Synopsis: A light beam passes through it

Experiments confirm a decades-old prediction that carefully tailoring the shape of a barrier lets light of many colors pass through it without reflection.
Synopsis figure
A. Szameit et al., Phys. Rev. Lett. (2011)

Abrupt interfaces disrupt wave propagation. For example, light passing from air into a sheet of glass will partially reflect backwards. When the light exits back into air, there is a second reflection that can cancel the first for light of just the right frequency, given the refractive index and thickness of the sheet. The wave nature of electrons creates similar effects when they encounter a region with a changing electrostatic potential. But early in the history of quantum mechanics, theorists realized that certain smoothly varying potential profiles could eliminate the reflection of electrons over a wide range of frequencies.

As it turns out, the same concepts work for light: intense light pulses known as solitons create precisely this kind of profile in the refractive index of the surrounding medium, eventually becoming trapped. Creating permanent versions of such “reflectionless potentials” has, however, proved difficult. In Physical Review Letters, Alexander Szameit of the Technion in Haifa, Israel, and colleagues in Germany and Australia at last implement the lack of light reflection in the laboratory.

In their experiments, a beam of light travels along an array of closely spaced, parallel waveguides created in a glass sample through direct laser-writing. By changing the spacing between some of the waveguides, the researchers construct a stripe along the length of the array that has a different refractive index modulation relative to the rest of the array. For almost any change in spacing, light traveling diagonally across the stripe is partially reflected, as usual. But a stripe having the special variation suggested by theory generates almost no reflection. The technique adds to the bag of tricks that researchers have for manipulating light. – Don Monroe


Announcements

More Announcements »

Subject Areas

Optics

Previous Synopsis

Graphene

Carbon flowers

Read More »

Next Synopsis

Quantum Information

Photosynthesis disentangled?

Read More »

Related Articles

Synopsis: A Circularly Polarized Laser for All Labs
Optics

Synopsis: A Circularly Polarized Laser for All Labs

Researchers have developed a compact, circularly polarized x-ray source for studying biological materials. Read More »

Synopsis: The Helical Factor
Optics

Synopsis: The Helical Factor

An array of helical elements absorbs radiation of a certain frequency while casting no shadow in light over a range of other frequencies. Read More »

Focus: Nanoscale Device Amplifies Fiber-Optic Signals
Optics

Focus: Nanoscale Device Amplifies Fiber-Optic Signals

Researchers have demonstrated an amplifier for near-infrared light that is 20 times more powerful than previous devices and small enough to fit on an integrated circuit. Read More »

More Articles