We review various photonics applications of whispering gallery mode (WGM) dielectric resonators and focus on the capability of generating trains of short optical pulses using WGM lithium niobate cavities. We introduce schemes of optical frequency comb generators, actively mode-locked lasers, and coupled opto-electronic oscillators where WGM cavities are utilized for the light amplification and modulation.

A gain-flattened multiwavelength modelocked semiconductor laser generates 750 MHz pulse trains simultaneously into 168 discrete wavelength channels. Optical time division multiplexing multiplies the pulse-repetition rate to 6 GHz per channel to yield an aggregate pulse rate of 1 THz.

We report optical frequency comb drift stabilization of an external cavity semiconductor laser hybridly modelocked at the 10 GHz cavity fundamental using the Pound-Drever-Hall frequency stabilization scheme. Laser longitudinal mode comb was locked to a Fabry-Perot reference cavity with a finesse value of 214. The frequency error signal was fed back to the bias current of the semiconductor gain medium to change the effective laser cavity length through the coupling between carrier density and refractive index. The peak-to-peak 2.4 GHz frequency drift of the comb of longitudinal modes was reduced to a RMS fluctuation of 30 MHz for up to 5 minutes. To the authors’ knowledge, this is the first optical frequency comb stabilization of a modelocked semiconductor laser. The intended application of the optical frequency stabilization is to keep the laser optical frequency comb locked to a WDM filter that is used for spatially separating the individual longitudinal modes of the laser for photonic arbitrary waveform generation.

The generation of ultrastable picosecond pulses in the 1550 nm range is required for numerous applications including photonic analog-to-digital converter systems and high-bit rate optical communication systems. Mode-locked erbium-doped fiber ring lasers are typically used to generate pulses at this wavelength. In addition to stability and output power, the physical size of the laser cavity is of primary importance. The length of the erbium-doped fiber used as the gain medium may be on the order of meters or even tens of meters which makes packing of the laser rather difficult. However the length of the gain medium can often be reduced if the erbium ion concentration within the fiber is increased. This paper will investigate the performance of an erbium-doped fiber ring laser as a function of ion concentration within the gain medium. Results will be presented for mode-locked lasers consisting of Lucent HE980, HG980 and HC erbium-doped fibers. The parameters that will be compared between the lasers include the output power as a function of length and concentration, optical pulse width and spectral bandwidth. Phase noise measurements of the laser output will also be presented.

We present computer simulation results of noise in a modelocked fiber laser system designed to operate in the 1550nm regime. Signal-to-noise ratio is determined, accounting for supermode effects for pulse-widths raging between 0.10ps and 5.0ps, and for a modulating frequency ranging from 400MHz to 10 GHz. Also, the effect of noise on the stability of the laser output characteristics such as pulse drop-out and amplitude fluctuations will be discussed.

Boolean logic is an inherently irreversible, hence lossy operation. It has a well-known energy cost and an obvious time cost. To avoid those costs, we must do a different kind of logic. But, it is Boolean logic that we wish to do. We solved that dilemma by using a quantum optical logic gate that is fully reversible that yields the Boolean result after the irreversible loss of information in detection occurs.

During the past several years many new results have been obtained for Fresnel zone plate antennas having a focal length to diameter ratio (F/D) near unity. Although zone plates have been used for many years at optical wavelengths, the typical configuration has employed F/D values from 20 to 100, sometimes greater than that. This results in a small angle (a few degrees or less) at the focal region, whereas the focal angles for F/D near unity (between 0.5 and 2.0) range from 90° to 28.1°. The small-angle optical conditions permitted making approximate analytical solutions which do not apply to the large-angle case. The recent results for large-angle applications will be summarized for microwave and millimeter-wave examples, although they are valid at any wavelength. In addition, a description will be given of optimization of feed methods (typically corrugated horn antennas) to improve overall efficiency (including aperture efficiency and diffraction efficiency), while also improving (lowering) first-sidelobe levels. This involves solving the case of tapered amplitude illumination across the zone plate aperture, whereas most of the previous investigations have assumed uniform illumination. A truncated Gaussian amplitude distribution with a 10 dB taper at the edge of the aperture provides the optimum aperture efficiency, as well as low sidelobe levels. The utilization of zone plate antennas at terahertz frequencies will also be described. At these frequencies the thin structure of the planar zone plate offers much lower loss than that of a conventional lens. All transparent materials increase in attenuation (loss tangent) as one moves from microwave frequencies to the terahertz range, and conventional lenses have high attenuation. This makes the use of the zone plate lens a preferred choice, for certain configurations.

An RF network analyzer normally uses a reference port to excite a device under test. The return from the device is compared in amplitude and phase to the reference to characterize the S-Parameters (reflection and transmission) of the device under test (DUT). In this case, the DUT was 30 meteres of limestone above a mine in Northwest Pennsylvania, which was being tested for dielectric constant and attenuation at 3-33 MHz as part of a ground penetrating radar development effort. This paper describes the test configuration using a wideband fiber optic link for the reference signal, and provides plots of the experimental results.

Low-capacitance, two-section, curved-waveguide gain elements were packaged with lensed polarization-maintaining fiber within standard-sized butterfly-style packages and shown to produce low-jitter pulses when used within a harmonically modelocked sigma cavity laser (jitter = 25 fs; 10 Hz - 10 MHz). Incorporation of a high finesse etalon filter into the sigma-cavity loop resulted in greater than 25 dB suppression of the supermode spurs while maintaining low integrated phase noise (jitter = 30 fs; 10 Hz - 10 MHz). A module containing the in-line sigma-cavity modelocked laser source and packaged semiconductor optical amplifiers was developed to create a configurable low jitter pulse source.

In this paper a detailed analysis and design of guided-wave 2D photonic bandgap filters are presented by using the Floquet-Bloch approach. Significant performance has been obtained in one and three cavity PBG structures.

For the space flight mission MESSENGER, the Mercury Laser Altimeter (MLA) instrument required highly reliable optical fiber assemblies for the beam delivery system. A custom assembly was designed based on commercially available technologies to accommodate the requirements for the mission. Presented here are the results of environmental testing the MLA optical fiber assemblies. These assemblies consisted of W.L.Gore FLEX-LITE^TM cable with 200 micron core Polymicro Technologies optical fiber and the Diamond AVIMS connector kits. The assemblies were terminated to the NASA-STD-8739.5 in the Code 562 Advanced Photonics Interconnection Manufacturing Laboratory at NASA Goddard Space Flight Center. The technology validation methods that were used to characterize these assemblies for usage in a space flight environment have been established and well documented. Only the tests that are known to bring out the failure modes typical to optical fiber assemblies have been performed to assess the ability of these assemblies to withstand the environmental parameters that have been established for Mercury Laser Altimeter. Testing involved vacuum, vibration, thermal and radiation exposure and the data with results of those characterization tests are included here. For the radiation characterization, both the 200 micron core FLEX-LITE^TM (FON1173) and the 300 micron core FLEX-LITE^TM (FON1174) were tested. For all other environmental tests only the 200 micron core FLEX-LITE^TM /AVIMs assembly was tested since it was expected that the results of such testing would not differ much with core size.

Industrial, NASA, and DoD spacecraft designers have recognized the advantages of using fiber optic components and networks for their internal satellite data handling needs. Among the benefits are the total elimination of cable-to-cable and box-to-box EMI; significant size, weight and power reduction; greater on-orbit and integration and test flexibility and significantly lower integration and test costs. Additionally, intra-satellite data rates of 1 to 10 Gbps appear to be an absolute requirement for a number of advanced systems planned for development in the next few years. The only practical way to support these data rates is with fiber optics. Space Photonics and the University of Arkansas have developed fiber optic components (FireFiber^TM) and networks that are designed specifically to meet these on-board, high data rate needs using NASA approved materials, packaging processes, and approved radiation tolerant devices. This paper will discuss recent developments in photonic components for spaceborne networks.

In this work the theoretical study of record and postexpositional amplification of holographic gratings in photopolymeric materials with light-induced optical attenuation has been carried out. The analytical model describing spatial-temporal transformation of holographic grating field during record and postexpositional amplification is developed. The model takes into consideration light-induced changing of optical attenuation and diffusion processes. Light-induced optical attentuation has been described with the help of the logarithmic function on the base of experimental data. The results of numerical simulation on the base of the model are presented. The basic physical parameters of photopolymers have been described with the help of the experimental data and the analytical model. The researched photopolymer was made in Institute of Organic Chemistry of the Siberian Separation of a Russian Academy of Sciences (Novosibirsk).

In the report the results of theoretical investigation of recording superimposed holographic gratings with the help of angle multiplexing in optical-absorbent photopolymeric materials are presented. We consider the case of serial record of superimposed holographic gratings. In the model presented the photopolymerization and diffusion mechanisms of record, temporal changing of the diffusion coefficient, depletion of monomer and dye during record process have been taken into consideration.

The given paper considers problems dealing with design of optoelectronic trigger devices with optic inputs based on devices with λ-volt-ampere characteristic including λ-diodes and λ-triodes. The paper contains basic parameters and characteristic of λ-devices, as well as shows factors influencing the choice, change in wide ranges and regulation of basic parameters of λ-devices, such as: V=1.5 25V, V_off=1 15V, I_max=50μA 30mA, I_off=0.1 10nA. The advantage of such triggers is law energy consumption in the mode of logic levels storage (from units up to tenths of nanowatts at V=5V) and voltage of logic levels practically does not differ from potentials of the earth and supply (Δ≈10μV) such devices enable to be commutated with frequencies up to 360 MHz if the duration of optic pulses t=0.8ns and power 100mW (using photodiodes having responsivity 0.5A/W). That corresponds to the switching energy of 80pJ, average consumption power from supply circuits of 58mW. The decrease of switching frequency at the expense of increase of porosity of supplied pulses and usage of photoreceivers with high conversion efficiency of A/W allows to decrease energy consumption of trigger. Thus, if commutation frequency is 100kHz and duration of optic pulses is 320ns, power - 80μW, that corresponds to switching energy of 26pJ, and usage of photopreceivers having responsivity of 2.5 A/W, the consumed average power of considered optoelectronic trigger from supply circuit is 9μW. That permits to carry out their integration with the number of elements in a matrix is 32×32 and more. We consider simulation results of such optoelectronic triggers based on λ-devices with different circuits, principles of optical and electronic control and show advantages of such optoelectronic triggers and their multifunctionality.

This paper presents a new concept for the realization of a high-speed, high-resolution Analog-to-Digital Converted (ADC). The approach modifies an analog fiber optic link with a recirculating optical loop as a means to store a time-limited microwave signal so that it may be digitized by using a slower, conventional electronic ADC. Detailed analytical analysis of the dynamic range and noise figure shows that under appropriate conditions the microwave signal degradation is sufficiently small so as to allow the digitization of a multi-gigahertz signal with a resolution greater than 10 effective bits. Preliminary experimental results are presented to support the theory.