Shiro Horiguchi

Time-resolved electron density measurements in an ArF excimer laser discharge

Abstract The electron density in an ArF excimer laser discharge has been measured by means of a time-resolved optical interferometric method. By comparing the behavior of electron density in the absence of F 2 gas with that in the presence of F 2 gas, the dissociative attachment rate is estimated from graphical calculation.

Oscillation and gain characteristics of high power co-axially excited N2 gas lasers

Abstract A new type of co-axial discharge gas laser has been developed as a nitrogen laser, and the gain properties have been measured. The co-axial discharge tube consists of a ceramic pipe of inner diameter of 5 mm and length of 15 cm with two metallic electrodes at both ends. The excitation discharge was activated using a capacitor transfer circuit with a special pre-ionization discharge through the ceramic pipe. When the tube is used as an oscillator, an output laser energy of 0.45 mJ was obtained with pure N2 gas at pressure of 933 Pa (7 Torr). The time resolved gain measurement of N2 laser was made in the oscillator–amplifier configuration, and the value of the peak gain coefficient was estimated to 0.1 cm−1. The circuit analysis of the discharge circuit was also made to estimate discharge resistances, inductances and currents in the excitation circuit. The laser output increased up to 1.95 mJ at the charging voltage of 28 kV when the length and inner diameter of the discharge tube were increased to 30 cm and 9 mm respectively.

Optimization of the discharge characteristics of a laser device employing a plasma electrode

Discharge characteristics have been investigated of a laser device in which the surface‐discharge plasma from a dielectric surface is used as a preionizer and an electrode, the plasma electrode. It is demonstrated that a highly homogeneous discharge can be obtained by optimizing the delay time of the main volume discharge with respect to the surface discharge. The output energy from the device used as a N2 laser is also discussed.

Experimental study of formation kinetics in a discharge-pumped F2 laser

Abstract In a discharge-pumped F 2 laser, it is known that the major mechanisms for formation of the population density of the laser upper level (F 2 ∗ (D′)) are the neutral channel and the ion channel reactions. In order to study the degree of contribution of the neutral channel or the ion channel reactions, the population densities of the fundamental species, such as the excited F and He atoms and a F − ion and an electron, have been measured by means of the optical interferometric and absorption methods. On the basis of these experimental results, the population density of the laser upper level is estimated with the aid of simple rate equations, and the formation processes of laser upper level molecules have been discussed.

Small-signal gain measurements in a discharge-pumped F2 laser

In a discharge-pumped F2 laser, time-resolved net-small-signal gain has been measured to study the population inversion by employing an oscillator-amplifier configuration. Characteristics of the gain and the fluorescence are studied under various conditions in two cases of He and Ne buffer gases. The peak of the net-small-signal gain in He/F2 and Ne/F2 show values of about 17%/cm and 9%/cm, respectively. The formation processes of the upper laser level F2(D′) are discussed on the basis of these experimental results.

Time-resolved gain measurements in a KrCl laser

Abstract The oscillation characteristics of a discharge excited KrCl excimer laser has been studied experimentally for two different buffer gases, He and Ne. Optical gains were measured with nanosecond time-resolution, and compared with the experimental results on the breakdown voltage, the delay time of the laser oscillation with respect to the starting of discharge, and the pressure dependence of the laser output. The small signal gain coefficient was 0.056 cm -1 for the Ne buffer, while it was 0.041 cm -1 for the He buffer.

Pressure-dependent transient behaviour of the population of atomic and molecular metastables in He discharge

Abstract The transient behaviour of the population of excited state helium atoms (2 3 S 1 , 2 1 S 0 , 2 3 P) and molecules (2sσ 3 Σ + u ) under a fast pulsed discharge excitation in pure helium has been studied experimentally using the optical interferometric method and the absorption method with nanosecond time-resolution. Experimental results are presented of the time dependent behaviour of these populations in the afterglow over a wide range of gas pressure from 35 Torr to 3 atm.

Excitation mechanisms responsible for the 615. 0-nm oscillation in a He-Hg ion laser

Selective excitation processes responsible for the lasing of singly ionized mercury at 615.0 nm in a He‐Hg pulsed discharge have been studied by observing the time variation of the populations of the reactants using the Hook method and the side‐light method. It is found that in the decaying plasma of a pulsed discharge, the principal process is the Penning reaction, while during the discharge the charge‐transfer‐type reaction predominates.

Pumping mechanism of mercury‐ion laser

In a pulsed discharge in a He‐Hg gas mixture favorable for laser oscillation of Hg ion at the green line, the temporal and spatial behavior of the population densities of Hg(63P2) and He(21S0) atoms has been studied experimentally. These reactants are thought to be responsible for the Penning‐like excitation process. It is found that the depression of the population of reactants coincides in space and time with the occurrence of the laser oscillation.

Gain measurements of Ar 2* excimer formed by high-pressure homogeneous discharge using plasma electrode

Highly homogeneous discharges have been obtained in pure Ar gas at high pressures of 10 - 20 atm by using a discharge device in which the surface discharge plasma from a dielectric surface is used as a preionizer and an electrode, the plasma electrode, aiming at an Ar2* excimer laser. The plasma electrode consists of a ceramic pipe with a length of 290 mm. The same electrode is used as a cathode and an anode. The electrode separation is 2 mm to generate the main discharge. The fluorescence of Ar2* excimer radiation has been investigated at a wavelength of around 126 nm. Time-resolved electron density and gain measurements have been carried out with nanosecond time-resolution. The electron density was over 16th power of ten at 10 atm. The optical gain at 126 nm has been observed at an Ar gas pressure of 15 atm, and the peak gain was 8.6%/cm.