Dye laser - Wikipedia. Close- up of a table- top CW dye laser based on rhodamine 6. G, emitting at 5. The emitted laser beam is visible as faint yellow lines between the yellow window (center) and the yellow optics (upper- right), where it reflects down across the image to an unseen mirror, and back into the dye jet from the lower left corner. The orange dye- solution enters the laser from the left and exits to the right, still glowing from triplet phosphorescence, and is pumped by a 5. The pump laser can be seen entering the dye jet, beneath the yellow window. A dye laser is a laser which uses an organic dye as the lasing medium, usually as a liquidsolution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths, often spanning 5. The wide bandwidth makes them particularly suitable for tunable lasers and pulsed lasers. ![]() The dye rhodamine 6. G, for example, can be tuned from 6. Contents Introduction iv Bibliography vi 1 Basic Stu 1 Trigonometry Parametric Di erentiation Gaussian Integrals erf and Gamma Di erentiating Integrals. PHYSICS HIGHER SECONDARY FIRST YEAR VOLUME - I TAMILNADU TEXTBOOK CORPORATION COLLEGE ROAD, CHENNAI - 600 006 Untouchability is a sin Untouchability is a. About HyperPhysics. Rationale for Development. HyperPhysics is an exploration environment for concepts in physics which employs concept maps and other linking. Sorokin and F. SSDL use dye- doped organic matrices as gain medium. Construction. The internal cavity of a linear dye- laser, showing the beam path. This domain name is for sale (100,000 USD): uploading.com Write us for more information @. This pdf file contents introduction to CATIA User Interface, Using the Mouse Function, Panning & Zooming Objects, Moving the Tree, Adjusting and Expanding the Tree. The pump laser (green) enters the dye cell from the left. The emitted beam exits to the right (lower yellow beam) through a cavity dumper (not shown). A diffraction grating is used as the high- reflector (upper yellow beam, left side). The two meter beam is redirected several times by mirrors and prisms, which reduce the overall length, expand or focus the beam for various parts of the cavity, and eliminate one of two counter- propagating waves produced by the dye cell. The laser is capable of continuous wave operation or ultrashort picosecond pulses (trillionth of a second, equating to a beam less than 1/3 of a millimeter in length). P- pump laser beam; G- gain dye jet; A- saturable absorber dye jet; M0, M1, M2- planar mirrors; OC–output coupler; CM1 to CM4- curved mirrors. A dye laser uses a gain medium consisting of an organic dye, which is a carbon- based, soluble stain that is often fluorescent, such as the dye in a highlighter pen. The dye is mixed with a compatible solvent, allowing the molecules to diffuse evenly throughout the liquid.
The dye solution may be circulated through a dye cell, or streamed through open air using a dye jet. A high energy source of light is needed to 'pump' the liquid beyond its lasing threshold. A fast discharge flashtube or an external laser is usually used for this purpose. Mirrors are also needed to oscillate the light produced by the dye’s fluorescence, which is amplified with each pass through the liquid. The output mirror is normally around 8. The dye solution is usually circulated at high speeds, to help avoid triplet absorption and to decrease degradation of the dye. A prism or diffraction grating is usually mounted in the beam path, to allow tuning of the beam. Because the liquid medium of a dye laser can fit any shape, there are a multitude of different configurations that can be used. The dye cell is often a thin tube approximately equal in length to the flashtube, with both windows and an inlet/outlet for the liquid on each end. The dye cell is usually side- pumped, with one or more flashtubes running parallel to the dye cell in a reflector cavity. The reflector cavity is often water cooled, to prevent thermal shock in the dye caused by the large amounts of near- infrared radiation which the flashtube produces. Axial pumped lasers have a hollow, annular- shaped flashtube that surrounds the dye cell, which has lower inductance for a shorter flash, and improved transfer efficiency. Coaxial pumped lasers have an annular dye cell that surrounds the flashtube, for even better transfer efficiency, but have a lower gain due to diffraction losses. Flash pumped lasers can be used only for pulsed output applications. In a ring laser, the mirrors of the laser are positioned to allow the beam to travel in a circular path. The dye cell, or cuvette, is usually very small. Sometimes a dye jet is used to help avoid reflection losses. The dye is usually pumped with an external laser, such as a nitrogen, excimer, or frequency doubled. Nd: YAG laser. The liquid is circulated at very high speeds, to prevent triplet absorption from cutting off the beam. This leads to a better gain from the lasing medium. A thin sheet of liquid is passed between the windows at high speeds. The windows are set at Brewster's angle (air- to- glass interface) for the pump laser, and at Brewster's angle (liquid- to- glass interface) for the emitted beam. Stokes shift in Rhodamine 6. G during broadband absorption/emission. In laser operation, the Stokes shift is the difference between the pump wavelength and the output. The dyes used in these lasers contain rather large, organic molecules which fluoresce. Most dyes have a very short time between the absorption and emission of light, referred to as the fluorescence lifetime, which is often on the order of a few nanoseconds. Liquid dyes have an extremely high lasing threshold. In addition, the large molecules are subject to complex excited state transitions during which the spin can be . In this state, the molecules emit light via fluorescence, and the dye is transparent to the lasing wavelength. Within a microsecond or less, the molecules will change to their triplet state. In the triplet state, light is emitted via phosphorescence, and the molecules absorb the lasing wavelength, making the dye partially opaque. Flashlamp- pumped lasers need a flash with an extremely short duration, to deliver the large amounts of energy necessary to bring the dye past threshold before triplet absorption overcomes singlet emission. Dye lasers with an external pump- laser can direct enough energy of the proper wavelength into the dye with a relatively small amount of input energy, but the dye must be circulated at high speeds to keep the triplet molecules out of the beam path. Due to their high absorption, the pumping energy may often be concentrated into a rather small volume of liquid. With a dye jet, one avoids reflection losses from the glass surfaces and contamination of the walls of the cuvette. These advantages come at the cost of a more- complicated alignment. Liquid dyes have very high gain as laser media. The beam needs to make only a few passes through the liquid to reach full design power, and hence, the high transmittance of the output coupler. The high gain also leads to high losses, because reflections from the dye- cell walls or flashlamp reflector cause parasitic oscillations, dramatically reducing the amount of energy available to the beam. Pump cavities are often coated, anodized, or otherwise made of a material that will not reflect at the lasing wavelength while reflecting at the pump wavelength. The greatest losses in many lasers and other fluorescence devices is not from the transfer efficiency (absorbed versus reflected/transmitted energy) or quantum yield (emitted number of photons per absorbed number), but from the losses when high- energy photons are absorbed and reemitted as photons of longer wavelengths. Because the energy of a photon is determined by its wavelength, the emitted photons will be of lower energy; a phenomenon called the Stokes shift. The absorption centers of many dyes are very close to the emission centers. Sometimes the two are close enough that the absorption profile slightly overlaps the emission profile. As a result, most dyes exhibit very small Stokes shifts and consequently allow for lower energy losses than many other laser types due to this phenomenon. The wide absorption profiles make them particularly suited to broadband pumping, such as from a flashtube. It also allows a wide range of pump lasers to be used for any certain dye and, conversely, many different dyes can be used with a single pump laser. CW dye- lasers can have a linear or a ring cavity, and provided the foundation for the development of femtosecond lasers. Narrow linewidth dye lasers. Dye lasers' emission is inherently broad. However, tunable narrow linewidth emission has been central to the success of the dye laser. In order to produce narrow bandwidth tuning these lasers use many types of cavities and resonators which include gratings, prisms, multiple- prism grating arrangements, and etalons. Although dyes have very broad fluorescence spectra, the dye's absorption and emission will tend to center on a certain wavelength and taper off to each side, forming a tunability curve, with the absorption center being of a shorter wavelength than the emission center. Rhodamine 6. G, for example, has its highest output around 5. A wide variety of solvents can be used, although most dyes will dissolve better in some solvents than in others. Some of the solvents used are water, glycol, ethanol, methanol, hexane, cyclohexane, cyclodextrin, and many others. Solvents are often highly toxic, and can sometimes be absorbed directly through the skin, or through inhaled vapors. Many solvents are also extremely flammable. The various solvents can also have an effect on the specific color of the dye solution, the lifetime of the singlet state, either enhancing or quenching the triplet state, and, thus, on the lasing bandwidth and power obtainable with a particular laser- pumping source. Output power of 1. Rhodamine 6. G with COT in methanol- water solution. Excitation lasers. Flashlamps and several types of lasers can be used to optically pump dye lasers. A partial list of excitation lasers include. Greene, and C. Shank demonstrated, in 1. Such kind of laser is capable of generating laser pulses of ~ 0. In addition to their recognized wavelength agility these lasers can offer very large pulsed energies or very high average powers. Flashlamp- pumped dye lasers have been shown to yield hundreds of Joules per pulse and copper- laser- pumped dye lasers are known to yield average powers in the kilowatt regime.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
August 2017
Categories |