Laser ruby

As July draws to a close the glowing warmth of a ruby is somehow mirrored by stunning summer sunrises and sunsets. The dance that light does in and out of different gemstones changes according to the light source, and I feel that sunlight in rubies create an intensity and complexity of colour that few other gemstones can rival.

Unless quenched by inclusions of iron, the natural fluorescence of rubies, the red variety of Corundum, is very easy to spot. A good ruby, large or small, will ‘glow’. I talk about this ‘glow‘ with emeralds too. The more inclusions and fillers a stone has, the more muted this glow will be. Under the spectroscope, the chromium inclusions that interact with the atomic structure of ruby are revealed by a characteristic ’emission line’.

Flame fusion

The particular behaviour of ruby crystals and light have an industrial purpose too, and that is in the production of lasers. Synthetic rubies have been manufactured through the flame fusion process since 1902–originally published by French chemist August Verneuil. There are now several methods of synthesising rubies. Making the most of the crystal structure of rubies (aluminium oxide Al₂O₃), where some of the aluminium atoms are replaced by the colour-causing chromium atoms, physicists in the 1960s were able to produce a powerful and consistent beam of light at a consistent wavelength. It was Theodore Maiman that properly developed the ruby laser in 1960 after a flurry of technological advances originally based on controlling microwave wavelengths (known as the ‘maser’). Apart from applications such as precision cutting of materials, ruby lasers were also used to measure distances, including from the Earth to the Moon. This application was vital in the race to reach the Moon in the 1960s.

Ruby-created art

While undertaking gemmology training in 2021/22, I found a beautiful and well-formed Verneuil ruby boule on eBay. I was pleased to correspond with the vendor who used to work with lasers. This boule was manufactured around 1975 by a crystallographer at an electrical company in Salford, UK. It was produced to make lasers for data transmission. It retains a small label showing the chromium content that was added (1%). I am fascinated by the story of this beautiful, glowing boule.

Talking to Tom Goskar, archaeologist and 3D imaging specialist, about this, I learned about another application of ruby lasers: LiDAR (Light Detection And Ranging) which uses infrared lasers to 3D map the landscape. The first ever LiDAR used synthetic ruby in 1960 upon its invention. Nowadays government environmental agencies use LiDAR to track changes in the landscape, particularly to monitor the effects of climate change. A by product of this 3D aerial mapping is that it records human-made features like archaeological earthworks and whole town and city buildings too. Tom began experimenting with creating 3D maps of our home town and when I looked at them I thought how beautiful these 3D point clouds looked. I further experimented with different designs by changing the elevations and angles of the 3D map of dots. I thought they would make interesting textile designs so I had one printed onto sateen.

With my newly-purchased Verneuil laser ruby boule and my point cloud fabric sample, I set up a photoshoot for fun. The boule is lit up by long-wave UV and set on a scene created from a LiDAR point cloud of where in live in Cornwall. Some of the UV light is lighting up the abstract point cloud creating a fabulous set of gemmy colours.