KTP segmented waveguides as concurrent Bragg reflectors and second harmonic generators

Abstract
A periodic modulation of optical nonlinearity by means of ferroelectric domain reversal has led to the generation of blue light by quasi-phase matching in waveguides of, e.g. lithium niobate1,2, lithium tantalate3,2, and potassium titanyl phosphate (KTP)4. When the linear optical constant (index) is also periodically modulated along the propagation direction, these waveguides may serve also as distributed Bragg reflectors5,6. The back reflection of light in a narrow band of wavelengths, subject to the Bragg condition, has been utilized to stabilize a diode laser pump, forcing it to oscillate in a narrower band of wavelengths suitable for second harmonic generation.