Acousto-optic signal processors for transmission and reception of phased-array antenna signals

Novel acousto-optic processors for control and signal processing in phased-array antennas are presented. These processors can operate in both the antenna transmit and receive modes. An experimental acousto-optic processor is demonstrated in the laboratory. This optical technique replaces all the phase-shifting devices required in electronically controlled phased-array antennas

Switchless hybrid analog-digital variable optical delay line for radio frequency signal processing

The author proposes the design of a novel switchless variable optical delay line (VFODL) for radio frequency (rf) signals that combines an analog mode VFODL with a discrete-state VFODL. This hybrid VFODL proposes the use of a laser with smart, fast (e.g., 1 ns) wavelength tuning in combination with flat-top passband design spatially and temporally dispersive optical elements to simultaneously provide both long and short time delays, thus finely covering a wide nanoseconds delay range. An example design indicates a 9.6-ns time delay range with 6-ps increments, giving 1600 independent delays using a no-moving-parts signal-processing structure. VFODL applications include rf antenna array processing, radar testing, and precision electrical timing systems

Demonstration of three dimensional imaging of blood vessel using a no moving parts electronic lens-based optical confocal microscope

To the best of our knowledge, for the first time, biological Three Dimensional (3-D) imaging has been achieved using an electronically controlled optical lens to accomplish no-moving parts depth section scanning in a modified commercial 3-D confocal microscope. Specifically, full 3-D views of a standard CDC blood vessel (enclosed in a glass slide) have been obtained using the modified confocal microscope operating at the red 633 nm laser wavelength

Liquid crystal agile photonics: from fiber to the free-space domain

Liquid Crystals (LC) are excellent low loss large area programmable materials for smart optical device design leading to agile photonics. This paper describes work by the Riza group to enable intelligent system design from the fiber-optic realm to the freespace optics domain of applications. Specifically, novels works will be described in fiber-optic attenuator design, freespace optical scanners, fiber-optic switches, fiber-optic delay lines, and laser beam profilers. Both theory and experimental demonstrations will be highlighted

Scanning Heterodyne Optical Interferometers

Compact, high performance, scanning heterodyne optical interferometers are introduced for interferometric phase-based measurement applications. The novel, in-line, almost common-path optical interferometer design offers robustness to externally induced phase noise via mechanical vibrations, thermal effects, and other environmental effects. Novel instrument designs are introduced for both transmissive and reflective interferometry. These instruments use acousto-optic devices or Bragg cells to implement rapid (e.g., /scan spot) optical scanning of the test medium. Although the read optical beam scans a given test region, the double Bragg diffraction optical design of the instrument makes the final interfering output beams stationary on the two high speed photodetectors used for radio frequency signal generation via heterodyne detection. One photodetector acts as the fixed phase reference, while the other fixed photodetector picks up the test medium phase information as the optical beam scans the test region. The transmissive design instrument is built in the laboratory using flint glass Bragg cells. A typical 120 MHz heterodyne detected signal output had a carrier-to-noise ratio of 108.9 dBc/Hz measured at a +160 kHz offset using a spectrum analyzer resolution bandwidth of 30 kHz. The corresponding single-sideband phase noise was estimated at -101.57 dBc/Hz at 160 kHz offset. The measured instrument radio frequency dynamic range was similar to 60 dB or an equivalent of 30 dB optical dynamic range, with a 1/1000 of a fringe cycle phase measurement accuracy. Test medium optical phase mapping was successfully tested with the instrument using a large area, 6 mu m thick, birefringent-mode nematic liquid crystal cell. Our instrument allows the use of high continuous wave or peak power, broad spectral linewidth, coherent light sources. The instrument can have a high 50% optical power efficiency. High speed two-dimensional optical scanning of a test medium is possible with our instrument by using a fixed one-dimensional output high speed detector array, or via the use of high speed nonmechanical electro-optic deflectors

Acoustic-optic techniques for phased array antenna processing

An acousto-optic phased array antenna beamformer with independent phase and carrier control capability is experimentally demonstrated using single-sideband signals driving two acousto-optic devices. A dynamic range of 66.6 dB @+2 MHz and carrier-to-noise of 126.9 dBIHz @+2 MHz is measured. This beamformer has wide antenna tunable bandwidth and intrapulse beamforming capabilities

Coded access optical sensor (CAOS) imager and applications

Starting in 2001, we proposed and extensively demonstrated (using a DMD: Digital Micromirror Device) an agile pixel Spatial Light Modulator (SLM)-based optical imager based on single pixel photo-detection (also called a single pixel camera) that is suited for operations with both coherent and incoherent light across broad spectral bands. This imager design operates with the agile pixels programmed in a limited SNR operations starring time-multiplexed mode where acquisition of image irradiance (i.e., intensity) data is done one agile pixel at a time across the SLM plane where the incident image radiation is present. Motivated by modern day advances in RF wireless, optical wired communications and electronic signal processing technologies and using our prior-art SLM-based optical imager design, described using a surprisingly simple approach is a new imager design called Coded Access Optical Sensor (CAOS) that has the ability to alleviate some of the key prior imager fundamental limitations. The agile pixel in the CAOS imager can operate in different time-frequency coding modes like Frequency Division Multiple Access (FDMA), Code-Division Multiple Access (CDMA), and Time Division Multiple Access (TDMA). Data from a first CAOS camera demonstration is described along with novel designs of CAOS-based optical instruments for various applications

Minimally invasive optical beam profiler

Proposed and demonstrated is a minimally invasive optical beam profiler using a non-pixelated liquid crystal spatial light modulator. The profiler features high detection sensitivity in the visible band, high 50 lines/mm spatial resolution, beam observation zone 100 % fill factor and magnification flexibility, and video rate operations. Applications for this beam profiler includes plug and test beam measurements with minimal interruptions and feedback effects introduced into the optical beam system under test

Agile optical confocal microscopy instrument architectures for high flexibility imaging

Ideally, a no-moving parts fast and agile scanning confocal microscope system is required that can produce true real-time 3-D scans with precision and repeatability. In this paper, such agile optical confocal microsopy designs are proposed that enable high speed precise non-invasive 3-D imaging. These compact confocal microscopes can provide real-time pin-point focussed imaging to enable confocal slices in-vivo, thus greatly reducing motion artifacts. These microscopes can be modified into interferometric microscopes for phase contrast imaging. The proposed microscopes can also greatly improve confocal fluorescence imaging as needed for cancer detection. An ultracompact confocal probe tip connected to a single ultra-thin fiber is another design option allowing flexibility for usage in tight cavities

All-fiber connectorized compact fiber optic delay-line modules using three-dimensional polarization optics

Compact and all-fiber connectorized photonic delay-line modules based on three-dimensional bulk polarization optics are proposed and experimentally demonstrated. The modules are built on a single optical microbench and demonstrate optical leakage noise performance of -40 dB at switching speeds of 10 mu s. Insertion loss analysis is also performed. A special gradient-index lens fiber optic collimator design is proposed to further reduce the optical insertion loss of the delay-line module. A wavelength-dependent design is also proposed for expanding the applicability of the PDL module to multichannel operation