  Nonlinear processes in integrated, guiding systems are fundamental for both
classical and quantum experiments. Integrated components allow for compact,
modular and stable light-processing systems and as such their use in real-world
systems continues to expand. In order to use these devices in the most
demanding applications, where efficiency and/or spectral performance are
critical, it is important that the devices are fully optimized. In order to
achieve these optimizations, it is first necessary to gain a thorough
understanding of current fabrication limits and their impact on the devices
final performance. In this paper we investigate the current fabrication limits
of titanium in-diffused lithium niobate waveguides produced using a masked
photolithographic method. By dicing a long (~cm) sample into smaller pieces and
recording the resulting phasematching spectra, the fabrication error present in
the UV photolithographic process is characterized. The retrieved imperfections
fit well with theoretical expectations and from the measured imperfection
profile it is shown that one can directly reconstruct the original distorted
phasematching spectrum. Therefore, our measurements directly quantify the
intrinsic limitations of the current standard UV photolitographic technique for
the realization of integrated waveguides in lithium niobate.
