THz Signal Generator Using a Single DFB Laser Diode and the Unbalanced Optical Fiber Interferometer

Abstract

This paper presents a frequency-modulated optical signal generator in the THz band. The proposed method is based on a fast optical frequency sweep of a single narrowband laser diode used together with an optical fiber interferometer. The optical frequency sweep using a single laser diode is achieved by generating short current pulses with a high amplitude, which are driving the laser diode. Theoretical analysis showed that the modulation frequency could be changed by the optical path difference of the interferometer or optical frequency sweep rate of a laser diode. The efficiency of the optical signal generator with Michelson and Fabry–Perot interferometers is theoretically analyzed and experimentally evaluated for three different scenarios. Interferometers with different optical path differences and a fixed optical frequency sweep rate were used in the first scenario. Different optical frequency sweep rates and fixed optical path differences of the interferometers were used in the second scenario. This paper presents a method for optical chirp generation using a programmable current pulse waveform, which drives a laser diode to achieve nonlinear optical sweep with a fixed optical path difference of the interferometer. The experimental results showed that the proposed signals could be generated within a microwave (1–30 GHz) and THz band (0.1–0.3 THz).

A Novel System for Quasi-Continuous THz Signal Transmission and Reception

“…The emitted light from the DFB laser diode is modulated within the unbalanced optical fiber Michelson interferometer. In the preliminary work [14], a modulation frequency up to 300 GHz was achieved and confirmed with the measurement. Regarding the analysis of the current waveform, structure of the DFB laser diode and high-frequency modulation using the optical fiber interferometer, the theoretical limit of the system was set to 1.25 THz.…”

“…The proposed OSG consists of a fast frequency swept laser source and an unbalanced optical fiber interferometer for optical signal modulation. The theoretical model of optical modulation in unbalanced optical fiber interferometers is presented in [14]. The backreflected optical intensity from the interferometer is described as…”

“…In the proposed optical signal generator, T s is equal to the driving current's waveform duration. An overlap efficiency factor was introduced in [14], which defines the fraction of the signal subjected to the interference in the optical fiber interferometer…”

“…In this paper, we proposed a quasi-continuous wave (QCW-THz) system that utilizes an optical signal generator (OSG), presented in a preliminary work [14], with the PCA emitter and PCA detector. The proposed OSG is based on commonly available and low-cost electronic components used widely in telecommunications.…”

Propagation and Transformation of Vortexes in Linear and Nonlinear Radio-photon Systems

“…Finally, we can mention some alternative solutions for the THz generation. The terahertz signal in [37] is formed by fast tuning of the DFB laser optical frequency using a fiber optical interferometer. In [38], a terahertz signal with a power of the milliwatt order is nonlinearly generated using an optimized mid-infrared quantum cascade laser.…”