Periodically-poled lithium niobate devices

Periodically-poled lithium niobate (PPLN) offers many properties that make it attractive for devices. It provides a significantly increased nonlinearity compared with bulk lithium niobate: it allows phase-matching of frequency-conversion processes for any frequencies in its wide transmission bandwidth: it can be fabricated with special structures, such as an aperiodic grating, which allow effects to occur that have no counterparts in bulk nonlinear media. These properties offer novel devices and major enhancement in many existing devices. We will review a number of these devices, giving particular emphasis to parametric devices such as optical parametric oscillators, amplifiers and generators. The high parametric gain achievable with modest pump powers has allowed an important convergence between the pump power requirements of PPLN devices and the powers available from fibre laser devices. Prospects that stem from this convergence will be considered