Terahertz Radiation Shaping Based on Third-Order Dispersion and Self-Phase Modulation in Standard Single-Mode Optical Fiber Jesús Palací & Borja Vidal Received: 26 December 2011 / Accepted: 9 April 2012 / Published online: 21 April 2012 # Springer Science+Business Media, LLC 2012 Abstract Third-order dispersion and self-phase modulation in standard single-mode fibers are employed in a fiber-based THz time domain spectroscopy system for radiation shaping. Ultra-short optical pulses are converted into trains of pulses, thus shaping the THz radiation emitted by photoconductive antennas operating at telecom wavelengths. The proposed archi- tecture allows narrowband and wideband THz emission as well as tunability of the central frequency. Since the shaping takes place in standard optical fiber the architecture could be potentially implemented without requiring any additional device. Experiments showing the principle of operation have been performed demonstrating tunability of the central frequency between 350 and 800 GHz and bandwidth from 150 GHz to the full bandwidth of the system. Keywords Terahertz spectroscopy . Photoconductive materials . Nonlinear optics . Optical signal processing 1 Introduction Radiation generated in the sub-millimeter band is finding an increasing number of applica- tions in different fields from astronomy and spectroscopy to communications, non- destructive material testing, imaging and biology/medical sciences [1, 2]. However, strong challenges persist unsolved in terms of efficient and versatile generation and detection. Notable progress has been done for signals in the lower part of this band by electrical upconversion from the microwave region with several commercial solutions being available. Quantum-cascade lasers [3] have attracted great interest because they are able to provide relatively high THz power. However they usually work at high frequencies, limiting their deployment to the upper part of the THz region, and require cryogenic cooling. On the other side photonic-based approaches offer reasonable power levels and flexibility to implement J Infrared Milli Terahz Waves (2012) 33:605–614 DOI 10.1007/s10762-012-9896-8 J. Palací (*) : B. Vidal Valencia Nanophotonics TechnologyCenter, Universidad Politécnica de Valencia, Camino de Vera s/n, 46022, Building 8F, Valencia, Spain e-mail: jespalpe@ntc.upv.es