At the beginning of this year, my friend Jacquelyn Gill (who blogs over at The Contemplative Mammoth) suggested an interesting resolution for academics like us: read at least one scientific paper a day for the entire year. This has been hashtagged on twitter as #365papers and, as I am always up for the latest fad, I decided to join in. I seem to be too unfocused to actually tweet details about each paper I read, so I thought I would summarize my reading every week or so right here, with a short description of what each paper is about!
So, without further ado… here’s part 1 of 365 papers!*
1/1: Multichannel computer-optics components matched to mode groups, V.I. Adzhalov, M.A. Golub, S.V. Karpeev, I.N. Sisakyan and V.A. Soĭfer (1990). As part of my in-progress textbook on singular optics, I’ve been studying various methods to generate and detect vortex beams. This paper is one of a series that covers an optical element dubbed a “modan,” which uses holographic techniques to diffract different vortex modes into different directions.
1/2: Partially coherent beam propagation in atmospheric turbulence [Invited], G. Gbur (2014). My own paper, which may be cheating a little, but I needed to refresh my memory on the topic in preparation for a talk! In short: when light propagates in the atmosphere, the random fluctuations due to turbulence produce unacceptable fluctuations in the light beam. By using a partially coherent (pre-randomized) beam, it is possible to “wash out” these fluctuations.
1/3: Direct Observation of Transfer of Angular Momentum to Absorptive Particles from a Laser Beam with a Phase Singularity, H. He, M. E. J. Friese, N. R. Heckenberg, and H. Rubinsztein-Dunlop (1995). One highly practical aspect of vortex beams is that they carry angular momentum, and that angular momentum can be imparted to microscopic particles to set them spinning! This paper was the very first to observe the use of vortex beams to trap and spin particles.
1/4: Scale and rotation invariant optical correlator, Y. Saito, S. Komatsu, H. Ohzu (1983). In the 1980s, there was a big push to do image processing, such as facial recognition, entirely using optical devices. This was before high-power computers existed that could do the job. One problem with such an optical strategy? Most systems were highly sensitive to slight changes in the size or orientation of an image. Saito and collaborators designed a complicated system that is completely sensitive to such variations.
1/5: Wave-optics description of self-healing mechanism in Bessel beams, A. Aiello and G.S. Agarwal, (2014). A paper by one of my colleagues, G.S. Agarwal! “Bessel beams,” beams which have a transverse profile in the form of a Bessel function, are also known as “non-diffracting beams” because they have the surprising ability to propagate long distances without spreading. Even stranger, they have long been known to “self-heal”: when partially obstructed by an obstacle, they reconstitute into their original form further downstream. In this paper, a simple explanation of this effect is given using wave optics.
1/6: Geometrical transformations in optics, O. Bryngdahl (1974). I’ve spent a lot of time on this blog talking about transformation optics, a mathematical technique by which optical cloaks, among other devices, can be created through the use of sophisticated geometrical techniques. This paper by Bryngdahl is a sort of precursor to that idea: he describes the creation of optical devices which can perform geometric transformations on optical beams. Bryngdahl’s strategy was used in the paper of 1/4 above.
1/7: Products of Schell-model cross-spectral densities, Z. Mei, O. Korotkova, and Y. Mao (2014). Another paper by a colleague, O. Korotkova! In describing the statistical properties of light, which is needed to study partially coherent light as in the paper of 1/2, one must introduce mathematical correlation functions that describe how light between two spatially separated points is correlated. However, it is quite hard to find unique correlation functions, as relatively few are known and they must satisfy strict mathematical requirements. In this paper, conditions under which the products of multiple correlation functions is still a valid correlation function itself is considered.
1/8: Optical coherence gratings and lattices, L. Ma and S.A. Ponomarenko (2014). Remember what I said about correlation functions being hard to find? In this paper, by a former classmate (Ponomarenko), it is shown that it is possible to make the correlations of light periodic, i.e. repeating in space and/or time. It is an interesting result which may have many practical implications.
1/9: Position, rotation, and scale invariant optical correlation, D. Casasent and D. Psaltis (1976). Another paper that takes advantage of Bryngdahl’s geometric transformations to design optical pattern recognition devices. Obviously, I am discussing this topic in some detail in my textbook!
1/10: Deformation invariant optical processors using coordinate transformations, D. Psaltis and D. Casasent (1977). One final paper on optical pattern recognition, this article generalizes the principle to make the device resistant to a broad class of deformations beyond rotation and scaling.
1/11: Speckle-free laser imaging using random laser illumination, B. Redding, M.A. Choma and H.Cao (2005). Lasers are really great light sources, but they are problematic for imaging for the same reason they are problematic in atmospheric turbulence. Coherent lasers will produce interference patterns that can make it very difficult to recognize details in an image — this “speckle” can be seen as the graininess when you shine a laser pointer on the wall. Can we keep the high power of ordinary lasers but reduce the speckle? Yes, by the use of random lasers, which bounce light around in a random medium before allowing it to escape. This paper compares the use of random lasers in imagine with ordinary lasers and more conventional light sources.
I’ll discuss more #365papers in a week or so!
* Not sure if I’ll keep this up all year, but we’ll see.