High Peak Power Laser Pulses Research Articles

Non-equilibrium electrons, holes and phonons in YBa 2Cu 3O 7−x

We report an observation by picosecond Stokes/anti-Stokes Raman spectroscopy of high non-equilibrium O(4) apical oxygen and Cu-O plane buckling phonon populations in insulating and metallic YBa 2Cu 3O 7−x induced by high peak power pulsed laser excitation. Different excitation and probe geometries were used to selectively measure the non-equilibrium phonon populations of the two phonons. We attribute the effects to strong coupling of photoexcited carriers to the lattice. A photoinduced metal-insulator transition is observed in insulating YBa 2Cu 3O 6.2 accompanied with a qualitative change in nonequilibrium behaviour for the two phonons and an increase in carrier lifetime upon increasing doping. A polaronic model is used to discuss the observations.

Protection of laser power meters when used with pulsed laser beams of moderate waist and high peak-power

A simple and safe way is presented to protect power meters when dealing with moderate waist and high peak-power pulsed laser beams, such as Nd:YAG laser beams.

高尖頭値パルスレーザーのアブレーション作用

高尖頭値パルスレーザーのアブレーション作用

Non-resonant and resonant multiphoton ionization of (NO) n and Ar n NO clusters with picosecond laser pulses

High peak power laser pulses have been used to effect multiphoton ionization (MPI) in supersonic nozzle expansions of nitric oxide in argon. The (NO)n⩽5 clusters have been detected for the first time by a multiphoton laser technique. The Ar2 and Arn⩽7NO complexes were also observed. Results from a number of different visible and ultraviolet wavelengths are compared and interpreted with references to the known electronic states of (NO)n and (NO)+n.When resonant with the dissociative B1 state of (NO)2 at ca. 217 nm, cluster ions are observed with picosecond but not with nanosecond laser pulses. In contrast, non-resonant MPI at certain wavelengths results in parent cluster ions with either nanosecond or picosecond lasers. The use of such high-peak-power lasers for the characterization of cluster beams is discussed and compared with more conventional electron-impact techniques.

Very high resolution CARS spectroscopy in a molecular beam

Signal-to-noise calculations are presented for coherent anti-Stokes Raman spectroscopy (CARS) in a molecular beam. Using high peak power pulsed lasers and a high density molecular beam, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S/N</tex> for the H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> Q(1) line is expected to be <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sim 10^{4}</tex> , with a Doppler width reduction from 1100 to 20 MHz.

Generation of Giant Pulses from a Neodymium Laser with an Organic-Dye Saturable Filter

There has been much recent interest in the production of high-peak power laser pulses by regeneration switching. Organic dyes have been used as saturable filters for both the ruby (cyanine dyes) and neodymium (a polymethine dye) to produce single high-power spikes. The cyanine dye, in suitable concentration and path length, can also be used to produce a long train of slightly enhanced (gain about 10) regular Q-switched spikes from the ruby laser, but the neodymium laser can apparently only be operated in the single-pike mode. This paper reports the discovery of saturable filter action in a common dye, rose bengal, a derivative of fluorescein, which permits the production of an extremely regular sequence of enhanced spikes from the neodymium laser. Unlike the previous dyes, the transition corresponding to the saturable absorption occurs between two excited states, not between the ground state and an excited state. The population of the lower excited state is achieved by optical pumping of the dye solution, and, by varying the intensity of the pumping flash lamp, the optical density of the filter may be altered thus changing the spacing between light spikes as well as their height.