On the other hand, passively Q-switched microchip lasers ( with very short resonators ) have generated pulses with durations far below one nanosecond and pulse repetition rates from hundreds of hertz to several megahertz ( MHz )

However, Q-switched lasers can also be used for measurement purposes, such as for distance measurements ( range finding ) by measuring the time it takes for the pulse to get to some target and the reflected light to get back to the sender.

Q-switched lasers are also used to remove tattoos.

Super alloy drilling ( for gas turbine parts ) typically uses pulsed Nd: YAG lasers ( millisecond pulses, not Q-switched ).

Neodymium-YAG is the most widely used active laser medium in solid-state lasers, being used for everything from low-power continuous-wave lasers to high-power Q-switched ( pulsed ) lasers with power levels measured in the kilowatts.

In a Q-switched laser, the population inversion is allowed to build up by introducing loss inside the resonator which exceeds the gain of the medium ; this can also be described as a reduction of the quality factor or ' Q ' of the cavity.

Similar measurements were obtained later the same year by a Soviet team at the Crimean Astrophysical Observatory using a Q-switched ruby laser.

A typical Q-switched laser ( e. g. a Nd: YAG laser ) with a resonator length of e. g. 10 cm can produce light pulses of several tens of nanoseconds duration.

Large-scale laser systems can produce Q-switched pulses with energies of many joules and peak powers in the gigawatt region.

It is also very easy to actively Q-switch a CO < sub > 2 </ sub > laser by means of a rotating mirror or an electro-optic switch, giving rise to Q-switched peak powers up to gigawatts ( GW ) of peak power.

However, some studies show that treatment may be possible with a Q-switched alexandrite ( 755 nm ) laser.

When the Q is raised, lasing builds up from the initial seed, producing a Q-switched pulse that has characteristics inherited from the seed.

This provides a " seed " of light that can aid in the buildup of the next Q-switched pulse.

* Regenerative amplification: In regenerative amplification, an optical amplifier is placed inside a Q-switched cavity.

In this Q-switched mode, output powers of 250 megawatts and pulse durations of 10 to 25 nanoseconds have been achieved.

Advances in design of diode lasers and optical parametric oscillators promote developments in fluorescence and ionization spectrometry and also in absorption techniques where uses of optical cavities for increased effective absorption pathlength are expected to expand.

Faster reactions are usually studied with ultrafast laser spectroscopy where utilization of femtosecond lasers allows short-lived transition states to be monitored at time scaled down to a few femtoseconds.

The primary advantages of a pistol caliber carbine are increased accuracy due to the buttstock and longer barrel ( and with it, sight radius ), relatively low muzzle blast / flash / recoil, higher muzzle velocity and energy of a longer barrel for increased wounding potential and penetration ( depending on the particular load used ), and ( sometimes, but not always ) greater adaptability for easily accepting accessories such as optics, weaponlights, and lasers.

Holmium is used in yttrium-iron-garnet ( YIG )- and yttrium-lanthanum-fluoride ( YLF ) solid-state lasers found in microwave equipment ( which are in turn found in a variety of medical and dental settings ).

Holmium lasers emit at 2. 08 micrometres, and therefore are safe to eyes.

And although temporal coherence implies monochromaticity, there are even lasers that emit a broad spectrum of light, or emit different wavelengths of light simultaneously.

There are some lasers which are not single spatial mode and consequently their light beams diverge more than required by the diffraction limit.

However all such devices are classified as " lasers " based on their method of producing that light: stimulated emission.

Because the microwave predecessor of the laser, the maser, was developed first, devices of this sort operating at microwave and radio frequencies are referred to as " masers " rather than " microwave lasers " or " radio lasers ".

In most cases these lasers are still termed " continuous wave " as their output power is steady when averaged over any longer time periods, with the very high frequency power variations having little or no impact in the intended application.

Some lasers are pulsed simply because they cannot be run in continuous mode.

Such mode-locked lasers are a most versatile tool for researching processes occurring on extremely short time scales ( known as femtosecond physics, femtosecond chemistry and ultrafast science ), for maximizing the effect of nonlinearity in optical materials ( e. g. in second-harmonic generation, parametric down-conversion, optical parametric oscillators and the like ) due to the large peak power, and in ablation applications.

These lasers are often pumped by electrical discharge.

Solid-state lasers are usually pumped by flashlamps or light from another laser.

Semiconductor lasers are typically very small, and can be pumped with a simple electric current, enabling them to be used in consumer devices such as compact disc players.

In more complex lasers, configurations with four or more mirrors forming the cavity are used.

Such lasers are said to be superluminescent, and emit light with low coherence but high bandwidth.

Since they do not use optical feedback, these devices are often not categorized as lasers.

Mirrors are also used in scientific apparatus such as telescopes and lasers, cameras, and industrial machinery.

Optical isolators are one-way devices that are commonly used with lasers.

Some neodymium-doped glasses are also used in lasers that emit infrared light with wavelengths between 1047 and 1062 nanometers.

Neodymium-doped crystals ( typically Nd: YVO < sub > 4 </ sub >) generate high-powered infrared laser beams which are converted to green laser light in commercial DPSS hand-held lasers and laser pointers.

Most so-called " single wavelength " lasers actually produce radiation in several modes having slightly different frequencies ( wavelengths ), often not in a single polarization.

However some high power lasers may be multimode, with the transverse modes often approximated using Hermite-Gaussian or Laguerre-Gaussian functions.

Ytterbium is often used as a doping material ( as Yb < sup > 3 +</ sup >) for high power and wavelength-tunable solid state lasers.

Diffraction gratings are often used in monochromators, spectrometers, lasers, wavelength division multiplexing devices, optical pulse compressing devices, and many other optical instruments.

While civilian drones do generally match humans in intelligence, drones built especially as Contact or Special Circumstances agents are often several times more intelligent, and imbued with extremely powerful senses, powers and armaments ( usually forcefield and effector-based, though occasionally more destructive weaponry such as lasers or, exceptionally, " knife-missiles " are referred to ) all powered by antimatter reactors.

The penetration depth of Holmium lasers is < 0. 4 mm, avoiding complications associated with tissue necrosis often found with the deeper penetration and lower peak powers of Nd: YAG lasers used in the 1990s.

Most microscopes, however, have their own adjustable and controllable light source – often a halogen lamp, although illumination using LEDs and lasers are becoming a more common provision.

Nonlinear optics often takes advantage of the high peak powers of these lasers, offering applications such as 3D optical data storage and 3D microfabrication.

Optical mice often use LEDs for illumination, even though they are sometimes colloquially referred to as ' lasers '.

For ultrashort pulse lasers, a hyperbolic-secant-squared ( sech < sup > 2 </ sup >) pulse shape is often assumed, giving a time-bandwidth product of 0. 315.

DVD burners ' lasers often peak at about 200 mW, either in continuous wave and pulses, although some have been driven up to 400 mW before the diode fails.

However, typically, the term " terahertz " is used more often in marketing in relation to generation and detection with pulsed lasers, as in terahertz time domain spectroscopy, while the term " submillimeter " is used for generation and detection with microwave technology, such as harmonic multiplication.

Warships often mount up-sized versions of such energy weapons, including three sizes of capital PPCs and three of capital lasers.

However in high power HeNe lasers having a particularly long cavity, superluminescence at 3. 39 μm can become a nuisance, robbing power from the lasing medium, often requiring additional suppression.

Multiple-prism dispersion theory | Multiple prisms are often used to tune the output of a dye laserDye lasers emission is inherently broad.

Since both concepts have major importance for biophotonics the umbrella term " ultrachrome lasers " is often used.

Since cw lasers often have free-running linewidths in the MHz range, and pulsed even larger, it is non-trivial to couple laser light effectively into a high finesse cavity.

Such mirrors are often used as beamsplitters, and as output couplers in lasers.

This design produces the smallest possible beam diameter at the cavity mirrors for a given cavity length, and is often used in lasers where the purity of the transverse mode pattern is important.

Cavities at points exactly on the line are marginally stable ; small variations in cavity length can cause the resonator to become unstable, and so lasers using these cavities are in practice often operated just inside the stability line.

Modern jewel pivots are often made using high-powered lasers, chemical etching, and ultrasonic milling.