Items tagged with "photons"
The concept of temperature is critical in describing many physical phenomena, such as the transition from one phase of matter to another. Turn the temperature knob and interesting things can happen. But other knobs might be just as important for studying some phenomena. One such knob is chemical potential, a thermodynamic parameter first introduced in the nineteenth century by scientists for keeping track of potential energy absorbed or emitted by a system during chemical reactions.
From NIST TechBeat--It’s not lightsaber time, not yet. But a team including theoretical physicists from JQI and NIST has taken another step toward building objects out of photons, and the findings hint that weightless particles of light can be joined into a sort of “molecule” with its own peculiar force. Researchers show that two photons, depicted in this artist’s conception as waves (left and right), can be locked together at a short distance.
Ring resonators are circular waveguides that are used as optical cavities. They look like tiny racetracks and are often fabricated from silicon. Photons can enter and exit a resonator and even move to neighboring waveguides through evanescent coupling. The micro-rings only let light waves circulate-- “resonate”-- if they have the right wavelength. This image, featured on the cover of the December 2013 issue of Nature Photonics, depicts an array of ring resonators designed to be a photonic analog to electrons experiencing quantum Hall physics. Read more to learn more about these micro-racetracks.
Optical cavities can be made by arranging two mirrors facing each other. In this example, light bounces back and forth, forming a standing wave between the mirrors. One of the mirrors is designed to leak out a fraction of the light. Because of the boundaries created by the mirrors, the cavity will only build up light that satisfies a resonance condition--the light's wavelength must be a half-integer multiple of the cavity length. This means that cavities can be used to create narrow frequency sources. Read more to learn more about a cool research result using cavities.
Polarization refers to the orientation of traveling waves with respect to a well-defined direction. Polarized sunglasses shield your eyes from light having certain orientations. Projectors that display images having different polarizations are used to generate the 3D effects seen in movies. In quantum information research, two different polarization states of light can make up a photonic qubit.
In this week’s issue of Nature Photonics scientists at the Joint Quantum Institute (*) report the first observation of topological effects for light in two dimensions, analogous to the quantum Hall effect for electrons. To accomplish this, they built a structure to guide infrared light over the surface of a room temperature, silicon-on-insulator chip.