What makes excimer lasers so complex, rare and expensive? We all can agree that UV lasers are extremely useful, but we (poor majority) are still struggling with 355nm DPSS ones, while excimer lasers being prohibitively expensive (let's say at 1-10W average power, or 100Hz @ 0.1J pulse).
What is the reason for this? What is the complexity, making excimer lasers (namely, 248nm KrF / 308 XeCl ones) so complex? 
Mirrors & optics is simpler than for CO2 ones, gas is not expensive too... What am I missing?
Just reread my laser optics book - it needs aggressive laser pumping (50kV @10-30ns pulses), forced 'gas mixing' (just like in high-power CO2 ones), also needs preionization, but nothing too scary...
 A: Interestingly exicmer laser development was originally funded, in part, due to interest in inertial confinement fusion.
Original excimer lasers required: rare-gas atoms (e.g., Xe) at high pressures, 10 atm; very high voltages, 400 keV, were required to create an electron beam through a metal foil; high current densities, on the order of 1000 amps/cm$^2$, were required to reach sufficient laser gain. Unfortunately they did not scale appropriately so fast-discharge lasers were then pursued.
The Navy, for communication applications, as well as interest in molecular laser isotope separation, helped spur development of laser discharge technology. Pre-ionized laser discharge requires a very fast high-voltage pulse that is controlled by a very fast and complex circuit. The problem with sparking is the creation of dust and erosion of the spark source and that they cannot sustain long-term operation. Thyratrons in combination with a magnetic switch are required to reach 100 Hz. Reaching 10 W in a KrF lasers was reached by replacing the pre-ionization source with a corona discharge.
Thyratrons were gradually replaced by thyristors. New pulsed power circuitry has been developed. New ways of delivering the gases, specifically the halides, has been developed. The expenses have been dropping over time, but the expensive parts today are the circuitry required for handling the fast pulses and high voltages, the gas handling system (halides are dangerous and corrosive and must be replenished often during operation), cooling systems, a sufficiently inert laser discharge chamber and the parts of the laser must be designed to be easy to repair and replace.
A: This laser is a type of ultraviolet laser often used in UV photolithography in eye surgery. 
The term excimer comes from excited dimer English (excited dimer) 
This uses a combination of inert gas such as argon, krypton or xenon, with reactive gas. Under appropriate conditions of electrical stimulation, a pseudo-molecule is formed, which exists only in an excited state and can cause laser light in the ultraviolet range. 
The excimer laser removes tissue with an accuracy of 0.25 microns. Currently in the second decade of use, the technologically sophisticated Excimer Laser has added a tremendous range of precision, control and security for the correction of vision errors. Using this remarkable technology, the cornea is reshaped to suit the requirements of your glasses or lenses, while reducing or eliminating dependence on corrective lenses for life. 
Ultraviolet light from the excimer laser is absorbed well into tissues and organic compounds. Instead of cutting or burning, the excimer laser has enough energy to separate the bonds between molecules of the tissues. The excimer laser has the ability to lift or remove small and thin layers of cells without damaging tissue. is rare because most of excimer lasers (like this) are of noble gas halides.
and is complicated by the action of laser excimer molecule is because it has an associated state excited but also has a non-associative. 
this is because the noble gases like xenon and krypton are inert and do not tend to form chemical compounds. However, in an excited state molecules can be temporarily linked with themselves (dimers) or halogen atoms such as fluorine and chlorine (forming complexes excited). I hope this serves as an answer.
