Thursday 19 December 2013

The Working Of An RGB Laser

By Cornelia White


An RGB laser is that laser that emits three primary colors of light. These are red light, green light and blue light, hence the acronym RGB. These can be produced in a single beam for all the three colors or separate beams for each of the color. Through the process of optical amplification of stimulated emissions of electromagnetic radiations, it is possible to obtain many more colors from these primary colors.

RGB lasers are being exploited as an alternative to arc lamps sources (beamers). Although arc lamps have been used for a long period as a source of beams particularly because they are much cheaper, they suffer from setbacks such as limited lifetime, high wall-plug efficiency is impossible, poor image quality as a result of poor spatial coherence and the fact that available color space is not wide enough. For this reasons, the former is becoming more popular RGB sources are much more popular.

Beams from these sources are known to be coherent in both wavelengths, both in time and space allowing for inferences. If the change in phase properties is able to take place at the same time over a long distance and at the same period of time, then such waves will produce a very clear image. It is possible to cancel such waves with a similar with opposite phase.

The narrow optical bandwidth of the three types of beams produced put them close to monochromatic beams, a property that makes them able to produce very sharp and clear images on color mixing. For this reason, their applications are increasing, not forgetting the use in cathode tubes, lamp based beamers, color printers and many types of projectors.

These beamers however are known to emit beams that are low in power. With cinema projectors requiring over 10 W of power per color, the use of RGB sources is limited. In addition to power insufficiency, there other challenges include maturity and cost effectiveness. There is also a need of better quality of beam for efficient working of these beamers.

External optical modulators are normally used in these types of beamers although RGB sources are fitted with power-modulators for better signals in situations where the optical modulator use is made impossible as a result of low power miniature devices. Laser diodes for instance are used to achieve modulation bandwidth between 10 to 100 megahertz or even much higher resolutions.

The construction of RGB lasers can be achieved in several manners with the most common ones involving the use of three different lasers with each producing one of the three colors. This method of visible beams however comes with several limitations in comparison to the other methods that employ the use of near infrared rays.

The other method is the use of an infrared solid-state laser where a single near-infrared laser generate a single color that then undergoes through different stages of nonlinear frequency conversion to produce the three colored beams. There are many other schemes of producing the desired wave lengths such as through combination of parametric oscillators, some frequency mixers and even frequency doublers in addition to other methods.

Technological advancement is however set to completely address the challenges in with an RGB laser. Just like other forms of lasers, they are set to be used in all other areas where there are need for lasers like in hospital machines, cutting technology and in entertainment industry among others.




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