The image was taken using the Zeiss Gemini scanning-electron microscope in KTH’s Electrum lab in Kista. It depicts a broken nitride membrane (purple) on a silicon substrate (pink) that had been exposed to a KOH bath. The inverse-pyramid-shaped hole in the silicon stems from the KOH etching. The membrane is ruptured due to strain. False colors are added using GIMP. Thin membranes like this can be used for, among others, combined PL-AFM-TEM (PL: photo luminescence) measurements of quantum dots spun onto the membranes, high-throughput parallel optical DNA sequencing (with DNA strings with PL-color-coded base pairs pulled through nanopores fabricated in such a thin membrane), and spin filtering of electrons (after coating with extremely thin magnetic metal films). (image and text: Benjamin Bruhn)
An image of the light from a halogen lamp radially filtered through a 0.5 mm diameter iris. The image is taken through a nominally 150 um diameter pinhole, serving as a "lens". Several bands of concentric “rainbow” Airy rings form by diffraction. It can be seen that this image has less blue and more red components that the above picture due to the lower color temperature of the halogen light as compared with the sun. Photo taken with a Thorlabs 150 um diameter pinhole mounted about 50 mm from the CMOS-detector of a Sony a300 digital camera mounted on an optical bench.
Picture shows the effect of a spark on a KTP crystal captured by an optical microscope. During periodically poling the crystal a short circuit happened due to inappropriate isolation between electrodes. This results in a spark which break the crystal in a tree shape as it is shown in the picture.
An image of the sun taken through a nominally 50 um diameter pinhole as a "lens". Had the pinhole been perfectly circular, several bands of concentric “rainbow” Airy rings would have formed. However, as dust had attached to the inner surface of the pinhole, the Fourier image of the non-circular hole formed, with the spectral components of the sun appearing periodically (as in a rainbow) in the radial direction. Photo taken with a Thorlabs 50 um diameter pinhole mounted about 50 mm from the CMOS-detector of a Sony a300 digital camera mounted on a tripod. Exposure time ¼ s at ISO 200.
Ultra‐broadband frequency downconversion to the infrared and simultaneous upconversion from that infrared band to the visible produced in a nonlinear crystal (periodically poled LiTaO3) by a beam at 806 nm. The crystal is seen as a white and red‐orange rectangle on the right in the photo, the input beam entering from the right. Within the crystal the downconversion process produces an octave spanning (180THz) supercontinuum in the infrared. The non‐visible supercontinuum gives rise to sum-frequency generation in the very same crystal, causing a set frequency components within the continuum to be upconverted to visible frequencies. Hence, the wide range of colours seen in the photo offers a way to illustrate the broadness of the continuum. In the photo, the visible light is imaged on a screen after passing through a beam splitting cube (seen due to a reflection of green within the cube), where shorter wavelengths are reflected at 90 degrees (away from the camera) and longer wavelengths are transmitted to the left. One example of the various applications of ultra‐broad downconversion is the amplification of ultra‐ short laser pulses, ultimately enabling table‐top x‐ray sources and tools for resolving in time the movement of a single electron of an atom.