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A guided optics component for the coherent summation of up to 19 optically carried microwave signals was designed and characterized. This microwave photonics summation device achieves very low loss, high responsivity, and is suitable for use up to the Ku band. Such a component is believed to be an efficient and powerful solution for optically driven phase arrayed antennas in receive mode and for other microwave photonics systems like filters.

A phase modulated analog optical link is studied using electrical circuit modeling. This link based on Mach–Zehnder interferometer is compared to a classical intensity modulated link. The analog performances are evaluated by circuit representation of optoelectronic and optical components in the electrical domain. The models include noise and nonlinear properties of those components and require careful formulation of simulation parameters. One of the advantages of this approach is that electronic circuits are combined to photonic components to fully analyze the system analog performances like gain, distortion and noise figure. The models can be easily implemented on a well-established electrical domain simulation tools with efficient simulation algorithms dedicated to microwave systems. It is shown that modeling tools are vital for such system design and can be used to performance evaluation of relevant and complex microwave photonic systems.

We describe a compact, ultralow noise, and high-power semiconductor laser implemented in a high performances wideband externally modulated optical link. The laser is based on a vertical external cavity surface emitting laser (VECSEL) designed for high-power and low-noise operation. Thanks to a specific design of the gain chip, the half-VCSEL, based on a metamorphic Bragg mirror and a report on a copper substrate, an optical power of 110 mW is obtained at 1.55 μm in the single frequency regime. For low-noise operation, the laser cavity is designed for free-relaxation-oscillations operation, i.e., in the so-called class-A regime. The Class-A VECSEL exhibits a relative intensity noise below −170 dB/Hz over a wide frequency bandwidth, from 300 MHz to 40 GHz, except at the laser free spectral range (20.4 GHz). In the low-frequency range, the laser noise, mainly due to transfer of pump noise to laser noise, goes from −110 dB/Hz at 1 kHz down to −158 dB/Hz at 10 MHz. Two externally modulated optical links are implemented and compared in terms of the RF gain and the noise figure. The first optical link is based on the ultralow noise class-A VECSEL and the second one is based on a low noise class-B DFB laser. Thanks to the outstanding noise properties of the designed VECSEL, the VECSEL-based optical link outperforms the DFB-based one, in particular for frequencies larger than 20 GHz.

Following the increasing availability of reliable optical components, issued from the telecom domain, analog-optical links based on commercial modules have achieved performances which are close enough to system requirements to be extensively considered. With accurate understanding and modeling of these components, it has been demonstrated that RF photonics can be implemented to transmit and process RF signals in equipment. We report on recent progress concerning the development of several photonic modules to implement transmissions of radar (and electronic-warfare) signals in airborne environment.

We describe a compact, ultra-low noise and high-power laser implemented in a wideband externally-modulated optical link. The laser is based on a Vertical External Cavity Surface Emitting Laser designed for free-relaxation-oscillations operation, i.e. in the so-called class-A regime. Thanks to a specific design of the 1/2-VCSEL, a metamorphic Bragg mirror and a report on a copper substrate, an optical power of 110 mW is obtained at 1.55μm in the single frequency regime. The Class-A VECSEL exhibits a relative intensity noise below -170 dB/Hz over a wide frequency bandwidth, from 300 MHz to 40 GHz, except at the laser free spectral range (20.4 GHz). A VECSEL-based optical link and a low RIN Class-B DFB-laser-based optical link are implemented and compared in terms of gain and noise factor. Thanks to its flat and ultra-low noise over a wide frequency bandwidth, the VECSEL outperforms the DFB laser, in particular for frequencies larger than 30 GHz.

Following the increasing availability of reliable optical components, issued from the telecom domain, RF-optical links based on commercial modules have achieved performances which are close enough to system requirements to be extensively considered. With accurate understanding and modeling of these components, it has been demonstrated that RF photonics can be implemented to transmit and process RF signals in equipments. We report on recent progress concerning the development of several photonic modules to implement transmission of radar and EW signals in airborne environment.

The improvement of radar reliability may require the detection and monitoring of its handled power. For this purpose, a new sensor concept based on an optically remoted RF probe was investigated. This work presents such a dedicated photonic system. The optical probe allows dual-regime operations: testing both radar transmit and receive operations. This monitoring performs not only “Go — No Go” tests, but could also be used for calibration. The paper reports the preliminary demonstrations. A new optoelectronic transducer was realised and a mock-up of probe was assembled and tested.

We report in this paper the direct sampling of a band-limited signal in the Ka Band by optical means. The sampling approach that has been used was based on a photoconductive switch made from low-temperature grown GaAs. The Photonic sampler may be used to down sample RF signals to base band before further conversion in digital by an electronic ADC. Thanks to this approach, the usual frequency mixers used for down-conversion are suppressed and replaced by the Photonic sampler. This very simple approach has a lot of benefits such as high level of integration, extremely low cost, no need of external electrical synchronization signals.

In this paper we present the remarkable characteristics of quantum dash mode-locked lasers and how they could be used for low phase noise signal generation, for high data rate wireless transmission and radar in the millimeter wave frequency range.

This paper reports on microwave photonics design and characterization of optically-controlled MMIC oscillator. Microwave photoconductive switches (MPCS) design methodology under continuous, intensity-modulated and pulsed optical control has led to microwave predictions of an oscillating device in GaAs integrated technology, under these optical control formats. Microwave oscillations at a frequency of 5 GHz during 2 ns have been experimentally achieved thanks to device illumination using fs optical pulses at 80 MHz repetition frequency.

Theoretical and experimental study of photoconductive optically controlled microwave oscillator on GaAs substrate is described. This oscillator gives a 5 GHz output signal if a suitable light power is applied (ON state) and without illumination oscillations disappear (OFF state). The light is applied on the 50mum microstrip photoswitching device which presents different impedances with several light intensities

The availability of optoelectronic components operating in the multi-gigahertz domain (up to 20 GHz) is very attractive for implementing basic optical processing functions of microwave signals such as spectrum analysis, adaptive filtering, and correlation suitable in radar and electronic communication systems. We present an opto-electronic free-space processor for filtering up-link and down-link signals in UMTS base stations. The system uses a liquid-crystal spatial light modulator to set programmable filtering functions. We have demonstrated signal rejections higher than ?40 dB at 2.3 GHz (from 2.1 GHz) and low insertion losses of ?18 dB. Moreover, tunability of the filters implemented in the free-space demonstrator has also been successfully addressed.

An optical architecture enabling time delay analysis of large bandwidth microwave signals is presented. It permits to determine time delays between microwave signals with a resolution better than 10 ps.

We present an overview of optical summation principles and technologies, related to architectures for signal processing and optical beam forming networks (OBFN). This paper relates theoretical analysis as well as experimental demonstrations for advanced radar and electronic warfare concepts.

The dynamic properties of low-temperature-grown GaAs (LT- GaAs) depend critically on growth and annealing conditions, such as substrate temperature during the MBE process (T s ), annealing temperature (T a ) and duration ((tau) a ). Previous empirical models based on carrier rate- equations introduce parameters, such as carrier lifetime, that cannot be directly correlated with growth and annealing conditions. The Schockley-Read-Hall model we use here introduces deep donor (N DD ) and acceptor (N A ) concentrations, instead of lifetimes. In LT-GaAs, deep donors are in majority constituted by an As-antisite related defect. The acceptors, in absence of doping, are most likely constituted either by Ga vacancy defects or by the residual doping during MBE growth. The samples studied are grown on GaAs semi-insulating substrates at different T s and annealed under different conditions. For each sample, we first measure N DD using X-ray diffraction analysis. Then we fit both continuous photoconductivity and pump-probe reflectometry measurements using N A as the only adjustable parameter. From the set of data obtained, we can relate T s , T a and (tau) a with N DD and N A . This gives us a way to predict LT-GaAs dynamics from growth and annealing continues. This approach has been used to fabricate ultrafast photoconductive switches showing high sensitivity and good insulation.

An adaptive correlation-based tracker has been developed. It uses discriminant nonlinear filters which offer more robustness to noise, background, and object distortions. Computers simulations show test results for a small target tracking, and good capabilities are demonstrated without post-processing of the correlation plane. The algorithm developed here works where well-known linear filters failed.

This paper describes a robust radio-over-fiber wireless link system for use in wireless extension and mobile backhaul applications. The wireless link operates at 71-75 GHz E-band carrier frequencies and can transmit ultra-high access data such as Gigabit Ethernet or OC-48 up to 2.5 Gbps. Enabling photonic technologies, system configurations, and lab trials are presented.