Showing papers on "Single-mode optical fiber published in 1969"

Modes of propagating light waves in thin deposited semiconductor films

Abstract: We report theory and experiment on modes of propagating light waves in deposited semiconductor films. The modes are excited by a novel prism‐film coupler which is also used for the measurement of their phase velocities. Up to 50% of the incident laser energy has been fed into a single mode of propagation. The positions and linewidths of the modes, the wave intensity inside the film, and a dramatic view of the mode spectrum displayed by the scattered light are discussed in detail.

Bends in optical dielectric guides

Abstract: Light transmission through a curved dielectric rod of rectangular cross section embedded in different dielectrics is analyzed in closed, though approximate form. We distinguish three ranges: (i) Small cross section guides such as a thin glass ribbon surrounded by air—Making its width 1 percent of the wavelength, most of the power travels outside of the glass; the attenuation coefficient of the guide is two orders of magnitude smaller than that of glass, and the radius of curvature that doubles the straight guide loss is around 10,000Λ. (ii) Medium cross section guide for integration optics—It is only a few microns on the side and capable of guiding a single mode either in low loss bends with short radii of curvature or in a high Q closed loop useful for filters. Q's of the order of 108 are theoretically achievable in loops with radii ranging from 0.04 to 1 mm, if the percentage refractive index difference between guide and surrounding dielectric lies between 0.1 and 0.01. (iii) Large cross section guides—They are multimode and are used in fiber optics. Conversion to higher order modes are found more significant than radiation loss resulting from curvature.

Excitation and Scattering of Modes on a Dielectric or Optical Fiber

Abstract: A technique similar to that of Kirchhoff is used to obtain an analytic expression for mode Iaunching on a semi-infinite rod. The approximation is quasi-optical and only valid for small angles of incidence /spl theta/. When /spl theta/ = 0 only HE/sub 1M/ modes are excited; however, for /spl theta/<<1 many modes can be launched. The effect on HE/sub 11/ mode propagation of small imperfections in a dielectric waveguide is analyzed. At the frequency of interest for optical communication (cutoff for the TM/sub 01/ mode) the radiated power is 160 times larger than that scattered into the HE/sub 11/ mode.

Tunable single mode operation of gas lasers using intracavity tilted etalons.

Abstract: The use of a tilted solid etalon inside the resonator of a gas laser, for the purpose of obtaining a tunable single mode output from the laser, is described and analyzed. This technique is illustrated by single mode spectra and gain profiles obtained with various argon ion laser transitions.

Single Mode Oscillation of a Pulsed Singly Resonant Optical Parametric Oscillator

Abstract: Single mode oscillation of a pulsed singly resonant optical parametric oscillator was achieved by placing a tilted mode selecting Fabry‐Perot etalon inside the oscillator cavity. The output power was 25% of that obtained in multimode oscillation without the etalon. Good agreement was obtained between observed and expected spectral width both with and without the etalon inside the optical cavity.

A 10.6-micro Optical Heterodyne Communication System.

Abstract: A 10.6-μ optical heterodyne communication system is described that uses two stable single mode and single frequency CO2 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 CO2 around 10.6 μ. 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.

Spikeless single-mode laser

Abstract: A laser structure comprising a rod-type lasing element and including means for pumping the element to produce light emission from the ends thereof. Optical means responsive to the light emission create a traveling wave of the light which passes through the rod-type lasing element numerous times to produce a single mode output beam of coherent radiation. A nonlinear light absorber interposed in the single-mode output beam path absorbs large portions of light energy in the traveling wave as the intensity thereof increases. Such arrangement is operative so as to reduce the inherent spiking of the output light beam characteristic.

Recent Developments in Optoelectronic and Spectroscopic Techniques at Queen’s University, Belfast

Abstract: Recent developments of the fixed gap, spherical mirror confocal Fabry-Perot interferometer for time resolved high resolution laser spectroscopy, including the measurement of spatial coherence, are described and illustrated with an interferogram of a pure single mode giant pulse ruby laser of 4 × 108 mW/cm2/sr brightness. Applications of a new multiple-beam image tube framing camera, producing up to ten consecutive frames on a nanosecond time scale, are discussed together with limitations arising from photocathode saturation in single stage image tube streaking and framing cameras. Properties of dye lasers, including spectral narrowing to a single longitudinal cavity mode and mode locking, are reported, and a simple coaxial linear pinch flashtube pumped dye laser system is described. A direct measurement of an optical frequency Stark shift of the 7699-A potassium resonance line has been obtained employing a ruby pumped dye laser as a background continuum source, and subpicosecond pulses from a Nd in glass relaxation oscillator have been measured.

Infrared and Optical Lases

Abstract: The extension of maser techniques to the infrared and optical region is considered. It is shown that by using a resonant cavity of centimeter dimensions, having many resonant modes, maser oscillation at these wave-lengths can be achieved by pumping with reasonable amounts of incoherent light. For wavelengths much shorter than those of the ultraviolet region, maser-type amplification appears to be quite impractical. Although use of a multimode cavity is suggested, a single mode may be selected by making only the end walls highly reflecting, and defining a suitably small angular aperture. Then extremely monochromatic and coherent light is produced. The design principles are illustrated by reference to a system using potassium vapor.

Fiber for distortion-free propagation

Abstract: A fiber for use in the propagation of light pulses with the attendant elimination of distortion. The fiber is useful as a delay line storage device for computer information with an extremely high-packing density capability for the bits of information. Another application is in a broadband communication system as a transmission line and in any application the fiber may be ''''active'''' as either a laser amplifier or oscillator. Basically, the invention involves the choice of fiber core and cladding size and other parameters to counteract, with the anomalous dispersion associated with the waveguide transmission, the normal dispersion of the bulk glass from which the fiber is made. The pulses of light are thereby propagated undistorted since the various frequency components within the light pulse are propagated with an effective velocity which is independent of wavelength in the spectral interval of the pulse.