Lev S. Sadovnik

SINGLE-MODE POLYMER WAVEGUIDE MODULATOR

We report herein the first single‐mode polymer waveguide modulator which can be formed on any surface regardless of its conductivity and refractive index. These include semiconductor, conductor, and insulator surfaces. The tunability of the refractive index of the polymer film allows us to shift the guiding layer from a stepped index profile to a graded index profile. The phase‐matching condition for optical power transfer is achieved through current‐induced index modulation. Thirty‐six dB extinction ratio, which includes 3 dB absorption loss and 33 dB phase‐matched cross coupling, was observed with a current injection density of ∼1.8 μA/μm2. Unlike the conventional symmetrical dual channel coupler, the disparity of the collinear waveguide pair provides us with a much larger dynamic range of waveguide dimension suitable for generating the required phase‐matching condition and thus easing the requirement of waveguide fabrication.

Millimeter‐wave optically scanning antenna based on photoinduced plasma grating

The photocontrolled millimeter-wave (MMW) antenna is an alternative approach to the phased array. It offers a high potential to decrease fabrication cost. We describe a new MMW scanning antenna controlled by light. The basic antenna element is a semiconductor plate containing a photoinduced plasma grating (PIPG). By changing the grating period and rotating the grating, the device is able to scan a MMW beam in two dimensions. To enhance antenna efficiency, we use an antenna design that takes advantage of the reflectance of the MMW mirror behind the semiconductor plate. We found that the pulse duration of the pumping light can strongly affect the antenna’s output. Our calculations demonstrate that diffusion is responsible for decay of antenna efficiency.

Scale-, rotation-, and shift-invariant wavelet transforms

In this paper we present a class of nonlinear wavelet transforms (WT) that are invariant under scale, rotation, and shift transformation of the input image. We provide an analytical proof of the invariance property of the WT as well as numerical simulation supporting this concept.

Helicopter obstacle detection radar system

We have analyzed and experimentally tested the feasibility of thin wire detection using millimeter wave radar. The radar system includes a novel, fast scanning antenna and a transceiver/signal processor unit from BAE systems.

Submicrometer lithography using lensless high-efficiency holographic systems

A hologram recording geometry that was total internal reflection of the reference and reconstruction beams from a photosensitive material surface is used to achieve 0.5-microm resolution at lambda = 457 nm in the readout of a reconstructed image on a photoresist. Such a geometry has demonstrated stable image quality for parallel displacement within the illuminated area and diffraction efficiency tolerance within a +/-2 degrees tilt about the axis of the reconstruction beam. The total-internal-reflection recording system provides double-fringe sets for each plane component inside the volume hologram; therefore, a diffraction efficiency as high as 80% was observed. The result is applicable to highvolume submicrometer lithography and can be expanded to a 20-cm (8-in.) semiconductor submicrometer pattern. The use of a large-aperture, well-collimated laser beam provides us with much higher throughput than that of existing lithography machines.

Real-time visualization using a 2D/3D imaging MMWave radar

This paper describes a novel approach to the real-time visualization of 3D imagery obtained from a 3D millimeter wave radar. The radar system uses two scanning beams to provide all weather 3D distance measurements of objects appearing on the ground. This information is displayed using our high-end 3D visualization engine capable of delivering models of up to 100,000 polygons with 30 frames per second. The resulting 3D models can then be viewed from any angle and subsequently processed to integrate match them against 3D model data stored in a synthetic database. The resulting Synthetic Radar Vision System will provide a truly novel way to obtained all weather 3D images. The paper will focus on the real-time imaging and display aspects of our solution, and will discuss technical details of the radar design itself. Engineering challenges will be outlined in the context of a practical application.

GaN : based terahertz sources

We discuss possible new sub-millimeter sources based on group-III Nitrides superlattices. It is shown that traveling dipole domains in biased GaN/InGaN and GaN/AlGaN short- period superlattices can generate electromagnetic power in the terahertz region.

Novel passive millimeter-wave imaging system: prototype fabrication and testing

A novel passive millimeter wave imaging (PMMW) system that utilizes a special arrangement of N equals 36 focal plane elements is presented. N MMW radiometric receivers generate a N X N PMMW image. We discuss the system fabrication and testing.

MMW optically scanning antenna based on plasma-induced grating

A light-induced grating aperture (LIGA) is a semiconductor plate containing a periodic structure formed of nonequilibrium light-induced electron-hole plasma. The presence of excess charge carriers in a semiconductor medium locally changes the dielectric constant of the material. Such a light-induced periodic structure can serve as a diffraction grating for millimeter waves (MMW), and generates diffracted beams propagating in directions distinct from that of the incident beam. The angle between the incident and diffracted beams depends on the period (Lambda) of the light-induced grating, a parameter that can be controlled using a liquid crystal display (LCD). The effect is strong enough not only for academic study but for practical application as well. The authors fabricated a new scanning MMW antenna in which MMW is diffracted by a LIGA.

Indium tin oxide single-mode waveguide modulator

We have successfully demonstrated an In203:Sn semiconductor thin film waveguide. The energy gap of the film can be manipulated from 3.1 eV (0.4 pm) to 3.7 eV (0.335 mm) by changing the ratio of In203 and Sn02. Waveguide propagation losses of 3 dB/cm for transverse magnetic (TM) and 8 dB/cm for transverse electric (TE) guided waves were experimentally confirmed at the wavelength of 632.8 mm. A phase modulator containing an indium tin oxide waveguide, two holographic mirrors, two microprisms, and two ohmic contacts was fabricated. Electro-optic (current injection) and all optical modulations were conducted. A modulation depth of 18% was experimentally confirmed for the current injection device, using 15-volt applied voltage, and a modulation depth of 15% using 250 mW 355 nm UV light as the activation sources. An In203:Sn waveguide device working at the cutoff boundary was made. A modulation depth of 26 dB was measured with an applied voltage of 30 volts. An array of applications, including use in current sensors, ozone UV sensors, attenuated total reflection (ATR) modulators, delay lines for phased array antennae and multi-quantum wells are highly feasible.