Showing papers in "High-power lasers and applications in 2002"
TL;DR: The conclusion of the test program is that the SILEX system has excellent performances qualifying the system for operational use by SPOTIMAGE in parallel with a detailed technological experimentation program involving the twoSILEX terminals, ESA's optical ground station on Tenerife, and also NASDA's OICETS, once ARTEMIS has acquired its final orbital position.
Abstract: The Semi conductor Inter satellite Link EXperiment, SILEX, consists of two terminals, one terminal embarked on the French LEO observation satellite SPOT4 and one terminal embarked on ESA's GEO telecommunication satellite ARTEMIS. The objective of SILEX is to perform optical communication experiments in orbit and on an operational basis transmit SPOT4 Earth observation data to ARTEMIS, which will relay the data to ground via its Ka band feeder link. SPOT4 was successfully launched on 22nd March 1998. The ARTEMIS launch on 12th July 2001 left ARTEMIS in an orbit with too low apogee, necessitating orbit raising to a circular parking orbit, altitude 31000 km, using a large fraction of the chemical propellant on board. The remaining 5000 km to GEO stationary orbit will be achieved using the low thrust innovative electric propulsion system necessitating specific attitude control software. The final orbit raising will last about 6 months and the expected lifetime of ARTEMIS after station acquisition is 5 years. While waiting for the establishment of the new attitude control software and the beginning of the final orbit raising maneuvers a test program has been undertaken to characterize the performances of the SILEX system. Testing was performed every fifth day when ARTEMIS was visible over Europe. The test program involves Optical Ground Station acquisition and tracking, inter-satellite link acquisition and tracking, bit error rate measurements and transmission of Earth observation data. The paper reports on results of the in orbit testing, giving comparisons with predictions. The conclusion of the test program is that the SILEX system has excellent performances qualifying the system for operational use by SPOTIMAGE in parallel with a detailed technological experimentation program involving the two SILEX terminals, ESA's optical ground station on Tenerife, and also NASDA's OICETS, once ARTEMIS has acquired its final orbital position.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
223 citations
TL;DR: In this article, the authors have demonstrated a fully automated quantum key distribution (QKD) system that is capable of operations at any time of day over a horizontal range of several kilometers.
Abstract: Free-space quantum key distribution (QKD), more popularly know as quantum cryptography, uses single-photon free-space optical communications to distribute the secret keys required for secure communications. At Los Alamos National Laboratory we have demonstrated a fully automated system that is capable of operations at any time of day over a horizontal range of several kilometers. This has proven the technology is capable of operation from a spacecraft to the ground, opening up the possibility of QKD between any group of users anywhere on Earth. This system, the prototyping of a new system for use on a spacecraft, and the techniques required for world-wide quantum key distribution will be described. The operational parameters and performance of a system designed to operate between low earth orbit (LEO) and the ground will also be discussed.
77 citations
TL;DR: In this article, a survey of laser transmission welding of polymers using high power diode lasers is presented, where the fundamental process strategies as well as decisive process parameters are illustrated, and the importance of optical, thermal and mechanical properties is discussed.
Abstract: Laser welding of polymers using high power diode lasers offers specific process advantages over conventional technologies, such as short process times while providing optically and qualitatively valuable weld seams, contactless yielding of the joining energy, absence of process induced vibrations, imposing minimal thermal stress and avoiding particle generation. Furthermore this method exhibits high integration capabilities and automatization potential. Moreover, because of the current favorable cost development within the high power diode laser market laser welding of polymers has become more and more an industrially accepted joining method. This novel technology permits both, reliable high quality joining of mechanically and electronically highly sensitive micro components and hermetic sealing of macro components. There are different welding strategies available, which are adaptable to the current application. Within the frame of this discourse scientific and also application oriented results concerning laser transmission welding of polymers using preferably diode lasers are presented. Besides the used laser systems the fundamental process strategies as well as decisive process parameters are illustrated. The importance of optical, thermal and mechanical properties is discussed. Applications at real technical components will be presented, demonstrating the industrial implementation capability and the advantages of a novel technology.
72 citations
TL;DR: Preliminary results are presented on the space-to- ground bi-directional link, including pointing acquisition and tracking (PAT) performance, received beam characterization and BER measurements, as well as new tracking algorithms at OGS control system in order to correct for ARTEMIS new orbit.
Abstract: ESA and the Instituto de Astrofisica de Canarias (IAC) reached an agreemenet for building the Optical Ground Station (OGS), in the IAC Teide Observatory, in order to perform In Orbit Testing (IOT) of Optical Data Relay payloads onboard communication satellites, the first being ARTEMIS During its recent launch, ARTEMIS was put into a degraded orbit due to a malfunction on the launcher's upper stage ESA rapidly adopted a recovery strategy aimed to take the satellite to its nominal geostationary position After completion of the first manoeuvres, ARTEMIS was successfully positioned in a circular parking orbit, at about 31,000 kilometers, and turned into full operation In this orbit, its optical payload has been tested with the OGS, before establishing the link with SPOT IV New tracking algorithms were developed at OGS control system in order to correct for ARTEMIS new orbit The OGS has established a bi-directional link to ARTEMIS, behaving, seen from ARTEMIS, as a LEO terminal Preliminary results are presented on the space-to- ground bi-directional link, including pointing acquisition and tracking (PAT) performance, received beam characterization and BER measurements
66 citations
TL;DR: In this article, surface coatings that minimize nonspecific binding while preserving the optical properties of the sensor are proposed. But they do not consider the non-specific binding of biomolecules on microfabricated glass surfaces.
Abstract: Optical sensing of biomolecules on microfabricated glass surface requires surface coatings that minimize nonspecific binding while preserving the optical properties of the sensor.
64 citations
TL;DR: In this paper, the authors used a rate equation model considering multiphoton ionization and avalanche ionization to numerically simulate the temporal evolution of the free electron density during the laser pulse for a given irradiance, and to calculate the irradiance dependence of free-electron density and volumetric energy density reached at the end of a laser pulse.
Abstract: The irradiance threshold for femtosecond optical breakdown in aqueous media is approximately equals 1.0x1013W cm-2. At the breakdown threshold, a plasma with a free electron density of about 1021cm-3 is generated, and the energy density in the breakdown region is sufficiently high to cause the formation of a bubble which can be experimentally observed. We found previously that plasmas with a free electron density <1021cm-3 are formed also in a fairly large irradiance range below the breakdown threshold. The present study investigates the chemical, thermal, and thermomechanical effects produced by these low-density plasmas. We use a rate equation model considering multiphoton ionization and produced by these low-density plasmas. We use a rate equation model considering multiphoton ionization and avalanche ionization to numerically simulate the temporal evolution of the free electron density during the laser pulse for a given irradiance, and to calculate the irradiance dependence of the free-electron density and volumetric energy density reached at the end of the laser pulse. The value of the energy density created by each laser pulse is then used to calculate the temperature distribution in the focal region after application of a single laser pulse and of series of pulses. The results of the temperature calculations yield, finally, the starting point for calculations of the thermoelastic stresses that are generated during the formation of the low-density plasmas. We found that, particularly for short wavelengths, a large 'tuning range' exists for the creation of spatially extremely confined chemical, thermal and mechanical effects via free electron generation through nonlinear absorption. Photochemical effects dominate at the lower end of this irradiance range, whereas at the upper end they are mixed with thermal effects and modified by thermoelastic stresses. Above the breakdown threshold, the spatial confinement is partly destroyed by cavitation bubble formation, and the laser-induced effects become more disruptive. Our simulations revealed that the highly localized ablation of intracellular structures and intranuclear chromosome dissection recently demonstrated by other researchers are probably mediated by free-electron- induced chemical bond breaking and not related to heating or thermoelastic stresses. We conclude that low density plasmas below the optical breakdown threshold can be a versatile tool for the manipulation of transparent biological media and other transparent materials. (enabling, e.g., the generation of optical waveguides in bulk glass). Low density plasmas may, however, also be a potential hazard in multiphoton microscopy and higher harmonic imaging.
53 citations
TL;DR: In this article, the scattering cross section due to rain is derived from the density of different raindrop sizes and the raindrops fall velocity is derived using the overall rainfall rate, and the temperature and relative humidity measurements are considered to effectively build the rain model.
Abstract: With recent advances and interest in Free-Space Optics (FSO) for commercial deployments, more attention has been placed on FSO weather effects and the availability of global weather databases. The Meteorological Visual Range (Visibility) is considered one of the main weather parameters necessary to estimate FSO attenuation due to haze, fog and low clouds. Proper understanding of visibility measurements conducted throughout the years is essential. Unfortunately, such information is missing from most of the databases, leaving FSO players no choice but to use the standard visibility equation based on 2% contrast and other assumptions on the source luminance and its background. Another challenge is that visibility is measured using the visual wavelength of 550 nm. Extrapolating the measured attenuations to longer infrared wavelengths is not trivial and involves extensive experimentations. Scattering of electromagnetic waves by spherical droplets of different sizes is considered to simulate FSO scattering effects. This paper serves as an introduction to a series of publications regarding simulation of FSO atmospheric propagation. This first part focuses on attenuation due to rainfall. Additional weather parameters, such as rainfall rate, temperature and relative humidity are considered to effectively build the rain model. Comparison with already published experimental measurement is performed to validate the model. The scattering cross section due to rain is derived from the density of different raindrop sizes and the raindrops fall velocity is derived from the overall rainfall rate. Absorption due the presence of water vapor is computed using the temperature and relative humidity measurements.
52 citations
TL;DR: In this article, the performance of a free-space optical (FSO) communication system is investigated when communication is established via a short-range, turbulent optical channel, and the system under investigation utilizes on-off-keying (OOK) modulation combined with direct-detection to establish a duplex communication link.
Abstract: The performance of a free-space optical (FSO) communication system is investigated when communication is established via a short-range, turbulent optical channel. The system under investigation utilizes on-off-keying (OOK) modulation combined with direct-detection to establish a duplex communication link. It is further assumed that the optical beam obeys a Gaussian profile. The received signal is detected using a p-i-n diode which is followed by a trans-impedance amplifier (TIA), limiting amplifier, and a clock/data recovery subsystem. Furthermore, it is assumed that optical front-end provides a relatively large aperture so that the impact of turbulence is somewhat mitigated and that the channel/system parameters result in a weak turbulent condition. The performance of the proposed system for a bit error rate of 10-9 in the absence of forward error correction (FEC) is assessed in terms of probability of fade (PF), average number of fades per second (FPS), mean fade duration (MFD), mean-guard-to-mean-burst (MGMB) ratio, and mean time between fades (MTBF).© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
46 citations
TL;DR: This work presents a method that relies on the use of pulsed Terahertz radiation to gain 3-dimensional information from teeth samples and makes use of TeraHertz Pulse Imaging (TPI) to provide depth information.
Abstract: Generating images of layered tissue structures can give valuable information to clinicians. However, the provision of accurate imaging of certain tissue structures, like teeth, in 3-dimensions is still a difficult problem. We present a method that relies on the use of pulsed Terahertz radiation to gain 3-dimensional information from teeth samples. The method makes use of Terahertz Pulse Imaging (TPI) to provide depth information. Example images are shown where structures in teeth at depth are rendered. We discuss issues that arise using this imaging method and propose ways in which it could be used in clinical practice.
42 citations
TL;DR: In this paper, the experimental consequences of two picosecond infrared lasers, both tuned to 6.45micrometers and focused on ocular tissue, were investigated, and it was shown that the Mark-III consistently ablates tissue, while the OPA fails to ablate or to damage corneal tissue.
Abstract: We have investigated the experimental consequences of two picosecond infrared lasers, both tuned to 6.45micrometers and focused on ocular tissue. The exposure conditions were comparable, other than pulse repetition rate, where an optical parametric oscillator/amplifier laser (OPA) system operates at a kilohertz and the Mark-III FEL at 3 gigahertz. In both cases, the peak intensity was near 2x1014 W/m2 and the total delivered energy was approximately 125 mJ. The Mark-III consistently ablates tissue, while the OPA fails to ablate or to damage corneal tissue. In particular, there is no experimental evidence for protein denaturation due to OPA irradiation. WE account for these observations in terms of a theoretical model based on thermal diffusion and threshold conditions for superheating and chemical kinetics. We comment on the relevance of tissue geometry.
42 citations
TL;DR: In this paper, the beam can be focused to less than.001 inch allowing localized joining of very small geometries, and the high quality of the laser welds and the precise process control enable hermetic sealing.
Abstract: New joining techniques are required for the variety of materials used in the manufacture of microsystems. Lasers are emerging as a useful tool for joining miniaturized devices. The beam can be focused to less than .001 inch allowing localized joining of very small geometries. There is minimal heat input into the part so distortion and change in material properties is minimal. The high quality of the laser welds and the precise process control enable hermetic sealing.
TL;DR: The very low mechanical side effects enables the use of fs- laser in otoralyngology to treat ocecular bones and the precise cutting quality can be used in fields of cardiovascular surgery for the treatment of arteriosklerosis as well as in dentistry to remove caries from dental hard tissue.
Abstract: Ultrafast lasers have become a promising tool for micromachining and extremely precise ablation of all kinds of materials. Due to the low energy threshold, thermal and mechanical side effects are limited to the bu micrometers range. The neglection of side effects enables the use of ultrashort laser pulses in a broad field of medical applications. Moreover, the interaction process based on nonlinear absorption offers the opportunity to process transparent tissue three dimensionally inside the bulk. We demonstrate the feasibility of surgical procedures in different fields of medical interest: in ophthalmology intrastromal cutting and preparing of cornael flaps for refractive surgery in living animals is presented. Besides, the very low mechanical side effects enables the use of fs- laser in otoralyngology to treat ocecular bones. Moreover, the precise cutting quality can be used in fields of cardiovascular surgery for the treatment of arteriosklerosis as well as in dentistry to remove caries from dental hard tissue.
TL;DR: In this article, an XeCl excimer, 1x amplitude mask pattern projection, scan-and-repeat system was utilized in the evaluation work of line groupings of line widths varying from 8 to 30 micrometers with line length of 44 mm.
Abstract: Excimer-based ablative patterning of Indium Tin Oxide (ITO) thin film on flexible substrates has been evaluated for large format display applications. In display package manufacturing, excimer-based ITO ablation can provide a great advantage over conventional photolithographic processing. It can eliminate many steps from the manufacturing cycle, resulting in significant cost reduction. Flexible substrate display packaging is desirable for at least two reasons. It allows roll-to-roll low cost, large volume manufacturing. Its low weight provides for an easy scale up to larger format displays. An XeCl excimer, 1x, amplitude mask pattern projection, scan-and-repeat system was utilized in the evaluation work. The mask pattern had line groupings of line-widths varying from 8 to 30 micrometers with line length of 44 mm. Lines from all the groupings were simultaneously ablated in 150 nm-thick ITO layer on a flexible 100 micrometers thick Polyethylene terephtalate (PET) substrate using scanning with optimized dwell duration of 10 pulses and optimized fluence level of 350 mJ/cm2. Lines ablated with mask line groupings of line-width greater than or equal to 11 micrometers showed complete electrical isolation indicating complete ITO removal. Scanning electron Microscopy (SEM) showed the presence of a slight curling effect at ablated line edges. The effect was studied as a function of wavelength and imaging resolution. A CO2 cleaning method was evaluated for removing the extruding curled material.
TL;DR: The Nautilus Project was started in 1995 as a joint US-Israel feasibility study for using laser systems to defend against short-range artillery rockets as mentioned in this paper, which has now matured into a successful laser weapon demonstration program - the Tactical High Energy Laser (THEL) Advanced Concept Technology Demonstration (ACTD) Program.
Abstract: The Nautilus Project was started in 1995 as a joint US-Israel feasibility study for using laser systems to defend against short-range artillery rockets. It has now matured into a successful laser weapon demonstration program - the Tactical High Energy Laser (THEL) Advanced Concept Technology Demonstration (ACTD) Program. By now the THEL Demonstrator has engaged and destroyed a large number of artillery rockets in mid-flight in an extended series of demonstration tests at the US Army's White Sands Missile Range in New Mexico. The THEL ACTD hardware and development process are described in this paper, as well as the major test results. The paper also describes the operational concept for a deployed THEL weapon system and some possible growth paths for the THEL ACTD Program.
TL;DR: In this article, the influence of near-IR transparent plastics on the yield strength of their weldments has been studied: various colored plastics transparent to diode laser radiation were tested as the welding material.
Abstract: This paper deals with a development of laser welding of colored plastics. Welding of thermoplastics using near-IR lasers has been seen in wide industrial application. Most of thermoplastics are transparent to near-IR laser. Particular characteristic of near-IR laser radiation has the ability to heat the interface between the transparent part and absorbent one colored with pigments. However, it is difficult to weld a pair of transparent materials by a laser beam, since there is no absorption region within them. In this paper, the influence of near-IR transparent plastics on the yield strength of their weldments has been studied: various colored plastics transparent to diode laser radiation were tested as the welding material. The heat transfer within a welding system was also analyzed and assessed the appropriate absorptivity and transmittance of overlapping colored plastic.
TL;DR: In this paper, a direct-write microfabrication process involves the formation of an initial latent image in the glass via UV laser radiation and thermal-induced ceramization is utilized to develop the latent image into a permanent image.
Abstract: Photostructurable glass-ceramic materials have received significant attention due to their utility in aerospace engineering and micro technology. For example, the ability to fabricate structures in glass is important in the design and integration of micro scale electronic, optical and fluidic devices. Direct-write pulsed UV laser processing techniques have been utilized recently to create patterned 3D microstructures in a lithium-aluminosilicate glass. The direct-write microfabrication process involves the formation of an initial latent image in the glass via UV laser radiation. Thermal-induced ceramization is utilized to develop the latent image into a permanent image. Material removal and microstructure fabrication are then accomplished by preferential isotropic etching of the developed regions.
TL;DR: In this article, a diode-pumped titanium:sapphire laser has been developed which matches the requirements of industrial systems, like compact dimensions and stable laser operation, for best process speed combined with optimal cutting quality, focus has been laid upon high repetition rates at moderate pulse energies.
Abstract: Within the research project FEMTO, supported by the European Commission, a compact diode-pumped titanium:sapphire laser has been developed which matches the requirements of industrial systems, like compact dimensions and stable laser operation. To achieve this, the laser has been specially designed to be integrated directly into the machining system. For best process speed combined with optimal cutting quality, focus has been laid upon high repetition rates at moderate pulse energies. Typical average output powers are around 1.5W and repetition rates of up to 5 kHz. Accompanying to the laser development, a micro-machining system has been designed to meet the requirements of femtosecond laser micro-machining. In parallel to the machine development, machining processes have been investigated and optimized for different applications. The machining of delicate medical implants has been demonstrated as well as the machining system for general micro-machining of sensitive and delicate materials has been proven. Therefore, the developed machine offers the potential to boost the use of femtosecond lasers in industrial operation.
TL;DR: The historical contributions at the McDonnell Douglas Research Laboratory, the Rocketdyne Division of Rockwell International and Boeing's Laser and Electro-Optic Systems organization are briefly described in this paper.
Abstract: The historical COIL contributions at the McDonnell Douglas Research Laboratory, the Rocketdyne Division of Rockwell International and Boeing's Laser and Electro-Optic Systems organization are briefly described. The latter organization now contains the capabilities of the two heritage organizations. Boeing's new high pressure sealed COIL is also described.
TL;DR: The error budget required to achieving the 5 nrad rms jitter stabilization performance projected to be necessary for an operational Space Based Laser system is presented and a conceptual design for the HP-IPSRU is presented.
Abstract: Space based defense systems, such as a Space Based Laser (SBL), and space based surveillance systems share a common objective: extremely high resolution Line of Sight (LOS) target imaging. In order to achieve the mission objectives, their beam control subsystem must provide precise LOS pointing and tracking capabilities with suppression of LOS jitter. Draper Laboratory has developed concepts and instrumentation that address these needs based upon a stabilized inertial platform mechanization that holds a collimated light source, called the Inertial Pseudo Star Reference Unit (IPSRU). This paper describes the original IPSRU design and a design concept for a new High Performance version of the IPSRU system (HP-IPSRU) that meet the jitter stabilization needs of the SBL. The IPSRU provides an inertially stabilized optical probe beam that provides a precise pointing and tracking reference with nanoradian jitter performance. The IPSRU serves as a master reference for stabilizing imaging and weapon system pointing and tracking. This paper describes the IPSRU system, its measured error allocation and integrated performance. It presents the error budget required to achieving the 5 nrad rms jitter stabilization performance projected to be necessary for an operational Space Based Laser system. A conceptual design for the HP-IPSRU is presented.
TL;DR: The F2-laser nano fabrication facility at the University of Toronto delivers high-fluence 157-nm radiation at high resolution to micro fabricate highfinesse silica-based optical components.
Abstract: The F2-laser Nano fabrication Facility at the University of Toronto delivers high-fluence 157-nm radiation at high resolution to micro fabricate high-finesse silica-based optical components. The 7.9-eV photons drive strong material interactions near the band-edge states of fused silica and related glasses that help avoid microcrack formation, a common limitation of longer wavelength laser. The strong interactions provide for small and smooth excisions, offering depth control on a scale of tens of nanometers. A 157-nm beam homogenization system and a 25x Schwarzschild lens provided a uniform on-target fluence of 9 J/cm2 in a 0.25 mm by 0.25 mm field. Larger work are was enabled by synchronously driving the projection mask and target motion stages. The 0.4 NA lens supported the formation of high- aspect channel walls and surface-relief features as small as approximately 500 nm. Both mask projection and direct writing technique were employed. The novel aspects of the optical beam delivery system are presented together with results on fabricating micro-channels, cutting optical fiber, fabricating surface relief grating and cylindrical lens. The results demonstrate broad application directions for fabricating telecommunication devices, general optical and photonic components, and biological devices.
TL;DR: A pulsed UV laser volumetric direct-write patterning technique has been used to fabricate the structural members and key fluidic distribution systems of a miniature 100 gm mass spacecraft called the Co-Orbital Satellite Assistant (COSA).
Abstract: A pulsed UV laser volumetric direct-write patterning technique has been used to fabricate the structural members and key fluidic distribution systems of a miniature 100 gm mass spacecraft called the Co-Orbital Satellite Assistant (COSA). A photostructurable glass ceramic material enables this photo-fabrication process. The COSA is a miniature space vehicle designed to assist its host ship by serving as a maneuverable external viewing platform. Using orbital dynamics simulation software, a minimum (Delta) V solution has been found that allows a COSA vehicle to eject from the host and maneuver into an observation orbit about the host vehicle. The result of the simulant show that a cold gas propulsion system can adequately support the mission given a total fuel volume of 5 cm 3 . A prototype COSA with dimensions of 50 X 50 X 50 mm has been fabricated and assembled for simulation experiments on an air table. The vehicle is fashioned out of 7 laser patterned wafers, electronics boards and a battery. The patterned wafers include an integrated 2-axis propulsion system, a fuel tank and a propellant distribution system. The electronics portion of the COSA vehicle includes a wireless communication system, 2 microcontrollers for system, 2 microcontrollers for system control and MEMS gyros for relative attitude determination. The COSA vehicle is designed to be mass producible and scalable.
TL;DR: In this paper, a matrix assisted pulsed laser evaporation direct-write (MAPLE DW) was used to rapidly prototype temperature, biological and chemical sensor devices, which is compatible with a broad class of materials ranging from metals and electronic ceramics to chemoselective polymers and biom materials.
Abstract: The use of direct-write techniques in the design and manufacture of sensor devices provides a flexible approach for next generation commercial and defense sensor applications. Using a laser forward transfer technique, we have demonstrated the ability to rapidly prototype temperature, biological and chemical sensor devices. This process, known as matrix assisted pulsed laser evaporation direct-write or MAPLE DW is compatible with a broad class of materials ranging from metals and electronic ceramics to chemoselective polymers and biomaterials. Various types of miniature sensor designs have been fabricated incorporating different materials such as metals, polymers, biomaterials or composites as multilayers or discrete structures on a single substrate. The MAPLE DW process is computer controlled which allows the sensor design to be easily modified and adapted to any specific application. To illustrate the potential of this technique, a functional chemical sensor system is demonstrated by fabricating all the passive and sensor components by MAPLE DW on a polyimide substrate. Additional devices fabricated by MAPLE DW including biosensors and temperature sensors and their performance are shown to illustrate the breadth of MAPLE DW and how this technique may influence current and future sensor applications.
TL;DR: In this article, the authors present concept and scaling considerations for a solid-state laser with a gain medium disk operating in the active mirror mode, where the disk is of composite construction formed by bonding undoped optical medium to the peripheral edges of the gain medium.
Abstract: This work presents concept and scaling considerations for a solid-state laser with a gain medium disk operating in the active mirror mode. The disk is of composite construction formed by bonding undoped optical medium to the peripheral edges of a gain medium disk. Pump diode arrays are placed around the perimeter of the composite disk and pump light is injected into the undoped edge. With proper choice of lasant doping, diode placement and diode divergence, a uniform laser gain can be achieved across large portions of the disk. To mitigate thermal deformations, the gain medium disk is pressure-clamped to a rigid, cooled substrate. Effective reduction of thermo-optical distortions makes this laser suitable for operation at high-average power.
TL;DR: In this article, the fundamental performance limits and channel capacity of optical communications systems operating over the free space channel were examined using quantum detection theory, and the quantum detection model was applied to analyze the performance of optical communication systems.
Abstract: The fundamental performance limits and channel capacity of optical communications systems operating over the free space channel will be examined using quantum detection theory.
TL;DR: In this paper, a single and multi-mode waveguide with damping losses well below 1 dB/cm in fused silica is presented. But the waveguiding is observed in a stress-induced region surrounding the irradiated, amorphous area.
Abstract: Using tightly focused femtosecond laser pulses waveguides are fabricated inside glasses and crystalline materials. The guiding and attenuation properties at different wavelengths as well as the micro morphology of the irradiated samples are studied. We demonstrate the fabrication of single- and multi-mode waveguides with damping losses well below 1 dB/cm in fused silica. In crystalline quartz we found that the irradiated area has become amorphous due to the absorption of the laser radiation. In this case waveguiding is observed in a stress-induced region surrounding the irradiated, amorphous area.
TL;DR: In this paper, the site location chosen for a telescope used for optical communications must rely on knowledge of weather and cloud cover statistics for the geographical area where the telescope itself is located.
Abstract: Cloud opacity is one of the main atmospheric physical phenomena that can jeopardize the successful completion of an optical link between a spacecraft and a ground station. Hence, the site location chosen for a telescope used for optical communications must rely on knowledge of weather and cloud cover statistics for the geographical area where the telescope itself is located.
TL;DR: The European Space Agency (ESA) and the Instituto de Astrofisica de Canarias (IAC) reached an agreement for the building of the Optical Ground Station (OGS) in the IAC Teide Observatory, which consists of a 1-meter telescope and the suitable instrumentation for establishing and testing bi-directional optical links with satellites.
Abstract: The European Space Agency (ESA) has undertaken the development of Optical Data Relay payloads, aimed at establishing free space optical communication links between satellites. The first of such systems put into orbit is the SILEX project, in which an experimental link between a GEO satellite (ARTEMIS) and a LEO satellite (SPOT IV) will be used to relay earth observation data. In order to perform In Orbit Testing (IOT) of these and future optical communications systems, ESA and the Instituto de Astrofisica de Canarias (IAC) reached an agreement for the building of the Optical Ground Station (OGS) in the IAC Teide Observatory, which consists basically of a 1-meter telescope and the suitable instrumentation for establishing and testing bi-directional optical links with satellites. The presence of the atmosphere in the data path posses particular problems, with an impact on the instrumentation design. The transmission, reception and measurement functions, along with the overall control of the instruments, are performed at OGS by the Focal Plane Control Electronics (FPCE). The design and performance of this instrumentation is presented, emphasizing the Pointing, Acquisition and Tracking, the Tuneable Laser and the Master Control.
TL;DR: In this article, an optical ground-to-ground direct-detection transmission experiment over 61km is performed by the German Aerospace Center (DLR) in cooperation with the European Aeronautic Defence and Space Company (EADS) and Contraves Space AG, Switzerland.
Abstract: An optical ground-to-ground direct-detection transmission experiment over 61km is being performed by the German Aerospace Center (DLR) in cooperation with the European Aeronautic Defence and Space Company (EADS) and Contraves Space AG, Switzerland. Transmission direction is from the mountain Wallberg in the German Alps down to Oberpfaffenhofen (west of Munich). This beam path suffers strongly from optical turbulence especially at the near-ground part along the last kilometers before the receiver. This causes a very demanding situation regarding received-power scintillations. Transmit power from one data source is 1W at 980nm. Of special interest is the effect of secondary transmitter apertures with 4m lateral offset to the first. Under strong turbulence conditions this provides statistically independent speckle patterns at the receiver thus improving system performance dramatically. This paper presents measurements at the transmission channel, with emphasise on statistical parameters of the scintillations and angle-of-arrival variations with one and two transmitter sources.
TL;DR: In this paper, a diode was used as the Q-switch generator for a 2μm Tm:YAG laser operating in a pulsed mode, with an RTP Pockels cell as the generator.
Abstract: We report a diode pumped 2μm Tm:YAG laser operating in a pulsed mode, with an RTP Pockels cell as the Q-switch generator. A maximum output of 2.4mJ with a pulse width of 57ns was achieved. The crystal was pumped with an input energy of 85mJ at a rate of 20Hz. To the best of our knowledge, this is the first time that RTP was used as the Q-switch generator in a 2μm laser resonator.
TL;DR: In this paper, the authors describe a high energy laser (HEL) concept based on a disk-type solid-state laser operating in active mirror mode, which shows excellent scalability to high average power required for directed energy applications and can be integrated into a simple, compact, lightweight, and affordable unit.
Abstract: This paper describes a high-energy laser (HEL) concept based on a disk-type solid-state laser operating in active mirror mode. The gain medium disks have high-performance real-time cooling that allows the laser to operate continuously. This configuration of the laser shows excellent scalability to high-average power required for directed energy applications and can be integrated into a simple, compact, lightweight, and affordable unit. The paper also discusses engineering concepts for integrated HEL, power-size-weight scaling model, as well as options for prime power and thermal management.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.