THz applications of multimode laser diodes: a review

Abstract

Investigations are ongoing to develop cheaper THz time-domain spectroscopy (THz-TDS) systems. In this context, many studies have been published in which multimode laser diodes (MLDs) are used as light sources in THz- TDS systems. There is another method for cost-reduction. Photomixing employs two single-mode LDs and does not require a pulse laser, and then realizes a reduced-cost system. A comprehensive report has been presented by examining the work done up to now. In these studies, it has been shown that the characteristics of MLDs, the effects of antenna structures on THz signal production, the difficulty of collimation of the MLD radiation beam, and the contribution of fiber-based systems are of utmost importance. It has also been determined that mode spacing has a significant role in THz radiation generation. In addition, successful SN ratio enhancement and imaging studies have shown that a more compact and cheaper THz-TDS system can be established using MLDs as a light source. Macor and RC51HF samples have been analyzed using a MLD-TDS created in the same way as in previous studies and results are given.