T.D. Drysdale

CMOS Photodetectors Integrated With Plasmonic Color Filters

A single-pixel plasmonic complementary metal oxide semiconductor (CMOS) photo sensor consisting of a plasmonic color filter integrated on a CMOS photodiode was fabricated using electron beam lithography and dry etch. The photocurrent measurement results confirmed the three primary color filtering responses that could be achieved in a single layer of nanostructured aluminium film. Finite-difference time-domain simulation demonstrated a good agreement of the reflection spectra with the measured result. This research can lead to the development of advanced CMOS image sensors with low cost and low crosstalk.

A CMOS Image Sensor Integrated with Plasmonic Colour Filters

Multi-pixel, 4.5u2009×u20099xa0μm, plasmonic colour filters, consisting of periodic subwavelength holes in an aluminium film, were directly integrated on the top surface of a complementary metal oxide semiconductor (CMOS) image sensor (CIS) using electron beam lithography and dry etch. The 100u2009×u2009100-pixel plasmonic CIS showed full colour sensitivities across the visible range determined by a photocurrent measurement. The filters were fabricated in a simple process utilising a single lithography step. This is to be compared with the traditional multi-step processing when using dye-doped polymers. The intrinsic compatibility of these plasmonic components with a standard CMOS process allows them to be manufactured in a metal layer close to the photodiodes. The incorporation of such plasmonic components may in the future enable the development of advanced CIS with low cost, low cross-talk and increased functionality.

Narrowband multispectral filter set for visible band

We design, fabricate and characterise a narrowband Fabry-Pérot multispectral filter set for the visible range (400-750 nm) that is suitable for integration onto complementary-metal oxide-semiconductor image sensors. We reduce the fabrication steps by fixing the physical cavity length and altering the effective optical length instead. Using electron-beam lithography, a sub-wavelength hole array is patterned in a silicon nitride cavity layer, backfilled with poly(methyl methacrylate), and bounded by aluminium mirrors to create 23 filters with full-width half-maximums of 22-46 nm. Additionally, for colourmetric reproduction applications, using as few as 10 filters gives a colour difference (CIEDE2000) of 0.072, better than trichromatic filters.

RC Variability of Short-Range Interconnects

Line edge roughness (LER) in end-of-the-roadmap integrated circuit interconnects causes variability in their resis- tance R, capacitance C and hence also their RC delay. We present an analysis of LER-induced variability of resistance, capacitance and delay of short-range interconnects within standard cells at the 32, 22 and 18 nm technology nodes using both a commercial RC extraction tool as well as a fast quasi-analytical (QA) method. Our QA method includes size dependent resistivity which, when coupled with LER, reveals increased resistance variability and total resistance in interconnects at these technology nodes. For example, the QA method predicts variability of 52% in resistance, 16% in capacitance and 36% in RC delay. When LER is the dominant source of variability there is a correlation of �0.8 between resistance and capacitance. Our results indicate interconnect variability is a significant and worsening problem, which should be included in statistical models of standard cells.

Automated Design, Fabrication, and Characterization of Color Matching Plasmonic Filters

Plasmonic filters, with spectral responses matching the 1931 International Commission on Illumination (CIE) color matching functions, have been fabricated for use in digital imaging. The color matching filters are useful for effectively communicating color between color detection and output devices. A fully automated genetic algorithm that incorporated on-demand 3-D finite-difference time-domain simulations determined the dimensions for the red (600 nm), green (555 nm), and blue (445 nm) filters. The filters demonstrated resonances in the desired spectra with transmission of 25%-35%. These filters were simultaneously fabricated in a single electron beam lithography cycle using materials common to standard complementary metal-oxide-semiconductor production.

Multi-channel homodyne detection of continuous-wave terahertz radiation

We demonstrate the principle of multichannel spectral data capture using an all-optoelectronic terahertz photomixing system. Two independent laser diodes, each emitting in multiple longitudinal modes, are used to generate and detect over ten terahertz frequencies simultaneously. The spectral composition can be altered by tuning the lasers, and filtering is achieved through the use of resonant antennas and tunable photonic crystal filters. Potential applications include gas phase spectroscopy and explosives detection.

Tunable photonic crystal filter for terahertz frequency applications

In this Paper we investigate a tunable metallic photonic crystal filter with a novel mechanical tuning method, suitable for use in terahertz frequency applications. Tuning has been demonstrated in a micrometer-driven prototype at 70 - 110 GHz in accordance with rigorous full-vector electromagnetic simulations (finite-difference time-domain). The measured pass band has a Q of 11 and can be tuned over a 3.5 GHz range. The insertion loss is only 1.1 to 1.7 dB, while the stop band attenuation is >10 dB. The filter has the advantages of inexpensive, robust and compact construction and tunable operation that readily scales to any desired terahertz frequency.

Electromagnetic parameter retrieval at oblique incidence

Optical metamaterials are able to achieve optical properties that do not exist in nature. Approaches to the homogenization of optical metamaterials are becoming more and more complex in the desire to achieve accurate representation. Here we propose to modify an existing retrieval approach for metamaterials to characterize their properties. To extract the effective refractive index and material parameters from reflection and transmission coefficients for double negative metamaterial in the optical regime, the modified Nicholson-Ross-Weir (NRW) method is used. In order to obtain a true picture of these metamaterials, as a function of angle of incidence of the illumination, it is important to present not only the effective parameters of permittivity and permeability but also some other important parameters such as coupling coefficients, that represent the inherent anisotropy.

Measured and simulated performance of a ceramic micromechanical beam steering device at 94 GHz

We report the first experimental demonstration of a transmission-mode micromechanical beam steering device for use in standoff terahertz imaging and spectroscopy. The device was constructed by laminating laser-cut 96% alumina sheets to form two plates with interlocking rectangular gratings of 762 microm period and was characterized at 94 GHz in a free-space measurement setup with an automated elevation scan. Plate tilts as great as 6 degrees deflected the transmitted beam by 6 degrees for the transverse electric (TE) polarization and by 4 degrees for the transverse magnetic polarization. Finite-difference time-domain simulations of the TE performance were in good agreement with the measurements.