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The secret weapon of the laser world: Why are dye lasers so special?
In the world of laser technology, dye lasers are considered unique because their tunability makes them important in many scientific and industrial applications. While many laser types exist, dye lasers, with their flexible wavelength tuning, have become the tool of choice for many researchers and engineers.
A tunable laser is a laser that can change its operating wavelength in a controlled manner. Changes in its wavelength range provide unparalleled flexibility for many applications.
Adjustability type
Single line tuning
While there is no true monochromatic laser, most lasers can emit light within a certain range, which is called the linewidth of the laser transfer. Many lasers have relatively narrow linewidths; for example, the transferred linewidth of an Nd:YAG laser at 1064 nm is approximately 120 GHz. Tuning of the laser output can be achieved by placing selective optical elements, such as interferometers, in the laser optical cavity to select specific longitudinal modes.
Multi-line tuning
Most laser gain media have multiple transfer wavelengths. For example, Nd:YAG has weaker transfer lines at other wavelengths (such as 1052 nm, 1074 nm, etc.) in addition to the main 1064 nm output line. Typically, these wavelength lines operate with the gain of strong shifts being suppressed. If a diverging element, such as a prism, is introduced into the optical cavity, the laser can be tuned by tilting the cavity mirror.
Narrow bandwidth tuning
Some types of lasers can be continuously tuned by changing the laser's cavity length. Distributed feedback (DFB) semiconductor lasers and vertical-cavity surface-emitting lasers (VCSELs) utilize regularly distributed Bragg reflector (DBR) structures to form mirrors of the optical cavity. If the temperature of the laser is changed, the exponential change in the DBR structure will cause its peak reflection wavelength to shift, thereby changing the wavelength of the laser.
Widely tunable laser
Example Grid Distributed Bragg Reflection Laser (SG-DBR) has a larger tunable range. Certain laser technologies can achieve higher wavelength tuning ranges, making them very important in various types of systems, especially DWDM systems.
With the continuous advancement of science and technology, more and more applications and technologies have been integrated into the use of tunable lasers, making them an important tool in many scientific research fields.
Application Scope
Tunable lasers have a wide range of applications. They can be combined with suitable filters to be tuned over a range of several hundred nanometers, and the spectral resolution can be tuned to the wavelength range. These lasers are used in fields such as optical communications, spectroscopy, photochemistry, and laser isotope separation of atomic gases.
In the latest research, these tunable lasers are also used to develop hyperspectral imaging technology to detect early retinal diseases, which requires lasers to provide efficient illumination over a wide wavelength range.
Tunable lasers can be effective tools for reflection and transmission spectroscopy, photobiology, detector calibration, and steady-state pump-probe experiments.
Historical background
In 1966, the first truly widely tunable laser appeared, the dye laser. In 1972, Hänsch introduced the first narrow linewidth tunable laser. Over time, many models of tuning technology have been proposed, making the applications of laser technology more diverse.
It is worth noting that many emerging technologies are developing rapidly, and future laser technology will develop in a more efficient and flexible direction.
How will these amazing technologies change our future scientific and industrial applications?
