Satellite laser ranging work at the Goddard Space Flight Center

Laser ranging systems, their range and accuracy capabilities, and planned improvements for future systems are discussed, the systems include one fixed and two mobile lasers ranging systems. They have demonstrated better than 10 cm accuracy both on a carefully surveyed ground range and in regular satellite ranging operations. They are capable of ranging to all currently launched retroreflector equipped satellites with the exception of Timation III. A third mobile system is discussed which will be accurate to better than 5 cm and will be capable of ranging to distant satellites such as Timation III and LAGEOS

Laser Micromachining: An Enabling Technology for Functional Surfaces and Materials

L'abstract è presente nell'allegato / the abstract is in the attachmen

All-semiconductor High Power Mode-locked Laser System

All-optical synchronization and its application in advanced optical communications have been investigated in this dissertation. Dynamics of all-optical timing synchronization (clock recovery) using multi-section gain-coupled distributed-feedback (MS-GC DFB) lasers are discussed. A record speed of 180-GHz timing synchronization has been demonstrated using this device. An all-optical carrier synchronization (phase and polarization recovery) scheme from PSK (phase shift keying) data is proposed and demonstrated for the first time. As an application of all-optical synchronization, the characterization of advanced modulation formats using a linear optical sampling technique was studied. The full characterization of 10-Gb/s RZ-BPSK (return-to-zero binary PSK) data has been demonstrated. Fast lockup and walk-off of the all-optical timing synchronization process on the order of nanoseconds were measured in both simulation and experiment. Phase stability of the recovered clock from a pseudo-random bit sequence signal can be achieved by limiting the detuning between the frequency of free-running self-pulsation and the input bit rate. The simulation results show that all-optical clock recovery using TS-DFB lasers can maintain a better than 5 % clock phase stability for large variations in power, bit rate and optical carrier frequency of the input data and therefore is suitable for applications in ultrafast optical packet switching. All-optical timing synchronization of 180-Gb/s data streams has been demonstrated using a MS-GC DFB laser. The recovered clock has a jitter of less than 410 fs over a dynamic range of 7 dB. All-optical carrier synchronization from phase modulated data utilizes a phase sensitive oscillator (PSO), which used a phase sensitive amplifier (PSA) as a gain block. Furthermore, all-optical carrier synchronization from 10-Gb/s BPSK data was demonstrated in experiment. The PSA is configured as a nonlinear optical loop mirror (NOLM). A discrete linear system analysis was carried out to understand the stability of the PSO. Complex envelope measurement using coherent linear optical sampling with mode-locked sources is investigated. It is shown that reliable measurement of the phase requires that one of the optical modes of the sampling pulses be locked to the optical carrier of the data signal to be measured. Carrier-envelope offset (CEO) is found to have a negligible effect on the measurement. Measurement errors of the intensity profile and phase depend on the pulsewidth and chirp of the sampling pulses as well as the detuning between the carrier frequencies of the data signal and the center frequency of the sampling source. Characterization of the 10-Gb/s RZ-BPSK signal was demonstrated using the coherent detection technique. Measurements of the optical intensity profile, chirp and constellation diagram were demonstrated. A CW local oscillator was used and electrical sampling was performed using a sampling scope. A novel feedback scheme was used to stabilize homodyne detection

Nanosecond Peak Detect And Hold Circuit With Adjustable Dynamic Range

This article presents a novel peak detect and hold (PDH) circuit for the measurement of the peak voltage of electromagnetic-field probes. These probes are used to capture the fields generated by electrostatic discharge (ESD) events in nongrounded portable devices. Therefore, a circuit combining small size, low power consumption, and nanosecond operation is needed. A topology using a discrete bipolar transistor structure with operational transconductance amplifier (OTA) and common-base storage capacitor charge control optimally meets the requirements. The circuit performance is demonstrated for different bias point settings. The error between the captured value and the actual pulse peak value is shown as a function of rise time, pulse length, amplitude, and bias settings. A comparison with the literature shows unmatched performance with respect to speed and power consumption. Using the bias settings, the PDH circuit can be adjusted to the sensor\u27s frequency response to minimize power consumption in a multichannel system containing sensors of different bandwidths

Broadband Setup for Magnetic-Field-Induced Domain Wall Motion in Cylindrical Nanowires

In order to improve the precision of domain wall dynamics measurements, we develop a coplanar waveguide-based setup where the domain wall motion should be triggered by pulses of magnetic field. The latter are produced by the Oersted field of the waveguide as a current pulse travels toward its termination, where it is dissipated. Our objective is to eliminate a source of bias in domain wall speed estimation while optimizing the field amplitude. Here, we present implementations of this concept for magnetic force microscopy (MFM) and synchrotron-based investigation

Nonlinear optical properties of novel nanostructured ion implanted laser ablated silicon using femtosecond pulse excitation

The study of the nonlinear optical properties of novel nanostructured ion implanted and laser ablation of Silicon is motivated by the need for materials that exhibit large values of the real part of the third order nonlinear susceptibility (χ(3)Re). This property is essential for light controlled phase or refractive index modulation at low power, where the optical properties are used for optical switching devices. Previous nanosecond (ns) measurements indicated values of-2.8 x 10 -5; esu ( γ = 532 nm) for χ(3)Re. The characterization of nonlinear optical properties of the samples was studied by the Z-scan techniques using ~ 100 fs pulses. The Z-scan technique is a relatively simple and direct measurement of both the real and imaginary part of χ(3), where the nonlinear refractive index (n 2) is related to χ(3)Re and the nonlinear absorption ( β ) to χ(3) Im Femtosecond pulse excitation measurements were performed to study ultrafast dynamics by inducing nonlinear optical changes, such as photo-induced absorption and measuring the nonlinear response. For fast optical switching applications, a fast and relatively large electronic nonlinearity is required

Optics and Quantum Electronics

Contains table of contents for Section 2 and reports on twenty research projects.Charles S. Draper Laboratory Contract DL-H-404179Joint Services Electronics Program Contract DAALO3-89-C-0001National Sciences Foundation Grant EET 87-00474National Science Foundation Grant EET 88-15834U.S. Air Force - Office of Scientific Research Contract F49620-88-C-0089National Science Foundation Grant ECS 85-52701International Business Machines CorporationMassachusetts General Hospital Contract N00014-86K-0117National Institutes of Health Grant 2-RO1-GM35459U.S. Department of Energy Grant DE-FG02-89-ER14012Lawrence Livermore National Laboratory Subcontract B04870

Femtosecond pulsed laser ablation and patterning of 3C-SiC films on Si substrates for MEMS fabrication

Femtosecond pulsed laser (FPL) micromachining is a direct-writing technique in which an ultrashort pulse laser beam is focused to dimensions of a few microns inside or on the surface of the substrate and then moved around using a X-Y positioning table, thereby creating either features or patterns as required. It outperforms conventional micromachining technologies due to advantages such as precise resolution, minimal thermal or shock damage, and absence of discrimination among materials. 3C-SiC is a very important semiconductor in electronics and opto-electronics and more recently regarded as an optimal candidate for structural or coating applications in microelectromechanical systems (MEMS) used under harsh and high-temperature environments. However, it is a very difficult material to be machined or etched by mechanical or chemical methods.;In this work, fundamental studies on the interaction of femtosecond pulsed beam with 3C-SiC films were performed. The influence of laser parameters such as pulsed energy on the ablation and calculations of damage thresholds and ablation rates were determined. Based on these results, MEMS structures including micromotors, microturbine rotors, and lateral resonators were patterned with good quality and repeatability. Research demonstrates that FPL micromachining is capable of offering a unique solution to overcome the traditional barriers in SiC machining method, opening up opportunities for SiC materials to be used in industrial environment.;As a spinoff of femtosecond pulse micromachining, nanostructuring of 3C-SiC films on Si was observed. Nanoparticle surfaces were further studied in terms of formation conditions and characterizations of crystal structure and related properties. Incubation effects were identified and Coulomb explosion mechanism was proposed to be responsible for the generation of nanoparticles.;Results of research enhance our current understanding of ultrashort pulse-matter interactions and offer potential applications for SiC-MEMS