Siegen, Universiẗat, Diss., 2003.

A physics-based model incorporating the UTC (uni-traveling carrier) photodiode (PD) in the limit of weak nonlinearity was used in order to characterize the effects of nonlinearity on high speed and high power photodiodes. The combined influences of a) optical illumination, b) photocurrent, and c) interaction of the photodiode with an external circuit, were incorporated into three equations which described the phasor dynamics of the photodiode, which could be used to approximate the diode voltage, the depletion region thickness, and the electric field at the beginning of the depletion region by the Newton-Raphson Method. Then a frequency response plot as well as a third-order intermodulation distortion (IMD3) plot were obtained in order to evaluate the effects of nonlinearity on the photodiode. The third-order intercept point (IP3) was determined to be approximately 27.5 dB, illustrating its slight nonlinearity. For both the frequency and the IMD3 plots, it was shown that modulation bandwidth is predominantly RC-limited and that the stated assumptions were true: that the average electron transit time through the depletion region is expected to be significantly smaller than the period of the optical stimulus. Finally, nonlinearity was minimized by compensating the heavy loading and space charge effects on junction capacitance, and a surface plot was obtained demonstrating this behavior.

Afin d’adresser la problématique liée aux limitations des interconnections métalliques en termes de débits notamment, la photonique Si s’est imposée comme une technologie de choix. Un des composants de base des circuits photonique Si est le photodétecteur : Il permet de convertir un signal optique en signal électrique. Les photodétecteurs à base de Ge sur Si ont montré leur potentiel et offrent la meilleure alternative aux photodétecteurs III-V, pour une intégration dans les circuits photoniques Si.Dans ce contexte, les photodiodes à base de Ge su Si ont été étudiées. L’optimisation des photodiodes p-i-n a permis l’obtention de résultats à l’état de l’art. Une nouvelle approche utilisant une double hétéro-jonction latérale Si/Ge/Si a été proposée afin d’augmenter la responsivité mais aussi afin de proposer une meilleure solution d’intégration, avec les modulateurs Si notamment. Pour augmenter encore la sensibilité des récepteurs, l’utilisation de photodiodes à avalanche est cependant nécessaire. La structure SACM (Separate Absorption Charge Multiplication), combinant le faible bruit de multiplication du Si et l’absorption du Ge aux longueurs d’onde télécom, a d’abord été étudiée. Des modèles ont été développées afin d’optimiser le fonctionnement, et ces photodiodes ont été fabriquées et caractérisées. Les résultats obtenus sur des photodiodes éclairées par la surface (produit Gain-Bande passante de 560GHz à seulement -11V) sont très encourageant pour une intégration avec un guide d’onde. D’autre part, les photodiodes p-i-n en Ge sur Si, ont été étudiées en avalanche. La faible largeur de la zone intrinsèque a permis de diminuer le bruit de multiplication par effet « dead space », et le fonctionnement à 10Gbits/s pour un gain de 20 et une puissance optique de seulement -26dBm, pour une tension de -7V, sans utilisation d’amplificateur (TIA), a pu être démontré. Ces développements ouvrent ainsi la voie vers des récepteurs rapides, à faible consommation électrique et grande sensibilité. / To address the issue related to the limitations of metallic interconnects especially in terms of bitrate, Si photonics has become the technology of choice. One of the basic components of photonic circuits is the photodetector: It allows to convert an optical signal into an electrical signal. Photodetectors based on Ge on Si have shown their potential and offer the best alternative to III-V photodetectors, for integration into Si photonic circuits. In this context, the Ge on Si photodiodes have been studied. The optimization of pin photodiodes enabled the achievement of state of the art results. A new approach using a double lateral Si/Ge/Si heterojunction was proposed to increase the responsivity but also to provide a better integration solution, especially with Si modulators. To further increase the sensitivity of the receivers, the use of avalanche photodiodes, is however necessary. SACM (Separate Absorption Charge Multiplication) structure, combining Si low multiplication noise and Ge absorption at telecom wavelengths was first studied. Models have been developed to optimize the devices, and the photodiodes have been fabricated and characterized. The results obtained on the surface illuminated photodiodes (Gain-bandwidth product of 560GHz only -11V) are very encouraging for waveguide integration. On the other hand, Ge on Si pin photodiodes have been studied in avalanche. The small width of the intrinsic region contributed to the multiplication noise reduction thanks to "dead space" effect, and operation at 10Gbps for a gain of 20 and an optical power of -26dBm at only-7V, without using amplifier (TIA), have been demonstrated. These developments open the way to fast, low power consumption and high sensitivity receivers.

Avalanche photodiodes are the primary choice for photodetection in optical access networks, due to their capacity to meet the current requirements of bandwidth and sensitivity introduced by NG-PON2. This work provides an effective tool for modeling and predicting the operation of an avalanche photodiode, paving the way to making better performing receivers. We employed Lumerical to obtain several steady state and transient parameters for a silicon germanium SACM waveguide avalanche photodiode, where close agreement is illustrated between our findings and measurements reported on fabricated devices. The utility of our work is further demonstrated by implementing and modeling a device, designed to meet certain fabrication specifications, where optimization guidelines are suggested afterwards. By providing an accurate approximation of the avalanche photodiode operation, we offer a cost-effective approach to address the problem of fabricating better devices in optical access networks. The introduced methods can be similarly used for other types of photodiodes, contributing to a vast range of applications. / Graduate

No description available.

We present a preliminary design for a neutron detection system that is compact, lightweight, and low power consuming, utilizing the CubeSat platform making it suitable for space-based applications. This is made possible using the scintillating crystal lithium indium diselenide ((LiInSe2)-Li-6), the first crystal to include Li-6 in the crystalline structure, and a silicon avalanche photodiode. The schematics of this instrument are presented as well as the response of the instrument to initial testing under alpha radiation. A principal aim of this work is to demonstrate the feasibility of such a neutron detection system within a CubeSat platform. The entire end-to-end system presented here is 10 x 10 x 15 cm(3), weighs 670 g, and requires 5 V direct current at 3 W. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)

No description available.

Universiẗat, Diss., 2000--Kassel. / Lizenzpflichtig.

Abstract The main focus of this work concerned with the development of integrated electronic and optoelectronic circuits and devices for pulsed time-of-flight laser rangefinding is on the construction of the receiver channel, system level integration aimed at realisation of the laser radar module and in integration of all the receiver functions of laser radar on one chip. Since the timing discriminator is a very important part of a pulsed time-of-flight laser rangefinder, two timing discrimination methods are presented and verified by means of circuit implementations, a leading edge discriminator and a high-pass timing discriminator. The walk error of the high-pass timing discriminator is ±4 mm in a dynamic range of 1:620 and the uncompensatable walk error of the leading edge discriminator is ±30 mm in a dynamic range of 1:4000. Additionally a new way of combining the timing discriminator with time interval measurement is presented which achieves a walk error of ±0.5 mm in a dynamic range of 1:21. The usability of the receiver channel chip is verified by constructing three prototypes of pulsed TOF laser radar module. The laser radar achieves mm-level accuracy in a measurement range from 4 m to 34 m with non-cooperative targets. This performance is similar to that of earlier realisations using discrete components or even better and has markedly reduced power consumption and size. The integration level has been increased further by implementing a photodetector on the same chip as the rest of the receiver electronics. The responsivity of the photodetector is about 0.3 A/W at 850 nm wavelength and the noise of the receiver is reduced by a factor of about two relative to realisations using an external photodetector, because of the absence of parasitic capacitances and inductances caused by packages, PCB wiring, bond wires and ESD and I/O cell structures. The functionality of a multi-channel pulsed TOF laser radar chip is demonstrated using the photodiode structure investigated here. The chip includes four photodetectors with receiver channels and a three-channel time-to-digital converter. The chip together with external optics and a laser pulse transmitter enables distances to be measured in three directions with a single optical pulse, thus showing the feasibility of implementing all the receiver functions of a pulsed time-of-flight imager on a single chip using a current semiconductor process.

No description available.