Population inversion versus time in a continuously pumped qswitched laser. Dynamic multimode analysis of qswitched solid state laser cavities. Following this is a more detailed description of the. The qswitched laser beam pulses last a mere billionth of a second. Unlike common laser pointers that create a continuous laser beam, qswitched lasers create laser beam pulses that last mere billionths of a second.
The theory for q switched nd yag laser machine youtube. Yag saturable absorber crystal were investigated function of temperature. The technique is mainly applied for the generation of nanosecond pulses of high energy and peak power with solidstate bulk lasers. Mechanical devices shutters, chopper wheel or spinning mirror. Yag absorbs mostly in the bands between 730760 nm and 790820 nm. The qswitch may use a rotating prism, a pockels cell or a shutter device to create the pulse. Highest power green hybrid fiber laser with timeshift pulse flexibility, pulse shaping and burst mode for high speed. Yag laser has been of particular interest in the field of laserassisted hair removal because of its early introduction in a shortpulsed or qswitched mode 4,15,16 and its known high safety profile. The preferred laser pulse repetition rate range of laser operation. The theory is applied to the analysis of a passively q.
We study theoretically and experimentally different methods to control the pulses emitted by solidstate lasers passively qswitched by a saturable absorber. Fundamentals, types, and operations n n e 0 e e 1 e 3 e 0 e e 1 2 fast decay fast decay fast decay pumping pumping lasing lasing a b figure 1. A qualityswitched laser qswitched is a noninvasive laser that creates highintensity pulsed beam light. These curves clearly show the dependence of the pulse characteristics on the pump to lasermode size. The energy emitted from a qswitched laser is concentrated into very powerful pulses. The most common type is the actively qswitched solidstate bulk laser. Acousticoptic qswitched cavityless weakfeedback laser.
Qswitching in order to store many atoms in an upper level, the flow to a lower level must first be limited. In a first phase, the gain medium is pumped, while the extraction of energy as laser light is prevented by keeping the resonator losses high that is, the q factor is kept low. Laser description contains a short section on laser theory regarding the nd. The mechanism of generation of a qswitched pulse is illustrated in fig. The theory is applied to the analysis of a passively qswitched nd. The validity of the model is directly verified in an experiment. Our model quantitatively reproduces the temporal structure of pulsation and is also attractive for analysis of laser stability and statistics. Because the energy from the laser is emitted in such a brief period of time, the energy is concentrated into very powerful pulses. Ultracompact diodepumped qswitched crystal lasers specifications laser crystals and wavelengths.
Analysis of passively qswitched lasers with simultaneous modelocking. Add to your bottom line by adding on indemand treatments with an advanced, fdacleared astanza laser device. The powerful, brief pulses from have two key benefits. Department of physics pulsed solid state laser with. It is a gas laser built by ali javan at mit, with a wavelength of 632. The resonator losses can basically be switched in different ways.
Also included is a discussion of the second, third and fourth harmonic laser output generated by the system. Diode pumped qswitched solid state laser what should i put in the request of the laser specifications beside the model number. Finally we present the qswitch theory and more precisely passive qswitch theory. Hightemperature operation of a diodepumped passively q. Pdf theory of the optimally coupled qswitched laser.
Q switching is a method for generating intense short pulses sometimes called giant pulses of light with a laser. Qswitching stability limits of continuouswave passive. Astanza lasers sophisticated qswitched aesthetic laser treatments can perform a range of popular procedures including. Qswitched aesthetic lasers, laser tattoo removal treatments. Qswitched laserpulses from micro to nanosecond are produced. The theory can also be applied to cwpumped, repetitively q switched systems through a simple multiplicative factor for the laser gain. Please provide your required following qswitched laser specifications.
The general equations describing qswitched laser operation are transcendental in nature and require numerical solutions, which greatly complicates the optimization of real devices. N 1 to achieve the condition of population inversion between e 2 and e 1 at moderate pumping. Highenergy pigmented selective laser, for example, 694 nm, qswitched ruby laser, 755 nm qswitched alexandrite laser, 532 nm frequency doubled qswitched ndyag laser, and 1064 nm qswitched ndyag laser had been studied for treatment of melasma with poor. Theory of the optimally coupled qswitched laser abstract.
Rp photonics encyclopedia qswitched lasers, q switching. The laser is pumped by a pump pulse with a length on the order. Pdf optimization of passively qswitched lasers researchgate. Rp photonics encyclopedia q switching, qswitched laser. Singleblock pulseon electrooptic qswitch made of linbo.
The theory of qswitching applied to slow switching and. These curves clearly show the dependence of the pulse characteristics on the pump to laser mode size. Influences of stimulated raman scattering on qswitched. Furthermore, an increased absorbed energy of the pump radiation was necessary at. The edge of laser resonator consists of two mirrors, output coupler oc and high reflected mirror hr.
We explore one and twoaxis laser schemes allowing to control the pulse duration, which is ruled by the saturation powers of the transitions in the absorber and in the gain medium. Weber, fundamentals of the semiclassical laser theory. In the experiments, the srs was investigated in the temporal and spectral domains based on an actively qswitched ytterbiumdoped doubleclad fiber laser. Generation of laser pulses by qswitching and cavity. Passively qswitched laser ultrafast optics and xrays. Yag crystal rods that are used in the labseries laser.
The highintensity pulses may be efficiently frequency doubled to generate laser light at 532 nm, or higher harmonics at 355, 266 and 2 nm. A continuous wave laser has a steady power output, measured in watts w. We propose a selfconsistent description of the laser dynamics. Lasers to which the qswitching technique is applied are called qswitched lasers. Qswitched lasers may produce a highpeakpower laser pulse of a few nanoseconds duration. Compared to other techniques for pulse generation with lasers, q switching allows lower pulse repetition rates, higher pulse energies, and longer pulse durations. Optimization of passively qswitched lasers quantum. Here, it is shown that, using the mathematical technique of lagrange multipliers, one can derive simple. Clinical applications of qswitched ndyag laser goel a. Yag crystal having an undoped endcap is singleend pumped with a fibercoupled laser diode array at 940 nm. Qswitched laser the technique produces light pulses with very high power much higher than would be produced by the same laser operating in a constant output continuous wave mode. Keller, experimentally confirmed design guidelines for passively q switched microchip lasers using semiconductor saturable absorbers.
Lasertissue interaction in tattoo removal by qswitched. The theory of the qswitched laser has been treated by numerous authors. Pdf the general equations describing q switched laser operation are transcendental in nature and require numerical solutions, which greatly. The laser can operate at a repetition up to 500 khz with the output power above 4w. The intracavity photon density and the initial populationinversion density in the diodepumped passively qswitched laser rate equations are assumed to be gaussian spatial distributions. A theory of qswitched cavityless weakfeedback laser is proposed for the first time, to our best knowledge. A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The laser configuration of our electrooptically qswitched laser is shown in fig.
In a modelocked laser the qswitching instability leads to a transition from the cw ml regime to the socalled qswitched ml regime. Yag laser previously reported in the literature and shown to give excellent agreement with the. There are many ways to qswitch a laser active qswitching 1. These spacedependent rate equations are solved numerically, and a group of general curves are generated. The term laser originated as an acronym for light amplification by stimulated emission of radiation. Thus, stimulated emission must be prevented by placing. Theory of the optimally coupled qswitched laser ieee. The performance of the novel qswitched laser and its temperature dependence were verified to be almost identical to those of a conventional pulseon. For pulsed lasers, the output generally refers to energy, rather than power.
In this qswitched mode, output powers of 250 megawatts and pulse durations of 10 to 25 nanoseconds have been achieved. In oneaxis lasers, it is shown that the adjustment of. Figure 1 displays a general schematic of electronic energy levels of. Maiman at hughes research laboratories, based on theoretical work by charles hard townes and arthur. Figure 1 shows the simple scheme of solid state laser with passive qswitch. Osa dynamics of a selfqswitched fiber laser with a. Keller, experimentally confirmed design guidelines for passively qswitched microchip lasers. Backward light scattering can cause passive q switching in fiber lasers. The latter regime is characterized by pulse amplitude modulated by the qswitching oscillation frequency that is typically on the order of a few giga. The random qswitched laser concept demonstrated herein can be straightforwardly extended to other wavelength regimes e. Qswitched lasers are able to shatter tiny fragments of pigmentation or ink. Simple concept of a solid state laser with passive qswitched.
Qswitching, or quality switching, of a laser is a mechanism used to control the light output by concentrating all the energy into intense bursts or series of pulses by modulating the intracavity losses, the socalled q factor of the laser resonator. Q switching in order to store many atoms in an upper level, the flow to a lower level must first be limited. In order to store many atoms in an upper level, the flow to a lower level must first be limited. Thus, stimulated emission must be prevented by placing an attenuator in the cavity to stop light from travelling back and forth note. This theory is very suitable for analyzing short pulses.
The output data make this qswitched co2 laser system an appropriate tool for material processing, infrared photochemistry, thin. Qswitching instability in a modelocked semiconductor laser. The first experimental demonstrations were performed in 1961 at hughes aircraft company 2, shortly after the demonstration of the first laser in the same laboratory. Q switched lasers an overview sciencedirect topics. Hellwarth and mclung 1962, 1963 give experimental details of qswitching together with theoretical expressions for the general features of the pulse. Solidstate gain media have a good energy storage capability, and bulk lasers allow for large mode areas thus for higher pulse energies and peak powers and shorter laser resonators e. The mechanism of generation of a q switched pulse is illustrated in fig. The general equations describing q switched laser operation are transcendental in nature and require numerical solutions, which greatly complicates the optimization of real devices. In the theory, the dynamic characteristics of srs in qswitching processes were analyzed by solving a set. Dynamical analysis of acoustooptically qswitched co 2 laser 3.