Hybrid organic–inorganic perovskites, while well examined for photovoltaic applications, remain almost completely unexplored in the terahertz (THz) range. These low-cost hybrid materials are extremely attractive for THz applications because their optoelectronic properties can be chemically engineered with relative ease. Here, we experimentally demonstrate the first attempt to apply solution-processed polycrystalline films of hybrid perovskites for the development of photoconductive terahertz emitters. By using the widely studied methylammonium-based perovskites MAPbI₃ and MAPbBr₃, we fabricate and characterize large-aperture photoconductive antennas. The work presented here examines polycrystalline perovskite films excited both above and below the bandgap, as well as the scaling of THz emission with the applied bias field and the optical excitation fluence. The combination of ultrafast time-resolved spectroscopy and terahertz emission experiments allows us to determine the still-debated room temperature carrier lifetime and mobility of charge carriers in halide perovskites using an alternative noninvasive method. Our results demonstrate the applicability of hybrid perovskites for the development of scalable THz photoconductive devices, making these materials competitive with conventional semiconductors for THz emission.

Optical Engineering (OE) publishes peer-reviewed papers reporting on research, development, and applications of optics, photonics, and imaging science and engineering.

Diamond is a promising material for terahertz applications. In this work, we use a non-invasive optical pump–terahertz probe method to experimentally study the photoinduced carrier dynamics in doped diamond monocrystals and a new diamond-silicon composite. The chemical vapor deposited diamond substrate with embedded silicon microparticles showed two photoinduced carrier lifetimes (short lifetime on the order of 4 ps and long lifetime on the order of 200 ps). The short lifetime is several times less than in boron-doped diamonds and nitrogen-doped diamonds which were grown using a high temperature–high pressure technique. The observed phenomenon is explained by the transport of photoexcited carriers across the silicon–diamond interface, resulting in dual relaxation dynamics. The observed phenomenon could be used for ultrafast flexible terahertz modulation.

An optical pump/terahertz probe method was utilized to evaluate the active impurity concentration and structural state in the sulfur-implanted (1018–1021 cm−3) surface layers of the crystalline silicon wafer, both in the as-implanted and nanosecond-laser annealed states. This method enabled, for the first time, non-contact electrical measurements of carrier scattering and recombination rates even in the implantation-disordered, poorly conducting hyperdoped Si samples. These measurements enabled the direct comparison of their active impurity content vs the concentration of implanted sulfur and its laser-annealing activation from the cluster form, indicating sulfur precipitation down to the equilibrium solubility limit in the as-implanted samples at the high impurity concentrations of 1020–1021 cm−3. These studies revealed the advanced potential modalities of the versatile optical pump/terahertz probe method for the unbiased non-contact acquisition of key electrical parameters in poorly conducting materials.

A method for generation of ultra-wideband electromagnetic pulses with a nanosecond length and a picosecond rise time has been proposed and studied. A horn antenna with a photoconductive switch irradiated by laser pulses has been used as an emitter. It is shown that the length of ultra-wideband electromagnetic pulses is determined by the antenna length and the semiconductor material and the rise front is determined by the front of laser pulses used to initiate a photoconductive switch. Typical pulse lengths of ~1 ns with a rise front of up to ~34 ps are reported.