Following Sharpless' visionary characterization of several idealized reactions as click reactions, the materials science and synthetic chemistry communities have pursued numerous routes toward the identification and implementation of these click reactions. Herein, we review the radical-mediated thiol-ene reaction as one such click reaction. This reaction has all the desirable features of a click reaction, being highly efficient, simple to execute with no side products and proceeding rapidly to high yield. Further, the thiol-ene reaction is most frequently photoinitiated, particularly for photopolymerizations resulting in highly uniform polymer networks, promoting unique capabilities related to spatial and temporal control of the click reaction. The reaction mechanism and its implementation in various synthetic methodologies, biofunctionalization, surface and polymer modification, and polymerization are all reviewed.

Thiol–Ene Click Chemistry

We review the field of femtosecond pulse shaping, in which Fourier synthesis methods are used to generate nearly arbitrarily shaped ultrafast optical wave forms according to user specification. An emphasis is placed on programmable pulse shaping methods based on the use of spatial light modulators. After outlining the fundamental principles of pulse shaping, we then present a detailed discussion of pulse shaping using several different types of spatial light modulators. Finally, new research directions in pulse shaping, and applications of pulse shaping to optical communications, biomedical optical imaging, high power laser amplifiers, quantum control, and laser-electron beam interactions are reviewed.

Femtosecond pulse shaping using spatial light modulators

Course Description This is an advanced course in which we explore the field of Statistical Optics. Topics covered include such subjects as the statistical properties of natural (thermal) and laser light, spatial and temporal coherence, effects of partial coherence on optical imaging instruments, effects on imaging due to randomly inhomogeneous media, and a statistical treatment of the detection of light. Development of this more comprehensive model of the behavior of light draws upon the use of tools traditionally available to the electrical engineer, such as linear system theory and the theory of stochastic processes.

http://ieeexplore.ieee.org/iel5/3/23094/01073023.pdf

Statistical optics

A large-scale silicon nanophotonic phased array with more than 4,000 antennas is demonstrated using a state-of-the-art complementary metal-oxide–semiconductor (CMOS) process, enabling arbitrary holograms with tunability, which brings phased arrays to many new technological territories. Nanophotonic approaches allow the construction of chip-scale arrays of optical nanoantennas capable of producing radiation patterns in the far field. This could be useful for a range of applications in communications, LADAR (laser detection and ranging) and three-dimensional holography. Until now this technology has been restricted to one-dimensional or small two-dimensional arrays. This paper reports the construction of a large-scale silicon nanophotonic phased array containing 4,096 optical nanoantennas balanced in power and aligned in phase. The array was used to generate a complex radiation pattern—the MIT logo—in the far field. The authors show that this type of nanophotonic phased array can be actively tuned, and in some cases the beam is steerable. Electromagnetic phased arrays at radio frequencies are well known and have enabled applications ranging from communications to radar, broadcasting and astronomy1. The ability to generate arbitrary radiation patterns with large-scale phased arrays has long been pursued. Although it is extremely expensive and cumbersome to deploy large-scale radiofrequency phased arrays2, optical phased arrays have a unique advantage in that the much shorter optical wavelength holds promise for large-scale integration3. However, the short optical wavelength also imposes stringent requirements on fabrication. As a consequence, although optical phased arrays have been studied with various platforms4,5,6,7,8 and recently with chip-scale nanophotonics9,10,11,12, all of the demonstrations so far are restricted to one-dimensional or small-scale two-dimensional arrays. Here we report the demonstration of a large-scale two-dimensional nanophotonic phased array (NPA), in which 64 × 64 (4,096) optical nanoantennas are densely integrated on a silicon chip within a footprint of 576 μm × 576 μm with all of the nanoantennas precisely balanced in power and aligned in phase to generate a designed, sophisticated radiation pattern in the far field. We also show that active phase tunability can be realized in the proposed NPA by demonstrating dynamic beam steering and shaping with an 8 × 8 array. This work demonstrates that a robust design, together with state-of-the-art complementary metal-oxide–semiconductor technology, allows large-scale NPAs to be implemented on compact and inexpensive nanophotonic chips. In turn, this enables arbitrary radiation pattern generation using NPAs and therefore extends the functionalities of phased arrays beyond conventional beam focusing and steering, opening up possibilities for large-scale deployment in applications such as communication, laser detection and ranging, three-dimensional holography and biomedical sciences, to name just a few.

/pdf/large-scale-nanophotonic-phased-array-c260q1wn41.pdf

Large-scale nanophotonic phased array

Foreword. Series Editor's Foreword. Preface. 1. Liquid crystal physics.* Introduction.* Thermodynamics and statistic physics.* Orientational order.* Elastic properties of liquid crystals.* Response of liquid crystals to electro-magnetic fields.* Anchoring effects of nematic liquid crystal at surfaces. 2. Propagation of light in anisotropic optical medium.* Electromagnetic wave.* Polarization.* Propagation of light in uniform anisotropic optical media.* Propagation of light in cholesteric liquid crystals. 3. Optical modeling methods.* Jones matrix method.* Mueller matrix method.* Berreman 4x4 method. 4. Effects of Electric field on Liquid Crystals.* Dielectric interaction.* Flexoelectric Effect.* Ferroelectricity in liquid crystals. 5. Freedericksz transition.* Calculus of variation.* The Fredeericksz transition: statics.* The Freedericksz transition: dynamics. 6. Liquid Crystal Materials.* Introduction.* Refractive indices.* Dielectric constants.* Rotational Viscosity.* Elastic constant.* Figure-of-merits.* Refractive index matching between liquid crystals and polymers. 7. Modeling of liquid crystal director configuration.* Electric energy of liquid crystals.* Modeling electric field.* Simulation of liquid crystal director configuration. 8. Transmissive liquid crystal display.* Introduction.* Twisted nematic cells.* In plane switching (IPS) mode.* Vertical alignment (VA) mode.* Multi-domain Vertical Alignment (MVA) Cells.* Optically compensated bend (OCB) cell. 9. Reflective and Trasreflective display.* Introduction.* Reflective liquid crystal displays.* Transflector.* Classification of Transflective LCDs.* Dual-cell-gap Transflective LCDs.* Single-cell-gap Transflective LCDs.* Performance of transflective LCDs. 10. Liquid crystal display matrices, drive schemes and bistable displays.* Segmented displays.* Passive matrix displays and drive scheme.* Active Matrix Displays.* Bistable ferroelectric liquid crystal displays and drive scheme.* Bistable nematic displays.* Bistable cholesteric reflective display. 11. Liquid crystal/polymer composites. * Introduction.* Phase separation.* Scattering properties of liquid crystal/polymer composites.* Polymer dispersed liquid crystals.* Polymer stabilization liquid crystals.* Displays from liquid crystal/polymer composites. 12. Tunable liquid crystal photonic devices. * Introduction.* Laser beam steering.* Variable Optical Attenuators.* Tunable-Focus Lens.* Polarization-Independent LC Devices. Index.

Fundamentals of Liquid Crystal Devices

This paper shows how the dispersion associated with optical phased array beam steering can be limited to moderate values of 20 to 80 times the diffraction limit even for very large angle beam steering. Much of the remaining factor of 20-80 may be correctable using digital techniques. A significant obstacle associated with widespread implementation of optical phased array beam steering is the wavelength dispersion associated with resets. We discuss optical phased array beam steering using resets of greater than one wavelength. By using larger resets the unfolded phase front for wavelengths other than the design wavelength can be maintained closer to a prism, thus limiting dispersion. This technique can be implemented with the variable period beam steering approach and the variable blaze beam steering approach. One way to implement the variable blaze beam steering approach is using movable lenslets. This method of implementation is amenable to large value resets, so it is an attractive method of implementation for this multiple wavelength reset, limited dispersion, beam steering technique. By using resets of multiple wavelengths and limiting the dispersion we will be able to steer passive, broadband, electrooptical sensors over wide angles using optical phased array technology.

Design of optical phased array beam steering with limited dispersion

This paper introduces and analyzes a revolutionary laser system architecture capable of dramatically reducing the complexity of laser systems while simultaneously increasing capability. The architecture includes 3 major subsystems. The first is a phased array of laser sources. In this paper we discuss diode-pumped fiber lasers as the elements of the phased array, although other waveguide lasers can also be considered. The second provides wavefront control and electronic beam steering. The third is subaperture receiver technology. Combining these three technologies into a new laser systems architecture results in a system that has graceful degradation, can steer to as wide an angle as individual optical phased array sub-apertures, and can be scaled to high power and large apertures through phasing of a number of sub-apertures.

Phased array of phased arrays (PAPA) laser systems architecture

Three dimensional imaging is a powerful tool for object detection, identification, and classification. 3D imaging allows removal of partial obscurations in front of the imaged object. Traditional 3D image sensing has been Laser Radar (LADAR) based. Active imaging has benefits; however, its disadvantages are costs, detector array complexity, power, weight, and size. In this keynote address paper, we present an overview of 3D sensing approaches based on passive sensing using commercially available detector technology. 3D passive sensing will provide many benefits, including advantages at shorter ranges. For small, inexpensive UAVs, it is likely that 3D passive imaging will be preferable to active 3D imaging.

New paradigms for active and passive 3D remote object sensing, visualization, and recognition

We describe our Innovative Multi Aperture Gimbaless Electro-Optical (IMAGE) testbed which uses coherent detection
of the complex field reflected off a diffuse target with seven hexagonally arranged apertures. The seven measured
optical fields are then phased with a digital optimization algorithm to synthesize a composite image whose angular
resolution exceeds that of a single aperture. This same post-detection phasing algorithm also corrects aberrations
induced by imperfect optics and a turbulent atmospheric path. We present the coherent imaging sub-aperture design
used in the IMAGE array as well as the design of a compact range used to perform scaled tests of the IMAGE array. We
present some experimental results of imaging diffuse targets in the compact range with two phase screens which
simulates a ~7[Km] propagation path through distributed atmospheric turbulence.

Active multi-aperture imaging through turbulence

The latest three-dimensional imaging results from Voxtel teamed with the University are Dayton are presented using Voxtel’s VOX3D™ series flash lidar camera. This camera uses the VOX3D series flash lidar sensor which integrates a 128×128 InGaAs p-i-n detector array with a custom, multi-mode, low-noise, complementary metal-oxide semiconductor readout integrated circuit. In this paper, results are presented of: short-range (< 10 m) three-dimensional lidar imaging performed at University of Dayton with a fast, low-power eye safe laser (20-μJ per pulse, 10-kHz) in high-bandwidth, windowed region-of-interest mode; and longer range (30 – 150 m) outdoor lidar tests performed at Voxtel with two different eye safe lasers (300-μJ and 3-mJ per pulse, 10-Hz) in full-frame low-bandwidth mode. The VOX3D camera achieves a single-shot timing precision of 23.2 cm and 10.7 cm in high-bandwidth and low-bandwidth modes respectively, with the timing precision in high bandwidth mode being limited by camera electronics. The VOX3D camera has a maximum range of 51 m and 159 m with 300-μJ and 3-mJ lasers in full-frame low-bandwidth mode, respectively.

Paul F. McManamon

Papers

Design of optical phased array beam steering with limited dispersion

Phased array of phased arrays (PAPA) laser systems architecture

New paradigms for active and passive 3D remote object sensing, visualization, and recognition

Active multi-aperture imaging through turbulence

3D imaging with 128x128 eye safe InGaAs p-i-n lidar camera