GREEN LASER

Done By B.Hemanth kumar1602-13-735-067

CONTENTS

1) What is LASER?2) Visible Light spectrum3) Importance of green over other

colours.4) Production of green laser

Green Gap Problem Solution to Problem

5) Applications in detail.6) Advantages and disadvantages.7) Future Enhancements.8) Conclusion.9) Bibliography.

WHAT IS A LASER ?• The acronym LASER stands for "light amplification by stimulated emission

of radiation.“

• How laser light is formed :

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VISIBLE LIGHT SPECTRUM• The spectrum of visible light ranges from 380nm to 750nm in terms of

wavelength.

WHY GREEN!!

Lies in middle of colour spectrum hence is balanced.

100% visible to human eye. 50 times brighter than red colour laser. Helps intensify contrast which will display much

richer colours than other systems. It enhances night vision. Green light propagates to greater distances

through water than any other colour, so it would improve underwater communications.

green light is ideally suited to burn thousands of spots into the retina which could cut the cost of a major eye treatment

What the world need now is a semiconductor laser that’s good, cheap, long lasting, powerful, and truly green.

PRODUCION OF GREEN LASER

DISADVANTAGE: The process is costly, inefficient and imprecise; the second crystal can heat up, altering the wavelength of the resultant green light.

DISADVANTAGE: For every watt of light that comes out of the original infrared laser, you get about 0.4 watt of green light.

REMEDY: Lasers that generate green light directly would avoid this problem.

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PRODUCION (cont.)3. After a flurry of research in the late 1960s and early 1970s ended in failure, practically no one in the field saw that the key to victory was an obscure material called gallium nitride.

DISADVANTAGE: The green gap problem.

THE GREEN GAP PROBLEM

• To make conventional GaN diodes, workers place a thin wafer of sapphire inside a reaction chamber . The layers grow in parallel with what is called the substrate’s c-plane.

• This problem becomes particularly acute as the colour of the emitted light shifts from violet to blue to green and red to green.

• As the current through the diode increases, the greater number of charge carriers partially blocks the internal electric fields .With these fields partially screened out, the electrons and holes then recombine at higher energies, shifting the light toward the blue end of the spectrum or red end of the spectrum.

GREEN GAP PROBLEM SOLUTION(Latest Development)

• Sapphire substrate was replaced with thin wafer of pure, crystalline GaN that was sliced along a larger crystal’s ‘m’-plane .

• Troublesome fields caused by polarisation and internal stress are much lower due to that arrangement.

• More efficient in producing light because of fewer crystalline defects, sub microscopic irregularities and mismatches at interface between successive layers.

• Also arrangement along ‘a-plane’ was more successful than that on ‘m-plane’.

LATEST TRENDS AND APPLICATIONS

• Three colour laser projector/hand held projector/mobile integrated projector.

• Underwater communication.

• Eye treatment for diabetic retinopathy.

• DNA sequencing.

• GCL 2-15 G combi laser for measurement and construction purpose.

1. THE THREE COLOUR PROJECTOR• It uses a property of change in the thickness of indium layer which directly

leads to change in wavelength and hence the colour in case of GaN semiconductor laser diode.

2. GCL 2-15 G COMBI LASER• Short-range leveling work in bright environments covering areas of up to 15 meters .

• When working in areas with bright ambient light, such as near windows, the green laser diodes of the Bosch GCL 2-15 G Professional combi laser can be seen significantly more clearly than the red laser lines of other tools on the market.

3. EYE TREATEMENT FOR DIABETIC RETINOPATHY

• It could cut the cost of a major eye treatment, stopping the proliferation of new blood vessels and ameliorating diabetic retinopathy.

4. DNA SEQUENCING

• Laser Sources for Underwater Applications since green light propagates to greater distances through water than any other colour. Hence giving an efficient way for underwater communications.

5. UNDERWATER APPLICATION

ADVANTAGES & DISADVANTAGESADVANTAGES

Reduces power consumption.

Long battery Life due to reduced heat generation.

Green light is 100% visible to human eyes.

Reduces cost and complexity in eye surgeries.

DISADVANTAGES

Cheap green lasers are hazardous to human and animal health.

Initial cost of production is high compared to other colour lasers.

FUTURE ENHANCEMENTS

Green laser to be used in Ophthalmic laser surgeries.

To use green laser in particle image velocimetry to map the flow of air over the aircraft using lasers and smoke

CONCLUSION

The Green Laser is a technology which suffered in production from the past and has now attained a stage of perfect production technique. Due to the amazing properties of green, it is balanced in nature and has a wide range of applications with provided advantages over other lasers.

BIBLIOGRAPHY

o www.ieeespectrum.com o www.efy.com

o www.scientificamerica.com

o www.wikipedia.com

o www.bosch-presse.de

o Google images