Guest Article: Spotlight on Lasers

I have the pleasure of introducing you to the work of Hollie Wright. Hollie is a physicist turned engineer based in Edinburgh. On Instagram (@holliewrightre) she shares her daily life in the lab, developing a technique for precision distance measurement using lasers. On her blog, sciencegeekette.wordpress.com she shares weekly posts about physics, tech, space or her experience of working in STEM. Thank you so much for writing this piece for A Short Scientist Hollie!

Many friends have admitted to me that when I told them I worked with lasers their first thought was of Star Wars lightsabers and Superman’s eyes. This is understandable as, for most of us, our first introduction to lasers was through action movies, making them feel like science fiction. In reality, lasers provide crucial functions in much of the technology of our everyday lives. Your DVD/blu-ray player reads disks with lasers; your phone’s facial recognition function shines invisible lasers on your face; if you’re unlucky, the police will catch you speeding with a laser-based speed camera… Lasers are anything but fiction! holliewrightrelasers

My favourite thing about lasers is that the inventors did not have a purpose in mind when they built the first one – they simply built it to see if their idea would work. The potential usefulness of a highly collimated, high power beam of light was quickly recognised and many applications were created. Medicine, defense, construction, technology and research all benefit from lasers, which is why the inventors were awarded the Nobel Prize in physics in 1964. With most inventions being driven by a requirement, there is something incredible about the way lasers were born without a purpose yet built-up an impressive resume of applications. And still, decades later, lasers continue to evolve for new applications.

Lasers were recognised with the Nobel Prize in physics again, in 2005. A new generation of lasers called frequency combs were characterised by the incredible stability of the rate (i.e. frequency) at which they produced pulses. Frequency combs opened up many new possibilities and allowed measurements not previously thought possible. For example, frequency combs have revealed the structure of energy levels in atoms [1], have investigated constants of nature [2] and have measured time with unparalleled precision [3].

Time is measured by observing something periodic, such as the rotation of the earth around the sun or the swinging of a pendulum. The most precise measurements of time are provided by atomic clocks. atom

You may remember from your high school chemistry class, that atoms are made up of a nucleus surrounded by electrons in different energy levels. In an atomic clock, the electrons are made to transition between energy levels: a second is defined as the time taken for an electron in a cesium-133 atom to make 9,192,631,770 transitions. The atomic clock is incredibly reliable – gaining a second every 1.4 million years – it currently provides the worldwide time standard!electronenergies

However, the frequency comb can beat the standard held by the atomic clock! As explained above, time is measured by observing something periodic therefore, the pulses released periodically by a stable frequency comb can be used to measure time. The National Institute of Standards and Technology (NIST) created a frequency comb which produced pulses so consistently, it could be used to measure time five times more precisely than the atomic clock! If it could run that long, the clock would neither gain nor lose a second in 400 million years [4]!

I hope that these few examples have convinced you that lasers are very interesting! If you would like to learn more about lasers and how I use them in my research, follow me on Instagram or Twitter at @holliewrightre, or visit my blog Science Geekette at sciencegeekette.wordpress.com

References:

  1. TH Udem, R Holzwarth, and TW Hansch. Optical frequency metrology. Nature, 416(6877):233–237, 2002.
  2. JP Uzan. The fundamental constants and their variation: observational and theoretical status. Reviews of  modern physics, 75(2):403, 2003.
  3. BJ Bloom, TL Nicholson, JR Williams, SL Campbell, M Bishof, X Zhang, W Zhang, SL Bromley, and J Ye. An optical lattice clock with accuracy and stability at the 10-18 level. Nature, 506(7486):71–75, 2014.
  4. NIST https://www.nist.gov/news-events/news/2006/07/mercury-atomic-clock-keeps-time-record-accuracy

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