High-power lasers and applications 

About: High-power lasers and applications is an academic journal. The journal publishes majorly in the area(s): Laser & Semiconductor laser theory. Over the lifetime, 2120 publications have been published receiving 10673 citations.

In-orbit test result of an operational optical intersatellite link between ARTEMIS and SPOT4, SILEX

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.

Narrow-gap semiconductor photodiodes

Abstract: At present efforts in IR detector research are directed towards improving the performance of single element devices and large electronically scanned arrays, and to obtain higher operating temperature of detectors. Another important aim is to make IR detectors cheaper and more convenient to use. Investigations of the performance of narrow gap semiconductor photodiodes are presented. Recent progress in different IR photodiode technologies is discussed: HgCdTe photodiodes, InSb photodiodes, alternative to HgCdTe III-V and II-VI ternary alloy photodiodes, and monolithic lead chalcogenide photodiodes. Investigations of the performance of photodiodes operated at short wavelength IR, 1-3 $mUm; medium wavelength IR, 3-5 micrometers ; and long wavelength IR, 8- 14 micrometers ; are presented. The operating temperature for HgCdTe detectors is higher than for other types of photon detectors. HgCdTe detectors with background limited performance operate with thermoelectric coolers in the medium wavelength range, instead the long wavelength detectors operate at approximately equals 100 K. HgCdTe is characterized by high absorption coefficient and quantum efficiency and relatively low thermal generation rate compared to other detectors.

Present and future free-space quantum key distribution

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.

Laser welding of polymers using high-power diode lasers

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.

The National Ignition Facility: the world's largest optics and laser system

Abstract: The National Ignition Facility, a center for the study of high energy density plasma physics and fusion energy ignition, is currently under construction at the Lawrence Livermore National Laboratory. The heart of the NIF is a frequency tripled, flashlamp-pumped Nd:glass laser system comprised of 192 independent laser beams. The laser system is capable of gen-erating output energies of 1.8MJ at 351nm and at peak powers of 500 TW in a flexible temporal pulse format. A descrip-tion of the NIF laser system and its major components is presented. We also discuss the manufacture of nearly 7500 pre-cision large optics required by the NIF including data on the manufactured optical quality vs. specification. In addition, we present results from an on-going program to improve the operational lifetime of optics exposed to high fluence in the 351-nm section of the laser.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.