Richard Michalak

High-speed AJL8/APC polymer modulator

High-speed polymer modulators were fabricated using low-Vpi AJL8 chromophore in amorphous polycarbonate, and highly calibrated frequency response measurements were obtained using convenient coplanar-microstrip transitions. These Mach-Zehnder modulators show good frequency response to 50 GHz, with a loss and velocity mismatch-limited Vpi at 50 GHz <12 V. The measurements establish AJL8 as an excellent candidate for future military analog optical links

Radiation resistance of electro-optic polymer-based modulators

Mach–Zehnder interferometric electro-optic polymer modulators composed of highly nonlinear phenyltetraene bridge-type chromophores within an amorphous polycarbonate host matrix were investigated for their resistance to gamma rays and 25.6 MeV protons. No device failures were observed and the majority of irradiated modulators exhibited decreases in half-wave voltage and optical insertion losses compared to nonirradiated control samples undergoing aging processes. Irradiated device responses were attributed to scission, cross-linking, and free volume processes. The data suggests that strongly poled devices are less likely to de-pole under the influence of ionizing radiation.

Behavior of NLO polymer modulators irradiated by gamma rays

Two second-order nonlinear optical chromophoric materials were investigated for their response to gamma-ray irradiations for doses ranging from approximately 10-104 krad(Si). Thin film polymer modulators composed of a mixture of amorphous polycarbonate and phenyltetraene [APC/CLD-1(CPW-1)] active regions with UV upper and lower UV claddings were investigated for their pre- and post-irradiation behavior. Modulator Vπ insertion loss, and extinction ratio responses were examined, while a blend of salmon deoxyribonucleic acid (DNA)- hexadeCetylTriMethylAmmonium Chloride (CTMA) film samples were studied for their spectral response following irradiations over the spectral range λ=240-2600 nm. Following irradiation ranging from 9.6-104 krad(Si), the DNA/CTMA films exhibited losses in transmissivity over the spectral range λ=882-2600 nm and increased transmissivity over portions of the 240 nm < λ < 882 nm band. Data from the study also suggested that strongly poled APC/CPW-1 modulators operating at λ=1550 nm and exhibiting low Vπ values were less likely to have their half-wave voltages affected by ionizing radiation. The optical insertion losses for the majority of the APC/CPW-1 irradiated mdolators were found to decrease following irradiation. Discussion of the experimental results and mechanisms believed responsible for the post-irradiation behavior and results are presented.

Radiation-resistant polymer-based photonics for space applications

Empirical data regarding the radiation induced responses of Mach Zehnder interferometric electro-optic polymer based modulators (PBMs) operating at 1310 and 1550 nm and broadband InP quantum dot (QD) polymer photodetectors (PPDs) operating into the near infrared (NIR) are reported. Modulators composed of spun-on materials and hybrid electostatically self assembled (ESA) and spun-on NLO materials are examined for changes to their half-wave voltage and insertion losses following a gamma-ray total dose of 163 krad(Si) and irradiation by 25.6 MeV protons at a fluence of ~1011 cm-2. Pre- and post- irradiation responses of ESA grown polymer detectors using InP QDs are examined for photovoltage degradation and aging effects. The data indicates and excellent potential for developing polymer based photonic (PBP) devices with increased radiation resistance suitable for transition to photonic space applications.

Blind source separation-based multi-user detection for multi-antenna QAM receivers with I/Q imbalances

This paper presents a blind multi-user detection technique for multi-antenna quadrature amplitude modulation (QAM) receivers with Inphase/Quadrature phase (I/Q) imbalances. The estimation of multiple users in the presence of I/Q imbalances is performed by Blind Source Separation (BSS) methods. While the complex-valued signal model for multi-antenna QAM receivers does not lend itself to BSS due to the effect of I/Q imbalances, reformulating the signal model to a real-valued equivalent form enables the application of BSS. The proposed method enables multiple users to share the same bandwidth simultaneously in different geographical locations, and avoids the need for the knowledge of the channel state information. In addition, despite of the presence of I/Q imbalances in all receiver branches, the number of antenna required in the receiver is equal to the number of users. Computer simulations are conducted using the popular Fast-ICA (Independent Component Analysis) algorithm, and the simulation results confirmed the effectiveness of the proposed technique.

Characterization of an electroabsorption modulator design with high-dynamic range for broadband analog applications

An electroabsorption modulator (EAM) is designed to optimize dynamic range performance over 20 GHz bandwidth. The single stripe waveguide enables an extremely compact and integrated package to be fabricated with single mode fiber pigtails. The transfer functions shape permits suppression of higher order intermodulation products, yielding a spur-free dynamic range exceeding that of Mach- Zehnder designs. A dilute optical core diverts energy flow from absorbing layers into low loss waveguide; the 20 dBm optical power tolerance is significantly higher than that of commercially available electroabsorption devices. The tunable performance over 20 GHz is characterized and applications are discussed. New approaches to the broadband impedance matching requirements are calculated and the impact on system performance is assessed.

Effect of electrode loss on the dynamic range of linearized directional coupler modulators

Numerical simulations were used to study the effect of electrode loss on the two-tone spur-free dynamic range (SFDR) of analog photonic links with linearized directional coupler modulators. Radio-frequency loss in the traveling wave electrode significantly limits the frequency bandwidth over which this class of electrooptic modulator can effectively enhance the SFDR

The uncertainty principle and entangled correlations in quantum key distribution protocols

Considerations of non-locality and correlation measures provide insights to Quantum Mechanics. Nonphysical states are shown to exceed limits of QM in both respects and yet conform to relativity’s ‘nosignaling’ constraint. Recent work has shown that the Uncertainty Principle limits non-locality to distinguish models that exceed those of QM. Accordingly, the Uncertainty Principle is shown to limit correlation strength independently of non-locality, extending interpretation of the prior work, and to underlie the security of Quantum Key Distribution. The established Ekert protocol[6] is compared with more secure variations, in particular H. Yuens Keyed Communication in Quantum Noise (KCQ) [7] and a new Time-Gating protocol which minimizes authentication and susceptibility to active eavesdropping.

Design and development of a package for a diluted waveguide electro-absorption modulator

Externally coupled electroabsorption modulators (EAM) are commonly used in order to transmit RF signals on optical fibers. Recently an alternative device design with diluted waveguide structures has been developed. [1] Bench tests show benefits of lower propagation loss, higher power handling (100 mW), and higher normalized slope efficiency. This paper addresses the specific issues involved in packaging the diluted waveguide EAM devices. An evaluation of the device requirements was done relative to the standard processes. Bench tests were performed in order to characterize the optical coupling of the EAM. The photo current maximum was offset from the optical power output maximum. The transmissions vs. bias voltage curves were measured, and an XY scanner was used to record the mode field of the light exiting from the EAM waveguide in each position. The Beam Propagation Method was used to simulate the mode field and the coupling efficiency. Based on the bench tests and simulation results, a design including mechanical, optical and RF elements was developed. A Newport Laser Welding system was utilized for fiber placement and fixation. The laser welding techniques were customized in order to meet the needs of the EAM package design.

Variable rate MIMO communication with airborne platforms: An experimental study

Motivated by the need for robust and high throughput communication with airborne platforms, a variable rate MIMO scheme that combines the D-BLAST architecture with per antenna spreading was proposed. This paper is focused on the experimental study of this approach. We developed a software defined radio implementation of the variable rate MIMO system based on GNU Radio. Over the air transmission and reception is enabled by Universal Software Radio Peripheral (USRP). The results demonstrate the effectiveness of the proposed scheme in realizing the throughput gain afforded by MIMO communication under potentially rank deficient channel conditions that are often present in an airborne environment.