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Explaining the Operation of Ruby Laser (with Diagram)

The Ruby laser is a particular kind of solid-state laser that works in the red color region of the visible light spectrum. Based on the idea of selective photothermolysis, which includes focusing on particular chromophores (pigments) in the skin or other materials, it was one of the first effective laser systems to be created.

In this guide, we review the aspects of operation of ruby laser, Is operation of ruby laser two level, What is the operation wavelength of ruby laser, and working of ruby laser in points.

Here is a description of how a Ruby laser works:

Medium: The aluminum oxide crystal known as ruby (Al2O3:Cr), which is essentially a crystal of aluminum oxide doped with chromium ions, serves as the solid-state medium for the Ruby laser. The laser’s distinctive red color output is a result of the chromium ions.

Pumping Mechanism: To “pump” energy into the crystal and raise the chromium ions to an excited state, the Ruby laser needs an external energy source. A high-energy flash lamp that delivers a powerful pulse of visible or near-infrared light is commonly used as the pumping mechanism. When activated, the flash bulb, which is positioned around the ruby crystal, emits a pulse of light.

Absorption and Population Inversion: When a pulse of light is emitted by the flash lamp, the ruby crystal absorbs the energy, which causes the chromium ions to switch from one energy level to another. Absorption is the term for this action. Population inversion is a phenomenon that occurs as the excited chromium ions fill higher energy levels inside the crystal.

Stimulated Emission: The laser activity is made possible by the population inversion. A chromium ion is stimulated to produce a second photon of the same wavelength and direction when it interacts with a photon of a certain wavelength (according to the energy difference between the excited and lower energy levels). Stimulated emission is the name of this procedure.

The ruby crystal is sandwiched between two mirrors that together make up an optical cavity. While one mirror is largely reflective and lets some light through, the other is extremely reflective and reflects the majority of light back into the crystal. As a result of the mirrors’ alignment, a feedback loop is created, amplifying the light as it passes through the ruby crystal several times.

As the photons experience stimulated emission and bounce back and forth between the mirrors, they travel through the ruby crystal and prompt more chromium ions to produce photons with the same wavelength and direction. A cascade of photons is produced as a result of this process, producing a coherent, red, monochromatic beam of light.

Output Coupler: The laser’s output, which is a portion of the laser beam that has escaped through the partly reflecting mirror. By altering the reflectivity of the mirrors and other elements like the size and temperature of the ruby crystal, it is possible to regulate the output beam’s quality and intensity.

The principles of light amplification by stimulated emission of radiation (LASER) underlie the operation of the Ruby laser. It emits a focused beam of bright red light that may be used in a variety of settings, including industrial, scientific, and medical ones.

Please be aware that although the details described here provide a broad idea of how a Ruby laser functions, they may differ depending on the design and setup of unique laser systems.

Explaining the operation of ruby laser

A ruby laser is a solid-state laser that uses the synthetic ruby crystal as its laser medium. Ruby laser is the first successful laser developed by Maiman in 1960.

Ruby laser is one of the few solid-state lasers that produce visible light. It emits deep red light of wavelength 694.3 nm.

Construction of Ruby Laser

A ruby laser consists of three important elements: laser medium, the pump source, and the optical resonator.

Laser medium or gain medium in ruby laser

In a ruby laser, a single crystal of ruby (Al2O: Cr3+) in the form of cylinder acts as a laser medium or active medium. The laser medium (ruby) in the ruby laser is made of the host of sapphire (Al2O3) which is doped with small amounts of chromium ions (Cr3+). The ruby has good thermal properties.

gain medium in ruby laser, pump source, and optical resonator

Pump source or energy source in ruby laser

The pump source is the element of a ruby laser system that provides energy to the laser medium. In a ruby laser, population inversion is required to achieve laser emission. Population inversion is the process of achieving the greater population of higher energy state than the lower energy state. In order to achieve population inversion, we need to supply energy to the laser medium (ruby).

In a ruby laser, we use flashtube as the energy source or pump source. The flashtube supplies energy to the laser medium (ruby). When lower energy state electrons in the laser medium gain sufficient energy from the flashtube, they jump into the higher energy state or excited state.

Optical resonator

The ends of the cylindrical ruby rod are flat and parallel. The cylindrical ruby rod is placed between two mirrors. The optical coating is applied to both the mirrors. The process of depositing thin layers of metals on glass substrates to make mirror surfaces is called silvering. Each mirror is coated or silvered differently.

At one end of the rod, the mirror is fully silvered whereas, at another end, the mirror is partially silvered.

The fully silvered mirror will completely reflect the light whereas the partially silvered mirror will reflect most part of the light but allows a small portion of light through it to produce output laser light.

Working of Ruby Laser

The ruby laser is a three level solid-state laser. In a ruby laser, optical pumping technique is used to supply energy to the laser medium. Optical pumping is a technique in which light is used as energy source to raise electrons from lower energy level to the higher energy level.

Consider a ruby laser medium consisting of three energy levels E1, E2, Ewith N number of electrons.

We assume that the energy levels will be E1 < E2 < E3. The energy level E1 is known as ground state or lower energy state, the energy level E2 is known as metastable state, and the energy level E3 is known as pump state.

Let us assume that initially most of the electrons are in the lower energy state (E1) and only a tiny number of electrons are in the excited states (E2 and E3)

Ruby laser is a three level solid state laser

When light energy is supplied to the laser medium (ruby), the electrons in the lower energy state or ground state (E1) gains enough energy and jumps into the pump state (E3).

The lifetime of pump state E3 is very small (10-8 sec) so the electrons in the pump state do not stay for long period. After a short period, they fall into the metastable state Eby releasing radiationless energy. The lifetime of metastable state E2 is 10-3 sec which is much greater than the lifetime of pump state E3. Therefore, the electrons reach E2 much faster than they leave E2. This results in an increase in the number of electrons in the metastable state E2 and hence population inversion is achieved.

After some period, the electrons in the metastable state E2 falls into the lower energy state E1 by releasing energy in the form of photons. This is called spontaneous emission of radiation.

When the emitted photon interacts with the electron in the metastable state, it forcefully makes that electron fall into the  ground state E1. As a result, two photons are emitted. This is called stimulated emission of radiation.

When these emitted photons again interacted with the metastable state electrons, then 4 photons are produced. Because of this continuous interaction with the electrons, millions of photons are produced.

In an active medium (ruby), a process called spontaneous emission produces light. The light produced within the laser medium will bounce back and forth between the two mirrors. This stimulates other electrons to fall into the ground state by releasing light energy. This is called stimulated emission. Likewise, millions of electrons are stimulated to emit light. Thus, the light gain is achieved.

Is operation of ruby laser two level

No, a two-level system is not the foundation for how a Ruby laser functions. This system has three levels. The laser transitions only happen between two energy levels in a two-level system. However, the laser activity in a Ruby laser requires switching between three different energy levels.

The Ruby laser’s three-level system is described in the following succinct manner:

Ground State: In the Ruby crystal, the chromium ions are in their ground state, which has the lowest energy. The chromium ions are in their stable, unexcited state in this situation.

Excited State: The chromium ions are raised to an excited state, which has a greater energy level than the ground state, when the Ruby crystal receives energy from the flash light. The chromium ions’ electrons migrate to higher energy orbits as a result of energy absorption.

There is a metastable state that exists within the excited state. The term “metastable state” describes a high-energy level with a lengthy half-life where the chromium ions can exist before decaying to their ground state.

The chromium ions in a Ruby laser change from the metastable state back to the ground state, which causes the laser activity. This transition causes the release of photons in the red spectrum at a certain wavelength. The released photons proceed through a process called stimulated emission, which causes other excited chromium ions to release more photons. As a result, there is a cascade effect that amplifies the light and causes a coherent laser beam to be produced.

A Ruby laser’s three-level structure enables population inversion and the creation of stimulated emission. This procedure makes it possible for the Ruby laser to produce a red light beam that is coherent and monochromatic.

It’s important to note that while the Ruby laser operates on a three-level system, different types of lasers may operate on different energy level schemes depending on the specific materials and dopants used in their construction.

Ruby Laser Construction and Working

What is the operation wavelength of ruby laser

The ruby laser was the first visible light laser to follow the early microwave masers. It produces red light at a wavelength of λ0 = 694.3 nm and is an example of a solid-state laser.

The active elements of ruby laser are Cr3+ ions, which are present as impurities in single-crystal Al2O3. The chromium ion, Cr+3, is introduced as a substitutional impurity replacing the aluminum ion Al+3 in the corundum structure of alumina. The corundum structure is hexagonal close packed (HCP), with its Al+3 ions in octahedral coordination filling two-thirds of the available sites in the HCP structure of the O−2 ions. The Cr3+ concentration is about 0.05% by weight. Ruby is typically brilliant red in gemstones, where the chromium concentration is about 1%. Chromium has an outer shell configuration of (3d)3 with five empty d orbitals. The color results from interlevel transitions between different chromium d orbitals.

Ruby is a three-level laser. Fig. 7.13 shows a rough sketch of the optical transitions of the ruby laser. In this laser, optical pump radiation from a flashlamp (xenon in pulsed operation) between 400 and 600 nm is absorbed by the Cr+3 ions, exciting carriers into the 4F2 band. This is followed by a rapid nonradiative transition (50 ns) to the 2E levels, which are split into a 2A level and an E level separated by 29 cm−1. The lasing transition is from the E level to the ground state, with a wavelength of 694.3 nm and a linewidth of 11 cm−1 (0.3 GHz, or 5.3 A). This makes ruby lasers three-level lasers. Ruby has a quantum efficiency of about 80%. The excited state lifetime is 3 ms, and t2 ≈ tspont. Assuming a threshold pump energy of 3 J/cm2 for a population inversion of 2 × 1019 atoms/cm3, a 1% pumping efficiency requires a flashlamp energy density of 300 J/cm3.

Explaining the Operation of Ruby Laser with Diagram Class 12

B.Y. Soon, J.W. Haus, in Encyclopedia of Modern Optics, 2005

Introduction

The invention of the ruby laser, in 1960, provided a revolutionary new light source, which emits an intense, highly collimated polarized beam of light. The new source opened the way for developments that have enabled new technologies, thus profoundly changing our way of life. One of these new frontiers opened by the laser was the field of nonlinear optics. In 1961, Franken et al. were the first to report the observation of second-harmonic generation from a quartz crystal, using ruby laser light. Third-harmonic generation (THG) was soon discovered by Terhune and co-workers in 1962.

THG has found applications as a spectroscopic tool to probe optical properties of materials, but recently it has been developed as a microscopy tool and a pulse measurement technique. More efficient THG is possible by engineering the materials; for instance, one way to improve conversion efficiency is to use periodic structured dielectric materials, called photonic bandgap structures.

Atomic, Molecular, and Optical Physics: Electromagnetic Radiation

Michael G. Littman, Xiao Wang, in Experimental Methods in the Physical Sciences, 1997

6.2.3 Q-Switching

Shortly after the invention of the ruby laser, the method of Q-switching was introduced by R.W. Hellwarth to create a high-intensity burst of light . Q is the quality factor of a resonator, and it is a measure of its energy storage ability. For a Q-switching operation, a population inversion is built up during a pumping period that in the ideal case matches the excited state lifetime of the laser medium.

(For the ruby laser this time is approximately 3 msec.) During this pumping period the laser cavity Q is kept at a low value by keeping closed an intracavity optical switch in order to prevent circulation of light within the cavity. At the end of this pumping period, when the upper level is heavily populated, the cavity Q is suddenly switched from a low to a high value by opening the optical switch. Laser action then builds up rapidly, beginning with random noise light due to spontaneous emission. (Excited quantum systems decay spontaneously by the emission of light when there are no external driving fields. Spontaneous emission allows laser oscillators to be self-starting. If there was no spontaneous emission, it would be necessary to inject light into a laser cavity to get it oscillating. Spontaneous emission is distinct from stimulated absorption and stimulated emission in that these latter two processes require external driving fields.) Spontaneous light that falls in a narrow range of angles defining the optic axis of the gain medium is reflected by the mirrors and coherently amplified by the stimulated emission process. In a very short time, corresponding to a few passes through the gain medium, most of the energy stored in the medium is extracted. (The stored energy in the gain medium falls to zero typically in several nanoseconds.) For most solid-state laser media, this duration is much shorter than their natural (spontane-ous emission) decay time. Q-switching is thus used to create a burst of light that is briefer and more intense than one would obtain without an optical switch.

If a laser medium has a long excited state lifetime, the population in the upper state can be built up gradually to a high level during that time, which can be accomplished using a modest pumping source. Therefore, Q-switching is easier to achieve in laser media with long excited state lifetimes, such as ruby. Other factors, such as the gain of the laser medium and the saturation fluence level of the medium, also influence the energy storage in the medium, and thus the efficiency of Q-switching,

P.M. Rentzepis, M.R. Topp, in Organic Scintillators and Scintillation Counting, 1971

Experimental

A train of mode-locked ruby laser pulses was passed through a red filter (F1) into a resonant cavity terminated by two dielectric mirrors (M) (100% reflecting at 420 nm, 90% transmitting at 695 nm). The optical length of the 420 nm (wd), and 694.3 nm (wr) cavities was the same. The maximum power in the pulse train was about 7 GW (7×109 W) and the pulses were separated by exactly 5 nsec. (Fig. 5)

The dye solution used in both cells C1 and C2 was dimethyl POPOP (DMP) in methyl cyclohexane. The train of mode-locked ruby laser pulses (wr) had a dual function in exciting the dye cell as follows. The frequency wr was used to excite dye cell C1 by two-photon absorption. The second harmonic of the red pulses (2wr generated by the KDP crystal) was used to generate the stimulated emission from the dye cell C2, which became mode-locked owing to the identity of the two laser cavity optical lengths.(25) The time-spacing of the two sets of mode-locked pulses (wr and wd) being identical (Fig. 6), a dye laser pulse was reflected from M1 simultaneously with, or slightly behind, the arrival of the succeeding wr pulse at M1. The pulses travelled together through C1 where wr excited the dye by two-photon absorption, and wd stimulated it to emit resulting in amplification of wd. The fluorescence lifetime of the dye (1.5 nsec) was sufficiently short that no excitation remained after the 5 nsec pulse separation and each amplification process could be considered to be a separate experiment.(18)

The gain within the cell C1 was monitored for each pulse by the same photodiode by observing the pulse before and after passing through the dye cell, corresponding to a separation of 1.5 nsec.

The response time of the photodiode-oscilloscope system was adequate to resolve the 1.5 nsec separation of the pulses. The inclusion of a reference trace of laser fundamental intensity gave an oscilloscope trace having three distinct trains. Hence, a series of data points could be obtained, which made possible the calculation of σII from Equation (1). The linearity of the plot indicated that gain saturation was not reached at this pumping level. The value of σII, obtained from the slope of the plot was found to be 4.0×10−48 cm4 sec photon−1.(18)

This method for the determination of the two-photon absorption cross-sections (σII) has certain advantages over other techniques in use at the present. Two-photon absorption is usually monitored by the fluorescence of the absorbing species, which provides an order-of-magnitude estimate for the quantity σII. The technique discussed here measures directly the population of excited states, and moreover, since a train of mode-locked pulses is used, one laser shot provides sufficient data for a determination of σII. The accuracy is within a factor of two, and is largely dependent upon the accuracy of the measurement of the laser pulse intensity. This method also enables one to measure σII easily for other fluorescent species, or for the same species in different solvents by changing the solution in the amplifier cell.

Interaction of Radiation with Matter: Absorption, Emission, and Lasers

Robert H. Kingston, in Optical Sources, Detectors, and Systems, 1995

2.5 Inversion Techniques

Three techniques are commonly utilized to obtain an inverted energy-level population in a laser medium. These are optical “pumping,” electric discharge energy transfer, and semiconductor electron injection. We leave the last for the next chapter, but here we briefly describe the first two techniques.

Optical pumping, the inversion technique used in the original ruby laser, is an extension of the “three-level” maser scheme proposed by Bloembergen (Bloembergen, 1956) for microwave solid-state masers. In Figure 2.6 we show a system of three energy levels, whose occupation, as shown by the length of the bars, obeys the Boltzmann distribution. We now apply a “pump” or intense optical field at the frequency corresponding to transitions between the first and third energy levels. If the energy density is sufficient the level populations will equalize, that is, N1 = N3, and in this case N3 will become greater than N2, and the 2-3 system will be inverted. The equalization of the 1-3 system results from the pump-induced transitions completely overcoming the spontaneous and thermal radiation-induced transitions. This picture is of course vastly oversimplified, since there are, first, competing nonradiative transitions between levels and, second, the pump source may have a broad spectrum that induces transitions among other level spacings. In most systems, in fact, only the lowest or ground state is occupied at room temperature and the inversion of an upper pair of states is critically dependent on the energies of the states, the pump spectrum, and the relaxation or transition times between states. Albeit, laser action was first demonstrated by Maiman, using a photographic flashlamp and a cylindrical rod of ruby with partially reflecting silvered coatings on the parallel endfaces (Maiman, 1960).

Assume the energy levels in Figure 2.5 are equally spaced, U2 − U1 = U3 − U2 = kT, and the measured absorptioncoefficient for the 2-3 transition is 1 cm-1. The system is now “pumped” such that N1 = N3 and N2 remains fixed. We now wish to find the gain coefficient for the 2-3 transition, assuming the B coefficient for the 1-2 transition (at the same frequency) is negligible.

The gain is proportional to (N3-N2). The initial value of (N3 − N2) is given by N2(e−1 −1) = −0.63N2. The final value of N3 is one-half the sum of the initial values of N1 and N3 which is 0.5N2(e1 + e-1). Thus the final value of (N3 − N2) becomes N2[0.5(e1 + e−1) − 1] = 0.54N2. Finally, the gain becomes −1 cm−1 times the ratio of the final to the initial value of (N3 − N2) = 0.54/(−0.63) = 0.86, and is therefore + 0.86 cm−1.

The second common inversion technique involves the preferential transfer of energy between and among electrons, atoms, and molecules in an electrical discharge in a gas. The most common example of this type is the helium-neon or He-Ne laser. Here, electron-excited helium atoms transfer energy to an upper state of neon, which ends up with a population much larger than several lower intermediate states. The result is laser action at wavelengths of 3.39 and 1.15 μm and 633 nm or 6328 A. Another well-developed gas laser is the carbon dioxide system operating at wavelengths near 10 μm and yielding continuous powers as high as 50 kW! The resonator mirror spacing in these devices is usually many centimeters and alignment and diffraction losses can become serious. As a result, most if not all gas lasers use concave reflectors in the so-called confocal or modified confocal configuration. This technique confines the mode laterally as well as longitudinally and helps reduce diffraction losses as well as assure single-frequency-mode operation. Yariv gives a detailed discussion of these resonators as well as an in-depth analysis of the various laser systems (Yariv, 1991).

Halina Abramczyk, in Introduction to Laser Spectroscopy, 2005

4.1 RUBY LASER

Theodore Maiman constructed the world’s first laser from a ruby crystal. Since that first ruby laser, researchers have discovered many other materials for use as the gain medium, but the oldest laser still finds some applications. The large energy pulses and the red visible light radiation (694.3 nm) of the ruby laser still find applications in holography and dermatology. The ruby laser is utilized in dermatology to remove tattoos and pigment defects of the skin. The ruby laser is a pulsed laser of low repetition rate—the repetition rate being the number of pulses that are sent by a laser per 1 second. The pulse-duration is of the order of milliseconds, with an energy of 1 J, and an average pulse power of the order of kilowatts. The active medium of a ruby laser is a rod made of a synthetic sapphire (A12O3) doped with chromium (0.01–0.5%)—having the same valence number (+3) as the aluminum. The electronic transitions in a ruby laser are presented in Fig. 4.1.

The ruby laser is pumped with a xenon flash lamp. When the chromium ions, Cr+3, in a ruby crystal absorb photons of visible light at 400 nm or 550 nm, some electrons jump from their ground-state, E0, to the excited states E1 or E2. The electrons excited to these states almost immediately (ca. 100 ns) dissipate their excess energy to the surrounding crystal lattice. As a result of the radiationless transitions the electrons jump to one of two closely spaced metastable states, E or 2A, where they stay for the relatively long time of 3 ms at room temperature. This time is long enough to achieve population inversion. Stimulated emission occurs on the E → E0 transition, generating light at a wavelength of 694.3 nm. Because the whole cycle of excitation, relaxation, and stimulated emission, involves transitions between three energy levels, the ruby laser is known as a three-level laser. The three-level lasers are relatively inefficient because the laser transition terminates in the ground state, and large pumping energies are required to achieve population-inversion. In the three-level lasers, more than half the atoms have to be transferred to the excited state to create the population inversion between the metastable and the ground state. The energy produced in the active medium as a consequence of radiationless transitions heats the ruby crystal, limiting the repetition rate to several pulses during one second. This inconvenience of the three-level system is partially compensated for by a long lifetime of the metastable state. This long lifetime permits the ruby rod to store an amount of energy many times greater than that in the neodymium Nd:YAG rod under the same conditions and, as a consequence, to generate pulses of much larger energy.

Ruby lasers find wide application in holography, plasma diagnostics, and dermatology. In dermatological applications the Q-switched ruby lasers are utilized, generating pulses of energy of 2–3 J with a repetition rate of 0.5–1 Hz. Such an energy is sufficient to remove black, blue, and green pigments of skin tattoos, as well as stains caused by excess melanin. The laser beam destroys cells containing the pigment by inducing photochemical reactions, whereas the surrounding non-pigmented areas of skin do not absorb the light energy and experience only negligible damage. The lymphatic system then slowly removes dead cells during the following several months. The ruby laser does not remove red pigments since these do not absorb the red light at 694.3 nm. The ruby laser can also work in the modelocking regime, emitting pulses of 20–30 picosecond duration, with an energy of 1 mJ, and repetition rate of 20–30 Hz.

E.V. Browell, … S. Ismail, in Encyclopedia of Modern Optics, 2005

H2O DIAL Systems

H2O was first measured with the DIAL approach using a temperature-tuned ruby laser lidar system in the mid-1960s. The first aircraft-based H2O DIAL system was developed at NASA LaRC, and was flown in 1982, as an initial step towards the development of a space-based H2O DIAL system. This system was based on Nd:YAG-pumped dye laser technology, and it was used in the first airborne H2O DIAL atmospheric investigation, which was a study of the marine boundary layer over the Gulf Stream. This laser was later replaced with a flashlamp-pumped solid-state alexandrite laser, which had high spectral purity, i.e., little out-of-band radiation, a requirement since water vapor lines are narrow, and this system was used to make accurate H2O profile measurements across the lower troposphere.

A third H2O DIAL system, called LASE (Lidar Atmospheric Sensing Experiment) was developed as a prototype for a space-based H2O DIAL system, and it was completed in 1995. This was the first fully autonomously operating DIAL system. LASE uses a Ti:sapphire laser that is pumped by a double-pulsed, frequency-doubled Nd:YAG to produce laser pulses in the 815 nm absorption band of H2O (see Table 5). The wavelength of the Ti:sapphire laser is controlled by injection seeding with a diode laser that is frequency locked to a H2O line using an absorption cell. Each pulse pair consists of an on-line and off-line wavelength for the H2O DIAL measurements. To cover the large dynamic range of H2O concentrations in the troposphere (over 3 orders of magnitude), up to three line pair combinations are needed. LASE uses a novel approach of operating from more than one position on a strongly absorbing H2O line. In this approach, the laser is electronically tuned at the line center, side of the line, and near the wing of the line to achieve the required absorption cross-section pairs (on and off). LASE has demonstrated measurements of H2O concentrations across the entire troposphere using this ‘side-line’ approach. The accuracy of LASE H2O profile measurements was determined to be better than 6% or 0.01 g/kg, whichever is larger, over the full dynamic range of H2O concentrations in the troposphere. LASE has participated in over eight major field experiments since 1995. See Table 6 for a listing of topics studied using airborne H2O DIAL systems (Figures 6–8).

Table 5. Parameters of LASE H2O DIAL system

Table 6. Examples of significant contributions of airborne H2O DIAL systems to the understanding of H2O distributions (see also Figures 6–8)

W.R. Hunter, in Vacuum Ultraviolet Spectroscopy, 2000

16.6 Multiplate Resonant Reflectors

Multiplate resonant reflectors (MRRs) were introduced as mode selectors for giant pulsed ruby lasers . Such a resonator consists of two or more plates of a transparent material. The surfaces of each plate are plane-parallel, and the individual plates must be coaligned so that all surfaces are parallel. In the first designs of MRRs , the thicknesses of the plates and spacers were chosen by approximate methods. However, Watts showed that the true properties of an MRR can only be obtained using a thin-film calculation, that is, assuming that the components of the electromagnetic waves are coherent over the length of the resonator.

Because the plates of the resonator are not coated, the chance of damage to the resonator is reduced. Furthermore, when the beams reflected from the plate surfaces are in phase, the reflectance of the resonator can be quite large. These properties seem almost ideal for lasers operating in the VUV. Experiments in tuning an Ar excimer laser to 1216 Å, in which the author participated, showed that the output mirror coating, semitransparent Al + MgF2 on an MgF2 substrate, was easily damaged. In an attempt to produce a VUV laser output mirror, an MRR was designed and manufactured . MgF2 plates were used because of the difficulty in polishing LiF plates and their propensity to damage by chemisorption of water vapor.

working of ruby laser in points

Certainly! Here is a short, to-the-point description of how a Ruby laser operates:

Ruby crystal: The laser uses ruby (Al2O3:Cr), a man-made crystal, as its solid-state medium. Usually rod-shaped, the crystal contains chromium ions.

Pumping mechanism: A high-energy flash light is frequently used to pump the ruby crystal. The ruby crystal is able to absorb the flash lamp’s powerful light pulse.

Population inversion: As a result of the absorbed energy, the chromium ions inside the ruby crystal are stimulated, leading to a phenomenon known as population inversion. Because of this, there are more chromium ions in the excited state than in the ground state.

An excited chromium ion is stimulated to emit a second photon with the same wavelength and direction when it interacts with a photon of the right wavelength. Stimulated emission is the name of this procedure.

A ruby crystal is sandwiched between two mirrors to create an optical cavity. While one mirror is largely reflective and lets some light through, the other is extremely reflective and reflects the majority of light back into the crystal. A feedback loop that is created by the mirrors enhances the light as it passes through the ruby crystal several times.

Laser emission: The photons penetrate through the ruby crystal, experience stimulated emission, and ricochet back and forth between the mirrors. This causes more chromium ions to release photons. A coherent, monochromatic laser beam is produced as a result of the photon cascade that is set off.

Output coupler: The laser’s output, a portion of the laser beam that passes through the partly reflected mirror. By adjusting the reflectivity of the mirrors and other parameters, the output beam may be changed.

Properties of the Ruby laser: The Ruby laser generates predominantly red light, usually with a wavelength of 694 nanometers. It generates brief, intense light pulses.

Applications: Ruby lasers have been utilized for a wide range of tasks, including laser spectroscopy, range finding, and medical treatments.

It’s crucial to remember that while this review gives a general overview of a Ruby laser’s operation, specifics and variations may vary between various laser systems and designs.

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