Excimer gas laser

A schematic representation of the directed-beam laser writing scheme is shown in Figure 1. Although a carbon dioxide or excimer gas laser can be used, the most common laser used for directed-beam writing is the solid state YAG laser operated in the cw Q-switched mode. With typical laser powers of about 20 watts average power and a pulse repetition rate of 20,000 pulses per second, the laser beam when focused on the sample makes a small (about 0.1 mm diameter) dot for each pulse. By directing the laser beam using fast computer-driven mirrors... 

Gas lasers, 14 681-696 carbon dioxide, 14 693-696 excimer lasers, 14 691-693 helium-neon, 14 681-683 ion lasers, 14 683-688 molecular nitrogen, 14 688-691 Gas lift electrolyte circulation, 9 621 Gas-liquid base stocks, 15 217 Gas-liquid chromatography (glc), 6 374 analysis of sugars via, 23 476 silylation for, 22 692, 697 Gas-liquid contactor, reciprocating jet,... 

Most of the early gas lasers emitted in the visible region. Continuous-wave (CW) lasers such as Ar+ (351.1-514.5 nm), Kr+ (337.4-676.4 nm), and He-Ne (632.8 nm) are now commonly used for Raman spectroscopy. More recently, pulsed lasers such as Nd YAG, diode, and excimer lasers have been used for time-resolved and ultraviolet (UV) resonance Raman spectroscopy. 

Use Excimer, chemical, and gas lasers are available, as are gases for surgical lasers. 

Gas Lasers. A variety of ga.s lasers is available commercially. These devices are of four types (1) neutral atom lasers such as He-Ne (2) ion lasers in which the aciive species is Ar or Kr (3) molecular lasers in which the lasing medium Is CO, or Nil and (4) excimer lasers. The helium-neon laser is the most widely encountered of all lasers because of its low initial and maintenance costs, its great reliability, and its Kivv H)wcr consumption. The nuist important of its output lines is at 6.32.8 nm. It is generally operated in a continuous mode rather than a pulsed mode. 

The time profile of the laser pulse is not only determined by the amplification per round trip G t) (Vol. 1, Sect. 5.2) but also by the relaxation times t,-, Xk of the upper and lower laser levels. If these times are short compared to the rise time of the pump pulse, quasi-stationary laser emission is reached, where the inversion AN(t) and the output power FL(r) have a smooth time profile, determined by the balance between pump power Pp t), which creates the inversion, and laser output power Fl(0. which decreases it. Such a time behavior, which is depicted in Fig. 6.1a, can be found, for instance, in many pulsed gas lasers such as the excimer lasers (Vol. 1, Sect. 5.7). 

Fixed-wavelength gas Lasers helium-neon, rare-gas ion and excimer lasers... 

FIXED-WAVELENGTH GAS LASERS HELIUM-NEON, RARE-GAS ION AND EXCIMER LASERS... 

Andrews [9] and others [10] have listed the emission lines of the most commonly available discrete-wavelength lasers (such as ruby, Nd YAG, Er YAG, excimer lasers) over the range 100 nm-10 /u.m. Molecular lasers (HF, CO, CO2, NO) can be tuned to a large number of closely spaced but discrete wavelengths. Continuously tuneable lasers comprise some metal ion vibronic lasers (e.g. alexandrite and Ti sapphire [11]), some diode and excimer lasers, dye and free-electron lasers. Tuneable sources of coherent radiation span the electromagnetic spectrum from 300 nm to 1 mm, with limited tune-ability down to about 200 nm. Wavelength coverages of tuneable lasers have been reported [8]. In operation lasers can be either pulsed (e.g. various metal ion tuneable vibronic lasers, excimer and dye lasers, metal vapour) or continuous wave (major types atomic and ionic gas lasers, dye and solid-state lasers). Most lasers with spectral output in the UV are bulky and expensive devices (especially sub 200 nm) and operate in the pulsed mode. On the contrary, many visible lasers are available which are compact, require low maintenance expenses and operate in continuous-wave (CW) mode. 

Amplification of such short DFDL pulses in excimer laser pumped amplifer cells yields intense pulses with peak powers above 10 y and pulse durations down to 30 fs [11.82]. Optical frequency-doubled dye-laser pulses with a wavelength matched to the gain profile of the excimer laser can also be amplified in excimer-gas discharges [11.79]. 

Four groups He-Ne lasers, ion lasers (noble gas ions), molecular-gas lasers (CO, CO2), excimer lasers (F2, ArF, KrCl, KrF, XeCl, XeF)... 

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