Toshizo Nakaya

Polarization of dye laser light

The degree of polarization of dye laser light (Rhodamine B) under excitation by a beam of linearly polarized light (second harmonic of a ruby or neodymium-doped laser) has been studied experimentally by measuring the Stokes parameters of dye laser light at a wavelength of 0.6328 pm. The sign of degree of polarization is negative in the case of the ruby second harmonic (0,3471 pm), whereas it is positive in the case of the neodymium second harmonic (0.53 pm). Even in the case of illumination with the ruby second harmonic, the magnitude of the degree of polarization increases with the intensity of unconverted ruby laser light. The experimental fact that the degree of polarization of dye laser light is nearly as high as unity has been explained fairly well on the basis of the theory proposed by the authors.

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.

Electro-optical diagnosis of a TE N2 laser

The time variation of the voltage across the discharge channel of a TE N2 laser has been studied experimentally by means of the Pockels effect, with particular emphasis on the factors which affect the statistical time-lag. Functional relations to the mean statistical time-lag of the gas pressure, the repetition rate of discharge, and the coupling capacitor of the trigger wire for preionisation are examined. An attempt to obtain travelling wave excitation is also made by the use of a glass plate whose width linearly varies, taking advantage of the fact that the statistical time-lag becomes negligibly small, and the formative time-lag varies along the discharge channel.

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.

A high-power TEA N2 laser using a modified Marx generator

A new design of TEA N2 laser for producing high-density excitation by combined use of a modified Marx generator and a pair of high-speed capacitors is described. Laser output of 1.5 MW (1.2 mJ, 0.8 ns) is obtained from a 12 cm long uniform discharge at a charging voltage of 25 kV.

Time-resolved population studies of a N2 ion laser

In order to examine the lasing characteristics of the N2 ion laser excited by a fast discharge, time-resolved measurements of the gain for the 391.4 nm and 427.8 nm transitions were carried out. The temporal behaviour of the population densities of the laser lower levels were measured by means of the interferometric method. The time histories of the sidelight at the laser transitions, which reflects the relative upper level population, were also measured. On the basis of these experimental results, a fairly good explanation of the lasing characteristics of the two laser oscillations is given.

Influence of Giant Pulse Irradiation on a Ruby Laser

In an optical system, consisting of two ruby lasers (one is Q-switching operation, the other normal operation), the following phenomena have been studied on the basis of the experimental results obtained on the fractional metastable state population; 1) quenching of normal laser oscillation, 2) amplification of incident giant pulse by maser mechanism, and 3) changes in giant pulse characteristics by giant pulse irradiation in a Q-switching laser with saturable absorber.

Measurement of Fractional Metastable-State Population of Cr Ions in Ruby under Q-Switching Operation

The degree of the decrease in the population of ground-state Cr ions in ruby brought about by optical pumping with Xe flash light has been measured as a function of time under Q-switching operation. The measurement has been made by observing the decrease in absorbing power of the ruby crystal for a probe light (Hg 5461A), (γ), while Q-switching with a rotating prism or saturable absorber (Cryptocyanine). Observations of rapid change of (γ) due to the emission of giant pulse laser light have been carried out, with the very satisfactory results. At the occurrence of a giant pulse, the higher the initial value of (γ) is, the lower becomes the final value of (γ).

Measurement of Ground-State Population in Ruby under Optical Pumping

Depopulation of ground-state Cr ions in ruby (DGS) under optical pumping with a Xe flash light has been measured as a function of time. Experiments have been made by means of measuring the decrease in absorbing power for a probe light (5790 A or 5461 A) from a Hg lamp. DGS reaches its maximum value after some delay from the peak of Xe light, and decreases after discontinuation of optical pumping with a time constant of 3.4 ms, which is the lifetime of metastable-state 2E. During laser oscillation mean value of DGS is forced to take a constant value, which varies with the condition of laser oscillation. So long as the input energy to the Xe lamp is not altered, the shorter the duration of Xe flash light is, the higher becomes the maximum value of DGS. On the basis of the rate equation, these experimental results have been explained.