Basheer N.S.,Photonics Research Laboratory |
Kumar B.R.,Photonics Research Laboratory |
Kurian A.,Photonics Research Laboratory |
George S.D.,Manipal University India
Applied Physics B: Lasers and Optics | Year: 2013
The plasmonic absorption band of silver nanoparticles in the visible range of electromagnetic spectrum has been successfully exploited to alter the emission characteristics of the Rhodamine 6G dye molecule. The influence of the nanoparticle size on the fluorescence quantum yield of Rhodamine 6G is interrogated via steady state fluorescence as well as dual beam thermal lens technique. The potential of the thermal lens technique that probe nonradiative path in contrast to radiative path exhibited in the fluorescence spectra as a complementary method to measure the quantum yield of a dye molecule is exploited. Analysis of the results clearly indicates that the particle size and the spectral overlap between the emission spectra of Rhodamine 6G, and absorption spectra of the silver nanoparticles determine the quantum yield value of dye-nanoparticle mixture. © 2013 Springer-Verlag Berlin Heidelberg.
Dehbashi R.,Photonics Research Laboratory |
Shahabadi M.,Photonics Research Laboratory
IEEE Transactions on Antennas and Propagation | Year: 2014
By means of the commonly used transformation optics, and a general transformation function, new sets of external cylindrical invisibility cloaks are proposed. For the proposed cloaks, a rigorous analysis is performed and the results indicate zero scattering coefficients outside of the cloaks. Later, a numerical investigation shows that the material dynamic range (MDR) of the proposed cloaks can be as small as half of that of the previously introduced cloak which was based on a simple linear transformation function. The obtained analytical results are verified using a Finite-Element computational analysis. © 1963-2012 IEEE.
Sidharthan R.,Nanyang Technological University |
Kumar M.,Photonics Research Laboratory |
Joseph J.,Photonics Research Laboratory |
Murukeshan V.M.,Nanyang Technological University
Optics Communications | Year: 2014
A five beam interference configuration, with one central circularly polarized beam and four linearly polarized side beams incident at equal tilt angles in two orthogonal planes, is investigated for realization of three dimensional periodic structures. It was observed that when the two pairs of linearly polarized waves are TE-TM polarized, dumb-bell shaped pattern and body centered tetragonal lattice structures could be realized. And when all the four linearly polarized waves are TE polarized, with circularly polarized central beam, woodpile type structures and β-tin type structure could be formed. The obtained β-tin type structure was found to get transformed into diamond cubic type structure when the angle of incidence was increased to an optimum value. © 2014 Elsevier B.V.
Samsheerali P.T.,Photonics Research Laboratory |
Khare K.,Photonics Research Laboratory |
Joseph J.,Photonics Research Laboratory
Optics Communications | Year: 2014
We demonstrate quantitative phase imaging using single shot digital holography for a calibrated spiral phase object. A single frame of near on-axis digital hologram of a spiral phase plate is recorded and the complex object field in the hologram plane is retrieved using a constrained optimization approach. Experimental results show the feasibility of a quantitative phase imaging technique which has superior performance to conventional Fourier filtering methods. Single shot capability suggests that this method is suitable for holographic imaging of dynamic objects such as live biological cells. © 2014 Elsevier B.V.
News Article | February 15, 2017
Mable Fok, an assistant professor of engineering who also leads the university's Lightwave and Microwave Photonics Research Laboratory, received a National Science Foundation CAREER Award to study how photonics can be used to identify and harness unused holes in the radio frequency spectrum. The spectrum is used to keep everything from wireless personal devices like cell phones and computers to medical system technologies and national security defense mechanisms running smoothly. But with the ever-increasing number of technologies relying on the frequencies, space on the spectrum is tight. "Fundamentally, this spectrum is all we have," Fok said. "We cannot create more space. But we can make good use of what we have." All of the applications relying on the spectrum aren't in use around the clock, providing short-lived opportunities for others to use their space on the spectrum. But there currently is no way to rapidly identify which frequencies aren't being used, which is where Fok's research comes in. Fok will use photonics technologies to rapidly scan the spectrum and find frequencies that are not in use. Once identified, those gaps can be used to meet radio frequency needs of various devices. Fok's scheme not only allows the device to talk and listen at the same time using the same frequency, but it also enables the device to be "smart" enough to run away from interference and jamming. Inspired by the glass knifefish, a small electric freshwater family of fish that people sometimes keep as pets in aquariums, Fok's research will create a device to escape from the jamming frequency the same way the fish does. The fish use what's known as a jamming avoidance response, or JAR, to prevent their electromagnetic signals from interfering with those of other knifefish around them. "What if we can borrow the same algorithm and apply it to our radio frequency system?" Fok said. "If someone tries to jam our signal, we'll be able to just move someplace else that no one is using." Fok will also use the NSF grant to help develop an educational app that helps people learn more about the field of photonics. Most people know about fiber optic Christmas trees and high-speed internet, she said, but that's typically where the public's understanding of the emerging technology ends. But photonics offers a smaller, more efficient and less expensive alternative to traditional electronics. For example, electric cables can accommodate, say, 10 people who want to transmit information while optical fiber can service significantly more in less space. Explore further: A fish may hold the key to more efficient wireless networks