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Images 2015

Best image

"Through the thorns", by Miao Zhang

Through the thorns:  Sometimes one has to cut his own way through the thorns. It can be true even in nanoscale. The image shows a top-view of a free-standing silicon membrane with four (or 16) nano-meter-sized pores (nanopores) in the middle. The photograph was taken with a Zeiss optical microscope, using dark field configuration. The distance between nanopores is 4 µm, whereas the membrane is about 110 µm in width and 300 nm in thickness. The silicon membrane becomes almost invisible in the photo because of its flatness. Only a blue halo around implies the membrane is sunken because of the stress. However, fine details of the ‘thorns’ behind the thin membrane have been revealed, thanks to the large numerical aperture of the objective lens. It seemed that the buried oxide layer beneath the silicon membrane was not fully removed by HF, scattering into a shade of ‘a mysterious thorns’ on the photograph. If this membrane were employed in a DNA sequencing/ sensing experiment, DNA strands have to make their way through ‘the thorns’ in order to translocate the nanopores. Original image (jpg 221 kB)

Hornorable mentions

"Aurora in lab" by Aleksandrs Marinins

Aurora in lab: Basically, this is dispersion of white light on RGB prism with dichroic mirrors which we took from the old projector. Liquid Nitrogen is used for visualization. Some days ago northern lights were shining in Stockholm sky, but we were late to see it. Then we decided to create our own laboratory-grown northern lights. Original image (JPG 1016 kB)

"Channel waveguides on a Si chip" by Dimitri Geskus

Al2O3 channel waveguides on a silicon chip: The chip in the photograph has been designed to characterize the propagation loss of light in the Al2O3 waveguides. The waveguides are made in a wandering manner, to increase their length which increases the accuracy of the loss characterization. The bending radii are designed to be relatively large, to avoid additional bending loss. In the picture red light from a HeNe laser is coupled to one of the waveguides using an objective lens. One can clearly see that the intensity inside the waveguide reduces when propagating further towards the end of the waveguide. Still some light reaches the end of the chip, as can be seen by the tiny twinkle of light at the end of the waveguide. To quantify the propagation loss, a picture of the device is taken using a calibrated camera and the intensity reduction throughout the device is analyzed, using image processing software. Some experienced people, with calibrated eyes, can do this by just looking at the device. Original image (png 887 kB)

"and there was light ..." by Walter Margulis

and there was light…: The image shows sunlight focused by a 30 cm wide square Fresnel lens onto a 1-cm wide cylindrical glass rod with polished end faces. The picture is taken outside Electrum in Kista at 15:00 on a sunny afternoon in August. The camera used is a 2012 Iphone 4S camera. The lens holder is a vase made for outdoor gardens from Plantage with a square 30 cm opening and 50 cm length. The borosilicate glass rod is mounted through the bottom of the vase, at its center.  The dark background is obtained with black cardboard inside the vase. Smoke (Marlboro) is blown into the lens holder (vase) to image the light path. According to Fermat’s principle, light travels in straight lines (minimum distance between two points, minimizing the propagation time). In the absence of changes in refractive index (or strong gravitational effects) one does not expects rays of light to bend. Here, however, the source of light is extended and the image shows the envelope of all rays focusing on the surface of the glass rod. It is the envelope that has a curved shape, not the trajectory of each ray between the lens and glass rod. A focused laser beam near the beam waist is often drawn as the curved envelope image, as pictured here, but one often mistakes the optical light paths involved.The image is quite spiritual, suggesting a lit candle. It reminds one of the Biblical text from Genesis about the creation of light. Original image (jpg 493 kB)

"Glowing heart in darkness" by Elena Vasileva

Glowing heart in darkness:  Green light from laser pointer is coupled to the bunch of optical fibers. He-Ne Laser is used for illumination of the central part of the bunch. A bit of luck, and here you see the heart.  Original image (JPG 825 kB)

"Aragon spot" by Philip Bergström and Jonas Bederoff Eriksson (Ack: Marcin Swillo and Gunnar Björk )

Aragon spot: Due to diffraction at the object’s edges there is a bright spot in the center of the shadow. It is known as Arago’s spot or Poisson’s spot ( ). Although the phenomenon is well known today, it is seldom captured using white light since lasers offer a much simpler source of coherent light. The circular object used to create the spot is a metal sphere (a ball bearing ball) with a diameter of 2 mm. It is illuminated by a light beam from a halogen light-bulb. The light-bulb light was made transversely coherent by transmitting it through a single mode fiber and using the output end of the fiber as a “point source”. The photo was captured by illuminating the CMOS sensor-array of a Thorlabs camera and inserting the ball, glued to a transparent and antireflecting slightly focusing lens, inbetween the fiber end and the CMOS array. The distances between the fiber end and the ball, and the ball and the CMOS array, were both around 200 mm. Image is smoothened and contrast enhanced in Photoshop. Original image (jpg 125 kB)

"Mode beating in a slab-waveguide" by Saara-Maarit Reijn

Mode beating in a slab-waveguide: Simulations based on Green functions: In optics, we can easily solve light propagation for symmetrical systems and visualize their solutions by a plot. Nevertheless, in order to solve light propagation for asymmetric devices, we have to use more complex numerical methods. In this case we have used the Green function for stratified media to solve light propagation through a, 500 nm wide, slab-waveguide with an asymmetric perturbation located in the center. The fundamental mode is launched from the left and travels to the right, while it suddenly encounters an asymmetric perturbation in the center of the slab-waveguide. This perturbation causes the light to be partly reflected, transmitted and diffracted. The asymmetry of the perturbation also excites the first order mode inside the slab-waveguide which together with the fundamental mode generates the snake-like mode-beating pattern on the right. A much smaller part of the first order mode is reflected back to the left where we can also see a slight mode-beating pattern. In addition, we see scattering losses above and below the perturbed region where light leaks out of the slab-waveguide. Original image (png 573 kB)

"Routine job" by Sergei Popov

Routine job: Green laser light is propagating inside Rh6G. The setup is used for experimental investigation of polymer gain material. The pump beam is focused on the sample facet into the line. Typically, green light is absorbed by dye molecules emitting yellow light, however the concentration of dye molecules in this sample is very low, and scattering of green light is prevalent, so yellowish light is not explicitly seen on the picture. Original image (JPG 1.2 MB)

"Viking's horn" by Eleonora De Luca, Oscar Martinez, Ruslan Ivanov, Mounir Mensi

Viking's horn: It is indeed a SNOM probe. The 'helmet' is glue filled with glass microspheres used to bind an optical fiber to a tuning fork, while the 'horn' is the extremity of the tapered and coated optical fiber. The fiber is tapered using the CO2 laser pulling technique and coated with >100nm of aluminum. The tip has a radius of curvature of ca. 500nm. To open an aperture through the Al coating, the extremity was cut off using a focused ion beam.  Original image (jpeg 175 kB)

Page responsible:Max Yan
Belongs to: School of Engineering Sciences (SCI)
Last changed: Oct 21, 2015