A diffractive grating is a well-known optical component and is extensively used in many applications. This research work explores application of the diffractive grating in a photoconductive antenna (PCA) of a terahertz time domain spectroscopy (THz-TDS) system, by utilizing benefits of a sub-wavelength grating structure. The grating PCA structure was modeled and simulated by COMSOL Multiphysics software (COMSOL, Inc., Burlington, MA, USA). Performance of the proposed PCA design is studied in terms of its induced photocurrent. The effects of geometrical parameters of the grating are also investigated and analyzed through its optical and electrical responses. Thanks to the increase in absorption of the incident laser’s electric field, the simulation results show a 63% increment of the induced photocurrent in the grating PCA, compared with the conventional planar PCA.

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Lactose plays a significant role in daily lives as a constituent of various food and pharmaceutical products. Yet, lactose intolerance conditions demand low-lactose and lactose-free products in the market. These increasing nutritional claims and labels on food products entail simple and reliable methods of analysis that can be used for meeting quality standards, nutritional claims and legal requirements. In this study, terahertz time–domain spectroscopy (THz-TDS) was employed to analyse α-lactose monohydrate qualitatively and quantitatively in food products. Both absorption spectra and absorption coefficient spectra were investigated for their prediction performance. Regression models for lactose quantification using peak area and height of the absorption peaks 0.53 and 1.37 THz were developed and assessed in infant formula samples. Satisfactory prediction results were achieved in ideal conditions with pure standards, but not in all predictions of infant formula samples. Reasons and further implications are discussed.

One of the most important technological challenges that photoconductive devices in terahertz systems encounter is a viability of cost-effective and large-scale device production. We introduce an economical and mass producible approach to fabricate a substrate material of the photoconductive devices. By using an electron beam irradiator, material properties of GaAs were engineered in controllable manner, achieving comparable performance to that of a well-known photoconductive substrate, LT-GaAs. THz emission of the irradiated substrates was tested and found to be superior to a commercial device in terms of high-power THz signal emission and ability to withstand a high bias voltage.

A metamaterial absorber in the Terahertz (THz) range is simulated and experimentally investigated in this work. The desired absorption frequency, efficiency, and bandwidth can be tuned by changing the metal and dielectric geometric parameters. An absorption greater than 85% for TM polarized light with an incident angle up to 70 • at any azimuthal direction is observed in a circular disc THz metamaterial structure. By adjusting the dielectric silicon dioxide (SiO 2) thickness to 4 µm, an optimal absorption greater than 95% can be achieved at a resonance frequency of 0.97 THz. The experimental results also indicate that using Titanium (Ti) as a metamaterial metal layer provides four times broader absorption bandwidth than Aluminium (Al). This study, which works on polarization-insensitive and wide-angle metamaterial absorbers, can be fundamentally applied to many THz applications including THz spectroscopy, imaging, and detection.