  Computer-aided design (CAD) has become a critical element in the creation of
nanopatterned structures and devices. In particular, with the increased
adoption of easy-to-learn programming languages like Python there has been a
significant rise in the amount of lithographic geometries generated through
scripting and programming. However, there are currently unaddressed gaps in
usability for open-source CAD tools -- especially those in the GDSII design
space -- that prevent wider adoption by scientists and students who might
otherwise benefit from scripted design. For example, constructing relations
between adjacent geometries is often much more difficult than necessary --
spacing a resonator structure a few micrometers from a readout structure often
requires manually-coding the placement arithmetic. While inconveniences like
this can be overcome by writing custom functions, they are often significant
barriers to entry for new users or those less familiar with programming. To
help streamline the design process and reduce barrier to entry for scripting
designs, we have developed PHIDL, an open-source GDSII-based CAD tool for
Python 2 and 3.
