Design for high efficiency, high power traveling wave electroabsorption modulator using Intra-Step-Barrier Quantum Well (IQW) and Peripheral Coupled waveguide (PCW) designs are presented. Both of these designs have separately yielded EAMs with high optical power handling and low Vp properties, in an analog fiber link configuration. The IQW EAM has low Vp (~0.73 V) and high power handling (100 mW). The lumped element IQW EAM has achieved a link gain of -16 dB, a multi-octave SFDR of 110 dB-Hz2/3 and a single-octave SFDR of 121dB-Hz4/5 at the 1543 nm wavelength. The PCW MQW EAM with lumped element configuration can achieve a low link low, a high multi-octave SFDR at the same wavelength. The traveling wave properties of these EAMs are under investigation.

The two-section gain-coupled DFB laser can be designed to exhibit self pulsing. The self-pulsing dynamics have been exploited to demonstrate a variety of application in high-speed optical communication systems, including wavelength and polarization-independent all-optical clock recovery up to 100 Gb/s and conversion from the NRZ or RZ format to CSRZ format.

The generation of ultrastable picosecond pulses in the 1550 nm range is required for numerous applications that include photonic analog-to-digital converter systems and high-bit rate optical communication systems. Mode-locked erbium-doped fiber ring lasers (EDFLs) are typically used to generate pulses at this wavelength. In addition to timing stability and output power, the physical size of the laser cavity is of primary importance to the Air Force. The length of the erbium (Er)-doped fiber used as the gain medium may be on the order of meters or even tens of meters which adds complexity to packaging. However, with the recent advancements in the production of multi-component glasses, higher doping concentrations can be achieved as compared to silicate glasses. Even more recent is the introduction of Er-doped multi-component glass waveguides, thus allowing the overall footprint of the gain medium to be reduced. We have constructed a novel harmonically mode-locked fiber ring laser using the Er-doped multi-component glass waveguide as the gain medium. The performance characteristics of this Er-doped waveguide laser (EDWL) including pulse width, spectral width, harmonic suppression, optical output power, laser stability and single sideband residual phase noise will be discussed in this paper.

We explore the effect of auxiliary cavities on various schemes used in modeling fiber laser systems having a main cavity and an auxiliary. These include the effects of incorporating a) passive elements and b) active elements in the auxiliary cavity for actively modelocked, passively modelocked, as well as Raman fiber lasers. The focus is on the enhancement of laser performance including stability, pulse compression and pulse repetition rate. The study shows that incorporating external cavity greatly enhances the operating range as well as performance of fiber laser systems. Pulse widths ranging from femtosecond to picoseconds (20fs to 20ps) have been reported, pulse repetition rates from kilohertz to gigahertz (40KHz to 40GHz), and noise reduction and instability reduction (30 to 140 dBc/Hz) have been reported. In addition incorporating auxiliary cavity allows for design flexibility using cavity dynamics, parametric control, nonlinear effects, pulse shaping, gain switching, and noise dynamics.

We describe a chip-scale version of a multiwavelength modelocked semiconductor laser that produces discrete wavelength channels on a 25 GHz grid in the 1550 nm spectral region. The laser utilizes a two-section semiconductor optical amplifier (SOA) device in a partially external cavity which enables tuning of the laser cavity length. Since the wavelength channels are simply the longitudinal modes of the laser cavity, the channel spacing can be easily adjusted to match arbitrary wavelength division multiplexing (WDM) protocols. The hybridly modelocked semiconductor laser produces 5 ps FWHM pulses at 25 GHz pulse-repetition rate. Conversely, we demultiplex individual axial modes and employ them as continuous wave (CW) WDM sources. The modes are characterized through relative intensity noise (RIN) measurement as well as eye-diagrams of pseudorandom data imposed by an external modulator. The modelocked laser functions dually as a compact source of high speed, ultrashort pulses and as an economical source of CW WDM channels.

The optical heterodyne detection for an extremely densely channelized coherent communication systems using phase coherent optical combs is demonstrated by using a passively modelocked semiconductor laser injection locked to a master laser oscillator. The single sideband noise of the heterodyne beat tone at 13.160 GHz was reduced to -123 dBc/Hz at 100 kHz offset from the carrier by exploiting the excellent noise rejection performance of a commercially available microwave bandpass filter. A signal-to-noise ratio of over 65 dB/Hz has been achieved in a single channel filtered from two analog RF signals detuned by only 200 MHz. These results show improved signal-to-noise ratio and superior crosstalk reduction between densely packed neighboring channels via electrical manipulation of the optical heterodyne detection signal.

Advanced analog-optical sensor, signal processing and communication systems could benefit significantly from wideband (DC to > 50 GHz) optical modulators having both low half-wave voltage (Vpi) and low optical insertion loss. An important figure-of-merit for modulators used in analog applications is Tmax/Vpi, where Tmax is the optical transmission of the modulator when biased for maximum transmission. Candidate electro-optic materials for realizing these modulators include lithium niobate (LiNbO3), polymers, and semiconductors, each of which has its own set of advantages and disadvantages. In this paper, we report the development of 1.5-um-wavelength Mach-Zehnder modulators utilizing the electrorefractive effect in InGaAsP/InP symmetric, uncoupled semiconductor quantum-wells. Modulators with 1-cm-long, lumped-element electrodes are found to have a push-pull Vpi of 0.9V (Vpi*L = 9 V-mm) and 18-dB fiber-to-fiber insertion loss (Tmax/Vpi = 0.018). Fabry-Perot cutback measurements reveal a waveguide propagation loss of 7 dB/cm and a waveguide-to-fiber coupling loss of 5 dB/facet. The relatively high propagation loss results from a combination of below-bandedge absorption and scattering due to waveguide-sidewall roughness. Analyses show that most of the coupling loss can be eliminated though the use of monolithically integrated inverted-taper optical-mode converters, thereby allowing these modulators to exceed the performance of commercial LiNbO3 modulators (Tmax/Vpi ~ 0.1). We also report the analog modulation characteristics of these modulators.

Enhanced electrooptic coefficient of GaInAsP three-step quantum wells (3SQW) for high power electrorefraction modulator applications is reported. Measured electrooptic coefficient of the 3SQW is nearly three times higher than the conventional rectangular quantum well (RQW) at lambda=1.55 um. Higher electrooptic effect, combined with a low optical absorption coefficient α<1 cm-1 in the 3SQW increased the modulator figure of merit by nearly 53 times, and decreased the power consumption by nearly one order of magnitude compared with a conventional RQW design.

We have developed 20 mA or higher photocurrent handling InGaAs photodiodes with 20 GHz bandwidth, and 10 mA or higher photocurrent handling InGaAs photodiodes with >40 GHz bandwidth. These photodiodes have been thoroughly tested for reliability including Bellcore GR 468 standard and are built to ISO 9001:2000 Quality Management System. These Dual-depletion InGaAs/InP photodiodes are surface illuminated and yet handle such large photocurrent due to advanced band-gap engineering. They have broad wavelength coverage from 800 nm to 1700 nm, and thus can be used at several wavelengths such as 850 nm, 1064 nm, 1310 nm, 1550 nm, and 1620 nm. Furthermore, they exhibit very low Polarization Dependence Loss of 0.05dB typical to 0.1dB maximum. Using above high current handling photodiodes, we have developed classical Push-Pull pair balanced photoreceivers for the 2 to 18 GHz EW system. These balanced photoreceivers boost the Spurious Free Dynamic Range (SFDR) by almost 3 dB by eliminating the laser RIN noise. Future research calls for designing an Avalanche Photodiode Balanced Pair to boost the SFDR even further by additional 3 dB. These devices are a key enabling technology in meeting the SFDR requirements for several DoD systems.

Direct write microprinting technologies are now being developed and used across a wide spectrum of optoelectronic applications, because they provide opportunities for manufacturing a series of components in micrometer scales and in large array size with reduced cost. Micro-optic structures have been printed not only as stand-alone components, but also directly onto other active and passive components, such as VCSEL, photodiode, optical fiber, etc., to form high performance assemblies. These assemblies can be further integrated with electronic circuits via solder ball printing to construct miniature and high sensitivity sensing devices, such as photodiode array detector, fluorescence probe, etc. By implementing MEMS technologies, micro-clampers have also been developed for the alignment and packaging of miniature, multi-channel sensing devices.

We report an optical switch that is based on the beam steering of an optical waveguide formed by injection of electrons in a p-i-n slab waveguide structure. The structure consists of an undoped InGaAsP multiple quantum well (MQW) layer, with a total thickness of 0.28 μm that is sandwiched between n-doped InP cladding layers. Zinc is diffused into the top cladding layer through a silicon nitride mask to form the p-regions on top of which a pair of 10 um wide parallel titanium-zinc-gold contact stripes are deposited by evaporation and lift-off. The gap between the stripes is 20 μm wide and the device is cleaved to a length of 800 um. Electrical currents are injected through the electrodes and a laser beam is launched into the middle of the gap region. The injected electrons accumulate in the MQW layer and spread sideways by diffusion. The regions that are saturated with electrons experience a decrease in refractive index and surround a narrow high index region effectively forming a channel waveguide. By carefully controlling the current ratio through the two parallel stripes, the waveguide can be shifted, thereby steering the guided laser beam.

This paper presents a novel method of wavefront measurement for adaptive optic systems by using a photonic crystal. In adaptive optics the wavefront shape of the incident wave is measured and used to set a reconfigurable mirror array to compensate for the aberration, reduce distortion and improve image and beam quality. In a 2D approach, the tilted wavefront at each pixel enters a V-shape structure of waveguides in a photonic crystal. By measuring and comparing the output power in the two waveguides, we can determine the tilted angle of the incident light at that pixel. This method can also be applied in a 3D approach.

Current aircraft cargo bay fire detection systems are generally based on smoke detection. Smoke detectors in modern aircraft are predominately photoelectric particle detectors that reliably detect smoke, but also detect dust, fog, and most other small particles. False alarms caused by these contaminants can be very costly to the airlines because they can cause flights to be diverted needlessly. To minimize these expenses, a new approach to cargo bay fire detection is needed. This paper describes a novel fire detection system developed by the Goodrich Advanced Sensors Technical Center. The system uses multiple sensors of different technologies to provide a way of discriminating between real fire events and false triggers. The system uses infrared imaging along with multiple, distributed chemical sensors and smoke detectors, all feeding data to a digital signal processor. The processor merges data from the chemical sensors, smoke detectors, and processed images to determine if a fire (or potential fire) is present. Decision algorithms look at all this data in real-time and make the final decision about whether a fire is present. In the paper, we present a short background of the problem we are solving, the reasons for choosing the technologies used, the design of the system, the signal processing methods and results from extensive system testing. We will also show that multiple sensing technologies are crucial to reducing false alarms in such systems.

A cable, having two optical fibers, is buried in a two foot wide swath surrounding a facility containing buildings and grounds. The fibers are connected to directional couplers to form two fiber Sagnac interferometer loops. By making one loop longer than the other, with an additional fiber spool, not only can an intruder across the perimeter be detected but also the location of the intruder along the perimeter can be ascertained. The proposed system is described and analyzed. Simulation shows that such a system provides an excellent means of perimeter protection at low cost.

Planar waveguide technology has long been touted as the major platform for optical integration, which could dramatically lower component/module size and cost in optical networks. This technology has finally come to maturity with such waveguide-based optical products as wavelength multiplexers, switches, splitters and couplers, which are common nowadays. However, its potential as a complete solution for integration of a subsystem on a chip has so far been limited by the lack of integrated active elements providing gain to deteriorating optical signals. As the signal propagates through the fiber-optic network, it dissipates its energy and requires amplification in the network subsystems to maintain a required signal to noise ratio. Discrete fiber amplifiers are designed into systems and maintain required signal levels. However, if new components are introduced or the current ones are changed, current amplifiers have a limited ability to compensate for changes. Inplane's solution to the signal degradation problem is an optical amplifier that can be integrated onto the same planar waveguide platform as the other passive elements of the subsystem. Subsystems on such a platform will be able to automatically and internally adjust signal optical power, and enable simple interfacing between optical modules, module replacement and upgrades in the network. Inplane Photonics has developed Er-doped waveguide amplifier (EDWA) technology, which is fully compatible with the glass-on-silicon waveguide platform. In this paper we will present recent EDWA performance that approaches that of a fiber amplifier. Furthermore, we will demonstrate several examples of practical integration between passive and active building blocks on a single optical chip.

In this paper, we propose the use of optoelectronic joint transform correlator (JTC) and multifractal analysis based quality control (QC) to provide accurate, real-time identification of precipitation in weather data collected from meteorological-radar volume scans. The multifractal based QC algorithm is an objective algorithm that minimizes human interaction. The algorithm utilizes both textural and intensity information obtained from the two lower-elevation reflectivity maps. The multifractal exponents are obtained using the JTC system. Computer simulations are provided to show the effectiveness of this system.

A semiconductor laser based microwave/millimeter wave fiber-optic link is proposed and demonstrated. The microwave/millimeter-wave frequency response is realized using optical injection locking. This narrow-band high-frequency link can operate in the frequency-modulated (FM), phase-modulated (PM) and QAM formats.

The realization of a high-speed, high-resolution Analog-to-Digital Converted (ADC) is presented. 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.

This paper describes an electrode-less, all-optical, wideband electric field sensor fabricated in an electro-optic lithium niobate substrate. The sensor component is an integrated optic Mach-Zehnder interferometer. The electric field sensor uses the electro-optic properties of lithium niobate to modulate the phase of the light propagating in each arm of the Mach-Zehnder interferometer. The phase modulated light is then converted to intensity modulation at the output of the interferometer. The unique feature of the sensor device is that the orientation of the crystal in one arm of the Mach-Zehnder interferometer is inverted to provide push-pull optical modulation for an applied electric field. Optical fibers are connected to the input and output of the sensor device. The basic device is an all-dielectric intensity modulator. The ability to operate the sensor without the use of any metal antenna permits its use in extremely high field conditions without any danger of damaging the sensor. The optical fiber connections provide optical isolation to the instrumentation to protect the instrumentation from possible overload conditions. The electrode-less sensor is designed specially for measuring high field strengths similar to the conditions in electromagnetic pulse, high power microwave and high voltage power lines. Sensitivity improvements are possible by using carrier suppression techniques.

This paper presents a brief overview examining the recently reported research and development of polymer based modulators and photodetectors that have been advanced for aerospace and space applications, and discusses the reported radiation resistance of several device technologies. Preliminary results of focused investigations to develop polymer based photonic technologies capable of surviving in the naturally occuring near-earth space ionizing radiation environment environment as well as the expected performance of these technologies on elevated radiation environments are presented.

This paper summarizes our recent work on high-speed photonic analog-to-digital conversion (A/D) technologies, where picosecond pulses generated by a 10 GHz mode-locked laser source were used to accomplish low-jitter photonic sampling. In addition, we describe our progress in the generation of 40 GHz wavelength-coded pulses for time-interleaved A/D, and the demonstration of photonic bandpass (at 1.6 GHz) Δ-∑ quantizers clocked at 10 GHz.

We demonstrate tunable optical filters fabricated from metalized lithium niobate disk resonators and discuss further applications of the resonator chains for tunable photonic delay lines.

This paper will examine how Avalanche Photodiodes (APD) and Infrared Pulsed lasers (PL) are used and optimized to provide the "intelligence" to smart weapons. The basics of APD's and PL will be covered and the principle "time of flight ranging" which is the underlining principle of 3D laser radar will be illustrated. The time of flight principle is used for range finding, lidar, 3D laser radar and speed measurements - this information can then be used to provide intelligence to the smart weapon. Examples of such systems are discussed and illustrated, for example: Cluster bombs, Proximity fuses, and how laser range finding systems can be incorporated with GPS to produce effective and lethal weapons. The APD's that are discussed include silicon APD's for cost effective weapons, and 1550nm APDs for eye-safe systems. An overview of the different PL's will be outlined, but the focus will be on 905nm laser pulsars for cost effective laser weapons.