Malvin Carl Teich

On the optimization of heterostructure avalanche photodiodes

We use the modified dead-space multiplication theory (MDSMT) that incorporates both the initial energy effect and the heterostructure effect to predict the optimal performance of two-layered-multiplication APDs. We first consider an Al/sub 0.6/Ga/sub 0.4/As homojunction APD with a multiplication layer (i-layer) of width 140 nm, and then a device with a multiplication region consisting of two layers: Al/sub 0.6/Ga/sub 0.4/As and GaAs for which carriers are injected into the Al/sub 0.6/Ga/sub 0.4/As layer. From a design perspective, maximizing the initial energy is clearly the key in reducing noise. Unfortunately, the ability to control the initial energy in the fabrication stage is apparently not yet well established at this point of time. However, for a given initial energy of the injected electrons, the heterostructure APD would result in improved noise performance if the Al/sub 0.6/Ga/sub 0.4/As layer is either 30 nm or 110 nm wide. Moreover, the 30 nm Al/sub 0.6/Ga/sub 0.4/As case would result in less uncertainty in the excess noise factor than the 110 nm case (/spl Delta/F=0.7 vs. /spl Delta/F =2.3), which is attributed to the unknown initial energy.

Photonic Circuits for Quantum Information Processing in Two-Mode Integrated Diffused-Channel Waveguides

We present designs of photonic circuits for the generation, separation, and manipulation of modal, polarization, and spectral photonic qubits generated in two-mode diffused-channel Ti:LiNbO3 waveguides via spontaneous parametric downconversion.

Parameter Estimation in Quantum Optical Coherence Tomography

Quantum optical coherence tomography (QOCT) has been used for axial imaging based on quantum interferometry. We demonstrate a technique for the estimation of sample parameters (positions of reflecting layers, refractive indices, dispersion coefficients) for closely spaced layered media, based on measurement of QOCT interferograms.

Generation and Analysis of Entangled Two-Photon States in Spatial-Parity Space

We demonstrate the generation of two-photon states entangled in the parity of their transverse spatial coordinates. Continuous superpositions of the |Φ+> and |Ψ+> Bell states are synthesized and analyzed with simple linear optical components.

Engineering Robust Optical Entanglement for Quantum Communication

A robust source of polarization-entangled photons for quantum communication at telecom wavelength is implemented. The benefits of using Superconducting Photon Counting Detectors (SSPD) have been evaluated.

Quantum Cryptography with Optical Entanglement at 1.5 μm

We report on the engineering, preparation, and utilization of polarization entangled-photon states in the telecommunications window of 1.5 μm for secure quantum key distribution.

Breakdown characteristics of In/sub 0.52/Al/sub 0.48/As-InP heterojunction APDs

This paper describes the breakdown characteristics of In/sub 0.52/Al/sub 0.48/As-InP heterojunction APDs. This work also calculates the breakdown characteristics triggered by dark counts resulting from thermal generation or trapped carriers in the multiplication region. Finally, an attempt is done to further improve the breakdown probabilities by considering multistage heterojunction APDs.

Counterpropagating entangled photons in a periodically poled nonlinear waveguide

Entangled photons, which may be generated through the process of spontaneous parametric down-conversion (SPDC) in a crystal with /spl chi//sup (2)/ nonlinearity, have long been in the spotlight for quantum-optics experiments. The generation of entangled photons by quasi-phase matching (QPM) in lithium niobate offers the promise of increased photon-pair production and, with the integration of a waveguide structure, control of the spatial characteristics of the down-converted photons. It turns out that the use of a waveguide structure, in conjunction with periodic poling to achieve quasi-phase matching, offers another critically important feature: the possibility of generating counterpropagating signal and idler photons. We consider the conditions required for generating counterpropagating photon beams and explore some of the unique properties of this source of light using a periodically poled LiNbO/sub 3/ waveguide.

Prediction of excess noise factor and frequency response for thin avalanche photodiodes

Summary form only given. Recent experimental measurements from InP and InAlAs avalanche photodiodes (APDs) with thin multiplication regions, collected by J.C. Campbell and collaborators at the University of Texas at Austin, show that, for a fixed gain the excess noise factor is significantly lower than that predicted by the conventional McIntyre theory. The observed dependence of the noise on the multiplication-region width cannot be explained using the conventional theory in which the excess noise factor is a function only of the mean gain and the ionization coefficient ratio. In the dead-space-multiplication theory (DSMT), a carrier must travel a certain distance, called the dead space, before gaining sufficient energy for impact ionisation to occur. Because this dead space regularizes the ionisation locations, the randomness of the avalanching mechanism is reduced. For thin multiplication-region APDs, this effect is proportionally higher and thus the noise is lower. We applied the DSMT to the experimental results for GaAs and AlGaAs and more recently for InP and InAlAs APDs. We were able to fit the ionization coefficients associated with devices of various thicknesses, as a function of the electric field, within the confines of a single exponential model.