We describe the use of GaAs-based semiconductor optical waveguides for nonlinear frequency conversion of femtosecond pulses in the infrared. Different techniques for the realization of phase matching, including artificial birefringence, quasi-phase-matching and modal dispersion, are reported and analysed and key issues relating to efficiency, practicality and applicability are discussed. Using the data obtained from these experiments, an overall comparison is made with other prominent techniques in order to identify the most promising and viable route to the development of efficient semiconductor waveguide frequency conversion devices for incorporation in the future generation of integrated photonic networks. Millenia Ti:Sapphire PPLN OPO Signal / Idler RG 850 P M T Lock-In Amp. Chopper Drive Voltage Control Beam Diagnostics λ /2 @ 1.55 µ m Chopper Monochromator Flipper Mirrors Polarizing Beam splitter IR Camera Sample X 40 X 20 X 40 X 20 Beam Diagnostics λ /2 @ 1.55/2.0 µ m Flipper Mirrors Polarizing Beam splitter IR Camera