Search

A small helium-neon gas laser was assembled and tested. The unit features temperature-compensated cavity design, electromagnetically tunable cavity length, wide axial mode separation to assure single TEM oon mode operation, control circuitry for frequency sweep and AFC, and rugged coaxial construction. The re-entrant mirror mounts and the invar main-body assure negligible changes of the cavity length during warm-up and with changes of temperature, through proper choice of the respective expansion lengths. The high-gain double-walled plasma tube renders single-ended power output in excess of 200 microwatts at the 6328 A wavelength.

A solution is given to the electrodynamic problem of the spectrum and threshold of modes in a multilayer resonator in which the permittivity along the resonator axis is a piecewise-linear periodic function of the coordinate. This resonator is proposed for stable single-mode emission from semiconductor lasers.

The ratio of the clockwise to counterclockwise intensities in a multimode HeNe ring laser was measured as the strength of unidirectional coupling between the two intensities was varied. These results are compared to calculations based on a gain saturation with field coupling model which indicates that intensity ratios >102 are possible. With the addition of an etalon in the laser cavity, stable single‐mode operation is observed.

A simple new mode-selective mirror configuration is realized for obtaining single-mode operation of a six-mode He/Ne laser. Stable single-mode operation could be maintained without active stabilization methods over periods of more than 5 min.

w One way of increasing the power of a gyrotron [i] consists in a matched increase in the diameters of the cathode and the resonator, making it possible to generate intense electron streams and to convert their energy effectively into electromagnetic radiation. As the relative (in the wavelength scale) transverse dimensions of the resonator increase, however, the natural-frequency spectrum becomes compressed so that to insure stable single-mode operation it is necessary to employ ever more precise methods for electronic and electrodynamic mode selection [2].

Calculation of the second order correlation function for light that is a mixture of laser light and chaotic light of the same central frequency has been done by several groups. We have measured the two-photon counting rate in a mixed light beam and have found good agreement with these calculations. Half of the light in this beam originated in a stable single mode 633 nm He:Ne laser, and the other half in a low pressure He:Ne discharge tube. The d.c. discharge tube was about 20 cm long and was viewed end-on. Because the 633 nm Ne transition in a He:Ne discharge shows gain, the tube is a thick source, the line is slightly narrowed compared with a thin source, and the useful intensity is several times higher than any previously available narrow band chaotic source. For reasonable tube lengths, the amplitude distribution from this type of source is expected to be Gaussian.

Techniques are presented for obtaining stable, single mode output from an optical parametric oscillator and for aligning such an oscillator with a molecular or atomic transition. A line width of 10(-3) cm(-1) or less was obtained with a long term frequency stability of 10(-3) cm(-1) or better. It has been demonstrated that an OPO can stay aligned for several hours with an absorption line of half-width 0.01 cm(-1).

A 10.6-micro optical heterodyne communication system is described that uses two stable single mode and single frequency CO(2) lasers of high frequency stability. Wavelength control on both lasers allows the use of one and the same transition of the rotation-vibration band of CO(2) around 10.6 micro. The system has a bandwidth of 1 MHz, and simultaneous operation in baseband and on a 50-kHz carrier has been achieved. Heterodyne detection with mercury cadmium telluride detectors yielded signal-to-noise ratios within 3 dB of the coherent photon noise limit.