Articles about Optics and Photonics, Lasers, Fiber Bragg gratings and FBG sensors

Fiber optic probes demonstrate molecular bonds

on June 21, 2019

carbon-2222968_640In one very popular movie, they say that the possibility to send a person into the quantum reality and bring them back would be a “billion-to-one cosmic fluke”. In reality, it is also difficult to shrink a light laser beam to a nanometer-sized point to observe quantum-scale light-matter interactions and get the data information. Recently researchers from the USA have designed a new fiber optic technology based on the use of optical fiber probes to tunnel light into the quantum realm at an unprecedented efficiency.

Thus, the world’s first fiber optic device for nanoscopy process is portable and inexpensive, the used fiber technology combines a glass optical fiber with a silver nanowire condenser. The fiber optic probe produces a high-efficiency round-trip light tunnel that compresses visible light by a laser beam to the very tip of the condenser for providing local interaction with molecules and transmits the information that allows decrypting and demonstrating the nanoworld.

It should be noted that the possibility to go up the object fine details is reduced by the wave nature of light. Unfortunately, despite the half-century of developments in fiber optic technology still remains quite esoteric and applied by few. The thing is that it is quite difficult to transmit light produced by a laser beam through a tiny pinhole that is a thousand times thinner than a human hair, and not all photons or light particles are able to pass the pinhole and achieve the necessary object; it is almost impossible to get a one-way ticket, but a round trip ticket is almost a dream.

Nowadays in spite of the fact that modern fiber optic probes enable only one in 1,000 photons to reach the object, while the novel optical fiber device transmits half the photons to the tip. The principle of operation includes a gradual increase in the wavelength of the far-field light as it goes down a thin optical fiber, herewith, its frequency remains constant.

At the moment when it reaches the wavelength of the electron density wave in the silver nanowire keeping on top of the optical fiber,  all energy is got in the electron density wave and starts to travel on the surface of the nanowire instead. Then this wave inspissates to a few nanometers at the tip apex step by step.

To be precise, this fiber optic device presents a small silver needle with light coming off the tip resembling Harry Potter’s wand. This fiber optic probe is applied to map out the frequency of molecular vibrations that enable to analyze chemical bonds that hold atoms together in a molecule. Therefore, this is about tip-enhanced Raman spectroscopy, the most challenging area of near-field fiber optic microscopy because it is concerned with quite weak signals.

The fiber optic probe allows achieving 1-nanometer resolution on simple portable equipment, in the near future, this optical fiber device could become a powerful analytical tool that helps to discover a new world of information to researchers in all fields of nanoscience.

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