Active coherent beam combining and beam steering using a spatial mode multiplexer.

Coherent beam combination is one promising way to overcome the power limit of one single laser. In this paper, we use a Multi-Plane Light Converter to combine coherently 12 fibers at 1.03 µm with a phase locking setup.

Optical coherent combining of high-power optical amplifiers for free-space optical communications.

Highly efficient coherent beam combining (CBC) of two very-high-power optical amplifiers (VHPOA) with applications to long-range FSO communications such as ground-to-space feeder links is presented. The CBC setup is designed to minimize the telecom signal degradation, with a polarization beam splitter used to minimize the power fluctuations and to control the output polarization state of the beam. The system delivers 80 W output power and is proven to be compatible with 25 Gb/s telecom signals with a less than 1 dB power penalty.

Free space optical communication receiver based on a spatial demultiplexer and a photonic integrated coherent combining circuit.

Atmospheric turbulence can generate scintillation or beam wandering phenomena that impairs free space optical (FSO) communication. In this paper, we propose and demonstrate a proof-of-concept FSO communication receiver based on a spatial demultiplexer and a photonic integrated circuit coherent combiner. The receiver collects the light from several Hermite Gauss spatial modes and coherently combine on chip the energy from the different modes into a single output.

Orbital angular momentum beams generation from 61 channels coherent beam combining femtosecond digital laser.

We report on the use of a 61 beamlets coherent beam combination femtosecond fiber amplifiers as a digital laser source to generate high-power orbital angular momentum beams. Such an approach opens the path for higher-order non-symmetrical user-defined far field distributions.

Coherent beam combining of 61 femtosecond fiber amplifiers.

We report on the coherent beam combining of 61 femtosecond fiber chirped-pulse amplifiers in a tiled-aperture configuration along with an interferometric phase measurement technique. Relying on coherent beam recombination in the far field, this technique appears suitable for the combination of a large number of fiber amplifiers. The 61 output beams are stacked in a hexagonal arrangement and collimated through a high fill factor hexagonal micro-lens array.

Coherent beam combining of seven fiber chirped-pulse amplifiers using an interferometric phase measurement.

Coherent beam combining in tiled-aperture configuration is demonstrated on seven femtosecond fiber amplifiers using an interferometric phase measurement technique. The residual phase error between two fibers is as low as λ/55 RMS and a combination efficiency of 48% has been achieved. The combined pulses are compressed to 216 fs, delivering 71 W average power at a repetition rate of 55 MHz.

Fully embedded photonic crystal cavity with Q=0.6 million fabricated within a full-process CMOS multiproject wafer.

A two dimensional photonic crystal (PhC) resonator, based on a recent design concept, entirely embedded in Silica, is fabricated in a CMOS full-process multiproject wafer, including additional steps such as implantation, metalization, Germanium deposition and planarization. A large loaded Q-factor (5.9 × 10) is achieved without removal of the silica cladding.

High-performance and power-efficient 2×2 optical switch on Silicon-on-Insulator.

A compact (15µm × 15µm) and highly-optimized 2×2 optical switch is demonstrated on a CMOS-compatible photonic crystal technology. On-chip insertion loss are below 1 dB, static and dynamic contrast are 40 dB and >20 dB respectively. Owing to efficient thermo-optic design, the power consumption is below 3 mW while the switching time is 1 µs.

Digital holography for coherent fiber beam combining with a co-propagative scheme.

We present a technique for passive coherent fiber beam combining based on digital holography. In this method, the phase errors between the fibers are compensated by the diffracted phase-conjugated -1 order of a digital hologram. Unlike previous digital holography technique, the probe beams measuring the phase errors between the fibers are co-propagating with the phase-locked signal beams.

Integrable microwave filter based on a photonic crystal delay line.

The availability of a tunable delay line with a chip-size footprint is a crucial step towards the full implementation of integrated microwave photonic signal processors. Achieving a large and tunable group delay on a millimetre-sized chip is not trivial. Slow light concepts are an appropriate solution, if propagation losses are kept acceptable.

Time delay generation at high frequency using SOA based slow and fast light.

We show how Up-converted Coherent Population Oscillations (UpCPO) enable to get rid of the intrinsic limitation of the carrier lifetime, leading to the generation of time delays at any high frequencies in a single SOA device. The linear dependence of the RF phase shift with respect to the RF frequency is theoretically predicted and experimentally evidenced at 16 and 35 GHz.

Collective coherent phase combining of 64 fibers.

A new architecture for active coherent beam combining of a large number of fibers is demonstrated. The approach is based on a self-referenced quadriwave shearing interferometer and active control with arrays of electro-optic ceramic modulators. Coherent phase combining of 64 independent amplified fibers is obtained.

Broadband true time delay for microwave signal processing, using slow light based on stimulated Brillouin scattering in optical fibers.

We experimentally demonstrate a novel technique to process broadband microwave signals, using all-optically tunable true time delay in optical fibers. The configuration to achieve true time delay basically consists of two main stages: photonic RF phase shifter and slow light, based on stimulated Brillouin scattering in fibers. Dispersion properties of fibers are controlled, separately at optical carrier frequency and in the vicinity of microwave signal bandwidth.

Intermodulation distortion in microwave phase shifters based on slow and fast light propagation in semiconductor optical amplifiers.

We show theoretically and validate experimentally the effect of filtering on the nonlinear behavior of slow and fast light links based on coherent population oscillations in semiconductor optical amplifiers. The existence of a dip in the power-versus-current characteristics for the fundamental frequency, as well as for the third-order intermodulation product, is clearly evidenced. These two dips occur at different bias currents.

Experimental demonstration of enhanced slow and fast light by forced coherent population oscillations in a semiconductor optical amplifier.

We experimentally demonstrate enhanced slow and fast light by forced coherent population oscillations in a semiconductor optical amplifier at gigahertz frequencies. This approach is shown to rely on the interference between two different contributions. This opens up the possibility of conceiving a controllable rf phase shifter based on this setup.

Dynamic saturation in Semiconductor Optical Amplifiers: accurate model, role of carrier density, and slow light.

We developed an improved model in order to predict the RF behavior and the slow light properties of the SOA valid for any experimental conditions. It takes into account the dynamic saturation of the SOA, which can be fully characterized by a simple measurement, and only relies on material fitting parameters, independent of the optical intensity and the injected current. The present model is validated by showing a good agreement with experiments for small and large modulation indices.

Theoretical study of the spurious-free dynamic range of a tunable delay line based on slow light in SOA.

We developed a predictive model describing harmonic generation and intermodulation distortions in semiconductor optical amplifiers (SOAs). This model takes into account the variations of the saturation parameters along the propagation axis inside the SOA, and uses a rigorous expression of the gain oscillations harmonics. We derived the spurious-free dynamic range (SFDR) of a slow light delay line based on coherent population oscillation (CPO) effects, in a frequency range covering radar applications (from 40 kHz up to 30 GHz), and for a large range of injected currents.

Near-infrared active polarimetric and multispectral laboratory demonstrator for target detection.

We report on the design and exploitation of a real-field laboratory demonstrator combining active polarimetric and multispectral functions. Its building blocks, including a multiwavelength pulsed optical parametric oscillator at the emission side and a hyperspectral imager with polarimetric capability at the reception side, are described. The results obtained with this demonstrator are illustrated on some examples and discussed.

Dual-frequency single-axis laser using a lead lanthanum zirconate tantalate (PLZT) birefringent etalon for millimeter wave generation: beyond the standard limit of tunability.

We demonstrate the generation of optically carried, broadly tunable, millimeter-wave signals with a dual-frequency single-axis Nd:YAG laser. A frequency difference as high as 127 GHz is reached thanks to an intracavity electro-optically tunable etalon made of lead zirconate tantalate (PLZT) ceramic. We show that the available frequency range is actually limited by the bandwidth of the amplification medium, namely, far beyond the usually accepted free spectral range value in the case of a single-axis laser.