Simultaneous amplitude modulation and wavelength conversion in a monolithic periodically-poled lithium niobate

We report simultaneous frequency conversion and amplitude modulation in an optical second harmonic generator by electro-optically controlling the relative phase between the 1064-nm fundamental and the 532-nm second harmonic fields in a dispersion crystal section between two periodically poled lithium niobate (PPLN) sections. Theoretical derivation and experimental demonstration were carried out for two novel crystal configurations, including a linear cascaded configuration in which a 1-cm dispersion section is sandwiched between two 2-cm PPLN sections, and a folding-crystal configuration in which the mixing waves traverse twice in a 2-cm PPLN section through total internal reflections in a 1.5 cm dispersion section. Due to the coherence enhancement in the constructive phase between the two SHG fields in the two PPLN sections, we measured a 30% increase in conversion efficiency compared to a continuous 4-cm PPLN under the same condition. The measured half-wave voltage for the amplitude modulation is 1.1 volt × d(μm) / l_d (cm), where d is the separation of the electrodes and l_d is the length of the electrodes.