Divergence of high order Gaussian modes

A simple expression for the beam divergence from a laser oscillating in a high order Gaussian mode can be derived from the properties of the mathematical expressions for these modes

Ion lasers-the early years

The paper is a personal, anecdotal history of the discovery and early development of ion lasers, particularly the argon ion laser. A brief discussion of the mechanisms that make this laser work, and the engineering challenges and developments that make it practical are included. Some early applications in night reconnaissance and imaging are include

Flexible dielectric waveguides with powder cores

Flexible dielectric waveguides have been demonstrated at 10 GHz and 94 GHz using thin-wall polymer tubing filled with low-loss, high-dielectric-constant powders. Absorptive losses of the order of 10 dB/m were measured at 94 GHz. with nickel-aluminium titanate and barium tetratitanate powder in polytetrafluoroethylene (PTFE) lightweight electrical tubing. Bending losses at 94 GHz were negligible for curvature radii greater than 4 cm. M.H. Kuhn's (1974) theory of three-region cylindrical dielectric waveguide was used to calculate dispersion curves for the lower-order modes for several combinations of dimensions and dielectric constants. Good agreement was obtained between experimental and theoretical values of guide wavelength. A scheme is proposed for classifying hybrid modes of three-region guides based on the ratio |Ez/Hz|. For two-region guides, this reduces to E. Snitzer's (1961) familiar scheme

Transverse mode control and switching in gas laser arrays

Theoretical and experimental investigations of multiple transverse mode laser oscillation involving spatially varying gain and loss are carried out. The effect of gain and loss distribution on mode competition is analyzed. Numerical examples are given for a CO2 waveguide laser array. Experimental results of CO2 laser arrays are found to be consistent with the theory, and robust in-phase coupled mode array operation has been achieved

Computer Analysis of Dielectric Waveguides: A Finite-Difference Method

A method for computing the modes of dielectric guiding structures based on finite differences is described. The numerical computation program is efficient and can be applied to a wide range of problems. We report here solutions for circular and rectangular dielectric waveguides and compare our solutions with those obtained by other methods. Limitations in the commonly used approximate formulas developed by Marcatili are discussed

Bandwidth of linearized electrooptic modulators

Many schemes have been proposed to make high dynamic range analog radio frequency (RF) photonic links by linearizing the transfer function of the link's modulator. This paper studies the degrading effects of finite transit time and optical and electrical velocity dispersion on such linearization schemes. It further demonstrates that much of the lost dynamic range in some modulators may be regained by segmenting and rephasing the RF transmission line

Comparison of Analog R-F Photonic Links Using a Variety of Linearized Electro-Optic Modulators

The potential applications of high dynamic range analog r-f photonic links include antenna remoting, photonic-coupled phased-array antennas, and cable-television transmission. This paper compares the results obtained with a number of different modulator types and link configurations and gives recent experimental results. Further details on the analysis and results for some of the schemes can be found in a review paper that will appear later this year

Intermodulation distortion in high dynamic range microwave fiber-optic links with linearized modulators

Linearization of integrated optic intensity modulators significantly reduces the two-tone intermodulation distortion. The resulting intermodulation distortion produced by these modulators then varies as the input power to the fifth-order link system, the overall intermodulation product is a combination of third-order and higher-order terms. The authors determine the dynamic range of a cascaded microwave network consisting of a preamplifier, a high-dynamic-range fiber-optic link with a highly linear modulator, and a postamplifier. An expression is found that relates the intermodulation power at the output to the relative suppression from the signal level. As an example, a hypothetical 10-GHz low-distortion fiber-optic link that has a dynamic range of 125 dB in a bandwidth of 1 Hz is cascaded with various preamplifiers, and it is shown that the dynamic range of the system is reduced by as much as 20 dB, depending on the third-order intercept of the amplifier

Distortion in linearized electrooptic modulators

Intermodulation and harmonic distortion are calculated for a simple fiber-optic link with a representative set of link parameters and a variety of electrooptic modulators: simple Mach-Zehnder, linearized dual and triple Mach-Zehnder, simple directional coupler (two operating points), and linearized directional coupler with one and two dc electrodes. The resulting dynamic ranges, gains, and noise figures are compared for these modulators. A new definition of dynamic range is proposed to accommodate the more complicated variation of intermodulation with input power exhibited by linearized modulators. The effects of noise bandwidth, preamplifier distortion, and errors in modulator operating conditions are described

Measurement of the Dielectric Constant and Loss Tangent of Thallium Mixed Halide Crystals KRS-5 and KRS-6 at 95 GHz

The dielectric constants and loss tangents of KRS-5 and KRS-6 thallium halide mixed crystals have been measured at 95 GHz using both the shorted waveguide (SWG) reflection method and the Fabry-Perot (F-P) transmission method on samples filling standard WR-10 waveguide. The results--KRS-5: epsilon'/sub r/ = 31; tan delta = 1.8 x 10/sup -2/; KRS-6: epsilon'/sub r/ = 29, tan delta = 2 x 10/sup-2/-- agree reasonably well with a simple theoretical fit to the far-infrared Iattice absorption of TIBr and TICI centered at about 1400 GHz. The dielectric samples were hot-pressed into copper wafers with dimensions matching WR-10 waveguide, and then machined and polished to obtain flat, parallel air-dielectric interfaces