High pulse energy near-infrared ultrafast optical parametric oscillators

A source-demand in the near- and mid-IR wavelength spectrum exists for various applications such as waveguide inscription, multiphoton imaging, and nonlinear spectroscopy. All of the applications seek for higher repetitions rates for faster processing speed, better signal to noise ratios or to improve the results for applications like laser waveguide inscription. This is in contrast to the high pulse energies, required to drive the nonlinear processes involved with these applications. Available systems are either based on low-energy, high-repetition-rate optical parametric oscillators or high-energy, low-repetition-rate optical parametric amplifiers. In this thesis a sources was developed that can bridge the wide gap between these two extremes, providing sufficient energy to drive nonlinear processes, with repetition rates in the MHz domain. This was achieved by introducing three techniques previously employed for energy scaling in laser cavities. Firstly an exchange from the conventionally used Ti:sapphire pump to a commercial high power Yb:fibre laser system readily scaled the usable pump energy. This was combined with a technique known as cavity-length extension, which allows a lowering of the cavity roundtrip time offering the build-up of pulses with increased energy. In a final stage, cavity-dumping on basis of an acousto-optic modulator was introduced into the a redesigned cavity. The combination of these three techniques, novel to synchronously pumped optical parametric oscillators, enabled the extraction of record-high pulse energies and peak power

Exploration of a Polarized Surface Bidirectional Reflectance Model Using the Ground-Based Multiangle Spectropolarimetric Imager

Accurate characterization of surface reflection is essential for retrieval of aerosols using downward-looking remote sensors. In this paper, observations from the Ground-based Multiangle SpectroPolarimetric Imager (GroundMSPI) are used to evaluate a surface polarized bidirectional reflectance distribution function (PBRDF) model. GroundMSPI is an eight-band spectropolarimetric camera mounted on a rotating gimbal to acquire pushbroom imagery of outdoor landscapes. The camera uses a very accurate photoelastic-modulator-based polarimetric imaging technique to acquire Stokes vector measurements in three of the instrument's bands (470, 660, and 865 nm). A description of the instrument is presented, and observations of selected targets within a scene acquired on 6 January 2010 are analyzed. Data collected during the course of the day as the Sun moved across the sky provided a range of illumination geometries that facilitated evaluation of the surface model, which is comprised of a volumetric reflection term represented by the modified Rahman-Pinty-Verstraete function plus a specular reflection term generated by a randomly oriented array of Fresnel-reflecting microfacets. While the model is fairly successful in predicting the polarized reflection from two grass targets in the scene, it does a poorer job for two manmade targets (a parking lot and a truck roof), possibly due to their greater degree of geometric organization. Several empirical adjustments to the model are explored and lead to improved fits to the data. For all targets, the data support the notion of spectral invariance in the angular shape of the unpolarized and polarized surface reflection. As noted by others, this behavior provides valuable constraints on the aerosol retrieval problem, and highlights the importance of multiangle observations.NASAJPLCenter for Space Researc

Stabilized lasers for advanced gravitational wave detectors

Second-generation interferometric gravitational wave detectors require high-power lasers with approximately 200 W of output power in a linear polarized, single-frequency, fundamental-mode laser beam. Furthermore very high temporal and spatial stability is required. This paper discusses the design of a 200 W pre-stabilized laser (PSL) system and the underlying concepts. The PSL requirements for advanced gravitational wave detectors as well as for the laser system are described. The laser stabilization scheme proposed for the Advanced LIGO gravitational wave detector and the so-called diagnostic breadboard will serve as examples to explain the general laser stabilization concepts and the achieved performance and its limitations

High-Performance On-Chip Microwave Photonic Signal Processing Using Linear and Nonlinear Optics

Manipulating and processing radio-frequency (RF) signals using integrated photonic devices has recently emerged as a paradigm-shifting technology for future microwave applications. This emerging technique is referred to as integrated microwave photonics (IMWP) which enables the high-frequency processing and unprecedentedly wideband tunability in compact photonic circuits, with significantly enhanced stability and robustness. However, to find widespread applications, the performance of IMWP devices must meet or exceed the achievable performance of conventional electronic counterparts. The work presented in this thesis investigates high-performance IMWP signal processing from two aspects: the optimized IMWP processing schemes and the photonic integration. Firstly, we explore novel schemes to improve the performance of chip-based microwave photonic subsystems, such as RF delay lines and RF filters which are basic building blocks of RF systems. A phase amplification technique is demonstrated to achieve a Si3N4 chip-based RF time delay with a delay tuning speed at gigahertz level. A new scheme to achieve an all-optimized RF photonic notch filter is demonstrated, producing a record-high RF link performance and complete functionalities. To unlock the potential of RF signal processing, we investigate a new filter concept of pairing linear and nonlinear optics for a high-performance RF photonic filter. To reduce the footprint of the novel IMWP filter, the photonic integration of both the ring resonators and Brillouin-active circuits on the same photonic chip is achieved. To eliminate the use of integrated optical circulators for on-chip SBS, on-chip backward inter-modal stimulated Brillouin scattering is predicted and experimentally demonstrated in a Si-Chalcogenide hybrid integrated photonic platform. The study and demonstrations presented in this thesis make the first viable step towards high-performance IMWP signal processing for real-world RF applications

A remodulation scheme for wavelength-division multiplexing passive optical network using time-interleaved differential phase shift keying modulation format.

Li, Pulan.Thesis (M.Phil.)--Chinese University of Hong Kong, 2011.Includes bibliographical references (p. 60-66).Abstracts in English and Chinese.Chapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Overview of wavelength division multiplexed passive optical network (WDM-PON) and colorless optical network unit (ONU) --- p.1Chapter 1.2 --- Implementation of colorless ONU --- p.4Chapter 1.3 --- Rayleigh backscattering in WDM-PON --- p.6Chapter 1.4 --- Motivation of this thesis --- p.9Chapter 1.5 --- Outline of this thesis --- p.11Chapter Chapter 2 --- Previous works of remodulation for WDM-PON --- p.12Chapter 2.1 --- Introduction --- p.12Chapter 2.2 --- Devices utilized by colorless ONU in remodulation schemes --- p.13Chapter 2.2.1 --- Injection-locked Fabry-Perot laser diode at ONU --- p.13Chapter 2.2.2 --- Reflective semiconductor optical amplifier --- p.15Chapter 2.2.3 --- Reflective electro-absorption modulator and semiconductor optical amplifier (REAM-SOA) --- p.17Chapter 2.3 --- Modulation methods in remodulation schemes --- p.18Chapter 2.4 --- Summary --- p.23Chapter Chapter 3 --- A remodulation scheme based on time-interleaved DPSK modulation format --- p.25Chapter 3.1 --- Introduction --- p.25Chapter 3.2 --- Operation principle: time-interleaving technology for phase-modulated signal --- p.27Chapter 3.3 --- System architecture --- p.28Chapter 3.4 --- Experimental results and discussion --- p.31Chapter 3.5 --- Effect of timing misalignment on proposed remodulation scheme --- p.33Chapter 3.6 --- Summary --- p.35Chapter Chapter 4 --- Enhanced Tolerance to Rayleigh Backscattering in Remodulation Scheme Using Time-Interleaved DPSK Format --- p.37Chapter 4.1 --- Introduction --- p.37Chapter 4.2 --- Studies on Rayleigh backscattering suppression in optical domain --- p.39Chapter 4.2.1 --- RB suppression in carrier-distributed schemes --- p.39Chapter 4.2.2 --- RB suppression in remodulation schemes --- p.40Chapter 4.2 --- Experimental setup and results --- p.42Chapter 4.3 --- Discussion on RB suppression effect of the proposed scheme --- p.46Chapter 4.3.1 --- Theoretical study and simulation results --- p.46Chapter 4.3.2 --- Experimental demonstration of spectral relationship between signals and RB crosstalk --- p.49Chapter 4.4 --- Summary --- p.53Chapter Chapter 5 --- Conclusion and Future Works --- p.55Chapter 5.1 --- Conclusion of this thesis --- p.55Chapter 5.2 --- Future works --- p.57List of Publications --- p.59Bibliography --- p.6

Cumulative index to NASA Tech Briefs, 1963-1965

Annotated bibliography of NASA technical briefs on electrical, energy sources, materials, life sciences, and mechanical informatio