Construction and working of Ruby laser

The following article will explain each and everything about Ruby laser that is  everything about the construction and working of Ruby laser:

The first laser to be operated successfully was ruby laser. First demonstration of laser action using ruby crystal was given by T.H. Maiman in 1960. It is a solid state laser.

Construction

Ruby is a crystal of aluminium oxide (Al2O3) in which some of the aluminium ions (Al3+) are replaced by chromium ions (Cr3+). This is done by doping small amounts of chromium oxide (Cr2O3) in the melt of purified Al2O3.

These chromium ions give the crystal a pink or red color depending upon the concentration of chromium ions. Laser rods are prepared from a single crystal of pink ruby which contains 0.05% (by weight) chromium. Al2O3 does not participate in the laser action. It only acts as the host. Continue reading “Construction and working of Ruby laser”

Drawbacks of ruby laser

Ruby laser has following drawbacks or disadvantages:

1. As the terminus of laser action is the ground state, it is difficult to maintain the population inversion. This fact results in ruby laser’s low efficiency.

2. The ruby laser requires high power pumping source.

3. The laser output is not continuous but occurs in the form of pulses of microsecond duration.

4. The defects due to crystalline imperfection are also present in ruby laser.

Reference: This article is referred from my authored book “optics and lasers” having ISBN 81-272-2948-2. In case of any doubt, post in the comment section.

Working of Ruby laser

In the last article, I have discussed construction of ruby laser. In this article, I will discuss working of ruby laser.

Ruby is a three level laser system. Suppose there are three levels E1, E2 and (E3 & E4). E1 is the ground level, E2 is the metastable level, E3 and E4 are the bands. E3 & E4 are considered as only one level because they are very closed to each other.

Pumping: The ruby crystal is placed inside a xenon flash lamp and the flash lamp is connected to a capacitor which discharges a few thousand joules of energy in a few milliseconds. A part of this energy is absorbed by chromium ions in the ground  state. Continue reading “Working of Ruby laser”

Construction of Ruby laser

The first laser to be operated successfully was ruby laser. First demonstration of laser action using ruby crystal was given by T.H. Maiman in 1960. It is a solid state laser.

Construction

Ruby is a crystal of aluminium oxide (Al2O3) in which some of the aluminium ions (Al3+) are replaced by chromium ions (Cr3+). This is done by doping small amounts of chromium oxide (Cr2O3) in the melt of purified Al2O3.

These chromium ions give the crystal a pink or red color depending upon the concentration of chromium ions. Laser rods are prepared from a single crystal of pink ruby which contains 0.05% (by weight) chromium. Al2O3 does not participate in the laser action. It only acts as the host.

The ruby crystal is in the form of cylinder. Length of ruby crystal is usually 2 cm to 30 cm and diameter 0.5 cm to 2 cm. As very high temperature is produced during the operation of the laser, the rod is surrounded by liquid nitrogen to cool the apparatus.

Active medium or active center: Chromium ions act as active centers in ruby crystal. So it is the chromium ions that produce the laser.

Pumping source: A helical flash lamp filled with xenon is used as a pumping source. The ruby crystal is placed inside a xenon flash lamp. Thus, optical pumping is used to achieve population inversion in ruby laser.

Optical resonator system: The ends of ruby crystal are polished, grounded and made flat. The one of the ends is completely silvered while the other one is partially silvered to get the output. Thus the two polished ends act as optical resonator system.

Note: I will explain the working in next article. Meanwhile, try to make the construction diagram yourself. In case of problem, contact me.

Reference: This article is referred from my authored book “optics and lasers” having ISBN 81-272-2948-2. In case of any doubt, post in the comment section.

Types of laser

The lasers can be classified on the basis of state as explained below:

a)      State of laser medium: According to the state of laser medium, we have solid state lasers like ruby laser,gas lasers like He-Ne laser and carbon dioxide laser, semiconductor laser and liquid laser like dye laser.

b)      Mechanism of pumping: According to it, we have optical pumping based lasers like ruby laser, electric discharge based lasers like He-Ne laser. Pumping can also be done through chemical reaction.

c)      Nature of output: According to nature of output, we have pulsed lasers like ruby laser and continuous wave lasers like He-Ne laser.

d)      Spectral region (wavelength) of output: According to it, we have ultra violet, visible and infrared lasers.

Note: Do you know what is pumping or how atoms/electrons are excited?