An Overview on the Erbium Doped Glass Lasers

Abstract

Erbium-doped glass serves as the active laser medium in an Er:glass laser, which is a solid-state laser. In order to increase the effectiveness of these lasers, ytterbium (Yb) is occasionally added. The infrared portion of the electromagnetic spectrum, which is typically between 1530 and 1560 nanometers, is where Er:glass lasers emit light.[22] There is a strong absorption peak for water at the precise wavelengths that Er:glass produces, which are around 1500 nanometers. Due to their high water content, the human cornea and lens efficiently absorb laser radiation, lowering the quantity of light that reaches the retina. The eye\'s light-sensitive layer, the retina, is especially susceptible to harm from strong lasers. As a result, Er:glass lasers are categorized as being more eye-safe than lasers that use wavelengths that can reach the retina. Because of their relative eye safety, Er:glass lasers can be employed in a wide range of settings, including public spaces and medical settings, where eye safety is required or preferred.[22] [23]

Introduction

A laser (Light Amplification by Stimulated Emission of Radiation) is a device that emits highly coherent, monochromatic, and directional light using optical amplification based on stimulated emission. The first laser was demonstrated in 1960 by Theodore Maiman, following earlier theoretical work by Townes and Schawlow. Lasers differ from ordinary light sources due to their spatial coherence (ability to focus to a small spot and remain collimated over long distances) and temporal coherence (very narrow frequency, or ability to produce ultrashort femtosecond pulses).

Lasers have numerous applications, including:

• Cutting and welding materials

• Barcode scanners, laser printers, CD/DVD drives

• Fiber-optic communication and free-space optical communication

• Medical surgery and skin treatments

• Semiconductor manufacturing (photolithography)

• Entertainment lighting and lidar systems

• Target marking and speed measurement in military/law enforcement

• Automobile laser headlights using blue/UV semiconductor lasers

Before lasers, the first device based on stimulated emission was the maser (microwave amplification). The term “laser” was created when the concept was extended to optical frequencies. Devices operating above microwave frequencies (IR, visible, UV, X-ray) are now all called lasers, while microwave devices remain masers.

LITERATURE REVIEW SUMMARY

The theoretical foundation of lasers began with Einstein (1916), who explained spontaneous and stimulated emission. Ladenburg (1928) observed stimulated emission experimentally.
Major developments:

• 1951–1953: Charles Townes built the first maser.

• 1958: Townes & Schawlow published the optical maser (laser) theory.

• 1960: Theodore Maiman built the first ruby laser.

• 1960: Javan, Bennett & Herriott created the first He–Ne gas laser.

• 1962: First semiconductor laser by Robert Hall.

Early lasers had limited applications but soon became essential in alignment, eye surgery, holography, supermarket scanners, CD players, laser printers, and many modern technologies.

PRINCIPLE OF LASER OPERATION

Laser action is governed by quantum energy levels and the transitions between:

1. Absorption

2. Spontaneous emission

3. Stimulated emission

A laser requires population inversion, where more atoms occupy a higher-energy state than a lower one. This is achieved through pumping (strong light or electric current).

Laser systems can be:

• Three-level lasers (e.g., ruby laser—pulse operation only)

• Four-level lasers (more efficient, allow continuous operation)

ELEMENTS & CHARACTERISTICS OF LASER BEAMS

Laser media include gases, solids, liquids, and semiconductors. Pumping creates excited states. An optical resonator—typically two mirrors—amplifies light as it bounces repeatedly through the gain medium.

Key characteristics of laser light:

• High coherence

• Monochromatic (narrow wavelength range)

• Highly collimated (low divergence)

• High intensity and focusability

The resonator supports specific longitudinal modes, and coherence length depends on the emitted wavelength bandwidth. Lasers may be continuous-wave or pulsed, with pulsed lasers capable of extremely high peak powers (up to 10¹? W in ultrashort pulses).

ERBIUM-DOPED GLASS (Er:Glass) LASERS

Er:glass lasers use erbium-doped solid-state glass as the gain medium, often co-doped with ytterbium for efficiency. They emit in the infrared range (1530–1560 nm).

Key features:

• Eye-safe wavelength (absorbed by cornea and lens, not reaching retina)

• Excellent for rangefinders due to low atmospheric absorption

• Well-matched to InGaAs and Ge photodiodes

• Often used in Q-switched form producing 1–10 mJ pulses

• Measurement range: up to ~10 km

Flash-lamp pumping gives slow repetition rates; diode pumping allows 10–20 Hz operation.

Conclusion

Er:glass lasers are employed in Fraxel Restore and other non-ablative laser skin resurfacing treatments. Water molecules in the skin tissue absorb a lot of the wavelength at 1540 nanometers. The water molecules are heated by this absorption, causing controlled thermal damage (thermolysis) in the top layer of the skin. The skin\'s natural wound-healing response is triggered by this heat injury, which encourages the formation of new collagen fibers. Without entirely eliminating the outermost layers of skin, the Er:glass laser therapy attempts to reduce the look of fine lines, wrinkles, and uneven skin tone by promoting the creation of collagen. With shorter healing durations and a lower chance of scarring, this method is thought to be a kinder substitute for ablative laser resurfacing procedures.[25][26] [27]

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Copyright

Copyright © 2025 Muhammad Arif Bin Jalil. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.