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It is shown that interleavel binary block codes combined with pulse position modulation give the best practical coded systems yet devised for optical communication with photon detection. Linear block codes rather than convolutional codes are considered.
A document discusses a proposal to incorporate holographic optical elements into solar photon thrusters (SPTs). First suggested in 1990, SPTs would be systems of multiple reflective, emissive, and absorptive surfaces (solar sails) that would be attached to spacecraft orbiting the Earth to derive small propulsive forces from radiation pressures. An SPT according to the proposal would include, among other things, a main sail. One side of the sail would be highly emissive and would normally face away from the Earth. The other side would be reflective and would be covered by white-light holographic images that would alternately become reflective, transmissive, and absorptive with small changes in the viewing angle. When the spacecraft was at a favorable orbital position, the main sail would be oriented to reflect sunlight in a direction to maximize the solar thrust; when not in a favorable position, the main sail would be oriented to present a substantially absorptive/emissive aspect to minimize the solar drag. By turning the main sail slightly to alternate between the reflective and absorptive/ emissive extremes, one could achieve nearly a doubling or halving of the radiational momentum transfer and, hence, of the solar thrust.
Quantum optical experiments require all the components involved to be extremely stable relative to each other. The stability can be "measured" by using an interferometric experiment. A pair of coherent photons produced by parametric down-conversion could be chosen to be orthogonally polarized initially. By rotating the polarization of one of the wave packets, they can be recombined at a beam splitter such that interference will occur. Theoretically, the interference will create four terms in the wave function. Two terms with both photons going to the same detector, and two terms will have the photons each going to different detectors. However, the latter will cancel each other out, thus no photons will arrive at the two detectors simultaneously under ideal conditions. The stability Of the test-bed can then be inferred by the dependence of coincidence count on the rotation angle.
It has been a longstanding challenge to identify the mechanisms responsible for heating the solar corona, in part because heating, whether by waves or magnetic reconnection, is thought to be concentrated in thus far unresolved volumes with characteristic scales ≲100 km. The Coronal Microscale Observatory (CMO) is a mission concept designed to image these microscale heating events, identify the dominant physical mechanisms that control their initiation and evolution, and understand their effects on the formation of the solar wind. CMO positions three spacecraft and three instruments near the Sun-Earth L1 Lagrange point. One instrument is a cluster of 6 coaligned extreme ultraviolet (EUV) telescopes that image a common field of view with ultrahigh angular resolution (0.02−0.07 arcsec) in narrow wavelength bands, each sensitive to emission from plasma in a limited temperature range. The second instrument is a multi-band, full-disk, externally occulted coronagraph. Finally, a two-band fine scale EUV imager (resolution 0.3 arcsec) provides a larger field of view for context and additional science. The three CMO craft fly in precise formation to ensure that the EUV imagers point to a desired target on the Sun and the external occulter accurately blocks the solar disk. The novel mission architecture arises from the intrinsically long EUV focal length (≳100 m) of diffractive optics known as photon sieves, which achieve nearly diffraction-limited EUV imaging but require a distributed telescope, in which the optics and- the image sensors are on separate spacecraft. Two spacecraft are also needed to position an external occulter 200 m in front of the coronagraph, which enables visible-light imaging of the corona very close to the solar limb with undiminished angular resolution. Recent advances in fabricating ultraprecise and smooth reflective optics suggest that a conventional (single spacecraft)EUV “microscope” may now be feasible in an Explorer-class mission that could achieve a subset of the scientific objectives of CMO.
Angular resolution and photon-collecting area are the two most important factors that determine the power of an X-ray astronomical telescope. The grazing incidence nature of X-ray optics means that even a modest photon-collecting area requires an extraordinarily large mirror area. This requirement for a large mirror area is compounded by the fact that X-ray telescopes must be launched into, and operated in, outer space, which means that the mirror must be both lightweight and thin. Meanwhile the production and integration cost of a large mirror area determines the economical feasibility of a telescope. In this paper we report on a technology development program whose objective is to meet this three-fold requirement of making astronomical X-ray optics: (1) angular resolution, (2) photon-collecting area, and (3) production cost. This technology is based on precision polishing of monocrystalline silicon for making a large number of mirror segments and on the meta-shell approach to integrate these mirror segments into a mirror assembly. The meta-shell approach takes advantage of the axial or rotational symmetry of an X-ray telescope to align and bond a large number of small, lightweight mirrors into a large mirror assembly. The most important features of this technology include: (1) potential to achieve the highest possible angular resolution dictated by optical design and diffraction; and (2) capable of implementing every conceivable optical design, such as Wolter-I, Wolter-Schwarzschild, as well as other variations to one or another aspect of a telescope. The simplicity and modular nature of the process makes it highly amenable to mass production, thereby making it possible to produce very large X-ray telescopes in a reasonable amount of time and at a reasonable cost. As of June 2017, the basic validity of this approach has been demonstrated by finite element analysis of its structural, thermal, and gravity release characteristics, and by the fabrication, alignment, bonding, and X-ray testing of mirror modules. Continued work in the coming years will raise the technical readiness of this technology for use by SMEX, MIDEX, Probe, as well as major flagship missions.
The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) has developed a laboratory transmitter and receiver prototype of a space-to-ground optical communications link. The system is meant to emulate future deep space optical communication links, such as the first crewed flight of Orion, in which the transmitted laser is modulated using pulse position modulation and the receiver is capable of detecting single photons. The transmitter prototype consists of a software defined radio, a high extinction ratio electro-optic modulator system, and a 1550 nm laser. The receiver is a scalable concept and utilizes a single-pixel array of fiber coupled superconducting nanowire single photon detectors. The transmit and receive waveforms follow the Consultative Committee for Space Data Systems (CCSDS) Optical Communications Coding and Synchronization Standard. A software model of the optical transmitter and receiver has also been implemented to predict performance of the optical test bed. This paper describes the transmitter and receiver prototypes as well as the system test configuration. System level tests results are presented and shown to align with predictions from software simulations. The validated software model can be used to in the future to reduce the design cycle of optical communications systems.
Non-intrusive and non-invasive optical imaging techniques has generated great interest among researchers for their potential applications to biological study, device characterization, surface defect detection, and jet fuel dynamics. Non-linear optical parametric amplification gate (NLOPG) has been used to detect back-scattered images of objects hidden in diluted Intralipid solutions. To directly detect objects hidden in highly scattering media, the diffusive component of light needs to be sorted out from early arrived ballistic and snake photons. In an optical imaging system, images are collected in transmission or back-scattered geometry. The early arrival photons in the transmission approach, always carry the direct information of the hidden object embedded in the turbid medium. In the back-scattered approach, the result is not so forth coming. In the presence of a scattering host, the first arrival photons in back-scattered approach will be directly photons from the host material. In the presentation, NLOPG was applied to acquire time resolved back-scattered images under the phase matching condition. A time-gated amplified signal was obtained through this NLOPG process. The system's gain was approximately 100 times. The time-gate was achieved through phase matching condition where only coherent photons retain their phase. As a result, the diffusive photons, which were the primary contributor to the background, were removed. With a large dynamic range and high resolution, time-gated early light imaging has the potential for improving rocket/aircraft design by determining jets shape and particle sizes. Refinements to these techniques may enable drop size measurements in the highly scattering, optically dense region of multi-element rocket injectors. These types of measurements should greatly enhance the design of stable, and higher performing rocket engines.
Phase change materials or PCMs are truly remarkable compounds whose unique switchable properties have fueled an explosion of emerging applications in electronics and photonics. Nonetheless, if we discount their use in optical discs, PCMs’ immense application potential in photonics beyond data recording has only begun to unfold in the past decade. While the material requirements for optical or electronic data storage have been succinctly summarized as five key elements “writability, archival storage, erasability, readability, and cyclability” decades ago, these requirements are not universally relevant to the diverse set of photonic applications now being explored. It also comes as no surprise that existing PCMs, which have been heavily vetted for data storage, are not necessarily the optimal compositions for different use cases in optics and photonics. PCMs with their attributes custom-tailored for specific applications are therefore in demand as phase-change photonics continue to expand. Here we discuss the PCM selection and design strategies specifically for photonic applications as well as our recent work developing active integrated photonic devices and metasurface optics based on new PCMs tailored for photonics.
The Photonics group top level processes regarding development and qualification of space flight hardware for optoelectronic components along with our contributions and successes with LIDAR systems, space flight reliability heritage, and our testing capabilities are conveyed with this power point presentation.
Silicon and metal are coevaporated onto a silicon substrate in a molecular beam epitaxy system with a larger than stoichiometric amount of silicon so as to epitaxially grow particles of metal silicide embedded in a matrix of single crystal epitaxially grown silicon. The particles interact with incident photons by resonant optical absorption at the surface plasmon resonance frequency. Controlling the substrate temperature and deposition rate and time allows the aspect ratio of the particles to be tailored to desired wavelength photons and polarizations. The plasmon energy may decay as excited charge carriers or phonons, either of which can be monitored to indicate the amount of incident radiation at the selected frequency and polarization.
Convolutional interleavers are used in many different communications systems to correct for burst errors due to atmospheric fades and scintillation. The interleaver size is related to the channel coherence time and the data rate. Small convolutional interleavers can be implemented in a field programmable gate array (FPGA) block random access memory (BRAM). However, large interleavers exceeding the size of the BRAM on the FPGA are necessary for channels with longer fades and higher data rates. Therefore, an implementation utilizing double data rate (DDR) memory external to the FPGA is necessary. Wide DDR memory data buses can make the use of DDR memory for convolutional interleavers inefficient when individual symbols are written to and read from the memory. DDR memory operational speeds can also limit the data rate of the interleaver. The Consultative Committee for Space Data Systems (CCSDS) Optical Communications High Photon Efficiency (HPE) standard utilizes a convolutional channel symbol interleaver. A previous implementation of the HPE standard utilized BRAM for the convolutional interleaver, but mission requirements for the upcoming Optical Artemis-2 Orion (O2O) communications demonstration dictate the use of an interleaver exceeding the size of the BRAM. An algorithm and method for implementing the convolutional interleaver in the FPGA with DDR memory is described in this paper.
Convolutional interleavers are used in many different communications systems to correct for burst errors due to atmospheric fades and scintillation. The interleaver size is related to the channel coherence time and the data rate. Small convolutional interleavers can be implemented in a field programmable gate array (FPGA) block random access memory (BRAM). However, large interleavers exceeding the size of the BRAM on the FPGA are necessary for channels with longer fades and higher data rates. Therefore, an implementation utilizing double data rate (DDR) memory external to the FPGA is necessary. Wide DDR memory data buses can make the use of DDR memory for convolutional interleavers inefficient when individual symbols are written to and read from the memory. DDR memory operational speeds can also limit the data rate of the interleaver. The Consultative Committee for Space Data Systems (CCSDS) Optical Communications High Photon Efficiency (HPE) standard utilizes a convolutional channel symbol interleaver. A previous implementation of the HPE standard utilized BRAM for the convolutional interleaver, but mission requirements for the upcoming Optical Artemis-2 Orion (O2O) communications demonstration dictate the use of an interleaver exceeding the size of the BRAM. An algorithm and method for implementing the convolutional interleaver in the FPGA with DDR memory is described in this paper.
We discuss the contribution of Population III stars to the near-IR (NIR) cosmic infrared background (CIB) and its effect on spectra of high-z, high-energy gamma-ray bursts (GRBs) and other sources. It is shown that if Population III is composed of massive stars, the claimed NIR CIB excess will be reproduced if only approx. 4% plus or minus 2% of all baryons went through these stars. Regardless of the precise amount of the NIR CIB due to them, they likely left enough photons to provide a large optical depth for high-energy photons from distant GRBs. Observations of such GRBs are expected following the planned launch of NASA's GLAST mission. Detecting such damping in the spectra of high-z GRBs will then provide important information on the emissions from the Population III epoch, and the location of this cutoff may serve as an indicator of the GRBs' redshifts. We also point out the difficulty of unambiguously detecting the CIB part originating from Population III in spectra of low-z blazars.
Silicon and metal are coevaporated onto a silicon substrate in a molecular beam epitaxy system with a larger than stoichiometric amount of silicon so as to epitaxially grow particles of metal silicide embedded in a matrix of single crystal epitaxially grown silicon. The particles interact with incident photons by resonant optical absorption at the surface plasmon resonance frequency. Controlling the substrate temperature and deposition rate and time allows the aspect ratio of the particles to be tailored to desired wavelength photons and polarizations. The plasmon energy may decay as excited charge carriers of phonons, either of which can be monitored to indicate the amount of incident radiation at the selected frequency and polarization.
The National Aeronautics and Space Administration (NASA) at Glenn Research Center (GRC) has developed an optical communications transmitter and receiver using Commercial-off-the-shelf (COTS) components. The goal of this project is to become fully compliant with Consultative Committee for Space Data Systems (CCSDS) High Photon Efficiency (HPE) Optical Communications Coding and Synchronization standard. The receive modem’s decoder has been modified using shift registers to enable the decoding of higher data rate pulse-position modulation (PPM) 4 and PPM-8 signals. PPM-4 and PPM-8 is then verified by comparing the codeword error rate (CWER) of a hardware implementation to a software simulation. The changes show the capability to decode PPM-4 and PPM-8 for a single decoder. This memorandum details the changes made, the performance achieved with the changes, and necessary future work.
Nonlinear optics is the result of laser beam interaction with materials and started with the advent of lasers in the early 1960s. The field is growing daily and plays a major role in emerging photonic technology. Nonlinear optics play a major role in many of the optical applications such as optical signal processing, optical computers, ultrafast switches, ultra-short pulsed lasers, sensors, laser amplifiers, and many others. This special review volume on Nonlinear Optics and Applications is intended for those who want to be aware of the most recent technology. This book presents a survey of the recent advances of nonlinear optical applications. Emphasis will be on novel devices and materials, switching technology, optical computing, and important experimental results. Recent developments in topics which are of historical interest to researchers, and in the same time of potential use in the fields of all-optical communication and computing technologies, are also included. Additionally, a few new related topics which might provoke discussion are presented. The book includes chapters on nonlinear optics and applications; the nonlinear Schrodinger and associated equations that model spatio-temporal propagation; the supercontinuum light source; wideband ultrashort pulse fiber laser sources; lattice fabrication as well as their linear and nonlinear light guiding properties; the second-order EO effect (Pockels), the third-order (Kerr) and thermo-optical effects in optical waveguides and their applications in optical communication; and, the effect of magnetic field and its role in nonlinear optics, among other chapters.
We present a field-programmable gate array (FPGA) implementation of a single photon-counting receive modem for a pulse position modulated signal. The modem is compliant with the Consultative Committee for Space Data Systems (CCSDS) High Photon Efficiency (HPE) Optical Communications Coding and Synchronization standard and is capable of a maximum data rate of 267 Mbps. The system is designed on a commercial off-the-shelf FPGA platform and utilizes superconducting nanowire single photon counting detectors, analog to digital converters (ADC s) to sample the detectors, and two FPGAs. Symbol timing recovery, photon counting, convolutional deinterleaving, and codeword synchronization areis performed in the first FPGA. The second FPGA performs iterative decoding on each codeword of the serially concatenated pulse position modulated (SCPPM) signal. A digital filter is included to compensate for timing jitter of the detector, and the decoder throughput can be modified adjusted through reconfigurable parallelization. The decoder also implements a resource-efficient, algorithmic polynomial interleaver and deinterleaver. Both FPGAs can be reconfigured to switch between pulse position modulation (PPM)-16 and PPM-32 with code rates 1/3, 1/2, and 2/3. In this paper, we describe the receiver architecture and FPGA implementation of the timing recovery loop and SCPPM decoder, FPGA utilization for the different modes, and receive modem characterization test results.
A receiver, transmitter, and photon counting detector for use in an optical communication link are disclosed. Also disclosed are methods of communicating using the transmitter, the receiver, and the photon detector.