Khayyam Festival is one of the high-prestigious national festival in which selection of the top thesis and dissertations takes place. We are happy to announce the winning of this award by our doctoral graduate, Dr. Foozieh Sohrabi in the Second National Festival on Research Thesis “Khayyam Award”.
Nonlinear optical measurements of the material showed strong saturable absorption and nonlinear optical extinctions induced by Mie scattering over broad temporal and wavelength ranges. Through comparative studies in thermal-optic switching, the researchers demonstrated that the biomaterial tellurium (Bio-Te) provided definite improvements in the thermal-optic decaying lifetime compared to the materials WS2 and graphene. Professor Werner J. Blau of Trinity College Dublin said that the biologically generated tellurium nanorods could be especially suitable for photonic device applications in the mid-infrared range. “This wavelength region is becoming a hot technological topic as it is useful for biomedical, environmental, and security-related sensing, as well as laser processing and for opening up new windows for fiber optical and free-space communications,” he said. While most optical materials are chemically synthesized, using a biologically based nanomaterial proved less expensive and less toxic, the team said. The team will continue to expand the biomaterial’s potential for use in all-optical telecom switches, and believes the material could be useful for expanding broadband capacity. “We need greater bandwidth and switching speeds,” University of Houston professor Seamus Curran said. “We need all-optical switches to do that.”
For more information:
https://doi.org/10.1038/s41467-019-11898-z
We demonstrate antenna-coupled spintronic terahertz (THz) emitters excited by 1550 nm, 90 fs laser pulses. Antennas are employed to optimize THz outcoupling and frequency coverage of ferromagnetic/nonmagnetic metallic spintronic structures. We directly compare the antenna-coupled devices to those without antennas. Using a 200 lm H-dipole antenna and an ErAs:InGaAs photoconductive receiver, we obtain a 2.42-fold larger THz peak-peak signal, a bandwidth of 4.5 THz, and an increase in the peak dynamic range (DNR) from 53 dB to 65 dB. A 25 lm slotline antenna offered 5 dB larger peak DNR and a bandwidth of 5 THz. For all measurements, we use a comparatively low laser power of 45mW from a commercial fiber-coupled system that is frequently employed in table-top THz time-domain systems.
Schematic of THz emission from photoexcited FMANM bilayers, plain and microstructured. (a) A femtosecond laser pulse triggers ultrafast spin transport from the FM into the NM layer where the spin current js flowing along the z axis is converted into a charge current jc along the y direction, acting as a source of THz radiation. The direction of the in-plane magnetization of the FM layer is set along the x axis by an external magnetic field Bext. (b) Current distribution in an unstructured (plain) bilayer and (c) the STE bilayer embedded in the gap of an antenna. Note that THz current generation by the ISHE is independent of emitter type and antenna choice