Pulse repetition rate

This is in contrast to lasers based on mby or neodymium in glass, which operate at much lower pulse-repetition rates. Nd YAG lasers are often operated as frequency-doubled devices so that the output is at 532 nm. These lasers are the most common type of soHd-state laser and have dominated sohd-state laser technology since the early 1970s. Nd YAG lasers having continuous output power up to 1800 W are available, but output powers of a few tens of watts are much more common. 

A typical example might involve use of a krypton fluoride excimer laser operating at 249 nm with a pulse duration around 100 nanoseconds and a pulse repetition rate which can be varied up to 200 Hz. For metal deposition, energy densities in the range from 0.1 to 1 J/cm per pulse are typical. 

W.m (see Ch.l4). To get enough return flux at the minimum laser power, one needs to optimize the laser specifications (continuous wave or pulsed, pulse width, pulse repetition rate, (average) power, spectral profile) taking into both saturation, technological, budget and operation constraints. This is the challenge described in detail in the above mentioned chapter. 

Experiments on the sky. Two experiments have been carried out at the sky, using two laser installations built for the American and French programmes for Uranium isotope separation, respectively AVLIS at the Lawrence Livermore Nat l Lab (California) in 1996 and SILVA at CEA/Pierrelatte (Southern France) in 1999. The average power was high pa 2 x 175 W, with a pulse repetition rate of 12.9 and 4.3 kHz, a pulse width of 40 ns and a spectral width of 1 and 3 GHz. Polarization was linear. The return flux was < 5 10 photons/m /s (Foy et al., 2000). Thus incoherent two-photon resonant absorption works, with a behavior consistent with models. But we do need lower powers at observatories ... 

Figure 22. Returned flux at 330 nm as a function of the power balance between the two beams at 589 nm and 569 nm. Circles spectral width at L>2 = 1 GHz. Squares spectral width at L>2 = 3 GHz. Filled symbols pulse repetition rate = 4.3 kHz open symbols rep rate= 12.9 kHz.

Saturation If the Rf field is applied continuously, or if the pulse repetition rate is too high, then a partial or complete equalization of the populations of the energy levels of an ensemble of nuclei can occur and a state of saturation is reached. 

To determine optical damage in bulk benzil crystals a Q-switched Nd YAG laser with 1KW peak power, pulse width of 0.1 ps and pulse repetition rate of 500Hz was used. The laser power was attenuated using a set of neutral density filters and focussed onto a bulk benzil crystal using a x10 microscope objective. No optical damage was observed with optical intensities of upto 100MW/cm - Also, no optical damage was observed in benzil cored fibres with similar optical intensities. 

If Tr represents the radar pulse repetition rate and A the operating wavelength, then the Doppler u>d contributed by (21) equals [1] [7] [11] [12]-... 

The commercially available laser source is a mode-locked argon-ion laser synchronously pumping a cavity-dumped dye laser. This laser system produces tunable light pulses, each pulse with a time duration of about 10 picoseconds, and with pulse repetition rates up to 80 million laser pulses/second. The laser pulses are used to excite the sample under study and the resulting sample fluorescence is spectrally dispersed through a monochromator and detected by a fast photomultiplier tube (or in some cases a streak camera (h.)) ... 

Figure 21.3 Nonlinear transmission of silver -dendrimer nanocomposites Ag(0) E at 532 nm. Pulse repetition rate- 10 Hz. Inset nonlinear transmission results for Ag(0) E in a concentration of 2.95x 10 4 mole/kg at 532 nm, with the variation of the pulse repetition rate t indicates the specific repetition periods.

Davis et al. reported the successful etching of PTFE using single-photon energies in the quartz UV (308 nm and a pulse duration of 25 ns) by sensitizing the fluoropolymer with polyimide. 72 The number of pulses varied depending on fluence and material composition in order to achieve ablated features whose depths were reproducible as measured by a stylus-type profilometer. The pulse repetition rate was on the order of about 200 Hz. In that study, dopant levels... 

Figure 7. Efficiency of green-emitting (Zn,Cd)S Cu,Al relative to LasO S.-Tb " as a function of electron beam current density (O) 30 kV, 25 kV, (A) 20 kV. Electron beam dwell is 0.5 fis and pulse repetition rate is 60 pps.

Here we will focus in detail on a UV pump-IR probe spectrometer described by Emsting and co-workers the system is based on an excimer laser and a dye laser operating with a pulse repetition rate ranging from 5 to 10 Hz. Pump pulses at 308 nm excite the sample and are followed at a selected time by probe IR pulses that range from 1950 to 4300 cm Absorbance changes can be recorded with a time resolution of 1.8 ps and with an accuracy in absorbance (A) of 0.001. 

Laser Ablation. A mixture of UFPs composed of TiN and Ti was synthesized by laser ablation of titanium in N2 gas at 0.1 MPa using an Nd YAG laser (wavelength 1.06 xm) with peak power of 10 kW for 200-ns pulse (33). This method, however, was not successful in obtaining nitride UFPs of Mo, Al, Fe, and Si. Pure TiN UFPs were produced using a high-power YAG laser generator maximum power of 80 J/pulse, repetition rate of 4-10 pulses/s (34). The particle size of TiN UFPs obtained was about 20 nnr at an ambient N2 gas pressure of 13.3 kPa, and decreased with decreasing N2 gas pressure. AIN UFPs can be synthesized by an excimer laser (12 J/cm2) ablation of aluminum under N2 gas pressure of 10 kPa and the subsequent calcination at 900°C for 2 hr under N2 flow (35). 

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