The optical homogeneity is observed on 19 ruby laser rods with a Twyman interferometer. The ruby rods are classified into three groups from which some characteristics of a ruby laser can be predicted. For example, laser oscillation will start from the most homogeneous portion of a ruby rod, and a rod of higher homogeneity will exhibit a far field pattern of higher symmetry.
The radiation emitted from forward-biased GaAs p-n junction diodes has been studied at liquid-N2 temperature. Above 5, 000 A/cm2, the emission intensity in a favored direction increases very rapidly and emission spectrum narrows markedly. Measurements of polarization of the beam show that J||>J⊥ and J⊥. varies as I2, where J|| and J⊥ are the emission intensities polarized with the electrical vector parallel and perpendicular to the junction plane, and I is the forward current. This implies that spontaneous emission is amplified by stimulated transitions and a transverse electric mode is the most favored so that it is amplified further by multiple reflection at radiating surfaces. At still larger currents (above 16, 000A/cm2), coherent oscillation within the diodes occurs and narrow emission lines appear at about 8640Å. Relative intensity of these lines depends current, time and direction of observation.
Harmonic generation utilizing ADP and quartz is mentioned. The spectrogram of 2nd harmo-nics and the emission pattern are photographed and the angular : dependence of harmonic output-is determined. The asymmetric characteristic of the emission pattern and of the angular dependence of output, curve is attributed to the divergence of focussed laser beam which causes assymmetry in direction, of intensely emitted 2nd harmonics due to the nature of index surfaces of fundamental ordinary rays; and harmonic extraordinary rays. Explicit explanation of the asymmetry of angular dependence; is made by extending the Kleinman's equation. Next, the wave-forms of fundamental and harmonic pulses are observed and comparison is, made between them by the use of a dual trace CRO for both ADP and quartz. The two wave-forms do not correspond exactly probably because of the directional nature of; each laser pulse. Simple discussion is developed.
The high-power laser consists of a pink-ruby rod 10mm in diameter and 150mm in length, a pair of double herical xenon flash lamps and a power source of 10 K joules stored energy. The peak output power and the total output energy are 15 kW and 5 joules, respectively. When the output is focused, one flash is enough to spotweld stainless steel or bore a hole in a piece of diamond, tungsten, iron, or other various materials. Raman scattering of CCl4 is successfully photographed by one flash of this laser.
Results of observation made on the optical homogeneity of Nd3+ and Pr3+ glass rods by Schlieren method and on near field patterns of the stimulated emission of these glass rods photographed on plates sensitized for infrared radiation show that the oscillation of glass lasers is seriously hampered by striae and that, with Nd3+ glass of homogeneous structure or nearly so, the oscillation begins at the center and at the periphery of the rod. The stria causes the threshold input energy of building up the laser oscillation to become much higher.
Optical characteristics of ruby rods as optical masers are studied by interference of polarized light and with Twyman interferometer. Output patterns are observed with a camera of usual type and a high-speed streak camera of special design. The oscillation patterns are not affected by local deviation of the rod axis and are easily built up in inhomogeneous portions where the streaks are observed by ordinary ray of the crystal and also in portions where the wave front of the light traveling in the axial direction is likely to converge. The near field pattern of a spike is different from that of another even in a oscillation. The oscillation patterns of some spikes are of ring type when input excitation energy exceeds some critical value.
An abnormal emission of ruby optical maser is observed. It has the form of plateau insteap of spikes of usual ruby lasers. From investigations on polarization, near-field pattern, far field pattern, directionality and spectral width of this type of emission, it is shown that such a type of emission is not of a continuous oscillation but of an intermediate between fluorescence and optical maser oscillation.
A He-Ne gaseous maser is operated by the use of external mirrors (two flat, one flat and one-spherical, and two spherical) and a discharge tube with Brewster angle windows. The constructions. of this optical maser with plane parallel, confocal, and concentric cavities are described in detail. The population enhancement of Ne 2s states by He metastable atoms is observed and the outputt of He-Ne maser is measured as a function of the exciting power.
Radiation patterns obtained with He-Ne optical masers using plane parallel, confocal and con-centric resonators are described and their dependence on the aperture, on the alignment of mirrcrs and on the exciting power is investigated. It is shown that, with a plane parallel resonator, the spot size of transverse mode depends on the aperture size, but not with a spherical resonator. When the cavity approaches the critical concentric setting, the spot size at the mirror increases and the radiation pattern becomes representative of the lowest order mode. These results obtained are in good agreement with the Boyd-Gordon's theory.
Bubble growth by electric discharge in water is taken up as an example to apply a newly devised high-speed cinemicrograph by the use of a ruby laser. The effective shutter speed is about 10-7 sec. and the time interval between exposures is of the order of 10 μsec. The light emitted by electric discharge does not disturb the observation, for the output of the laser is highly parallel and powerful. The micrograph disclosed that, prior to the electric discharge, a streamer grows from the cathode with the velocity estimated on the micrograph at not less than 106cm;/sec., suggesting that some change has been induced in water before the actual discharge.
Ultrasonic vibration of 15_??_25 kc/s is applied on a laser ruby rod in its axial direction in order to control the oscillation. The oscillation is found modulated down by this application; the oscillation spikes are concentrated at the definite phase of the ultrasonic vibration, the width of the individual spikes is decreased and the peak output power is increased. The control of oscillation is more marked when the ultrasonic amplitude is increased. This is considered to be a new phenomenon which is different from what we see in Q-spoiling experiments by the application of ultrasonic vibration on external media inserted into the resonator of the laser.
By the use of a highly efficient optical system developed by calculation and experiment on a light source for pumping and its light collecting system, a new tandem type ruby laser unit has been devised. For measuring the laser output, use of a photomultiplier with an interference filter is proposed whereby the peak value in a wide range of wattage and total output energy become measurable. In normal operation with one head, the measured threshold input energy for laser oscillation is only 75 joules that makes a new record. From far-field and interference patterns, the coherence of the laser output is determined. In a light amplification experiment, in which one head with resonator is used as oscillator and the other head without resonator is used as amplifier, gain of 3.8 dB is obtained.