Multilayer Dielectric Filters Research Articles

Mid-infrared filters using conducting elements

This paper presents measured data on mid-infrared filters using conducting elements based on a simple first-order design philosophy. To the best of our knowledge, the filter center frequencies are at least a factor of 10 higher than any previously reported. The use of conducting elements adds an additional degree of freedom, which may be exploited to obtain filter characteristics superior to simple multilayer dielectric filters.

Simple tunable dye laser using a dielectric multilayer filter

We describe a nitrogen laser pumped dye laser tuned by a dielectric multilayer filter. The construction is simple and the adjustment of tuning is easy. It is found that the tuning is possible over a range of 10 nm from 445 to 455 nm in alcoholic solutions of coumarin 1, that the linewidth (0.8 nm) is independent of the filter tilt angle, and that the output intensity is remarkably flat over this tuning range.

A simple optical thin film deposition monitor using LED’s and fiber optics

A thin film deposition monitor is described which can be used to monitor the rf-sputter deposition of dielectric and thin metallic films on transparent substrates in a multi-target system. The monitor uses a green and a red LED as a light-source, a bundle of optical fibers to transmit the light into and out of the sputtering chamber and Si-photocells as detectors. The LED’s are pulsed at two different frequencies and phase-sensitive detection allows the simultaneous monitoring of the substrate reflectivity at two different wavelengths. Applications of the deposition monitor include the exact control of individual layers in multilayer dielectric filter structures and monitoring the deposition of very thin, semitransparent metallic films.

Wavelength multiplexing in multimode optical fibers

The capacity of optical fiber transmission systems could be increased by multiplexing several signals at different wavelengths on each fiber. This paper considers various multiplex system designs that might be used with multimode fiber transmission systems. In each case, the required multiplexer size and material properties are calculated as functions of the basic parameters of the fiber system. For fiber systems of the type currently being tested, a compact (~2 mm in diameter x 1 cm long), rugged, three-channel multiplexer could be constructed using a blazed plane reflection grating and graded-refractive-index (GRIN) optics; and it appears that such devices could be produced using available materials and technology. Multiplexers using thick gratings or multilayer dielectric filters are larger, more complicated, and require materials at the very edge of available technology. Multiplexers using a multiple thick grating or hologram could be even smaller than the blazed-grating devices, but materials having the quired characteristics have not been demonstrated.

A 4-, 6-, 20-, and 30-GHz-Band Branching Network Using a Multilayer Dielectric Filter for a Satellite Communication Earth Station

This paper describes a four-frequency broad-band branching network for transferring microwave (4 and 6 GHz)- and millimeter-wave (20 and 30 GHz)-band signals between an antenna and transmitter-receivers in a satellite communication earth station. A filter for separating the microwave band from the millimeter-wave band employs a multilayer dielectric filter with matching layers and is included in the primary antenna feed system. The design method used for the multilayer dielectric filter and the construction and experimental results of the four-frequency broad-band branching network are described. Measurements show that its insertion loss, VSWR, and axial ratio are less than 1.2, 1.2, and 2.1 dB, respectively.

Method for Optimized Design of Dielectric Multilayer Filters

A method that can be easily programmed on a digital computer is presented for optimizing the design of dielectric multilayer filters. Certain rules have been formulated to allow one to construct the electric field transmittance explicitly for any thin film filter system. From the spectral distribution of transmittance functions, one can numerically choose the layer thickness to match the prescribed filter frequency spectrum, assuming that the refractive index of each layer is given. A synthesis procedure has been proposed in this paper for the filters that are composed of nondispersive and nonabsorptive stacks.

On a Dielectric Multilayer Fiber by Baumeister

It is well known that the reflection in the passband of dielectric multilayer filters can be appreciably reduced by small adjustments in the layer thicknesses. Baumeister designed such a filter using a computer program to refine an initial approximate design. This paper presents another design approach based on the concept of Herpin equivalent layer.

R 2 Line Optical Maser Action in Ruby

Optical maser action at the R2 line in ruby has been observed. Because of a fast thermal relaxation between the two 2E levels, it is not usually possible to satisfy the maser conditions at the R2 line when stimulated emission is occurring at the R1 line. However, if maser action can be suppressed at the R1 line, even at high inversion, it can be made to occur at the R2 line by the appropriate selection of operating conditions. This has been accomplished by using, for end reflectors, multilayer dielectric interference filters which have high transmission at the R1 line and low transmission at the R2 line. The selection of the operating conditions requires a correction of the absorption coefficients for the R1 and R2 lines based on the Boltzmann distribution between the two excited states. When the Boltzmann correction is made, the calculations show reasonable requirements on pumping threshold and reflectivities.

Comment on Multilayer Dielectric Filters

A recent note by Gascoigne (1959) on transmission in multilayer dielectric filters is interesting as an example of an adoption to a given problem of a result from an entirely different problem, namely, the Kronig-Penney model for metal lattices. However, one may wonder whether, in the long run, it would not be more economical of time, especially for students, to notice that the multilayer filter, the Kronig-Penney lattice, and for that matter many other problems, are all essentially forms of the same thing.

Note on Band Transmission in Multilayer Dielectric Filters

The existence of pass and stop bands for periodically stratified media, in particular for multilayer dielectric filters, is well known, but there seems to be no way of demonstrating this either without the use of a good deal of algebra or by appeal to relatively unfamiliar ideas, such as those of transmission line theory. Our purpose here is to show that for an infinite medium, this result can be established by a direct adaptation of the Kronig-Penney (1931) model for metal lattices. Accounts of this model are given in a number of textbooks (Rojansky 1942; Brillouin 1946) and also in undergraduate courses in this country, so that it may be considered well known. Mathematical details will accordingly be abbreviated; they may be found in the references cited.

Multilayer Dielectric Reflecting Films at Wave-lengths between 4000 and 4600 A.

IN a previous communication1, we gave some measurements of the performance of multilayer dielectric interference filters in the wave-length range 4000–4600 A. We are grateful to M. P. Giacomo for first pointing out that, in deducing from our results the properties of dielectric reflecting films, we failed to take into account the variation of phase change with wave-length, which has been treated by Dufour2. His results show that in our case the filters should have been considered not as of first order, but as of order 2.45. Our values of the reflexion, transmission and absorption coefficients for seven-layer reflecting films of cryolite and zinc sulphide on glass are then as in the table.