Xiao et al. demonstrate the generation of nanosecond mid-infrared pulses via fast modulation of thermal emissivity enabled by the absorption of visible pump pulses in unpatterned silicon and gallium arsenide. The free-carrier dynamics in these materials result in nanosecond-scale modulation of thermal emissivity, which leads to nanosecond pulsed thermal emission. To their knowledge, the nanosecond thermal-emissivity modulation in this work is three orders of magnitude faster than what has been previously demonstrated. They also indirectly observed subnanosecond thermal pulses from hot carriers in semiconductors. The experiments are well described by their multiphysics model. Their method of converting visible pulses into the mid infrared using modulated emissivity obeys different scaling laws and can have significant wavelength tunability compared to approaches based on conventional nonlinearities.
Light is a very powerful and precise tool, allowing us to control, shape and create new phases of matter. In such tasks, the magnetic component of a light wave is essential in defining the wave’s helicity, but it influences the optical response of matter only weakly. Chiral molecules offer a typical example, in which the weakness of magnetic interactions hampers their ability to control the strength of their chiro-optical response, limiting it at several orders of magnitude below the full potential. Here, they introduce and theoretically analyse a new type of chiral light: freely propagating, locally and globally chiral electric fields, which interact with chiral matter extremely efficiently. They show that this synthetic chiral light enables full control over the intensity, polarization and propagation direction of the nonlinear enantio-sensitive optical response of randomly oriented chiral molecules. This response can be quenched or enhanced at will in a desired enantiomer, opening up efficient ways to control chiral matter and for ultrafast imaging of chiral dynamics in gases, liquids and solids.
Footprint of Plexcitonic States in Low Power Green Blue Plasmonic Random Laser
S. F. Haddawi, M. Mirahmadi, H. Mbarak, A.K. Kodeary, M. Ghasemi, S. M. hamidi .
Green – blue plasmonic random laser is attained by two dimensional plexcitonic structure. The main gain plexcitonic media contained two dimensional periodic arrays of Gold nanowires which is covered by dye layer. Due to the change in the strength of exciton and plasmon coupling in these plexcitonic gain structures, different close loop and thus random lasing must be takes place. For this purpose, we fabricate six samples with different plexcitonic power and pumped fabricated two dimensional nanostructures by green nano-second pulsed laser. Our results show efficient coherent random lasing due to the plexcitonic nanostructure in the blue because two photon absorption and also green part of the visible spectral region considering its applicability in the design and fabrication of compact and miniaturized random laser sources.
Congratulations to our new paper “A design procedure for fan-out improvement in all-optical photonic crystal logic design” by Hojjat Sharifi, Seyyedeh Mehri Hamidi and Keivan Navi
In this paper, a general method is proposed to improve the fan-out parameter for all-optical logic gates and functions. Two different types of devices are designed to increase the fan-out of a logic operation and its inverted logic. Nonlinear cavities are used to design driving units. Silicon nanocrystal is used as the nonlinear material to create the required frequency shift for different values of input power. Plane wave expansion and finite difference time domain methods are used to simulate and analyze the proposed structures. The propagation delay of the proposed structure is less than 1.5 ps and the maximum required power for fan-out of three is 15 W.
Researchers from the University of Illinois at Urbana-Champaign have developed soft, microscopic, swimming biohybrid robots powered by skeletal muscle tissue that is stimulated by onboard motor neurons. The neurons have optogenetic properties — upon exposure to light, they fire to actuate the muscle tissue. The body of the biohybrid swimmer consists of a free-standing soft scaffold, skeletal muscle tissue, and an optogenetic stem cell-derived neural cluster containing the motor neurons. The research team had previously developed self-propelled swimming biobots powered by beating cardiac muscle cells derived from rats. “That generation of singled-tailed bots utilized cardiac tissue that beats on its own, but they could not sense the environment or make any decisions,” professor Taher Saif said. In the new study, the researchers applied an optogenetic neuron cell culture, derived from mouse stem cells, adjacent to muscle tissue to create a biohybrid robot.
The researchers believe that this advancement could lead to the development of multicellular engineered living systems able to respond intelligently to environmental cues, with applications in bioengineering, medicine, and self-healing materials technologies. “Given our understanding of neural control in animals, it may be possible to move forward with biohybrid neuromuscular design by using a hierarchical organization of neural networks,” Saif said. The team acknowledges that, like living organisms, no two biohybrid machines will develop to be exactly the same. “One may move faster or heal from damage differently from the other — a unique attribute of living machines,” Saif said.
For more information: https://doi.org/10.1073/pnas.1907051116
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:
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
Congratulations to our new paper”Control of nonlinear refractive index of AuNPs doped with nematic liquid crystal under external electric field” by H. Mbarak, A. K. Kodeary, S. M. Hamidi, E. Mohajarani, Y. Zaatar
In the present work, the nonlinear refractive index of gold nanoparticles (NP) doped with nematic liquid crystal (NLC) is determined using Z-scan technique. The gold NPs were synthesized by laser ablation (Nd: YAG laser at 1064 nm) dispersed in liquid deionized water. This work was especially done using a close aperture placed in front of the detector to show the effect of the nematic liquid crystal (E7) on the nonlinear refractive index of the Au NPs under an external electric field. It’s found experimentally, that the nonlinear refractive index of the gold nanoparticles doped with E7 can be varied by changing both the compositional percentage of gold NPs and NLC molecules. The obtained nonlinear refractive index of the samples showed that nematic liquid crystal (E7) can act as a good material for controlling the third order nonlinear coefficient due to its large nonlinear optical properties.