MIT researchers have developed a camera that can see around corners to view objects, that would otherwise be hidden from sight, by using ultra short bursts of light. To do this Ramesh Raska and his colleagues adopted the basic principle of a periscope, but instead of mirrors they use walls or floors or doors etc. Light that is emitted in femtosecond (10-15 of a second) long pulses scatters and reflects off the wall, entering unseen places, like for example a room with an articulated wooden doll, where once again a fraction of the light will reflect off the object, travel back along a similar path and reach a camera that can take pictures every 2 trillionths of a second. Knowing the time of arrival of the detected photons enables 3D reconstruction of the hidden object as shown in the video above.

Source: nature.com

In a game of tug of war, the two competing teams are in a fragile balance. A stronger pull on the rope on one side will result in a stronger pull on the other, in a feedback loop of brute force that will eventually end with the capitulation of one of the two teams. As the game progresses, though, the forces at play adjust in such a way as to counterbalance each other, resulting in a net force that produces close to no effect at all—muscles are tense, but neither the teams nor the rope move visibly. Feedback loops that iteratively reach a somewhat stable equilibrium are a common occurrence in everyday life and in physics. What is truly interesting, though, in some cases, is not the condition of equilibrium achieved but the feedback loop itself. Researchers at the Max Planck Institute for the Science of Light in Erlangen, in collaboration with Sapienza University in Rome, developed a theoretical description of light propagating through two narrow, adjacent and parallel strips of glass, each a fraction of a thousandth of a millimetre thick. In such a system, some light leaks out of each of the two parallel strips of glass, called optical waveguides, and—just like any kind of radiation does—exerts a tiny pressure that bends the two strips closer together or away from each other. The result of the bending is a change in the optical properties of the waveguide, which in turn causes the light travelling down the waveguide to spread out of it in a slightly different manner, thus changing the degree of bending once again. This process triggers a complex feedback loop that causes the light to not travel along the entire width of each strip, but rather in precise, orderly beams. This result, if confirmed by experiments, could have interesting applications in optical fibre technology and ultrafast optics. “Focus: A New Way to Channel Light”, APS Physics Butsch et al., “Optomechanical Self-Channeling of Light in a Suspended Planar Dual-Nanoweb Waveguide”, Physical Review Letters (2012)
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In a game of tug of war, the two competing teams are in a fragile balance. A stronger pull on the rope on one side will result in a stronger pull on the other, in a feedback loop of brute force that will eventually end with the capitulation of one of the two teams. As the game progresses, though, the forces at play adjust in such a way as to counterbalance each other, resulting in a net force that produces close to no effect at all—muscles are tense, but neither the teams nor the rope move visibly. Feedback loops that iteratively reach a somewhat stable equilibrium are a common occurrence in everyday life and in physics. What is truly interesting, though, in some cases, is not the condition of equilibrium achieved but the feedback loop itself. Researchers at the Max Planck Institute for the Science of Light in Erlangen, in collaboration with Sapienza University in Rome, developed a theoretical description of light propagating through two narrow, adjacent and parallel strips of glass, each a fraction of a thousandth of a millimetre thick. In such a system, some light leaks out of each of the two parallel strips of glass, called optical waveguides, and—just like any kind of radiation does—exerts a tiny pressure that bends the two strips closer together or away from each other. The result of the bending is a change in the optical properties of the waveguide, which in turn causes the light travelling down the waveguide to spread out of it in a slightly different manner, thus changing the degree of bending once again. This process triggers a complex feedback loop that causes the light to not travel along the entire width of each strip, but rather in precise, orderly beams. This result, if confirmed by experiments, could have interesting applications in optical fibre technology and ultrafast optics.

“Focus: A New Way to Channel Light”, APS Physics

Butsch et al., “Optomechanical Self-Channeling of Light in a Suspended Planar Dual-Nanoweb Waveguide”, Physical Review Letters (2012)

The light-field camera is a new piece of technology that will radically change the way we can take images, and potentially video, in the future. By using a micro-lens array in the plane of the CCD sensor, and relocating the chip to a distance equal to the focal length of the lenses, it is possible to detect both the intensity and direction of the incoming light rays. This means it is possible to post-process each image captured in order to alter the plane of focus. Furthermore, this technology enables multiple perspectives via parallax from a single picture. This video helps to describe the fundamental optical physics behind the technology soon to be released. The company that has produced the first of its kind—Lytro—is a spin-off project from research by Ren Ng, who obtained a PhD at Stanford University in 2006.

Last year the laser turned fifty. While the basic concepts that lead to the invention of the laser were developed between the 1910’s and the 1950’s, it was only in 1960 that the first functioning laser was operated. Nowadays, lasers have found countless applications. But how does a laser actually work? The video above shows how the amplified light leaks out of a laser cavity, while the linked video from Minute Physics covers the basics.