This PDF file contains the front matter associated with SPIE Proceedings Volume 8259, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

High resolution wavelength-tunable lasers are essential to sensing applications. For sensing applications, high resolution is needed to improve the spatial resolution and/or measurement accuracy, and fast tuning (sweeping) is required to enhance the measurement speed for dynamic sensing. However the demand of high resolution conflicts with the requirement of fast continuous wavelength tuning. The solution to this issue is tuning the wavelength of the output in a quasi-continuous way in which the length of each step is dependent on the frequency of a RF generator which is used to drive a single-sideband (SSB) modulator in the wavelength-swept optical system. In this paper, a principle of the step-tunable wavelength-swept optical system is proposed and demonstrated. The two optical features of narrow bandwidth and fairly high optical output power make the system unique for improving the accuracy of the measurement of the center-wavelength of a fiber Bragg grating (FBG) sensor. In addition, changing the tuning-step by adjusting the frequency of a RF generator electrically is user-friendly compared to the conventional wavelength swept systems by tuning optical elements mechanically.

We present a method for three-dimensional scene reconstruction in the millimeter-wave part of the electromagnetic spectrum. The millimeter waves captured by sparsely distributed antennas are up-converted to optical domain using electro-optic phase modulators. The modulation is a coherent process in that it preserves the phase information carried by the millimeter waves and encodes it in the phase of the optical carrier. In the optical domain, the signal is then transmitted using optical fibers to an optical cross-correlation engine where all pair-wise cross-correlation terms are measured. The 3D millimeter-wave representation of the scene is then reconstructed digitally from those crosscorrelation terms.

High-performance analog photonic links are discussed and the prevalent modulation formats are highlighted. Because of its multi-octave and millimeter-wave potential, special attention is given to intensity modulation with direct detection (IMDD) employing an external Mach-Zehnder modulator (MZM). The theory for IMDD is reviewed and some experimental results are discussed. Two limiting factors in multi-octave IMDD implementations are quantified. The MZM bias requirements in order to remain third-order limited are shown to be very stringent in high-performance links. Photodiode nonlinearities, perhaps the most inhibiting factor in present-day wideband analog photonics, are cast in terms of output intercept points and tied to the IMDD link performance.

We present here a widely tunable opto-electronic oscillator (OEO) based on an Er,Yb:glass Dual Frequency Laser (DFL) at 1.53 μm. The beatnote is stabilized with an optical fiber delay line. Compared to classical optoelectronic oscillators, this architecture does not need RF filter and offers a wide tunability. We measured a reduction of 67 dB of the phase noise power spectral density (PSD) at 10 Hz of the carrier optical fiber leading to a level of -27 dBc/Hz with only 100 m optical fiber. Moreover, the scheme offers a microwave signal tunability from 2.5 to 5.5 GHz limited by the RF components.

We have developed a system for generating widely tunable, narrow-line RF signals from a pair of injection-locked lasers. This system is based on injection seeding one laser with a selectable high-order sideband obtained from a second laser that is phase modulated by a narrow-line, low-frequency RF reference oscillator. When these coherent optical outputs are mixed on a fast photodiode, RF output is obtained, with linewidth and phase noise characteristics that are limited by the reference oscillator. The RF output can be tuned over a wide range, in multiples of the reference frequency, and can be fine-tuned by tuning the reference oscillator. In this paper, we present the results of our efforts to develop an integrated version of this system, based on a silicon-photonic integrated circuit coupled to III-V semiconductor gain chips. We describe the fabrication process of the integrated module using heterogeneous integration techniques, and present preliminary results including two lasers operating simultaneously on a single silicon-photonic chip.

In this work, an analog-to-digital converter architecture utilizing the precision timing and wide bandwidth capability of photonics technology and the versatility and efficient data processing of compressive sampling techniques is explored. The generation, control and transfer of the precision timing and sampled resolution to the final digitization stage is a key technical challenge to realizing the potential of the architecture; involving significant component, sub-system and interface developments as well as optimizations to capitalize on the unique benefits of compressive sampling techniques. Concept demonstration experiments, device and subsystem requirements and potential applications will be discussed.

Composite materials, such as polymer-matrix containing conductive fillers, are very attractive for shielding electromagnetic interference (EMI) due to their high shielding efficiency and seamlessness, processability, flexibility, light-weight and low-cost. Here, we report a development of novel, DNA-based EMI-shielding materials (DESM), consisting of DNA and metal nanoparticles. It has been shown that a thin DESM layer (typically ~30 - 50 μm) could block EMI radiations up to 60 dB effectively over an RF frequency range from KHz to tens GHz, exhibiting excellent EMI shielding efficiency. A wide selection of metal nanoparticle fillers for DESM has been tested for their performance in EMI shielding efficiency. Among them, silver and carbon-based nanoparticles have demonstrated the best performance and were selected for further investigation. The silver-doped DESM films could be also non-conductive while their EMI shielding efficiency is still well-preserved. The nonconductive DESM could have a great potential in the microelectronics industries for EMI shielding on electronic devices and circuit boards.

In this paper we present a novel implementation of high bandwidth constant modulation current circuit to the traditional small signal optical response technique used to determine the differential carrier lifetime of a semiconductor laser. This circuit is designed for the voltage to current conversion and to deliver a constant modulation current to the laser diode. The circuit rectifies parasitic effects of high value surface mount resistor at high frequencies used in the impedance independent optical technique and also has lower crosstalk. The application of this circuit can be generalized where the requirement arises for a high bandwidth constant modulation current circuit.

Optical phased arrays are promising candidates for both RF signal processing and optical beam forming and steering. These platforms not only enable accurate electrically controlled beam steering at high frequencies but also have the potential to significantly improve the performance of future free-space optical communications systems. In this work we exploit recent advancements in both nano-scale hybrid silicon-slot waveguides and electro-optic (EO) polymers to demonstrate an integrated optical phased-array antenna. Specifically, we create a hybrid integrated "photonic circuit" that connects an array of optical phase modulators, fed by a common optical signal and a 1x4 splitter, to a compact optical waveguide diffraction array for optical beam steering applications. The fundamental characteristics of the resulting integrated optical beam former, including the optical insertion loss, driving voltage, and phase control from the waveguide aperture are summarized in this letter.

An all-polymer high-frequency Mach-Zehnder modulator that can be fabricated using standard UV lithography is proposed. The optical waveguide structure consists of three polymer layers, two low-index, outer cladding layers and an organic-electro-optic material in a polymer host as the core. Lateral confinement is provided by a trench that is defined in the lower cladding layer, resulting in an inverted electro-optic polymer ridge waveguide. The inverted nature of this trench structure allows for a fabrication process in which the cladding layer is patterned, and the highly sensitive electrooptic material is simply spun on and cured. Microstrip transmission line electrodes patterned on the outer cladding, over the optical waveguides provide the modulation field. Similar devices using CLD1 or AJL8, as the electro-optic material have been numerically analyzed at up to 260GHz, and characterized at frequencies up to 40 GHz, but to date no electrooptic polymer device has been characterized at such high frequencies. A recently developed material, IKD-1-50, with electro-optic coefficients up to five times larger than CLD1 and AJL8 will be utilized as the core layer for the optical waveguide. The greater nonlinearity of these materials will yield a device with a lower Vπ. Additionally, high frequency characterization up to 300GHz will demonstrate the high bandwidth application possibilities of these new materials.

Modern high frequency applications necessitate the utilization of the millimeter wave band. Slot waveguides have previously been used for electro optic modulators as the enhancement of the electric field strength in the slot creates a large overlap with the electro optic material. We present a design that utilizes the field enhancement provided by a slot waveguide geometry for both the optical field and the RF modulating field. The dual RF and optical slot configuration maximizes the overlap of the optical field and the modulating field in the electro optic material, creating the maximum amount of phase change per applied volt of modulating signal. This design presents unique fabrication challenges.

High data rate photonic wireless systems operating at millimeter wave carrier frequencies are considered as a disruptive technology e.g. for reach extension in optical access networks and for mobile backhauling. Recently, we demonstrated 60 GHz photonic wireless systems with record data rates up to 27 Gbit/s. Because of the oxygen absorption at 60 GHz, it is beneficial for fixed wireless systems with spans exceeding 1 km to operate at even higher frequencies. Here, the recently regulated 10 GHz bandwidth within the E-band (60-90 GHz) is of particular interest, covering the 71-76 GHz and 81-86 GHz allocations for multi-gigabit wireless transmission. For this purpose, wideband waveguide photodetectors with high external quantum efficiency are required. Here, we report on double mushroom 1.55 μm waveguide photodetectors for integration in an E-band wireless transmitter module. The developed photodetector consists of a partially p-doped, partly non-intentionally doped absorbing layer centered in a mushroom-type optical waveguide, overcoming the compromise between the junction capacitance and the series resistance. For efficient fiber-chip coupling, a second mushroom-type passive optical waveguide is used. In contrast to the conventional shallow ridge waveguide approach, the mushroom-type passive waveguide allows to shift the center of the optical mode further away from the top surface, thus reducing waveguide losses due to the surface roughness. Experimentally, a very flat frequency response with a deviation up to ±1 dB in the entire E-band has been found together with an output power level of -15.7 dBm at 10 mA photocurrent and at a frequency of 73 GHz.

We present the theory, design, and experimental results obtained from a scanning passive W-band fully polarimetric imager. Passive millimeter-wave imaging offers persistent day/nighttime imaging and the ability to penetrate dust, clouds and other obscurants, including clothing and dry soil. The single-pixel scanning imager includes both far-field and near-field fore-optics for investigation of polarization phenomena. Using both fore-optics, a variety of scenes including natural and man-made objects was imaged and these results are presented showing the utility of polarimetric imaging for anomaly detection. Analysis includes conventional Stokes-parameter based approaches as well as multivariate image analysis methods.

Millimeter-wave (mm-wave) imaging is rapidly gaining acceptance as a security tool to augment conventional metal detectors and baggage x-ray systems for passenger screening at airports and other secured facilities. This acceptance indicates that the technology has matured; however, many potential improvements can yet be realized. The authors have developed a number of techniques over the last several years including novel image reconstruction and display techniques, polarimetric imaging techniques, array switching schemes, and high-frequency high-bandwidth techniques. All of these may improve the performance of new systems; however, some of these techniques will increase the cost and complexity of the mm-wave security portal imaging systems. Reducing this cost may require the development of novel array designs. In particular, RF photonic methods may provide new solutions to the design and development of the sequentially switched linear mm-wave arrays that are the key element in the mm-wave portal imaging systems. Highfrequency, high-bandwidth designs are difficult to achieve with conventional mm-wave electronic devices, and RF photonic devices may be a practical alternative. In this paper, the mm-wave imaging techniques developed at PNNL are reviewed and the potential for implementing RF photonic mm-wave array designs is explored.

Microwave photonics can provide superior advantages towards ultra-wideband wireless communications. In this work, we present an integration platform for 72GHz photodiode based wireless transmitter. The placement and positioning of discrete LNA and PA components, the bias-tee design parameters of photodiode, LNA and PA, and the design parameters for low-loss transition from CPW output of amplified electrical signal at the output of PA to E-band WR12 rectangular waveguide have to be carefully determined. We present general design principles of 72GHz photodiode integration platform. Further, we compare different substrates, which have been implemented into the platform, based on numerical results.