Volume 12, Issue 1, 01 January 1968
Index of content:
12(1968); http://dx.doi.org/10.1063/1.1651836View Description Hide Description
We report the suppression of low‐frequency noise in the He–Ne and argon lasers as a result of mode coupling by means of an internal phase modulator. Suppression of off‐axis modes and 20 to 30 dB of low‐frequency AM noise suppression have been obtained in both FM and phase‐locked operation, with no loss of output power.
12(1968); http://dx.doi.org/10.1063/1.1651837View Description Hide Description
Experimental evidence is presented which (1) allows quantitative determination of the redistribution of Si impurities between Ga and As sites after Li diffusion; (2) shows there is no loss of Si to complex or pair formation when N Si ∼ 1−2 × 1018 cm−3; and (3) indicates that the site symmetry of the Si is tetrahedral before and after redistribution.
12(1968); http://dx.doi.org/10.1063/1.1651838View Description Hide Description
The second harmonic pulse shape generated from ultrashort pulses is calculated. In long dispersive crystals the pulse width may be much broader than the incident pulse and the power conversion ratio may saturate at a low value. These effects should be prominent in LiNbO3 with 4 × 10−13 sec pulses.
12(1968); http://dx.doi.org/10.1063/1.1651831View Description Hide Description
Holograms of naturally illuminated objects are synthesized in two steps. A stereoscopic camera technique is used to record the objects' parallax qualities in white light; this photographic information is transformed into a hologram with coherent light. The image quality is excellent, and the method seems practical for making full‐color reconstructions using stereoscopic photographs taken with color film.
12(1968); http://dx.doi.org/10.1063/1.1651832View Description Hide Description
The generation of surfaceelastic waves by the transient surfaceheating of piezoelectric and nonpiezoelectric solids is described. A Q‐switched ruby laser produces the surfaceheating; the frequencies of the resultant surface waves are Fourier components of the laser waveform. The use of a spatially periodic illumination is shown to increase the effectiveness of generation at a selected frequency. This method of generating surface waves appears suitable for microwave frequency operation as well as operation at high wave amplitudes at low frequencies.
12(1968); http://dx.doi.org/10.1063/1.1651833View Description Hide Description
The microwave transmission characteristics of the ferromagneticsemiconductor CdCr2Se4doped with Ag have been measured as function of the applied magnetic and electric field. The results are interpreted in terms of active helicon‐spin wave interactions; and the agreement between experiment and theory is found to be very good qualitatively.
It is believed that the results presented in this Letter represent the first published evidence for active helicon‐spin wave interactions.
12(1968); http://dx.doi.org/10.1063/1.1651834View Description Hide Description
We have observed that at certain levels of laser power, an argon ion laser oscillates in only two strong modes. The frequency difference between these two modes is an integer multiple of the cavity fundamental beat frequency and increases with the laser power. Analysis of this effect shows that pulses from such a laser are 0.3π rather than π pulses.
12(1968); http://dx.doi.org/10.1063/1.1651835View Description Hide Description
The shift of the frequency of oscillation of the 00°1–10°0 rotation‐vibration band at 10.6 μ of a CO2 laser has been investigated as a function of total pressure, CO2 partial pressure, discharge current, and cavity mode position. The measurements were made by heterodyning two passively stabilized CO2 lasers, both oscillating in a single transverse mode and single frequency at the P branch of the 00°1–10°0 rotation‐vibration band of CO2. The result yielded a 5–8 MHz/torr frequency shift toward red due to an increase in total pressure and a 500–900 kHz/mA shift toward blue due to an increase in excitation. The amount of frequency shift due to excitation was found to be independent of the location of the cavity resonance with respect to the Doppler center. The dependence on CO2 partial pressure was also determined.