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Optical Tweezers: Principles and Scientific Applications
Optical tweezers, also known as optical traps, were first introduced in 1986 and since then have been widely used in different applications, being particularly successful in the field of biological studies, where optical tweezers are used to study DNA sequences, interactions of proteins, etc.
Optical tweezers have been used in numerous studies involving optical tweezers in order to trap single atoms, viruses, single-cell organisms, strands of DNA, bacteria, carbon nanostructures, and many others. The manipulation and assembly of structures on a nanoscale are the most promising advances right now.
How Optical Tweezers Work
The main principle of optical tweezing lies in the fact that light carries momentum that is in proportion to its energy, and the direction of light is the same as the direction of propagation. After interacting with an object, the light beam changes its momentum; the same happens with an object after interaction with a beam of light – it undergoes a change of momentum by an equal amount. These interactions result in a reaction force, which acts on the object.
In most optical tweezer setups, light is emitted by a laser beam that is focused on a particular spot. A trap that is able to hold a small dielectric object appears in the spot. The scattering force, which occurs when light hits the object and scatters off its surface, produces a momentum transfer that leads to the object being pushed by the beam of light. This method allows for trapping an object in all dimensions.
Ytterbium Lasers in Optical Tweezer Systems
Lasers used to create an optical trap must be highly stable. Ytterbium lasers are often used in optical tweezer systems as they produce a stable and high-power laser beam, which allows for interference-free optical trapping. Other properties of Yb lasers include:
- a simple electronic level structure;
- a small quantum defect, which provides an opportunity for high power efficiency;
- Yb lasers have a capacity for wide wavelength tuning;
- a low-noise beam that allows for the creation of an optical trap in a precise spot.
All of these characteristics make Ytterbium lasers one of the most optimal options for light emitters in optical tweezer systems. These lasers have already been used in multiple studies that utilize optical trapping for capturing micron-sized particles and living cells, with superior pointing stability being the main reason these lasers are chosen over other types.