Orbiting Rainbows: Optical Manipulation of Aerosols and the Beginnings of Future Space Construction

Our objective is to investigate the conditions to manipulate and maintain the shape of an orbiting cloud of dust-like matter so that it can function as an ultra-lightweight surface with useful and adaptable electromagnetic characteristics, for instance, in the optical, RF, or microwave bands. Inspired by the light scattering and focusing properties of distributed optical assemblies in Nature, such as rainbows and aerosols, and by recent laboratory successes in optical trapping and manipulation, we propose a unique combination of space optics and autonomous robotic system technology, to enable a new vision of space system architecture with applications to ultra-lightweight space optics and, ultimately, in-situ space system fabrication. Typically, the cost of an optical system is driven by the size and mass of the primary aperture. The ideal system is a cloud of spatially disordered dust-like objects that can be optically manipulated: it is highly reconfigurable, fault-tolerant, and allows very large aperture sizes at low cost. See Figure 1 for a scenario of application of this concept. The solution that we propose is to construct an optical system in space in which the nonlinear optical properties of a cloud of micron-sized particles are shaped into a specific surface by light pressure, allowing it to form a very large and lightweight aperture of an optical system, hence reducing overall mass and cost. Other potential advantages offered by the cloud properties as optical system involve possible combination of properties (combined transmit/receive), variable focal length, combined refractive and reflective lens designs, and hyper-spectral imaging. A cloud of highly reflective particles of micron-size acting coherently in a specific electromagnetic band, just like an aerosol in suspension in the atmosphere, would reflect the Sun's light much like a rainbow. The only difference with an atmospheric or industrial aerosol is the absence of the supporting fluid medium. This new concept is based on recent understandings in the physics of optical manipulation of small particles in the laboratory and the engineering of distributed ensembles of spacecraft clouds to shape an orbiting cloud of micron-sized objects. In the same way that optical tweezers have revolutionized micro- and nano-manipulation of objects, our breakthrough concept will enable new large scale NASA mission applications and develop new technology in the areas of Astrophysical Imaging Systems and Remote Sensing because the cloud can operate as an adaptive optical imaging sensor. While achieving the feasibility of constructing one single aperture out of the cloud is the main topic of this work, it is clear that multiple orbiting aerosol lenses could also combine their power to synthesize a much larger aperture in space to enable challenging goals such as exoplanet detection. Furthermore, this effort could establish feasibility of key issues related to material properties, remote manipulation, and autonomy characteristics of cloud in orbit. There are several types of endeavors (science missions) that could be enabled by this type of approach, i.e. it can enable new astrophysical imaging systems, exoplanet search, large apertures allow for unprecedented high resolution to discern continents and important features of other planets, hyperspectral imaging, adaptive systems, spectroscopy imaging through limb, and stable optical systems from Lagrange-points. Future micro-miniaturization might hold promise of a further extension of our dust aperture concept to other more exciting smart dust concepts with other associated capabilities

NIAC Phase II Orbiting Rainbows: Future Space Imaging with Granular Systems

Inspired by the light scattering and focusing properties of distributed optical assemblies in Nature, such as rainbows and aerosols, and by recent laboratory successes in optical trapping and manipulation, we propose a unique combination of space optics and autonomous robotic system technology, to enable a new vision of space system architecture with applications to ultra-lightweight space optics and, ultimately, in-situ space system fabrication. Typically, the cost of an optical system is driven by the size and mass of the primary aperture. The ideal system is a cloud of spatially disordered dust-like objects that can be optically manipulated: it is highly reconfigurable, fault-tolerant, and allows very large aperture sizes at low cost. This new concept is based on recent understandings in the physics of optical manipulation of small particles in the laboratory and the engineering of distributed ensembles of spacecraft swarms to shape an orbiting cloud of micron-sized objects. In the same way that optical tweezers have revolutionized micro- and nano-manipulation of objects, our breakthrough concept will enable new large scale NASA mission applications and develop new technology in the areas of Astrophysical Imaging Systems and Remote Sensing because the cloud can operate as an adaptive optical imaging sensor. While achieving the feasibility of constructing one single aperture out of the cloud is the main topic of this work, it is clear that multiple orbiting aerosol lenses could also combine their power to synthesize a much larger aperture in space to enable challenging goals such as exo-planet detection. Furthermore, this effort could establish feasibility of key issues related to material properties, remote manipulation, and autonomy characteristics of cloud in orbit. There are several types of endeavors (science missions) that could be enabled by this type of approach, i.e. it can enable new astrophysical imaging systems, exo-planet search, large apertures allow for unprecedented high resolution to discern continents and important features of other planets, hyperspectral imaging, adaptive systems, spectroscopy imaging through limb, and stable optical systems from Lagrange-points. Furthermore, future micro-miniaturization might hold promise of a further extension of our dust aperture concept to other more exciting smart dust concepts with other associated capabilities. Our objective in Phase II was to experimentally and numerically investigate how to optically manipulate and maintain the shape of an orbiting cloud of dust-like matter so that it can function as an adaptable ultra-lightweight surface. Our solution is based on the aperture being an engineered granular medium, instead of a conventional monolithic aperture. This allows building of apertures at a reduced cost, enables extremely fault-tolerant apertures that cannot otherwise be made, and directly enables classes of missions for exoplanet detection based on Fourier spectroscopy with tight angular resolution and innovative radar systems for remote sensing. In this task, we have examined the advanced feasibility of a crosscutting concept that contributes new technological approaches for space imaging systems, autonomous systems, and space applications of optical manipulation. The proposed investigation has matured the concept that we started in Phase I to TRL 3, identifying technology gaps and candidate system architectures for the space-borne cloud as an aperture

Compact near-infrared 3-dimensional channel waveguide lasers

This thesis presents the development of ultrafast near-infrared (NIR) waveguide laser sources, through the fabrication of waveguides in Yb-doped bismuthate glass using ultrafast laser inscription (ULI). An integrated linear cavity waveguide laser is demonstrated in the glass with output powers of 163 mW and a slope efficiency of 79%. The laser performance is comparable to bulk systems while providing additional advantages in terms of low threshold ~35 mW and system compactness. The simultaneous achievement of low propagation losses and preservation of the fluorescence properties of Yb ions after the ULI process is key to the outstanding laser performance. Based on the current interest in ultrafast laser development using graphene as a saturable absorber (SA), a systematic study of nonlinear absorption in graphene is presented. The nonlinear optical characterisation of graphene at the wavelengths of 1 μm and 2 μm contributes to the experimental evidence for the wavelength independent absorption saturation in the material. Ultrashort pulse generation from the Yb-doped bismuthate waveguide laser is investigated using SAs based on semiconductor technology and carbon nanostructures. The quasi-monolithic waveguide laser, employing a graphene SA generated ~485 mW output power with a slope efficiency of 49%. The laser generated ~1 ps pulses in a Q-switched mode-locked regime, with the mode-locked pulses measuring a high repetition rate of 1.5 GHz. Ultrafast laser development is also investigated based on a novel evanescent-wave mode-locker device, fabricated by ULI. The device consists of an orthogonal waveguide with the right-angle positioned along its angled facet. The substrate is converted into a mode-locker by depositing carbon nanotube SA at the angled facet. Mode-locked operation is demonstrated by incorporating the substrate in an Er-doped ring laser, generating ~800 fs pulses at 26 MHz. Some preliminary work is done to replicate the device design in an active gain medium, namely, Yb-doped bismuthate glass, for the development of compact laser sources

Changes in X-ray spectra of accreting pulsars on short and long time scales

The work regards a study of cyclotron resonance scattering features (CRSFs), or simply "cyclotron lines”, observed in the spectra of accreting pulsars, which are rotating neutron stars accreting matter from their optical companion stars. CRSFs are believed to form in accreted plasma in the vicinity of the neutron star’s polar caps where magnetic fields are extremely strong (~1012 G). Observations of cyclotron lines provide an opportunity to directly estimate magnetic field strengths of neutron stars, being the only direct method to do it. Variability of cyclotron lines also probes the dynamics of accretion processes, allowing testing physical models and the magnetosphere geometry. Based on a variety of observations performed with the NuSTAR X-ray space observatory, the thesis focuses in particular on the investigation of the luminosity and time dependences of the cyclotron line energy in the spectra of three accreting pulsars: Hercules X-1, Cepheus X-4 and V 0332+53. I have shown that the line energy and spectral hardness in Cepheus X-4 are positively correlated with X-ray luminosity, reflecting the sub-critical accretion regime in the source. I have also shown that V 0332+53 exhibits a bimodal dependence on X-ray luminosity, that is not only the negative correlation of the cyclotron line energy with X-ray luminosity, as known already, but also a positive one, which means that the source has undergone a transition from the super- to the sub- critical accretion regime. This makes this source the only one of its kind. The time dependence in V 0332+53 has also been investigated in detail, and we argue that this dependence is caused by changes in the geometry of the magnetosphere rather than by intrinsic changes in the magnetic field strength

Engineering planetary lasers for interstellar communication

Transmitting large amounts of data efficiently among neighboring stars will vitally support any eventual contact with extrasolar intelligence, whether alien or human. Laser carriers are particularly suitable for high-quality, targeted links. Space laser transmitter systems designed by this work, based on both demonstrated and imminent advanced space technology, could achieve reliable data transfer rates as high as 1 kb/s to matched receivers as far away as 25 pc, a distance including over 700 approximately solar-type stars. The centerpiece of this demonstration study is a fleet of automated spacecraft incorporating adaptive neural-net optical processing active structures, nuclear electric power plants, annular momentum control devices, and ion propulsion. Together the craft sustain, condition, modulate, and direct to stellar targets an infrared laser beam extracted from the natural mesospheric, solar-pumped, stimulated CO2 emission recently discovered at Venus. For a culture already supported by mature interplanetary industry, the cost of building planetary or high-power space laser systems for interstellar communication would be marginal, making such projects relevant for the next human century. Links using high-power lasers might support data transfer rates as high as optical frequencies could ever allow. A nanotechnological society such as we might become would inevitably use 10 to the 20th power b/yr transmission to promote its own evolutionary expansion out of the galaxy

Applications of scattering-type scanning near-field optical microscopy in the infrared

This thesis is split into two broad sections. These are defined by the various applications of scattering-type near-field optical microscopy (s-SNOM) in different parts of the electromagnetic spectrum; the near-infrared (700 - 1000nm) and the mid-infrared (6 - 10um). S-SNOM is a means of imaging surfaces at resolutions well below the diffraction limit - the level of recorded detail does not depend on the wavelength of light (as it does with traditional optical microscopy), but instead on the sharpness of a probe (usually around 10nm), meaning an image resolution approaching a thousandth of a wavelength in the mid-infrared. For the work presented in the near-infrared, the focus lies with the modelling and mapping of various plasmonic resonances supported by metallic nanostructures. These resonances have the ability to "squeeze" light into substantially sub-wavelength volumes which is useful for a variety of applications ranging from cancer treatments to molecular sensing. The mid-infrared section starts with the implementation of a pulsed quantum cascade laser (QCL) as the system's light source. This presents some instrumentation challenges as all s-SNOM imaging to date has been conducted with continuous-wave (CW) lasers. Using a pulsed laser also raises some significant signal-to-noise implications which are quantified and discussed. In terms of the experimental applications of such a setup, the first steps towards ultra-high resolution infrared chemical spectroscopy are made by studying the epithelial cells of an oesophageal biopsy. The thesis concludes with an examination of the major noise sources faced by s-SNOM, and makes a number of recommendations on how their effects can be mitigated.Open Acces

Applied Measurement Systems

Measurement is a multidisciplinary experimental science. Measurement systems synergistically blend science, engineering and statistical methods to provide fundamental data for research, design and development, control of processes and operations, and facilitate safe and economic performance of systems. In recent years, measuring techniques have expanded rapidly and gained maturity, through extensive research activities and hardware advancements. With individual chapters authored by eminent professionals in their respective topics, Applied Measurement Systems attempts to provide a comprehensive presentation and in-depth guidance on some of the key applied and advanced topics in measurements for scientists, engineers and educators