Reinhard Erdmann

Generation of highly entangled photon pairs for continuous variable Bell inequality violation

We propose a novel experimental technique based on the process of parametric downconversion for the generation of photon pairs characterized by ultra-high dimensional spectral entanglement. It is shown that a superlattice of nonlinear and linear segments can be exploited to obtain states exhibiting a remarkably large entanglement, with a Schmidt number in the region of 107. We furthermore consider the application of such highly entangled photon pairs for the violation of a Bell inequality constructed from a measurement of the transverse wavevector Wigner function; such an approach eliminates the need for filtering the photon pairs and consequently eliminates an important potential loophole.

Diamond shaped ring laser characterization, package design and performance

A semiconductor diamond-shaped ring laser was fabricated and packaged for further test and analysis as an element in digital photonic logic. The optical characteristics of the ring laser were quantified in order to design a prototype package. The mode field was found to be quasi-circular. Based on the mode field of the laser, coupling curves were calculated and Corning OptiFocustrade lensed fiber was chosen to use for the four fiber outputs. Each fiber placement was actively optimized. Output power measurements were made for each facet before and after fiber coupling. Reflections from fiber tips were found to affect the final output power distribution of the device even though the fibers were anti-reflection (AR) coated, and additional effort was put into minimizing its variance. The packaged devices were tested for performance in digital photonic logic applications. Tests conducted to this point indicate that the packaging enabled a multiple port device of this type to be sufficiently portable for field testing

Injection characterization of packaged bi-directional diamond shaped ring lasers at 1550 nm

The Air Force Research Laboratory, Binoptics Corp., and Infotonics Technology Center worked collaboratively to package and characterize recently developed diode based ring lasers that operate at 1550 nm in a diamond shaped cavity. The laser modes propagate bi-directionally; however, uniaxial propagation may be induced by optical injection or by integrating a mirror. Round trip cavity length was 500 μm in 3.5 μm wide ridge waveguides, and four polarization-maintaining lensed fibers provided access to the input and output modes. A signal from a tunable diode laser, incident at one port, served to injection lock both of the counter-propagating circulating modes. When the input signal was time-encoded by an optical modulator, the encoding was transferred to both modes with an inverted time-intensity profile. Performance, in terms of fidelity and extinction ratio, is characterized for selected pulsed and monochromatic formats from low frequencies to those exceeding 12 GHz. A rate equation model is proposed to account for certain aspects of the observed behavior and analog and digital applications are discussed.

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.

Harmonically mode-locked laser and applications

We have constructed a harmonically modelocked laser that includes an electronically driven modulator and an intracavity Fabry-Perot etalon. We use experimentally observed performance of this laser, and number simulations based on the operating parameters of this laser, to examine strategies for generating stable synchronized trains of ultrashort duration solitons at multi-GHz repetition rates. Introduction of a saturable absorber based on a mechanism that both saturates and recovers promptly is examined. This strategy provides means of generating stable trains of solitons, where the soliton durations are of the order of a few ps or less, as well as synchronizing those trains with optical pulsewidth precision. We identify a rapidly saturating and rapidly recovering saturable absorber with a shorter pathlength as a potentially useful improvement on the nonlinear loop mirror. Significant work remains, but generation and distribution of these synchronized ultrashort duration soliton trains over networks on a scale of km or more appear feasible.

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.

Synchronization of active/passive mode-locked erbium fiber lasers

Injection seeding of a passively mode-locked fiber laser by an actively mode-locked fiber laser source is described. The passively mode-locked laser employs a multiple quantum well saturable absorber to establish pulsed operation. Mode-locked synchronized operation was maintained with average injection powers as low as 1.3 mW. Stable synchronized pulses were observed with pulse widths as narrow as 10 ps.

Self-starting mode-locked erbium fiber laser using grating reflectors

The construction and operating characteristics of a compact self starting mode locked erbium fiber laser are described in this paper. The laser employs a Fabry-Perot cavity with a fiber grating as one reflector and a nonlinear mirror based on a saturable absorber as the other. It operates at a pump power of less than 50 mW and produces mode locked pulses of 16.5 ps duration at a frequency of 3.25 MHz and a peak power of about 20 W.

Non-local correlations in a hyper-entangled circuit

An authorized user receiving bunched photon states from the output of a hyper-entangled photon server can make use on average of one fourth of the total transmitted events to gain situational awareness of the communications channel. Another user receiving bunched states can do the same. Both users then gain greater situational awareness on the confidentiality and integrity of the remaining half of the total transmission events wherein they both perform non-local correlated measurements on anti-bunched photon states. Keyed communication in quantum noise1 (KCQ) is used to enhance confidentiality and efficiency. This depiction forms a baseline for more realistic models; all optical elements are perfect and propagation through channels is noiseless.