Laser Technology

Laser Technology Light Amplification by Stimulated Emission of Radiation (LASER) is a device for producing a narrow beam of light, capable of travelling over vast distances without dispersion, and of being focused to give enormous power densities. The uses of lasers include communications (a laser beam can carry much more information than can radio waves), cutting, drilling, welding, satellite tracking, medical and biological research, reading compact discs and bar codes and surgery. The idea of the laser was introduced by Charles Townes and Arthur Schawlow in 1958, and the first operational laser (a ruby laser) was constructed by Theodore Maiman in 1960. Laser technology is inherently expensive. In general, it is considered expensive not only to construct a laser, but also to maintain it in operation. Nevertheless, the usefulness and potential of lasers cannot be neglected even in a developing country like Bangladesh. Laser technology is now being used in the country in many fields.

Perhaps the most widespread use of lasers is in information storage and retrieval. CD (Compact Disk) writers use higher power lasers to write data on a disk coated with a photosensitive dye. Every CD player and CD-ROM (compact disk read-only memory) uses a low-power diode laser emitting a few milli-watts of power at a wavelength of 780 nanometers. DVD (digital videodisk) players use lasers emitting at shorter wavelengths which enable information to be retrieved at even higher density. With the decrease in the cost of diode lasers, these devices have become more affordable and their use has increased considerably in Bangladesh.

Laser line generators are used in construction and civil engineering applications wherever there is a need to define a sharp, bright, perfectly straight line on ground or water. Optical barcode readers employing visible diode lasers to quickly read barcodes pasted/printed on products, books and parcels are being used increasingly in departmental stores, libraries, postal services, etc.

In optical communications, a modulated laser beam confined in a thin silica optical fibre is used to transmit data (which can be voice, fax, video, or computer data) at a very high rate over long distances. The data transmission rate can be as high as several thousand megabites per second per optical fibre. Bangladesh Railways, and Telegraph and Telecommunication Board have already established a few optical fibre communication systems to meet their data transmission requirements. shahjalal university of science and technology and Rajshahi University have established optical fibre network backbone, which is used as the local area network (LAN) system of the university. Recently, arrangements have been made to establish a high-capacity undersea optical fibre link between Singapore and Bangladesh that will connect Bangladesh with the global optical fibre network. It is expected that more optical fibre systems will be introduced in different parts of Bangladesh, which will enable more people to communicate cheaply and effectively.

Since its early days, lasers have been used in surgical and opthalmological applications. The high powers generated by an argon laser can be used to re-attach the retina of the eye or to photocoagulate its blood vessels in the treatment of diabetic retinopathy. Several hospitals and medical centres in Bangladesh are equipped to treat such ailments. Lasers are also widely used in scientific research in physics, chemistry and biology. In physics, coherent beams of a helium-neon laser can be used to take a true three-dimensional photograph (known as a hologram) of an object. Later, the hologram can be illuminated by the laser to 're-create' the object. Such holograms were created at the Physics Department of Dhaka University several years ago. Lasers are also used to measure accurately the surface deformations of various objects and in Non-destructive Testing (NDT). The use of lasers in Bangladesh, though relatively recent and limited, is increasing rapidly. [Kazi Monowar Abedin]