Laser Technology in Medicine and Future

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Introduction

There are many things that we use but have never stopped to question their origin or how they work. We quite often use CD and laser pointers but have never bothered to question about how they came to existence. Many health care institutions have embraced the use of laser technology in trying to give medical care to their students.

This research paper will entail giving background or history of development of laser technology and why the developments cannot be dispensed with, the developments will try to explain the underlying optoelectronic and photonic principles and how the concepts of physics and materials were translated into a technology.

The barriers that were encountered during the evolution of the technology and how these obstacles were overcome will also be brought into perspective. Nevertheless, the impacts of the technology with respect to new technology, its growth into other technologies and market will be illuminated by this research paper.

The paper will endeavor to quantify the market size of this technology. The paper will finally list what has been learnt from the exercise and the future of the technology and the input of the students towards actualization of these aspirations.

History and development in laser technology

There have been major historical developments in laser technology. Einstein (1917) pioneered the research in laser technology when he came up with the idea of stimulated emission which had much to do with systems near equilibrium. This explains why laser was not basically invented in the 17^th century as laser is a none equilibrium system. Townes, Basov, and Prokhorov (1964) work contributed to the construction of lasers.

The three came up with the theory of lasers and gave details of how laser could be built from maser. It is indeed Maiman (1960) who built the first functioning laser. This induced the building of clumsy lasers that were witnessed on the onset of 1960. Townes et al theory of the laser effect still stands to describe all lasers in day to day use.

Gabor invented the basic ideas surrounding the holographic method, a very important application of laser technology. It started as a simple technique for creating 3-D pictures but has advanced to become an essential device for observing vibrating bodies. The modern day musical instruments make much use of the holograms.

To help avert surging crime levels in the society, holograms have been used in making credit cards and identity documents to make them forgery proof. Bloembergen and Schawlow (1981) are credited for their efforts in development of laser spectroscopy which has extensively been used in non linear optics where laser beams have permanently been joined hence steering of light beam by another.

This technology has proved helpful in optical fiber technology specifically in broadband application where myriad switches and amplifiers integrate aspects of nonlinear optical effects. Chu, Cohen-Tannoudji and Phillips (1997) came up with methods of cooling and trapping atoms with the help of laser light. By doing this, the atoms become induced hence relinquish their heat energy to laser light.

The atoms ultimately reach lower temperatures and aggregate. This serves to reveal some innermost aspects of the atoms nature. Alferov and Kroemer (2000) invented semi conductor physics. Much of their work revolved around studying substances that were initially used in building semi conductor lasers.

Their work has transformed the use of laser technology as many cheap and portable devices can now be made hence the beginning of optical information systems. From their discoveries, a lot of notable inventions have been made including appliances like the barcode reader extensively used in the supermarkets and the CD reader used in homes for entertainment.

Laser technology development and the underlying optoelectronic and photonic principles

The law that Schawlow formulated says that materials are bound to lase if they are pumped hard enough. This has been confirmed by a series of experiments that have indicated that many materials can serve as either lasers or optical amplifiers. Laser wavelengths range from the infra red to the x-ray region.

Shorter laser pulses can be used in researching for material dynamics. Amplification of femtosecond pulses can result in attainment of peak powers in petawatt range. When peak power levels are focused into diffraction limited spot intensities of 10²³ W/cm² can be achieved. Electrons in such fields get accelerated to relativistic range in a single optical cycle.

From such circumstances effects of quantum electrodynamics can be deduced (Bloembergen, 1999). Transition of iodine at a wavelength of 1.3 micrometers is a typical example of a large powerful chemical laser.

It is capable of producing 3 megawatts of power when mounted on an aircraft. Invention of dielectric and deformable mirrors has enabled for reliable focus of these beams on aircrafts carrying chemical and biological warheads hence their destruction. Such aircrafts can be destroyed when they are as far as 100 km away.

Laser technology has found widespread use in medicine where it is used both diagnostically and therapeutically (Deutsch, 1997). Its widespread use in medicine is prompted by its ability to interact albeit in-homogeneously with tissues through absorption and scattering. Melanin, a skin pigment, hemoglobin, and proteins are some of the examples of absorbers.

Water is the primary absorber at wavelengths that are longer than one micrometer. Dyes are used in tissues because of their ability to selectively absorb. Hematoporphyrin dye photosensitizer is basically used in treatment of cancer patients because of their ability to absorb in the range of 630 nm to 650 nm wavelength.

In such circumstances, local laser irradiation is directed at the urinary tract region or the esophagus depending on the location of the cancer tumor. Scattering in the tissues helps in limiting the extent of penetration of the radiation. Wavelength of one micrometer remarkably limits the penetration of radiation. Scattering process is very pivotal in breast cancer screening because of their perceived ability to produce high resolution images.

The manners in which the laser interacts with the tissue largely depend on whether the laser has been pulsed or CW. Short laser pulses normally result when thermal diffusion fails to occur during the pulse. Short laser pulses are pivotal in confining the depths of the effects of laser. Short laser pulses together with selective tuning laser wavelength in skin treatment, removal of spider veins, and removal of hair.

Non linear interactions like that employed in laser induced breakdown is imperative in treatment of kidney and gallbladder stones. Laser technology has gained widespread use in ophthalmic applications because the interior of the eye can be easily accessed with the use of light. Argon lasers are used in treating retinal detachment and bleeding from vessels that nourish the retina.

CO₂ and Nd: YAG lasers were used in general surgery because they are capable of cutting the tissues and coagulating the blood vessels. The recent dalliance Er: YAG lasers enjoy is occasioned by its ability to drastically reduce pain that accompanies dental procedures. Diagnostic procedures have embraced the use of laser technology especially in clinical practice.

This is evident in flow cytometer that uses laser beams to excite fluorescence in cell contents. The quantified fluorescent signals are normally used in analyzing and sorting of the cells. Flow cytometry has also found widespread use in immunophenotyping and measurement of contents of the DNA. Large numbers of human chromosome get physically separated with the help of flow cytometers.

The separated chromosomes usually provide DNA templates that are used in construction of recombinant DNA (r DNA) libraries. This is a very critical stage in genetic engineering. Guillermo et al (1997) attests to the introduction of medical imaging that integrates aspects of laser technology called optical coherence tomography otherwise called OCT.

This technology is capable of spatially resolving the tissues within a ten micrometer range. The resolution of ultrasound and magnetic resonance imaging is limited to a range of 100 micrometers to 1mm. The OCT technique can detect abnormalities that are associated with cancers and blood clots in the arteries at their onset because of its high resolution. OCT technology bears semblance with ultrasound.

The only difference lies in its ability to use bright, broad infrared light source that has a coherence length near 10 micrometers. The source of the light can be super luminescent diode, Cr: forsterite laser or mode locked Ti: sapphire. Optical ranging in tissues by OTC is done with the help of fiber optic Michelson interferometer.

OCT can be used in architectural morphology imaging in highly scattering tissues like the retina, the skin, the circulatory system, and the epithelia that lines the gastrointestinal tract. The very important spin-polarized gases technique is largely being considered in an effort to enhance images produced by MRI technology from the lungs and the brains.

Nuclear spins in Helium and Xenon are usually aligned using circularly polarized laser radiation. The aligned nuclei have magnetizations nearly 10⁵ times that for protons used for MRI imaging. Helium provides high contrast images. When laser light is directed towards dielectric bodies like cells, the light gets refracted thereby causing lensing effect.

This happens because of the force that is imparted to the cell by transfer of momentum from the bending light beam. Ashkin (1997) postulated that by varying the position and shape of the local volume in microscopic arrangement, a cell can be trapped by laser forces that use light intensities near 10W/cm².

Laser technology has extensively been used in physics especially in spectroscopies in electromagnetic spectrum. Raman scattering studies of phonons and excitations in 2D electrons gases have flourished since the invention of laser. Nonlinear laser spectroscopies have resulted in great increase in precision measurement. Laser technology has revolutionized telecommunications industry.

The emergence of voice communications has made people to demand for increased rate information transmission capacity. From the 70s rate of transmission of information has increased from 10 to 80 kilo hatz with respect to audio transmission. At this point of time, copper wires were largely being used to transmit information. Microwaves then ensued. 1980 witnessed remarkable information rate increase.

Data could be transmitted from one point to another, fax could be sent, and eventually image could also be sent. Optical fiber communication technology was then introduced. These made use of laser light sources. Internet use then came into play where computers were connected in a network for communication purposes.

Laser technology, its impact on other technologies in terms of quantitative growth

Laser technology has gained prominence in the market from the year 1997. Anderson and Steele (1998) adduced that total laser sales plummeted to 3.2 billion dollars. This accounted for an annual growth rate of 27 per cent. They projected that in 2000, the sales would increase to 5 billion dollars. The United States market recorded 60 percent in laser sales, where as Europe and Pacific realized 20 per cent sales each.

The 1997 laser market realized a 57 per cent sale in semiconductor diode lasers which translated into 30 per cent of the total market. Materials processing that involves applications like welding, soldering, and cutting of fabrics has formed a formidable market of laser technology applications. The largest currency earner in this category is the carbon dioxide lasers whose power lies in the range of 100W.

High power diode lasers have power output in the range of 1-20 W and wavelengths ranging between 750 to 980 nm. They are used in ophthalmic and general surgical procedures. They can also be used in instrumentation and sensing. Medical laser applications are gaining prominence because many patients have gained confidence in cosmetic laser procedures like skin resurfacing and removal of hair.

Materials made using laser technology that are used for optical storage purposes claim a market share of 10 per cent. Under this category fall the compact disk (CD) players which are basically used for entertainment and information technology market. The prices of CDs have fallen significantly because of the efficient manufacturer of GaAs semiconductors.

In 1997 alone, a whooping 200 million diode lasers were sold. Their wavelengths were in the range of 750 to 980 nm. They had a few milliwatts of power. They were basically produced for storage purposes. Studies have projected that there would be further growth in sales of optical storage devices with the invention of digital video disks (DVD) with the storage capacity of 4.7 gigabytes (Den Baars, 1997).

Image recording laser market is currently awash with desktop computer printers, fax machine and photocopying machine (Gibbs, 1998).

Atmospheric chemical detectors and air movement detectors are just but some few examples of materials that comprise the remote sensing laser markets. Laser ranging enables one to come up with detailed elevation of the earth surface. A total of 132 million dollars was accrued in revenue from laser applications used in basic research.

Future of laser technology

Industries that sell laser technology appliances have evolved a great deal and are likely to revolutionize the technology industry of this century. This is evidenced with the research that has seen the introduction of free electron laser (FEL) that makes use of relativistic electron beam undulating in a magnetic field (Sessler and Vaughan, 1987).

Jefferson Laboratories are currently developing electron beam accelerators that make use of microwave cavities capable of superconducting. The accelerating cavities produce high electromagnetic fields that efficiently generate FEL light that can be tuned from the infrared to the deep ultraviolet with power levels in the kilowatt range.

Presently, notable average power infrared FEL is at advanced stages and will definitely be upgraded to a powerful deep UV FEL. When such copious amounts of powers are produced, other relatively important technologies stand to be developed. Intense FEL pulses are likely to be used in thermal annealing and cleaning of surfaces of metals.

This kind of annealing is likely to lead an increase in the order of magnitude in hardness of machine tools. The high FEL power implies that laser enhanced tools will in the near future be commercially produced. This will be an advantage to those entrepreneurs that investing their time and resources in the commercial production of polymer wraps and clothes.

Intense pulse FEL can be used to induce production of antibacterial polymer surfaces that can be used in wrapping food. This can also be used in making clothes with appealing textures. These clothes can be very durable. Improvements in laser technology industry have made it even easier to make patterns on plastic material.

Petawatt-class laser is likely to revolutionize the usage of particle accelerators. Laser technology is likely to be used in laser communications between networks and satellite. Researches intending to come up with laser propelled aircrafts are at their advanced stages.

Many other experiments sanctioned by laser technology like the correction of atmospheric distortions and quantum electrodynamics are currently being undertaken. These experiments make use of ultra intense laser beams. The use of laser technology impacts lives of each and everyone.

Reference List

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