Ceramic Waveguide Research Articles

Are low-loss glass–ceramic optical waveguides possible?

The results of a cutback measurement of a glass-ceramic optical waveguide with single-mode fiber geometry have demonstrated that sub decibels per kilometer losses can be achieved. Difference spectra show that the limit of intrinsic scattering in these two-phase structures ought to be tens of decibels per kilometer.

A surface‐mountable ceramic 3‐dB directional coupler

AbstractIn the lossless symmetric reciprocal four port represented by the directional coupler, it is possible to cal culate an invariant from the measured results of the s parameters. As a result, an integrated directional coupler was fabricated with high‐permittivity ceramic waveguide (DEW: dielectric E‐plane waveguide) and a coupling of 3 dB was obtained.

Spatial structure of radiation from transversely rf-excited waveguide CO2lasers

An investigation was made of the spatial structure of the output radiation from static waveguide CO/sub 2/ lasers excited by a transverse rf field of 120 MHz frequency. The specific input energy was approx.2 W/cm. Measurements were made on circular waveguides having radii of 0.8--1.5 mm fabricated of BeO ceramic and glass and on a metal ceramic waveguide (Al+BeO) having a 2 x 2 mm cross section. It was established that in lasers with BeO waveguides and plane--plane resonators lasing is achieved in the HE/sub 11/ mode or in a superposition of the TE/sub 01/ and HE/sub 21/ modes. The lasing power in the HE/sub 11/ mode was 1.4--2 times higher than that in the superposed modes. The laser with the square waveguide emitted hybrid HE/sub n/m modes. A homogeneous distribution of the unsaturated gain over the cross section of the transverse rf discharge promoted excitation of higher-order modes.

Losses in BeO ceramic waveguides in the 10.6 μ region

Infrared reflection and Raman scattering spectra of a single crystal of BeO and of BeO ceramic were studied. It was then possible to establish the form of the permittivity function whose values determine the infrared Q factor of waveguides made from these materials. The ceramic was found to be a polycrystalline material whose damping constant for optical phonons exceeded the corresponding value for a single crystal by roughly 30%. Consequently, in the 10.6 μ region, the losses in an ideal ceramic waveguide (i.e., neglecting the irregularities of its internal surface) exceeded those in a waveguide made from a single crystal by a factor of roughly 1.5. A comparison of the infrared reflection spectra of the ceramic and of a single crystal indicated that when calculating the losses in real ceramic waveguides one must take these irregularities into account and so also the scattering processes associated with them and, possibly, the excitation of surface polaritons. The structure of the reflection spectra was found to be a function of the sintering regime of the ceramic.

A new ceramic waveguide window for use on X-band valves

During the development of all-ceramic klystron valves, the conventional resonant window, incorporating a thin ceramic disc sealed to a metal diaphragm, was found to have several disadvantages. A new window was therefore developed which simplifies the input and output structures of microwave valves.The new window consists basically of a length of circular waveguide filled with alumina-type ceramic, transmitting only the TE11 mode. At one end the ceramic protrudes into the valve resonant cavity sufficiently to give the correct coupling. At the other end there is a short transition from ceramic-filled circular waveguide to air-filled rectangular waveguide 16. The valve vacuum is maintained by a gold-brazed molybdenum-manganese seal between the ceramic and the copper ferrule which together make up the circular waveguide section. A flange is soldered or clamped to the end of the ferrule after valve processing, for connection between the valve and the external waveguide system.The window has been satisfactorily applied to the type SZ20 klystron and tests have shown that it is also capable of passing 1600 watts c.w. power. This corresponds to a power density in the ceramic of about 16 kW/in2.

Discussion on “A new ceramic waveguide window for use on X-band valves”

Discussion on “A new ceramic waveguide window for use on X-band valves”