The random Raman laser could open up a new world of the microcosmos, assisting biologists in discovering a wide range of new species of bacteria and viruses. The new design eliminates one of the defining characteristics of lasers to produce high-quality images.
Lasers are often used as sources of light in microscopes due to the fact they can produce high-intensity radiation that can be pulsed over a short period. This allows researchers to expose images over an extremely short period of time, recording the activity of biological processes.
These images are blurred, however, by a property found within traditional lasers known as "high spatial coherence." The effect, resembling speckles in the photographs, is quite apparent when biologists carry out wide-field microscopy, during which the entire side of a cell or organism is imaged.
Biologists have long sought a laser design in which the electric fields at various points in the beam do not align with one another. Such a low spatial coherence laser has now been developed by researchers in Texas.
"We found that random Raman lasing emission has a low level of spatial coherence. The emission can be used to produce a wide-field speckle-free quality image with a strobe time on the order of a nanosecond. This new, bright, fast, narrowband, low-coherence light source opens the door to many exciting new applications in bio-imaging such as high-speed, wide-field microscopy," Brett Hokr or Texas A&M University said.
Traditional laser designs produce a beam by bouncing light in a cylindrical chamber filled with one or more bases, such as helium and neon. The random Raman laser replaces this system with a powder or other diffuse material, producing amplification without coherent electromagnetism. The device is capable of producing photons a million times faster than a traditional light source over each unit of wavelength.
Barium sulfate, in powder form, was utilized in the laser, which was tested in a pair of experiments. Both of the tests revealed the new device was able to produce a laser beam with low spatial coherence.
"To further quantify the overall spatial coherence, they measured something known as the speckle contrast ratio, which gauges the statistical properties of the emission. These measurements were consistent in confirming the presence of a low level of coherence," researchers wrote in a university press release.
The new lasers were then used to record images of melanosomes, organelles in animal cells which produce, store and transport melanin, the primary light-absorbing pigment in skin. This experiment showed the random Raman laser is capable of producing images without the speckles seen using traditional laser designs. The eventual images should help researchers understand microbial intricate inner workings.
Photo: NIAID | Flickr
