1. Optical levitation
Yes, with lasers you can levitate stuff. Light is made up of photons which exert a force known as radiation pressure. This force is due to the interaction between electromagnetic radiation and matter. This can be absorption, reflection or a bit of both. Optical levitation is where you can use the radiation pressure force to overcome the gravitational force causing an object to levitate. A laser beam has an intensity profile where typically the intensity is higher in the center, which means there are more photons coming out at the center of a laser beam. More photons indicate that there is a larger radiation pressure. This is what is used to levitate small objects which are comparable to the size of the laser beam.
I’ve seen this for myself with my own eyes when I was shadowing some researchers at Imperial College London and it’s honestly incredible. Think about it, you can levitate stuff with just light. Hands down one of the coolest things I’ve seen.
2. Optical Tweezers
Using the radiation pressure aforementioned, scientists can make optical tweezers and manipulate objects as small as a single atom. Biologists are the most common users of optical tweezers and they use them to, for instance, measure the force of cell organelle movement inside living cells, capture and manipulate bacteria and cell sorting.
3. Laser Cooling
Normally, lasers are used to heat stuff up, but, you can also use lasers to cool stuff down. Laser cooling works by reducing the momentum of atoms or molecules. Since photons also have momentum, atoms or molecules moving in the opposite direction to a laser beam can be zapped with laser light which reduces the atom/molecule’s velocity. You can think of this as two billiard balls hitting each other and slowing each other down because of a transfer of momentum. The atom then emits a photon after this incident photon is absorbed. Over time, after continuous absorption and spontaneous emission of photons, the substance in question is cooled.
Lasers can be very powerful. With some of the most powerful lasers in the world the conditions found in the core of the Sun can be recreated in laboratories on Earth. Lasers can heat up materials to extremely high temperatures – more than a million degrees. At these temperatures, atoms can no longer exist and the electrons are stripped away from their respect nuclei, leaving behind a soup of ions and electrons. This form of matter is known as plasma and is the so-called fourth state of matter. By focusing a high-power laser onto a ‘fusion’ target it can turn into a plasma and cause an implosion. This forces the fusion material to fuse and release a huge amount of energy. Although we haven’t reached the commercial fusion stage yet, scientists are still working on creating ‘clean’ power generation, something that would do wonders for our future and the Earth.
5. Image biological reactions
With an x-ray laser, you can image biological reactions and make little science movies. X-rays have a very short wavelength which means they can image very small stuff, including individual atoms. The laser is pulsed which means it can take snapshot images of these reactions very quickly before the sample is destroyed. This method helps scientists learn more about biological reactions like photosynthesis which is vital for life on Earth.
Meriame Berboucha, Contributor