J. Harari

Modeling of waveguide PIN photodetectors under very high optical power

In this paper, the behavior under very high optical power of waveguide PIN photodetectors grown on InP substrate is simulated. The problem is solved using a pseudo-bidimensional drift-diffusion model which describes the electrical behavior of the device including the effects of the external circuit. The optical behavior of the device is analysed using FD 2D and 3D beam propagation method. First, we present the optical behavior of the device when the illumination conditions change. Influence of device structure, spot width, spot position and injection angle on the quantum efficiency of the photodetector is so studied. Second, the whole modeling is validated using experimental results given in the literature. Three typical multimode structures w hich allow a high cut-off frequency as well as a good responsivity are then modeled and compared. The smaller one has a cut-off frequency of 75 GHz in small signal conditions and the main effect decreasing the microwave output signal when the optical input power increases is the carrier effect in the depletion region of the photodetector. The maximum microwave power of each photodetector is calculated in typical conditions of use. >

Theoretical study of p-i-n photodetectors' power limitations from 2.5 to 60 GHz

In this paper, we present a theoretical study and a numerical simulation of various long wavelength top-illuminated p-i-n photodetectors in the frequency range of 2.5-60 GHz under high optical modulated power at 1.55-/spl mu/m wavelength. The modeling includes a monodimensional drift-diffusion model for the device and takes into account the external circuit. We considered six InP/GaInAs/InP photodetectors especially designed to work at 2.5, 10, 20, 30, 40, and 60 GHz, respectively. For the one with the highest frequency, we intentionally sacrificed the quantum efficiency in order to compare them at the end with the results already obtained in the case of waveguide p-i-n photodetectors. The results show the maximum microwave-output power for each photodetector at its specific working frequency. Additionally, we present the effects of the modulation depth, the back illumination, and the wavelength of 1.3 /spl mu/m.

Modeling of microwave top illuminated PIN photodetector under very high optical power

In this paper, we present a theoretical study and a numerical simulation of a classical long wavelength top illuminated PIN photodetector for microwave applications under very high optical power. The modeling includes a monodimensional drift-diffusion model for the device and takes into account the external circuit. At first, this modeling is validated using experimental results from the literature. Second, we consider a classical InP-GaInAs-InP photodiode grown on an N/sup +/ InP substrate. The presented results show that the distortion and the saturation of the microwave signal at 20 GHz are due to the space charge effect in the photodetector and also to the depolarization of the device because of the external circuit. The main parameters influencing these phenomena are the optical power, the bias voltage, the optical spot width and the modulation depth. In case of a small optical spot, the effect of the external circuit is neglectable, while it contributes to the decrease of the microwave responsivity in the case of a large spot. The maximum output power is calculated in different cases and we can expect up to 12 dBm microwave output power for a 5 V reverse bias voltage.

A THREE-TERMINAL EDGE-COUPLED INGAAS/INP HETEROJUNCTION PHOTOTRANSISTOR FOR MULTIFUNCTION OPERATION

A three-terminal edge-coupled InGaAs/InP phototransistor is reported. A dc photocurrent gain near 60 and an optical unity gain frequency of 40 GHz were measured. The mixing of a modulated optical signal and a microwave signal applied on the base terminal is presented. Optical and electrical modeling are used to analyze and improve the device performances.xa0© 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 408–412, 1998.

Optical devices for ultra-compact photonic integrated circuits based on III-V/polymer nanowires

We demonstrated the potential application of III-V/polymer nanowires for photonic integrated circuits in a previous paper. Hereby, we report the use of a spot size converter based on 2D reverse nanotaper structure in order to improve the coupling efficiency between the nanowire and optical fiber. A total coupling enhancement of up to a factor 60 has been measured from an 80 nm x 300 nm cross-section tip which feeds an 300 nm-side square nanowire at its both ends. Simultaneously, micro-radius bends have been fabricated to increase the circuit density; for a radius of 5 microm, the 90 masculine bend losses were measured as low as 0.60 dB and 0.80 dB for TE and TM polarizations respectively.

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

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.

Design, optimization and fabrication of an optical mode filter for integrated optics

We present the design, optimization, fabrication and characterization of an optical mode filter, which attenuates the snaking behavior of light caused by a lateral misalignment of the input optical fiber relative to an optical circuit. The mode filter is realized as a bottleneck section inserted in an optical waveguide in front of a branching element. It is designed with Bézier curves. Its effect, which depends on the optical state of polarization, is experimentally demonstrated by investigating the equilibrium of an optical splitter, which is greatly improved however only in TM mode. The measured optical losses induced by the filter are 0.28 dB.

InP Digital Optical Switch with 40dB crosstalk at 1.55μm wavelength

A New InP Digital Optical Switch especially designed for high crosstalks is proposed. More than 40dB crosstalk can be achieved at 1.55μm wavelength for switching current ranging from 35 to 90mA, depending on the optical polarisation.

InP Digital Optical Switch with 72dB microwave crosstalk at 1.55μm wavelength.

A new InP digital optical switch especially designed for high crosstalk is proposed. More than 72 dB microwave crosstalk can be achieved at 1.55 μm wavelength optical signal for a 56 mA switching current

High crosstalk InP digital optical switch for microwave applications

Because electro-optic switches are key elements for the synthesis of large bandwidth, high dynamic, true time delay optically controlled microwave antennas, we designed, fabricated and characterized a new digital optical switch grown on InP substrate, and based on carrier-induced effects. The switching time is short (3ns) and there is no added noise on the optical signal. By introducing this switch in a microwave optical link at 1GHz frequency, we demonstrate that a 72dB microwave crosstalk (more than 36dB on the optical signal) can be achieved. The low current consumption of 60mA makes our device suitable for the optical control of microwave antennas.