Optical mixing devices for the spectrum analysis of the scattered light from polymer solutions are reviewed. This newly developed technique has somedifference from the usual spectrometer in principle, and is able to carry an extremely high resolving power up to 1014. For the application to the polymer problem, however, there are still many points to be improved. In the present review, after giving a theoretical consideration, problems on the signal-to-noise ratio and the “depolarized light mixing” technique for the detection of the rotatory diffusion broadening are described in concentration. It must be emphasised that the technique has a unique field of observation which might be paired with the dielectric dispersion measurements. It could cover a low frequency region of 101_??_107 Hz far below the coverage of theusual Raman spectrometer.
Small signal impedance and power saturation mechanisms of Read type IMPATT diodes are described. Behavior of the diodes at small signals are presented by the use of phasor diagrams. Impedances are calculated for various d. c. current densities. From the results, meaning of the avalanche frequency becomes clearly comprehensive. Transient behavior of the conduction current from small to large amplitude oscillations differs depending on the relative magnitude of the avalanche frequency and the operating frequency. For large amplitude oscillations the current waveform is a pulse in both cases. It was found that the output power is mainly determined by the field distribution in the drift region and not in the avalanche region. It was concluded that in order to obtain high output power, the impurity profile of the diode must resemble that of a PNN+ type IMPATT diode.
The time variation of the output from a repeated pulsed D2O laser at 84 and 172μm was examined by using n-InSb and Ge: In detectors. The delay time, the pulse height, the width and the waveform of the repeated output pulses are found to be dependent on the rate of excitation, on the speed of mirror drive and on the degree of tuning for each laser line. The variation of delay time of 10_??_15μs in the 172μm oscillation vs. the cavity length is explained by taking into consideration the time variation of the electron density of order 1012_??_1013cm-3 during the pulse Width.
This paper reports the experimental and theoretical investigation onthe thermally induced self-defocusing effect of infrared CO2 laser beams which leads to not only an expansion but also a serious distortion of the laser beam when propagating in various liquids. To our knowledge, this is the first time such an effect has been observed with the output of CO2 laser at the wavelength of 10.6μm. This effect is attributed to the decrease of refractive index of the medium due to the thermal gradient arising from the heat conduction associated with the localized heating in the field of the propagating laser beam. By virtue of the thermal development method using the Kalvar film originally invented in the author's laboratory, we found the distorted crescent patterns of the laser beam arising from the fluid flow generated by the thermal convection in liquids. Also, the interference fringes due to spherical abberation in the thermal defocusing lens produced by the infrared laser beam were observed in both the CO2 laser beam itself and the probe red beam from a He-Nelaser superimposed on the former in the propagating liquid. Theoretical analysisbased on the thermal lens model gives a satisfactory explanation of the observedbehaviors in the beam distortion giving rise to a dip at the central portion of the beam as well as the beam expansion deforming to the non-Gaussian patterns.
The output power dependence of the laser lines on the length and diameter of laser tubes has been investigated experimentally. 24 laser-lines were obtained in air using laser-tubes beyond 1m in length and above 10mm in diameter. Among them, the 7.69 and 17.9μm laser-lines were studied in detail. The maximum obtainable output powers of the 7.69 and 17.9μm lines were approximately 40 and 1mW respectively, using a resonator 1m long and 13mm in internal diameter at a d. c. discharge current of 150mA. The gain increased with the decrease of the tube-diameter. The gain-values of the 7.69 and 17.9μm lines were 67 and 54%/m respectively, using an amplifier tube of 8mm in diameter at a discharge current of 150mA. The length-tuning of the resonator was found to be practically insensitive to the output power when the radii of curvature of the reflectors were sufficiently long compared with the resonator length.
Spectral characteristics of a CO2-N2 laser was studied in the P branch region of 00°1-10°0 vibrational band by using a grating-type infrared spectrometer. A single spectral output, for instance, inP (20) and P (22) branches was observed to vary in time in nearly periodic fashion, while by a simultaneous measurement the total output power exhibited little variation. This phenomenon seems to be attributable to the thermal detuning of the laser resonator due to local heating by various causes in the CO2-N2 laser system. Also, the simultaneous oscillation of P (3) branch of 00°1-10°0 band of the N2O molecule was observed during the CO2 laser action, when a mixture of CO2 and N2 was discharged in the laser tube.