Direct-write electron-beam lithography of an IR antenna-coupled microbolometer onto the surface of a hemispherical lens

This article describes a method for performing direct-write lithography of an IR antenna-coupled microbolometer onto the surface of a hemispherical lens. Antennas on a dielectric half-space receive power more efficiently from the substrate side than from the air side. The use of a hemispherical lens facilitates reception through the substrate as well as elimination of trapped surface waves that would normally occur in the substrate. Using direct-write lithography onto the surface of the hemispherical lens eliminates the potential of an air gap between the antenna and lens. Additionally, the accuracy of alignment between the antenna and the center of the lens is controlled at the lithographic step. As a result, there is increased responsivity is observed in the antenna-coupled microbolometer when illuminated from the substrate-side compared to air-side illumination. (c) 2006 American Vacuum Society

Relaxation time effects on dynamic conductivity of alloyed metallic thin films in the infrared band

The behavior of nanoscale infrared antenna elements depends upon the dynamic conductivity of thin metallic films. Spectroscopic ellipsometer measurements of noble metal films show that when the product of the incident radiation frequency and the relaxation time is greater than unity, anomalous dynamic electron transport effects occur. In this regime electron scattering increases the conductivity of alloyed metallic films as demonstrated by ellipsometry measurements of films from the Au-Cu system. A binary alloy thin film was fabricated with equal parts of Au and Cu, and the dynamic conductivity was measured to be 300% larger than the high frequency conductivity of pure Au or pure Cu films at wavelengths in the 3-5 mu m band. When electronic scattering is reduced, ellipsometer measurements of Au and Cu films taken near 4 K demonstrate that the IR conductivity decreases to 20% of the value measured at 300 K at wavelengths in the 3-5 mu m band. Using measured dc relaxation times, a model to explain deviations from Drude behavior was developed using the theory of the anomalous skin effect and frequency dependent relaxation time. This model was in quantitative agreement with the measured data. The ability to design an alloyed metallic thin film using a calculated ideal dc relaxation time to produce the greatest possible dynamic conductivity for infrared antennas and metamaterials was demonstrated

Vertical-via interconnection for infrared antennas

The authors present fabrication process details and test data for a vertical-via. interconnection suitable for low-frequency signal extraction from infrared antenna-coupled sensors. Electrical readout of the signal from an antenna-coupled bolometer was accomplished using two 300 nm diameter Au via structures that extended 300 nm in the vertical direction. These vertical vias passed through two isolation layers of SiO2 and through a 1500 X 600 nm(2) cutout in a ground plane. Electromagnetic, isolation of the antenna from its associated electrical-readout bondpads at 28.3 THz in the infrared was demonstrated by mapping the two-dimensional spatial response of the antenna and comparing it to spatial response data from a similar structure without the intervening ground plane. (c) 2006 American Vacuum Society

Use Of A Shack-Hartmann Wave-Front Sensor To Measure Deviations From A Kolmogorov Phase Spectrum

Experimental results indicate that the statistics of phase measured across a telescope aperture do not always obey the power laws associated with the Kolmogorov model of atmospheric turbulence. We show that the statistical relations between a wave front and its aperture-averaged f irst derivative previously derived for a Kolmogorov spectrum can be easily generalized for any power law. We also show that a Shack-Hartmann sensor can be used to measure the form of the structure function of phase f luctuations, and experimental data are presented. © 1995, Optical Society of America

Infrared Phased-Array Antenna

Phased addition of currents from multiple dipole antennas is demonstrated for the first time at a wavelength of 10.6 μm. Co-planar strip lines are used to interconnect the antennas, preserving the phase of the individual infrared-frequency currents, which are summed together at a common bolometric load. Angular pattern measurements on two-element dipole arrays show that the direction of maximum response depends on the phase difference between the currents contributed from each antenna, evaluated at the bolometer location. As more antennas are added together in phase, beam narrowing is observed. © 2008 Wiley Periodicals, Inc

Infrared Dipole-Coupled Bolometer Response On A Hemispherical Silicon Immersion Lens

Response of an infrared (λ = 10.6 μm) dipole antenna-coupled bolometer fabricated at the center of the flat side of a hemispherical silicon immersion lens is presented. Predicted and measured antenna patterns as well as the ratio of power from the lens-side to the air-side are provided as a function of illumination F/#. The power-division ratio, Φlens/Φair, is shown to be given by the square root of the lens dielectric constant, ε{lunate}Si1 / 2 = 3.4, for F/# larger than F/2 whereas as F/# decreases to F/1 the ratio increases to 5 due to off-axis features in the radiation pattern. © 2009 Elsevier B.V. All rights reserved