroom demonstration. The setup can be used to show the transverse modes of a cavity, and the difference between the group and phase velocity of a wave. It can also be used to determine the velocity of sound to an accuracy of 3%. We present the results of several experiments used to determine the acoustic modes present in transient whistlers. Our results differ significantly from a “geometrical acoustics” derivation of the acoustic whistler made in an earlier paper.