Vincent Magnin

High performance evanescent edge coupled waveguide unitraveling-carrier photodiodes for >40-gb/s optical receivers

We have demonstrated a low-cost high-bandwidth and high-responsivity evanescent waveguide unitravelling-carrier photodiode (PD) fabricated using all 2-in InP processing including on-wafer mirrors and coating. Optimization of the optical input waveguide was made using the method of the genetic algorithm associated with a beam propagation method. Optical fiber coupling to the PD is based on a diluted multimode waveguide allowing simple material epitaxial growth. The fabricated PDs exhibit simultaneously 0.76-A/W responsivity at 1.55 /spl mu/m, >50-GHz bandwidth, and more than 22-mA average saturation photocurrent at 50 GHz. The light polarization dependence is less than 0.1 dB.

Design, optimization, and fabrication of side-illuminated p-i-n photodetectors with high responsivity and high alignment tolerance for 1.3and 1.55-/spl mu/m wavelength use

We describe the design, optimization and fabrication of side-illuminated p-i-n photodetectors, grown on InP substrate, suitable for surface hybrid integration in low-cost modules. The targeted functionalities of these photodetectors were a very high responsivity at 1.3- and 1.55-/spl mu/m wavelengths and quasi-independent on the optical polarization, and had a high alignment tolerance. Moreover, in order to avoid any reliability problem, the principle of evanescent coupling was adopted. Two photodetectors were optimized, fabricated, and tested; the first was for classical cleaved fiber, and the second was for lensed fiber. Because the considered epitaxial structures were complicated to optimize, the method of the genetic algorithm was used, associated with a beam propagation method (BPM). The photodetectors are based on multimode diluted waveguides, which are promising structures in the field of optoelectronics and integrated optics. Starting from the presented comparisons between experimental and theoretical results, the interest of the design method is discussed and the complete performances of newly fabricated devices are presented. The aspect of the cutoff frequency is also considered.

Design and fabrication of a p-i-n photodiode with high responsivity and large alignment tolerances for 40-gb/s applications

This letter demonstrates an evanescently coupled p-i-n photodiode combined with a multimode diluted waveguide using a simple all 2-in InP processing that includes on-wafer mirrors etching and antireflection coating. A high responsivity of 0.81 A/W at 1.55 mum with less than 0.4-dB polarization dependence and a large -1-dB vertical alignment tolerance of 2.70 mum were achieved simultaneously with a bandwidth of 47 GHz. Stable operation for over 1000 h was obtained under bias stress and temperature at 200degC

Microwave On/Off Ratio Enhancement of GaAs Photoconductive Switches at Nanometer Scale

This paper reports on performances enhancement of photoconductive switches in term of On/Off ratio and insertion losses. The optimization parameters on which the research has been focused are gap dimensions reduction to nanometer scale. The device characterization results up to a microwave frequency of 40 GHz and under CW illumination at a wavelength of 800 nm are presented. On/Off ratio reveals a value of 13 dB at 20 GHz under 100 mW optical power.

1.55-

We report a GaNAsSb-based photoconductive switch for microwave switching application. The GaNAsSb layer was grown by molecular beam epitaxy in conjunction with a radio-frequency plasma-assisted nitrogen source and a valved antimony cracker cell. The switch shows a maximum ON-OFF ratio of 9 dB at 1.5 GHz under 1.55-m laser excitation at 80 mW. The switch also shows a positive ON-OFF ratio up to 10 GHz. This is the first successful demonstration of a photoconductive switch for microwave switching application under 1.55- m wavelength excitation. Further analysis suggests that the high contact resistance may degrade the performance of the photoconductive switch.

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We analyze waveguide InP photodetectors for millimeter wave applications. We start with the PIN waveguide photodetector pointing out key problems like optical coupling, microwave access and maximum available power. To benefit form an internal gain we introduce the waveguide InP heterojunction phototransistor showing its ability to operate up to 60 GHz.

m GaNAsSb-Based Photoconductive Switch for Microwave Switching

Currently, several ways are investigated concerning pico-cellular systems. Although optical feeding of base stations is involved, there are a lot of microwave signal transmission or generation schemes. Depending on the used scheme, the receiver will behave differently, either as a pure optoelectronic transceiver (microwave transmission) either as a non-linear optoelectronic system (optical microwave generation, optical locking of microwave oscillator, ...). In these fields, we present the work that we did on promising devices, i.e. InP/InGaAs edge-coupled heterojunction phototransistors in twoand three-terminal configuration. Three parts of this paper report modelling tools, device technology and characterization. Modelling tools include optical as well as optoelectronic modelling. A brief description of technological work follows. The characterization is carried out in terms of static response, frequency response and non-linear behaviour.

InP photodetectors for millimeter-wave applications

This letter demonstrates an original carrier-induced effects InP digital optical switch (DOS) designed to achieve a low optical crosstalk for 1.55-mum wavelength applications. It is based on a widened multimode Y-junction combined with a sinusoidal shape waveguide to increase the optical contrast ratio between the two output branches. The entire InP-InGaAsP-InP DOS was designed using a semi-vectorial three-dimensional beam propagation method. The fabricated InP DOS with lambdag = 1.3 mum heterostructure exhibits an optical crosstalk as low as -38.5 dB for a 33-mA switching current at 1.55-mum wavelength for a favourable polarized input light.

Edge-coupled InGaAs/InP phototransistors for microwave radio fibre links

In this paper, we present first experimental results obtained on two 1 and three terminal edge-coupled InP/InGaAs heterojunction phototransistors showing that these devices seem very promising for microwave and millimeter wave applications.

A New Low Crosstalk InP Digital Optical Switch Based on Carrier-Induced Effects for 1.55-

This letter demonstrates a 2times2 low optical crosstalk and low power consumption switching matrix device based on carrier-induced effects on an InP substrate. The matrix device comprises two digital optical switches (DOSs) with a wide multimode Y-junction associated with a sinusoidal passive integrated optical circuit with an optimized X-crossing. The passive structure was designed using a two-dimensional beam propagation method (BPM) and the entire InP-InGaAsP-InP DOS was designed using a semivectorial three-dimensional BPM. The fabricated 2times2 InP switching matrix heterostructure with lambdag=1.3 mum exhibits optical crosstalk as low as -30.5 dB for drive current of 52 mA at 1.55-mum wavelength. Maximum crosstalk change of 4 dB is measured under optical polarization variation.