Abstract
This work presents a study of photoconductive (PC) terahertz (THz) emitters based upon varied bow-tie (BT) antenna structures on the semi-insulating (SI) forms of GaAs and InP. The BT antennas have electrodes in the form of a Sharp BT, a Broad BT, an Asymmetric BT, a Blunted BT, and a Doubled BT. The study explores the main features of PC THz emitters for spectroscopic studies and sensors application in terms of THz field amplitude and spectral bandwidth. The emitters’ performance levels are found to depend strongly upon the PC material and antenna structure. The SI-InP emitters display lower THz field amplitude and narrower bandwidth compared to the SI-GaAs emitters with the same structure (and dimensions). The characterized Doubled BT structure yields a higher THz field amplitude, while the characterized Asymmetric BT structure with flat edges yields a higher bandwidth in comparison to the sharp-edged structures. This knowledge on the PC THz emitter characteristics, in terms of material and structure, can play a key role in future implementations and applications of THz sensor technology.
Highlights
Terahertz (THz) radiation lies within a distinct region of the electromagnetic spectrum, with frequencies spanning 0.1 to 10.0 THz, placing it between microwave and infrared spectra [1]
The spectra are given for SI-GaAs and SI-InP as the PC material, with the THz spectral amplitudes shown on a log scale in the upper insets and the scanning electron microscope (SEM) images of the structures shown in the lower insets
Each structure can be envisioned as two isosceles triangles, with their tips meeting at the PC gap, spectra are given for SI-GaAs and SI-InP as the PC material, with the THz spectral amplitudes shown on a log scale in the upper insets and the scanning electron microscope (SEM) images of the structures shown in the lower insets
Summary
Terahertz (THz) radiation lies within a distinct region of the electromagnetic spectrum, with frequencies spanning 0.1 to 10.0 THz, placing it between microwave and infrared spectra [1]. The resultant THz applications in fields such as spectroscopy and sensing are of growing interest with a trend seen towards THz on-chip sensors Such miniaturization can sacrifice performance, as seen through effects such as charge carrier screening and saturation—and so it becomes necessary to optimize (and understand) the THz emission process [2]. The characteristics of the emitted THz radiation rely heavily upon the PC THz emitter’s features—and so there is an ongoing struggle to understand the photoexcitation process and optimize the emission. This is often done with thought to the PC THz emitter’s material and structure. The PC material for the THz emitter will ideally have a high carrier mobility, high breakdown voltage, and suitable bandgap for the pump
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