On-chip pulsed terahertz systems and their applications

Performance characterization of a self-made terahertz photoconductive antenna

A terahertz (THz) photoconductive antenna is prepared using, to the best of our knowledge, a novel method, which has high yield and strong stability. It eliminates the stripping process of a thin-film THz antenna and effectively prevents the toxicity of the corrosion solution, the easy damage in the transfer process, and the weak bonding with the substrate. First, a 200 µm copper wire is bundled on a low-temperature GaAs epitaxial wafer, and then the electrode of the photoconductive antenna is fabricated using the vacuum evaporation method. Finally, the THz time-domain signal with a high signal-to-noise ratio and good repeatability is obtained using an 800 nm laser. Additionally, the influence of pump light and detection light power on THz signal intensity is studied when the total optical power is unchanged. Results show that when the total power of the laser is greater than a certain value, there is an optimal ratio between the pump power and the detection power, which can maximize the signal-to-noise ratio of the THz wave. This provides a basis for the effective application of a THz antenna and lays a foundation for improving the detection sensitivity of samples.

Single n+-i-n+ InP nanowires for highly sensitive terahertz detection

Developing single-nanowire terahertz (THz) electronics and employing them as sub-wavelength components for highly-integrated THz time-domain spectroscopy (THz-TDS) applications is a promising approach to achieve future low-cost, highly integrable and high-resolution THz tools, which are desirable in many areas spanning from security, industry, environmental monitoring and medical diagnostics to fundamental science. In this work, we present the design and growth of n⁺-i-n⁺ InP nanowires. The axial doping profile of the n⁺-i-n⁺ InP nanowires has been calibrated and characterized using combined optical and electrical approaches to achieve nanowire devices with low contact resistances, on which the highly-sensitive InP single-nanowire photoconductive THz detectors have been demonstrated. While the n⁺-i-n⁺ InP nanowire detector has a only pA-level response current, it has a 2.5 times improved signal-to-noise ratio compared with the undoped InP nanowire detector and is comparable to traditional bulk THz detectors. This performance indicates a promising path to nanowire-based THz electronics for future commercial applications.

Broadband Phase-Sensitive Single InP Nanowire Photoconductive Terahertz Detectors

Terahertz time-domain spectroscopy (THz-TDS) has emerged as a powerful tool for materials characterization and imaging. A trend toward size reduction, higher component integration, and performance improvement for advanced THz-TDS systems is of increasing interest. The use of single semiconducting nanowires for terahertz (THz) detection is a nascent field that has great potential to realize future highly integrated THz systems. In order to develop such components, optimized material optoelectronic properties and careful device design are necessary. Here, we present antenna-optimized photoconductive detectors based on single InP nanowires with superior properties of high carrier mobility (∼1260 cm(2) V(-1) s(-1)) and low dark current (∼10 pA), which exhibit excellent sensitivity and broadband performance. We demonstrate that these nanowire THz detectors can provide high quality time-domain spectra for materials characterization in a THz-TDS system, a critical step toward future application in advanced THz-TDS system with high spectral and spatial resolution.