Experiments

List of experiments used for the chapter outreach activities

# Experiment Description
E1 Water jet/total reflection A laser pointer is pointed towards a basin that has a pipe that lets water flow to the outside. The water jet forms a parabola due to the gravity and is collected by a basin on the floor. The laser light is pointed towards the water jet and total internal reflection is shown.
E2 Bouncing laser in sugar solution graded refractive index

 

A basin is filled with a sugar solution to create a graded index liquid. A laser pointer is coupled in from the side of the basin. The laser light gets refracted towards the bottom of the basin and then reflected, creating a “bouncing light” impression.
E3 MPL Holograms for laser pointers A hologram is put onto a laser pointer such that an MPL logo spatial mode is created.
E4 Hit spot in water basin Water has a different refractive index than air. As such, it is not so easy to hit a target inside a basin of water with a laser pointer. This would be a fun experiment for the Blue Night crowd to try out themselves.
E5 Crossed polarizers/Birefringence A white light source hits a 30x30cm polarizing sheet. The polarized light the travels through the encasing to finally hit another 90° crossed polarizer sheet. No light gets transmitted in this configuration. The fun is to hold objects in between and explain how they change the polarization and therefore the transmittance through the second polarizer. Birefringence causes nice colours.
E6 Optical Cloaking Two lenses form an optical setup, behind which a printed grid is portrayed. When an observer holds his hand near the focus of the two lenses, it seems that the hand disappears behind the lens.
E7 Optical 3D Hologram A smart phone, tablet or beamer light source with an animation playing is pointed at a sheet of plexiglass at 45° aoi. The observer looks at the reflection and the image appears behind the plexiglass like a “3D hologram”.
E8 Listening to quantum noise A bright laser beam is pointed at a photo diode. The power is chosen such that the shot noise power exceeds the electronic noise of the detector. Assuming shot noise limited operation and amplifying the detected noise, one may listen to the quantum vacuum noise.

Additionally, there is the possibility to modulate sound onto the laser beam and make it audible on the receiving end.

E9 Laser microphone A speaker is kept inside a plexiglass box, causing the box to vibrate from the sound. A laser is pointed at the box from the outside at an angle. The sound displaces the window and causes a displacement of the laser beam. A photo diode measures the laser beam and sees an amplitude modulation caused by the displacement. An audio amplifier is attached to the photo diode to make the sound inside the box audible.
E10 Google cardboard Virtual reality goggles are expensive. Google realized that they require just a display, some motion sensors, two lenses and a frame. All those things can be found in a smart phone. Just put your phone into one of the Google cardboard frames with two lenses inside and you have a cheap VR headset.
E11 Laser graffiti A laser pointer is pointed at a beamer screen. A webcam tracks the position of the laser pointer with a dedicated software. The software then changes the color at the position of the laser pointer. By that, people can paint with the laser pointer.