  The ability of photonic crystal waveguides (PCWs) to confine and slow down
light makes them an effective component to enhance the performance of many
photonic devices, such as optical modulators, optical sensors and optical
phased arrays (OPAs). However, the integration of PCWs in photonic applications
comes with various design challenges, most notably, engineering the PCW mode
dispersion and efficiently coupling to the modes of the PCW. Here, we solve
these challenges through the use of inverse design methodologies. The
dispersion relation of even and odd mode PCWs are engineered for a group index
of 25 over a bandwidth of 20nm and 12nm, respectively. For both PCW designs, we
create strip waveguide couplers, as well as free space grating couplers. The
transmission of optical delay devices constructed with the strip waveguide
converters are experimentally characterized and, using the PCW grating
couplers, the group index of both PCWs is measured. Finally, radiative losses
are introduced to our PCW designs while maintaining the dispersion relation of
the original PCW. With these loss and dispersion engineered PCWs, alongside the
strip waveguide couplers, we construct OPAs with different radiative strength.
The OPAs are experimentally characterized and shown to steer a light beam up to
20{\deg} in a 20nm bandwidth. The devices in this work illustrate how inverse
design methods can enable the use of PCWs in future LiDAR systems, optical
communication, and sensing applications.
