Biophotonics
Encyclopedia
The term biophotonics denotes a combination of biology
and photonics
, with photonics being the science and technology of generation, manipulation, and detection of photon
s, quantum
units of light
. Photonics is related to electronics
in that it is believed that photons will play a similar central role in future information technology
as electrons do today.
Biophotonics has therefore become the established general term for all techniques that deal with the interaction between biological items and photons. This refers to emission, detection, absorption, reflection, modification, and creation of radiation from biomolecular, cells, tissues, organisms and biomaterials. Areas of application are life science, medicine
, agriculture
, and environmental science
.
Similar to the differentiation between "electric" and "electronics
" a difference can be made between applications, which use light mainly to transfer energy via light (like Therapy
or surgery
) and applications which excite matter via light and transfer information back to the operator (like diagnostics). In most cases the term biophotonics is only referred to the second case.
and optical coherence tomography
. On the macroscopic scale, the light is diffuse and applications commonly deal with diffuse optical imaging and tomography (DOI and DOT).
In microscopy
, the development and refinement of the confocal microscope, the fluorescence microscope
, and the total internal reflection fluorescence microscope
all belong to the field of biophotonics.
The specimens that are imaged with microscopic techniques can also be manipulated by optical tweezers
and laser micro-scalpels
, which are further applications in the field of biophotonics.
DOT is a method used to reconstruct an internal anomaly inside a scattering material. The method is non invasive and only requires the data collected at the boundaries. The typical procedure involves scanning a sample with a light source while collecting light that exits the boundaries. The collected light is then matched with a model, for example, the diffusion model, giving an optimization problem.
s, SLED
s or lamps
play an important role. Typical wavelengths, which are used in biophotonics are between 600 nm (Visible) and 3000 nm (near IR).
- Argon Ion laser: 457.8 nm, 476.5 nm, 488.0 nm, 496.5 nm, 501.7 nm, 514,5 nm (multi-line operation possible)
- Krypton Ion laser: 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
- Helium-Neon laser
: 632.8 nm (543.5 nm, 594.1 nm, 611.9 nm)
- HeCd lasers: 325 nm, 442 nm
Other commercial gas lasers like carbon dioxide (CO2), carbon monoxide, nitrogen, oxygen, xenon-ion, excimer or metal vapor lasers have no or only very minor importance in biophotonics.
Major advantage of gas lasers in biophotonics is their fixed wavelength, their perfect beam quality and their low linewidth/high coherence. Argon ion lasers can also operate in multi-line mode. Major disadvantage are high power consumption, generation of mechanical noise due to fan cooling and limited laser powers. Key suppliers are Coherent, CVI/Melles Griot, JDSU, Lasos, LTB and Newport/Spectra Physics.
Most commoly used wavelengths from diode lasers in biophotonics are: 375, 405, 445, 473, 488, 515, 640, 643, 660, 675, 785 nm.
Laser Diodes are available in 4 classes:
- Single edge emitter/broad stripe/broad area
- Surface emitter/VCSEL
- Edge emitter/Ridge waveguide
- Grating stabilized (FDB, DBR, ECDL)
For biophotonic applications the most commonly used laser diodes are edge emitting/ridge waveguide diodes, which are single transverse mode and can be optimized to an almost perfect TEM00 beam quality. Due to the small size of the resonator, digital modulation can be very fast (up to 500 MHz). Coherence length is low (typically < 1 mm) and the typical linewidth is in the nm-range. Typical power levels are around 100 mW (depending on wavelength and supplier).
Key suppliers are: Coherent, Melles Griot, Omicron, Toptica, JDSU, Newport, Oxxius, Power Technology.
Grating stabilized diode lasers either have an lithographical incorporated grating (DFB, DBR) or an external grating (ECDL). As a result, the coherence length will raise into the range of several meters, whereas the linewidth will drop well below picometers (pm). Biophotonic applications, which make use of this characteristics are Raman spectroscopy (requires linewidth below cm-1) and spectroscopic gas sensing.
The most commonly used terminology are supercontinuum
lasers, which emit visible light over a wide spectrum simultaneously. This light is then filtered e.g. via acousto-optic modulators (AOM, AOTF) into 1 or up to 8 different wavelengths. Typical suppliers for this technology are Koheras or Fianium.
In another approach (Toptica/iChrome) the supercontinuum is generated in the infra-red and then converted at a single selectable wavelength into the visible regime. This approach does not require AOTF's and has a background-free spectral purity.
Since both concepts have major importance for biophotonics the umbrella term "ultrachrome lasers" is often used.
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
and photonics
Photonics
The science of photonics includes the generation, emission, transmission, modulation, signal processing, switching, amplification, detection and sensing of light. The term photonics thereby emphasizes that photons are neither particles nor waves — they are different in that they have both particle...
, with photonics being the science and technology of generation, manipulation, and detection of photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s, quantum
Quantum
In physics, a quantum is the minimum amount of any physical entity involved in an interaction. Behind this, one finds the fundamental notion that a physical property may be "quantized," referred to as "the hypothesis of quantization". This means that the magnitude can take on only certain discrete...
units of light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
. Photonics is related to electronics
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
in that it is believed that photons will play a similar central role in future information technology
Information technology
Information technology is the acquisition, processing, storage and dissemination of vocal, pictorial, textual and numerical information by a microelectronics-based combination of computing and telecommunications...
as electrons do today.
Biophotonics has therefore become the established general term for all techniques that deal with the interaction between biological items and photons. This refers to emission, detection, absorption, reflection, modification, and creation of radiation from biomolecular, cells, tissues, organisms and biomaterials. Areas of application are life science, medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, agriculture
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
, and environmental science
Environmental science
Environmental science is an interdisciplinary academic field that integrates physical and biological sciences, to the study of the environment, and the solution of environmental problems...
.
Similar to the differentiation between "electric" and "electronics
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
" a difference can be made between applications, which use light mainly to transfer energy via light (like Therapy
Therapy
This is a list of types of therapy .* Adventure therapy* Animal-assisted therapy* Aquatic therapy* Aromatherapy* Art and dementia* Art therapy* Authentic Movement* Behavioral therapy* Bibliotherapy* Buteyko Method* Chemotherapy...
or surgery
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
) and applications which excite matter via light and transfer information back to the operator (like diagnostics). In most cases the term biophotonics is only referred to the second case.
Applications
Biophotonics can be used to study biological materials or materials with properties similar to biological material, i.e., scattering material, on a microscopic or macroscopic scale. On the microscopic scale common applications include microscopyMicroscopy
Microscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye...
and optical coherence tomography
Optical coherence tomography
Optical coherence tomography is an optical signal acquisition and processing method. It captures micrometer-resolution, three-dimensional images from within optical scattering media . Optical coherence tomography is an interferometric technique, typically employing near-infrared light...
. On the macroscopic scale, the light is diffuse and applications commonly deal with diffuse optical imaging and tomography (DOI and DOT).
In microscopy
Microscopy
Microscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye...
, the development and refinement of the confocal microscope, the fluorescence microscope
Fluorescence microscope
A fluorescence 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...
, and the total internal reflection fluorescence microscope
Total internal reflection fluorescence microscope
A total internal reflection fluorescence microscope is a type of microscope with which a thin region of a specimen, usually less than 200 nm, can be observed.-Background:...
all belong to the field of biophotonics.
The specimens that are imaged with microscopic techniques can also be manipulated by optical tweezers
Optical tweezers
Optical tweezers are scientific instruments that use a highly focused laser beam to provide an attractive or repulsive force , depending on the refractive index mismatch to physically hold and move microscopic dielectric objects...
and laser micro-scalpels
Laser scalpel
A laser scalpel is a scalpel for surgery, cutting or ablating living biological tissue by the energy of laser light. In soft tissue laser surgery, a laser beam ablates or vaporizes the soft tissue with high water content....
, which are further applications in the field of biophotonics.
DOT is a method used to reconstruct an internal anomaly inside a scattering material. The method is non invasive and only requires the data collected at the boundaries. The typical procedure involves scanning a sample with a light source while collecting light that exits the boundaries. The collected light is then matched with a model, for example, the diffusion model, giving an optimization problem.
Light sources
The most dominantly used light source are beam lights. However also LEDLEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
s, SLED
Superluminescent diode
A superluminescent diode is an edge-emitting semiconductor light source based on superluminescence. It combines the high power and brightness of laser diodes with the low coherence of conventional light-emitting diodes. Its emission band is 5–100 nm wide.- History :In 1986 Dr. Gerard A...
s or lamps
LAMPS
LAMPS or Lamps may refer to:* Nickname for Frank Lampard, a Chelsea FC midfielder* Light Airborne Multi-Purpose System...
play an important role. Typical wavelengths, which are used in biophotonics are between 600 nm (Visible) and 3000 nm (near IR).
Lasers
Lasers play a more and more important role in Biophotonics. Their unique intrinsic properties like precise wavelength selection, widest wavelength coverage, highest focussability and thus best spectral resolution, strong power densities and broad spectrum of excitation periods make them the most universal light tool for a wide spectrum of applications. As a consequence a variety of different laser technologies from a broad number of suppliers can be found in the market today.Gas lasers
Major gas laser, which are used for biophotonics applications and their most important wavelengths are:- Argon Ion laser: 457.8 nm, 476.5 nm, 488.0 nm, 496.5 nm, 501.7 nm, 514,5 nm (multi-line operation possible)
- Krypton Ion laser: 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
- Helium-Neon laser
Helium-neon laser
A helium–neon laser or HeNe laser, is a type of gas laser whose gain medium consists of a mixture of helium and neon inside of a small bore capillary tube, usually excited by a DC electrical discharge.- History of HeNe laser development:...
: 632.8 nm (543.5 nm, 594.1 nm, 611.9 nm)
- HeCd lasers: 325 nm, 442 nm
Other commercial gas lasers like carbon dioxide (CO2), carbon monoxide, nitrogen, oxygen, xenon-ion, excimer or metal vapor lasers have no or only very minor importance in biophotonics.
Major advantage of gas lasers in biophotonics is their fixed wavelength, their perfect beam quality and their low linewidth/high coherence. Argon ion lasers can also operate in multi-line mode. Major disadvantage are high power consumption, generation of mechanical noise due to fan cooling and limited laser powers. Key suppliers are Coherent, CVI/Melles Griot, JDSU, Lasos, LTB and Newport/Spectra Physics.
Diode lasers
The most commonly integrated laser diodes, which are used for diode lasers in biophotonics are based either on GaN or GaAs semiconductor material. GaN covers a wavelength spectrum from 375 to 488 nm (commercial products at 515 have been announced recently) whereas GaAs covers a wavelength spectrum starting from 635 nm.Most commoly used wavelengths from diode lasers in biophotonics are: 375, 405, 445, 473, 488, 515, 640, 643, 660, 675, 785 nm.
Laser Diodes are available in 4 classes:
- Single edge emitter/broad stripe/broad area
- Surface emitter/VCSEL
- Edge emitter/Ridge waveguide
- Grating stabilized (FDB, DBR, ECDL)
For biophotonic applications the most commonly used laser diodes are edge emitting/ridge waveguide diodes, which are single transverse mode and can be optimized to an almost perfect TEM00 beam quality. Due to the small size of the resonator, digital modulation can be very fast (up to 500 MHz). Coherence length is low (typically < 1 mm) and the typical linewidth is in the nm-range. Typical power levels are around 100 mW (depending on wavelength and supplier).
Key suppliers are: Coherent, Melles Griot, Omicron, Toptica, JDSU, Newport, Oxxius, Power Technology.
Grating stabilized diode lasers either have an lithographical incorporated grating (DFB, DBR) or an external grating (ECDL). As a result, the coherence length will raise into the range of several meters, whereas the linewidth will drop well below picometers (pm). Biophotonic applications, which make use of this characteristics are Raman spectroscopy (requires linewidth below cm-1) and spectroscopic gas sensing.
Ultrachrome lasers
Many advanced applications in biophotonics require individually selectable light at multiple wavelengths. As a consequence a series of new laser technologies has been introduced, which currently looks for precise wording.The most commonly used terminology are supercontinuum
Supercontinuum
In optics, a supercontinuum is formed when a collection of nonlinear processes act together upon a pump beam in order to cause severe spectral broadening of the original pump beam. The result is a smooth spectral continuum...
lasers, which emit visible light over a wide spectrum simultaneously. This light is then filtered e.g. via acousto-optic modulators (AOM, AOTF) into 1 or up to 8 different wavelengths. Typical suppliers for this technology are Koheras or Fianium.
In another approach (Toptica/iChrome) the supercontinuum is generated in the infra-red and then converted at a single selectable wavelength into the visible regime. This approach does not require AOTF's and has a background-free spectral purity.
Since both concepts have major importance for biophotonics the umbrella term "ultrachrome lasers" is often used.