We (metalenz.com) use Julia extensively in our optical design/simulation/modeling workflows:

1. Design team keeps live sessions during interactive work, otherwise launches on virtualized servers (and things take sufficiently long to compute TTFX is a rounding error)

2. Above mentioned team is exclusively Julia. Julia shows up in other things we do (low-level computer vision), but not dominant nor exclusive

3. High performance & expressive programming and flexible autodiff system for scientific computation