The procurement and evaluation of a prototype laser satellite-tracking system Final report, 1 Jan. 1967 - 30 Sep. 1968

Pulsed ruby laser satellite tracking syste

Laser satellite-tracking system Progress report, 1 Feb. - 1 Jul. 1968

Description and test evaluation of prototype laser satellite tracking syste

A novel laser ranging system for measurement of ground-to-satellite distances

A technique was developed for improving the precision of laser ranging measurements of ground-to-satellite distances. The method employs a mode-locked laser transmitter and utilizes an image converter tube equipped with deflection plates in measuring the time of flight of the laser pulse to a distant retroreflector and back. Samples of the outgoing and returning light pulses are focussed on the photocathode of the image converter tube, whose deflection plates are driven by a high-voltage 120 MHz sine wave derived from a very stable oscillator. From the relative positions of the images produced at the output phosphor by the two light pulses, it is possible to make a precise determination of the fractional amount by which the time of flight exceeds some large integral multiple of the period of the deflection sinusoid

Diode-pumped laser altimeter

TEM(sub 00)-mode output energies up to 22.5 mJ with 23 percent slope efficiencies were generated at 1.064 microns in a diode-laser pumped Nd:YAG laser using a transverse-pumping geometry. 1.32-micron performance was equally impressive at 10.2 mJ output energy with 15 percent slope efficiency. The same pumping geometry was successfully carried forward to several complex Q-switched laser resonator designs with no noticeable degradation of beam quality. Output beam profiles were consistently shown to have greater than 90 percent correlation with the ideal TEM(sub 00)-order Gaussian profile. A comparison study on pulse-reflection-mode (PRM), pulse-transmission-mode (PTM), and passive Q-switching techniques was undertaken. The PRM Q-switched laser generated 8.3 mJ pulses with durations as short as 10 ns. The PTM Q-switch laser generated 5 mJ pulses with durations as short as 5 ns. The passively Q-switched laser generated 5 mJ pulses with durations as short as 2.4 ns. Frequency doubling of both 1.064 microns and 1.32 microns with conversion efficiencies of 56 percent in lithium triborate and 10 percent in rubidium titanyl arsenate, respectively, was shown. Sum-frequency generation of the 1.064 microns and 1.32 microns radiations was demonstrated in KTP to generate 1.1 mJ of 0.589 micron output with 11.5 percent conversion efficiency

Investigation of photoelectrons from molecules in a strong field

When intense and few-cycle laser pulses interact with an atomic/molecular beam highorder Above Threshold Ionisation (HATI) can take place. The resulting electrons can be re-scattered from the parent atoms/molecules and gain kinetic energy. The HATI electrons contain information about the atomic/molecular structure thus providing a method to probe atomic and molecular dynamics with sub-fs temporal and sub-angström spatial resolution. In this thesis the development of a Velocity Map Imaging apparatus capable of measuring the two-dimensional (2D) projection of the velocity distribution of electrons with energies up to 400 eV is described. This device was implemented with a molecular beam apparatus to study the electron re-scattering process that occurs when atoms/molecules are subjected to strong laser fields. Time-of-fight measurements were carried out to find the molecular beam. To perform the experiments a method to generate intense and few-cycle pulses based on hollow fibre pulse compression has been implemented. Pulses of 14 fs with energies of 500 μJ have been measured in a differentially pumped fibre set-up, with input pulses of 42 fs and 700 μJ using a home-made Frequency-Resolved Optical Gating device. The performance of the VMI apparatus was investigated by first studying the ATI rings formed by low energy electrons. Then, a study of the high energy electrons was carried out in different gases and re-scattered electrons with energies up to 100 eV were measured. The photoelectron spectra recorded with linearly polarised laser exhibit a plateau with a cut-off at 10 UP that is a characteristic of the re-scattering process. The observation of rescattered electrons was confirmed by two techniques: comparison of the data obtained with vertical polarisation (re-scattering) and circular polarisation (no re-scattering) and analysis of the structure in the angular distribution obtained in Xenon

Delayed-choice gedanken experiments and their realizations

The wave-particle duality dates back to Einstein's explanation of the photoelectric effect through quanta of light and de Broglie's hypothesis of matter waves. Quantum mechanics uses an abstract description for the behavior of physical systems such as photons, electrons, or atoms. Whether quantum predictions for single systems in an interferometric experiment allow an intuitive understanding in terms of the particle or wave picture, depends on the specific configuration which is being used. In principle, this leaves open the possibility that quantum systems always either behave definitely as a particle or definitely as a wave in every experimental run by a priori adapting to the specific experimental situation. This is precisely what is tried to be excluded by delayed-choice experiments, in which the observer chooses to reveal the particle or wave character -- or even a continuous transformation between the two -- of a quantum system at a late stage of the experiment. We review the history of delayed-choice gedanken experiments, which can be traced back to the early days of quantum mechanics. Then we discuss their experimental realizations, in particular Wheeler's delayed choice in interferometric setups as well as delayed-choice quantum erasure and entanglement swapping. The latter is particularly interesting, because it elevates the wave-particle duality of a single quantum system to an entanglement-separability duality of multiple systems

ARGOS: the laser guide star system for the LBT

ARGOS is the Laser Guide Star adaptive optics system for the Large Binocular Telescope. Aiming for a wide field adaptive optics correction, ARGOS will equip both sides of LBT with a multi laser beacon system and corresponding wavefront sensors, driving LBT's adaptive secondary mirrors. Utilizing high power pulsed green lasers the artificial beacons are generated via Rayleigh scattering in earth's atmosphere. ARGOS will project a set of three guide stars above each of LBT's mirrors in a wide constellation. The returning scattered light, sensitive particular to the turbulence close to ground, is detected in a gated wavefront sensor system. Measuring and correcting the ground layers of the optical distortions enables ARGOS to achieve a correction over a very wide field of view. Taking advantage of this wide field correction, the science that can be done with the multi object spectrographs LUCIFER will be boosted by higher spatial resolution and strongly enhanced flux for spectroscopy. Apart from the wide field correction ARGOS delivers in its ground layer mode, we foresee a diffraction limited operation with a hybrid Sodium laser Rayleigh beacon combination.12 page(s