Ruby Laser – Definition, Principle, 5 Application|Construction and Working of Ruby Laser

Ruby Laser is a type of solid-state laser that operates on the principle of stimulated emission to produce a coherent and monochromatic beam of light.

Developed in 1960, Ruby Laser was the first successful laser to be constructed and has since found numerous applications in scientific research, medicine, and industry.

In this article, we will discuss the working principle, applications of Ruby Laser, as well as its advantages and disadvantages and also the Ruby Laser construction and working. This comprehensive guide will provide you with a deep understanding of Ruby Laser and its potential.

Ruby Laser

Ruby laser is a solid-state laser that was developed by Maiman in 1960 using Ruby as an active medium. It operates on the principle of stimulated emission to produce a coherent and monochromatic beam of light.

Ruby is a crystal of Aluminum oxide. In which a part of the aluminum ion is substituted by chromium ion.

The active material in the Ruby is chromium ion. That is the energy level of chromium Ion takes part in the lasing action.

Ruby Laser Diagram

Principle of Ruby Laser

The working principle of a Ruby Laser is based on the process of stimulated emission. This involves the excitation of chromium atoms in a ruby crystal, the creation of a population inversion, the introduction of a photon to stimulate the release of energy, and the amplification and refinement of the laser beam through an optical resonator.

Ruby Laser Wavelength

The Ruby Laser emits laser light in the red region of the electromagnetic spectrum, having a wavelength of approximately 694.3 nanometers (nm).

Ruby Laser Construction and Working

Construction of Ruby Laser

A ruby laser constructs of three main parts:

• Laser medium or gain medium in ruby laser or An active material ( or laser medium).
• Pump source or energy source in ruby laser. A  present and system made of two parallel plates with a reflecting coating applied on them.
• Optical resonator – An exciting system usually made up of helical xenon. Flash tubes for achieving population inversion and a power supply source.

Ruby is a crystal of Aluminum oxide. In which a part of the aluminum ion is substituted by chromium ion. The active material in the Ruby is chromium ion. That is the energy level of chromium Ion takes part in the lasing action. The color (pink or red) of a Ruby crystal depends upon the amount of chromium in it.

The construction of a Ruby Laser involves several components:

A crystal of Aluminum oxide is specially grown with about 0.05% of the aluminum atom replace by chromium. Ruby crystals are grown in special furnaces, then annealed and shaped into rods.

Such Rods are 2 to 30 cm in length and 0.5 to 2 cm in diameter. Flat end faces of the rod are made strictly parallel, ground and polished to a high degree of precision.

Sometimes reflecting coating is applied not on special plates. But directly on the end faces of the Ruby Rod. The end faces of the rod are silver so that the Surface of the one end face becomes fully reflecting.

And that of the other end face becomes partially reflecting. Usually the light transmission coefficient of the partially reflecting end face of the ruby rod is about 10 to 25 per cent. Thus , Ruby Rod with its one end only reflecting and the other end partially reflecting acts as a resonant cavity.

Overall, the construction of a Ruby Laser involves precise assembly and alignment of the key components, including the ruby crystal, flashlamp, optical resonator, and cooling system. The result is a high-powered laser that can be used in a wide range of applications.

Working of Ruby Laser

The Ruby rod is arranged along the axis of a helical xenon flash tube. In such a manner that the will of the helix encloses the rod. The flash of the tube lasts several milliseconds.

During this period of time, the tube absorbs energy amounting to Several thousand joules and most of the energy is spent on heating the Apparatus.

This heat produced is removed by liquid nitrogen circulating around the Ruby rod. The remaining part of the energy in the form of blue and green radiation is absorbed by the Ruby. This energy ensures the excitation of chromium Ion from the ground state to the excited energy state for achieving population inversion. 

Energy level diagram of Ruby Laser

The optical pumping result when incident photons of wavelength 5500Å. Raise the chromium Ion from ground state E1 to higher excited state E3. These iron interact with the crystal lattice and decay to metastable state E2 by spontaneous emission where they can stay for a longer period (3 x 10^–3sec) Producing population inversion.

 That is, the number of chromium ions in the energy state E2 ( metastable state) is more than the number of chromium ions in excited energy state E3. Hence, population inversion is achieve by optical pumping source.

Production of a Laser Beam

The some of chromium Ion jumps from the metastable state E2  to the ground state E1 through spontaneous emission of radiation. During this transition, a photon of wavelength 6943Å is emitted.

This Photon Travels through the Ruby rod in a direction parallel to the axis of the rod and reflects back and forth (or to and fro) by the reflecting ends of the optical resonator until it Stimulates an excited chromium ion. Stimulated excited chromium Ion emits a photon exactly in phase with the stimulating photon.

The Stimulated transition of chromium Ion from metastable state E2 to the ground state E1  is known as laser transition. These in-phase photons stimulate more chromium ions and hence the number of photons emitted increases.

This process repeats and hence the in-phase photos get multiplied. Thus, a strong and coherent laser beam is obtained. Which comes out of the optical resonator through the partially reflecting face.

Output of Ruby Laser

In Ruby laser energy for excitation for population, inversion is supplied in the form of short flasher or pulse of light. So ruby laser has a pulse output and hence called pulse laser.

Spiking in Ruby Laser

In a ruby laser, an optical pumping source provides energy in the form of a basis of life of a few nanosecond duration. When a crystal or rod absorbs the flash or pulse of light, population inversion takes place.

Ruby laser determinate at the ground state. By emitting laser radiation (or photo) of wavelength 6943Å and hence meta stable state disappears. Therefore lasing action stops till another flash of light is available after a few nanoseconds for population inversion.

Thus, the output of a ruby laser is in the form of energetic pulses of very small duration ( of the order of nanosecond). Before the output power attains steady-state value through damped relaxation oscillations. These energetic pulses of very short duration are spikes and the phenomena of generating these pulses are spiking.

The output power of the ruby laser is not continuous. But it is in the form of pulses of short duration. In other words, the ruby laser operates in pulse mode and hence called pulsed laser. It is all about the Ruby laser construction and working. Now we have to study the advantages and disadvantages.

Advantages of Ruby Laser

• It has large power output.
• The pumping efficiencies can be increased by using cylindrical Mirrors. 
• It has a narrow linewidth.
• The pulse duration of the Ruby Laser is relatively long compared to other types of lasers.
• Visible Wavelength – The Ruby Laser emits laser light in the red region of the electromagnetic spectrum, which is visible to the human eye.
• Ruby Lasers are relatively low cost and simple to construct, which makes them accessible to a wider range of users.

Disadvantages of Ruby laser

• The output laser beam is not continuous but the light is emitted in pulses.
• The Monochromaticity may be affected by crystalline Imperfection. Thermal distortion and scattering.
• Frequent cooling is required as a lot of heat energy is produced during its operation.
• A large amount of energy is required to Trigger laser oscillations.
• Short lifetime: The lifetime of the flashlamp in a Ruby Laser is relatively short.

5 Applications of Ruby Laser

Ruby Lasers have a variety of applications in different fields. Some common applications include:

• It is used as a high power source of Pulse coherent radiation in interferometry and in pulsed holography.
• It is used for drilling brittle material, soldering,  welding, and in-range finding. 
• Military applications: Ruby Lasers have been used in some military applications, such as rangefinders and laser target designators.
• Medical procedures: Ruby Lasers are used in some medical procedures, such as tattoo removal and dermatology, where the laser beam is used to selectively remove tissue or pigmentation.
• Laser light shows: Ruby Laser emit visible red light which makes it popular for laser light shows, where the laser beam is used to create patterns and designs for entertainment purposes.

Characteristics of Ruby Laser

Properties of Ruby laser

• Optically Pumped.
• Solid State.
• High Peak Power.
• Visible Red Light.
• Narrow Bandwidth.
• Polarized Light.
• High-Quality Beam.

Ruby Laser Short Notes

1. Ruby Lasers are solid-state lasers that use a ruby crystal as the laser medium.
2. They are optically pumped by a flash lamp that provides the energy required to pump the laser crystal.
3. Ruby Lasers emit laser light at a specific wavelength of approximately 694.3 nanometers in the red region of the electromagnetic spectrum.
4. They have a relatively long pulse duration and a narrow spectral linewidth.
5. Ruby Lasers have high peak power and emit highly polarized laser light.
6. They require cooling to dissipate the heat generated during operation and have a limited pulse repetition rate.
7. Ruby Lasers are used in a variety of applications, including laser light shows, scientific research, industrial manufacturing, medical procedures, and military applications.
8. They have advantages such as high peak power and high-quality beam, but also have disadvantages such as relatively low efficiency and short flash lamp lifetime.
9. Ruby Lasers played a significant role in the development of laser technology and continue to be used in various fields today.

FAQ’s on Ruby Laser

What is the working of ruby laser?

The Ruby rod is arranged along the axis of a helical xenon flash tube. In such a manner that the will of the helix encloses the rod. The flash of the tube lasts several milliseconds. During this period of time, the tube absorbs energy amounting to Several thousand joules and most of the energy is spent on heating the Apparatus.

What is the active material in ruby laser?

The active material in the Ruby is chromium ion.

What is the output of ruby laser?

In Ruby laser energy for excitation for population, inversion is supplied in the form of short flasher or pulse of light. So ruby laser has a pulse output and hence called pulse laser.

What is spiking in ruby laser?

In a ruby laser, an optical pumping source provides energy in the form of a basis of life of a few nanosecond duration. When crystal or rod absorbs the flash or pulse of light, population inversion takes place. Ruby laser determinate at the ground state. By emitting laser radiation (or photo) of wavelength 6943Å and hence metastable state disappears.

What is ruby laser?

Ruby is a crystal of Aluminum oxide. In which a part of aluminum ion is substituted by chromium ion. The active material in the Ruby is chromium ion. That is the energy level of chromium Ion takes part in the lasing action.