After Image

The beauty of light, as seen on the last page of each OPN issue

Cuvettes with Fluorescent Dyes

Two plastic cuvettes, filled with different fluorescent dyes, are simultaneously excited by lasers operating at two different wavelengths. The left-hand cuvette, filled with Hoechst33342, shows greenish fluorescence with 375-nm laser excitation; the right-hand cuvette, with propidium iodide, fluoresces red with 488-nm excitation.

—Tatevik Chalyan, B-PHOT Brussels Photonics Team, Vrije Universiteit Brussel, Belgium

01 Apr 2020

Colored solar crescents

During a solar eclipse, the sun’s image, reflected from the screen of a mobile phone, is diffracted by the screen’s pixels, giving rise to multiple colored solar crescents.

—Akhileshwar Mishra, IISER Thiruvananthapuram, India

01 Mar 2020

The Soyuz MS-15 spacecraft

The Soyuz MS-15 spacecraft ascending into space after its launch from Kazakhstan on Wednesday, 25 September 2019, photographed from aboard the International Space Station.

—NASA Expedition 60 astronaut Christina Koch

01 Feb 2020

Two-photon fluorescence

Counter-propagating femtosecond laser beams excite two-photon fluorescence in dye cuvettes. A bright zone appears near the center where the pulses meet.

—Theodor W. Hänsch and Nathalie Picqué, MPI of Quantum Optics

01 Jan 2020

An optical fiber with 3-D printed doublet Fresnel lenses

An optical fiber with 3-D printed doublet Fresnel lenses is inserted into a water droplet for imaging the beam profile by an inverse microscope. A white-light laser, passed through the microscope objective for alignment, causes the 3-D printed structure’s blue color in the refracted image on the droplet surface. [OPN 2019 Photo Contest Editors’ Choice]

—Asa Asadollahbaik and Moritz Floess, 4th Physics Institute, University of Stuttgart, Germany

01 Dec 2019

The Tongue of Alaska’s Malaspina Glacier

False-color composite image made using infrared, near infrared and green wavelengths. The image was acquired by Landsat 7’s Enhanced Thematic Mapper plus (ETM+) sensor on 31 August 2000.

—NASA/USGS

01 Nov 2019

Output Light Field

Output light field of a tapered tip of an optical single-mode fiber, in which blue light and green light are coupled, reflected by a sheet of paper.

—Frederik N. Hasselmann, WWU Münster, Germany

01 Oct 2019

Hourglass toy

A ~532-nm green laser beam, passed through a pointer’s photonic-crystal cap to produce multiple diffracted beams, excites the pink dye in an hourglass toy, causing the dye to fluoresce in a golden-orange color along the path of the diffracted beams.

—Omar Khayyam and Syed Abuthahir Ziaudeen, Dr. Zakir Husain College, Ilayangudi, India

01 Sep 2019