The word biophotonics is a combination of biology and photonics. As the word photonics indicates the science and technology like generation, use and detection of photons (a quantum of electromagnetic radiation; an elementary particle that is its own antiparticle), and lights quantum units. As we know the importance of electrons today in the field of information technology, it is believed that photons also play a similar vital role in future information technology. Photonics is basically interrelated with electronics (is the branch of physics that deals with the emission and effects of electrons and with the use of electronic devices).

Biophotonics has become the well-known broad term for all the techniques interrelated with biological items and photons. Biophotonics refers to detection, reflection, emission, modification, absorption, and creation of radiation from cells, organisms, biomolecular (is any organic molecule that is produced by a living organism, including large polymeric molecules such as proteins, polysaccharides, and nucleic acids as well as small molecules such as primary metabolites, secondary metabolites, and natural products), tissues, and biomaterials (is any matter, surface, or construct that interacts with biological systems).

Areas of Application:

Biophotonics application areas are in medicine, life sciences, agriculture, and environmental science and many other techniques. It can be used to study materials or biological materials with properties. These properties are similar to biological materials, i.e., on a macroscopic or microscopic scale.

Common applications include;

On the microscopic level:

• Microscopy (is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye (objects that are not within the resolution range of the normal eye))
• Optical coherence tomography (is an optical signal acquisition and processing method. It captures micrometer-resolution, three-dimensional images from within optical scattering media (e.g., biological tissue))
• Confocal microscope (is an optical imaging technique used to increase optical resolution and contrast of a micrograph by using point illumination and a spatial pinhole to eliminate out-of-focus light in specimens that are thicker than the focal plane)
• The fluorescent microscope (is an optical microscope used to study properties of organic or inorganic substances using the phenomena of fluorescence and phosphorescence instead of, or in addition to, reflection and absorption.)
• Total internal reflection fluorescent microscope (is a type of microscope with which a thin region of a specimen, usually less than 200 nm, can be observed.)
On the macroscopic level:
• Diffuse optical imaging and tomography or DOI and DOT (non-invasive method inside a scattering material an internal glitch is reconstructed).

In further details, biophotonics has various other microscopic techniques that are manipulated by optical tweezers (are a scientific instrument that uses a highly-focused laser beam to provide an attractive or repulsive force) and laser micro-scalpels (is a scalpel for surgery, cutting or ablating living biological tissue by the energy of laser light).

Beam lights: source for biophotonics

The light source used for biophotonics are beam lights. Although light emitting diode or LED's (Diode such that light emitted at a p-n junction is proportional to the bias current; colour depends on the material used), SLED's, or lamps play an imperative role. The wavelengths used in biophotonics are between 600 nm (UV) and 3000 nm (near IR).

In biophotonics, lasers play more significant role. Lasers have unique inherent properties like;

• Widest wavelength coverage
• Precise wavelength selection
• Highest focus ability
• Best spectral resolution
• Strong power densities
• Broad spectrum of excitation

These properties of lasers make them the most widespread light device for a wide-ranging spectrum of applications. Many other different laser technologies are found from a broad number of suppliers in the market today.

Gas lasers

Most important gas lasers used for biophotonics applications are Argon Ion laser and its wavelength are 457.8 nm, 476.5 nm, 488.0 nm, 496.5 nm, 501.7 nm, 514,5 nm, Kypton Ion laser and its wavelength are 350.7 nm, 356.4 nm, 476.2 nm, 482.5 nm, 520.6 nm, 530.9 nm, 568.2 nm, 647.1 nm, 676.4 nm, 752.5 nm, 799.3 nm, another important gas laser Helium-Neon laser and its wavelengths are 632.8 nm (543.5 nm, 594.1 nm, 611.9 nm).

There are some other commercial gas lasers that have minor importance in biophotonics such as carbon dioxide (CO2), carbon monoxide, oxygen, nitrogen, xenon-ions and metal vapor lasers.

Advantage of gas laser in biophotonics:

• Their fixed wavelength
• Their perfect beam quality
• Their low line-width/high coherence

Disadvantage of gas laser in biophotonics:

• High power consumption
• Generation of mechanical noise (due to fan cooling)
• Limited laser powers

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