London: Now, a laser test that can determine if a whisky is counterfeit using just a drop of the alcoholic beverage, thanks to three Indian-origin physicists in Britain.

Praveen Ashok, Kishan Dholakia and Bavishna Praveen of the University of St Andrews says in their study, published in the 'Optics Express' journal, that their laser detector can instantly decide whether the liquid under test is genuine.

The test beams a ray of light thinner than a human hair through a transparent chip on which sits some of the precious liquid, say the researchers who found that firing light from one optical fibre and collecting it with another allowed them to analyse light scattered from the whisky.

It allows them to work out precisely how much alcohol is in a sample -- fake whisky often has less than the required 40 percent, a daily reported.

Praveen said: "Counterfeiting is rife in the drinks industry, which is constantly searching for new, powerful and inexpensive methods for liquor analysis. Using the power of light, we have adapted our technology to address a problem related to an industry which is a crucial part of Scottish culture and economy."

The researchers said the method exploits both the fluorescence of whisky and the scattering of light and shift in energy when it interacts with molecules, known as its Raman signature.

Ashok said: "Whisky turns out to be very interesting. We can not only gather information about the alcohol content but also (about) the colour and texture. These are dictated by the manufacturing process which of course influences greatly the type of whisky people enjoy."

Prof Dholakia added: "It is amazing to think that the technology we are developing for biomedical analysis can also be used to help us enjoy a wee dram."