  We demonstrate a monolithic frequency converter incorporating up to four
tuning degrees of freedom, three temperature and one strain, allowing resonance
of pump and generated wavelengths simultaneous with optimal phase-matching.
With a Rb-doped periodically-poled potassium titanyl phosphate (KTP)
implementation, we demonstrate efficient continuous-wave second harmonic
generation from 795 nm to 397 nm, with low-power efficiency of 72%/W and
high-power slope efficiency of 4.5%. The measured performance shows good
agreement with theoretical modeling of the device. We measure optical
bistability effects, and show how they can be used to improve the stability of
the output against pump frequency and amplitude variations.
