Generation of Therahertz Wave with Frequency 32-Tupling by Four Mach-Zehnder Modulators in Parallel

Abstract

A new method for the generation of terahertz wave with frequency 32-tupling adopting four Mach-Zehnder modulators connected in parallel is presented. The four MZMs can be regarded as two double parallel Mach-Zehnder modulators (DPMZMs) connected in parallel. When the difference of the initial phases of the radio frequency (RF) driving signals between two MZMs in the DPMZM is π/2, the signal from the DPMZM are the optical sidebands of ±4n order. When the difference of initial phase of the RF signals between the two DPMZMs is π/4, the output signals from the two DPMZMs are the optical sidebands of ±8n order, in which the carrier is cancelled by an adjustable optical splitter, the optical sidebands of ±8th order are restrained and the optical sidebands of ±8n (n > 2) order are ignored by setting the modulation index of MZM at a special value, the main optical sidebands left are ±16th order. When the ±16th order optical sidebands are injected the photodetector (PD), the 32-tupling frequency terahertz wave is generated. Principle analysis and simulation test indicate that the optical sideband suppression ratio (OSSR) and the RF spurious suppression ratio (RFSSR) are 46.82 dB, 46.25 dB and 40.8 dB, 42.3 dB, respectively. In addition, the impacts on the OSSR and RFSSR are studied when the values of device parameters deviate from their design values.