As part of the European Defense Agency-funded PICTURE project, we have investigated the potential of integrated photonics for radar systems, targeting a photonics-based architecture for electronically scanned active array antenna systems, including multifunctional signal generation and detection. In this context, we have developed integrated photonic transmit and receive modules with up- and down-conversion capability, powered by a mode-locked laser for frequency reference. Key elements such as narrowband optical bandpass filters are evaluated for different technology platforms (silicon-on-insulator and silicon nitride). Perspectives and lessons learned are presented, based on the evaluation of system performance with IF-to-RF and RF-to-IF conversion efficiencies.
In this paper we present the developments carried out at III-V lab in collaboration with CEA-Leti on the hybrid integration of III-V chips with ultra-low-loss silicon nitride circuits for optical detection and RF systems. Different types of hybrid circuits will be presented: 1- a narrow linewidth laser based on the combination of an InP R-SOA and a long Bragg grating on SiN, 2- a Kerr frequency comb based on a high-power InP DFB laser butt-coupled to a high-Q SiN micro-ring, 3- a long cavity mode-locked laser based on an R-SOA and a SiN circuit with a delay line and a Bragg grating.
Time and Frequency applications, such as time synchronization of complex networks, are in need of high accuracy and stability clocks. Optically pumped Cesium tube atomic clocks satisfy these demands. However, Size, Weight and Power (SWaP) are very important parameters considering easier implementation of atomic clocks in systems. The innovative principal of Coherent Population Trapping (CPT) clocks can meet these challenges. They require a 894nm (Cs D1 line) DFB laser modulated at half the clock frequency (4.6GHz). The modulation generates the side bands separated by 9.2GHz. The laser should also keep a linewidth below 1MHz. We grow the layers of our laser structure two steps Metal Organic Vapor Phase Epitaxy, with an Aluminum free active region. It includes a single GaInAsP compressively strained Quantum Well (QW) and a GaInP waveguide, on GaAs substrates. The use of Al free materials allows for the realization of a buried Bragg grating which induces a very stable single frequency operation as a function of current and temperature. We have investigated our actual 2mm long laser in light current characteristics, optical spectra, linewidth and direct modulation, showing high stability at different temperatures. The Cs D1 line is achieved near room temperature with a very high SMSR (50dB) and a low linewidth (<1MHz). The actual -3dB bandwidth is 2.3GHz at 80mA (48mW) at 25°C. We have designed a new laser structure allowing 10 GHz bandwidth, without reducing the cavity length.
In this paper, we present a novel RF interconnection technique for the integration of high-speed photodiodes allowing multi-band rectangular waveguide (RW) interface from a single device. It is based on the dielectric rod waveguide (DRW) technology, which is known to offer broad bandwidths. The signal from photodiode is coupled to a rectangular slab DRW by the near-field coupling from a planar transition. The DRW also offers mechanical compatibility with standard RWs. By achieving the fundamental mode excitation, a broad working bandwidth of 75 GHz to 330 GHz is achieved in the simulated model. This corresponds to four frequency bands of WR-10, WR-8, WR-5 and WR-3.
The last few years have shown the success of silicon nitride platforms for ultra-low loss tightly confining waveguides. In addition to the low optical losses, the high Kerr nonlinearity, the high power handling capability and small bending radii makes the platform ideal for nonlinear photonics. Therefore, the potential for applications is huge: LiDAR, microwave optics, quantum photonics, neuromorphic computing, telecommunication, sensors… Here, we present our 200mm platform based on 800nm-thick LPCVD Si3N4 with optical losses below 5dB/m. It is completed with a set of photonic components: grating couplers, edge couplers, MMI, directional couplers, Y-junction and AWG multiplexer, which constitute the building blocks for advanced applications.
KEYWORDS: Laser applications, RF photonics, Free space optics, Laser development, Free space optical communications, Frequency conversion, High power lasers, Telecommunications, Satellites, Laser damage threshold
This article reports the development of 200-mW 1.55-μm DFB laser module with RIN below -162 dB/Hz which are well suited for microwave photonics or free space optical communication applications. Specific design has allowed reaching high power (>300 mW), low noise and high spectral purity laser chip. The chip has been packaged in Butterfly module optimized for reducing the module power consumption. DFB laser module system validations have been done on three laboratory test-beds representative of target applications, namely high-frequency optical LO distribution, photonic RF frequency conversion, and free space optical communication links.
Interest in free space optical communications has increased in the last decades as it has many advantages over RF communications, especially for space-borne applications. However, high power, good spectral quality and beam quality are needed for efficient data transmission over long distances. To meet the need of having lightweight and compact laser sources with such qualities for FSO, semiconductor based MOPA systems (Master Oscillator Power Amplifier) have been developed. In this paper we present the experimental results and compare them to simulation results for a threesection monolithically integrated semiconductor Master Oscillator Power Amplifier emitting at 1.5 μm wavelengths, designed for LIDAR applications that can also be used for free space telecommunications. The MOPA includes a distributed feedback laser section for single mode light emission, an intermediate section for data modulation and a flared semiconductor optical amplifier section for power amplification, which allows us to generate a high power beam with good spectral characteristics. The impact of bias conditions of the different device sections and device design on performances have been studied. Single mode operation at 4 different wavelengths near 1550 nm is achieved for optical output power up to 400 mW in continuous-wave (CW) regime for a SOA current of 3 A and 800 mW for SOA pulsed operation for currents up to 5 A. Near-field profile is also analyzed for different modulator current. Small-signal dynamic response is measured and analyzed.
Nowadays the interest in high power semiconductor devices is growing for applications such as telemetry, lidar system or free space communications. Indeed semiconductor devices can be an alternative to solid state lasers because they are more compact and less power consuming. These characteristics are very important for constrained and/or low power supply environment such as airplanes or satellites.
Lots of work has been done in the 800-1200 nm range for integrated and free space Master Oscillator Power Amplifier (MOPA) [1]-[3]. At 1.5 μm, the only commercially available MOPA is from QPC [4]: the fibred output power is about 700 mW and the optical linewidth is 500 kHz.
In this paper, we first report on the simulations we have done to determine the appropriate vertical structure and architecture for a good MOPA at 1.58 μm (section II). Then we describe the fabrication of the devices (section III). Finally we report on the optical and electrical measurements we have done for various devices (section IV).
Photonics is progressively transforming from a highly- focused technology applicable to digital communication networks into a pervasive “enabling” technology with diverse non-telecom applications. However, the centre of mass on the R&D level is still mostly driven by, and invested in, by stakeholders active in the telecoms domain. This is due to the high level of investments necessary that in turn require a large and established market for reaching break-even and generation of revenues. Photonics technology and more specifically, fibre-optic technology is moving into non-telecom business areas with great success in terms of markets captured and penetration rates. One example that cannot be overlooked is the application of fibre-optics to industrial applications, where double-digit growth rates are recorded with fibre lasers and amplifiers constantly gaining momentum. In this example, several years of R&D efforts in creating high-power amplification solutions and fibre-laser sources by the telecom sector, were piggy-backed into industrial applications and laser cutting/welding equipment that is now a strong R&D sector on its own and commercially now displacing some conventional free space laser cutting/welding.
The accurate determination of the atmospheric distribution of carbon dioxide (CO2) on planetary scale is a key requirement for setting up modeling tools able to make reliable predictions of Earth climate dynamics which are essential for the understanding of such important issues as climate change and global warming. Nowadays, the concentrations of CO2 are mainly measured in-situ at a number of surface stations that are unevenly distributed over the planet. Air-borne and space-borne missions have the potential to provide a denser and better distributed set of observations to complement those provided by the surface network.
Semiconductor light sources like light emitting diodes (LEDs) or laser diodes (LDs) are the most important light sources for space applications. LEDs are used in the control panels or lightning systems in the spacecrafts and as growth lightning systems in a deep space.
Space-borne lidar systems require laser transmitters with very good performance in terms of output power, beam quality, conversion efficiency, long term reliability and environmental compatibility. Atmospheric gas sensing additionally requires spectral purity and stability.
We present experimental results on a three-section master oscillator power amplifier at 1.57 μm to be applied in an integrated path differential absorption LIDAR system for column-averaged atmospheric CO2 measurements. The application requires high power and good beam quality together with spectral purity and modulation capacity to be used in a random modulation CW LIDAR system. The device consists of a distributed feedback laser acting as master oscillator, a bent modulator section and a tapered optical amplifier section with a tilted front facet to avoid coupled cavity effects. The modulator section acts as an absorber or amplifier when driven at zero or positive bias. Devices with different geometries and epitaxial structures were fabricated and characterized, presenting CW output powers higher than 350 mW and stable single mode emission. At the frequency required by the application (12.5 MHz) a high optical modulation amplitude and extinction ratio were achieved.
We propose an integrated path differential absorption lidar system based on all-semiconductor laser sources and single photon counting detection for column-averaged measurements of atmospheric CO2. The Random Modulated Continuous Wave (RM-CW) approach has been selected as the best suited to semiconductor lasers. In a RM-CW lidar, a pseudo random sequence is sent to the atmosphere and the received signal reflected from the target is correlated with the original sequence in order to retrieve the path length. The transmitter design is based on two monolithic Master Oscillator Power Amplifiers (MOPAs), providing the on-line and off-line wavelengths close to the selected absorption line around 1.57 µm. Each MOPA consists of a frequency stabilized distributed feedback master oscillator, a bent modulator section, and a tapered amplifier. This design allows the emitters to deliver high power and high quality laser beams with good spectral properties. An output power above 400 mW with a SMSR higher than 45 dB and modulation capability have been demonstrated. On the side of the receiver, our theoretical and experimental results indicate that the major noise contribution comes from the ambient light and detector noise. For this reason narrow band optical filters are required in the envisioned space-borne applications. In this contribution, we present the latest progresses regarding the design, modeling and characterization of the transmitter, the receiver, the frequency stabilization unit and the complete system.
A comparative study of two different Photonic Integrated Circuits (PICs) structures for continuous-wave generation of millimeter-wave (MMW) signals is presented, each using a different approach. One approach is optical heterodyning, using an integrated dual-wavelength laser source based on Arrayed Waveguide Grating. The other is based on ModeLocked Laser Diodes (MLLDs). A novel building block -Multimode Interference Reflectors (MIRs) – is used to integrate on-chip both structures, without need of cleaved facets to define the laser cavity. This fact enables us to locate any of these structures at any location within the photonic chip. As will be shown, the MLLD structure provides a simple source for low frequencies. Higher frequencies are easier to achieve by optical heterodyne. Both types of structures have been fabricated on a generic foundry in a commercial MPW PIC technology.
We describe a hybrid III-V on Silicon laser designed for low noise class-A dynamics. The laser is based on an InP active region and a passive silicon region integrated in a long laser cavity. High-Q ring resonators are used as optical filters in order to achieve single frequency operation. A fiber-coupled output power of 4.6 mW and a 55 dB side mode suppression ratio are obtained. For a pumping rate of 5.2, the hybrid laser exhibits a Relative Intensity Noise below -145 dB/Hz over a wide frequency bandwidth, from 100 MHz to 40 GHz but still suffers from some noise excess due to relaxation oscillations phenomena and side modes noise. The optimization of the laser cavity design is discussed in order to reach class-A dynamics while reducing residual noise excess.
Indium phosphide and associated epitaxially grown alloys is a material system of choice to make photonic integrated circuits for microwave to terahertz signal generation, processing and detection. Fabrication of laser emitters, high speed electro-optical modulators, passive waveguides and couplers, optical filters and high speed photodetectors is well mastered for discrete devices. But monolithic integration of them while maintaining good performances is a big challenge. We have demonstrated a fully integrated tunable heterodyne source designed for the generation and modulation of sub-Terahertz signals. This device is to be used for high data-rate wireless transmissions. DFB lasers, SOA amplifiers, passive waveguides, beam combiners, electro-optic modulators and high speed photodetectors have been integrated on the same InP-based platform. Millimeter wave generation at up to 120 GHz based on heterodyning the optical tones from two integrated lasers in an also integrated high bandwidth photodetector has been obtained.
Monolithic semiconductor mode-locked lasers (MLLs) are rising considerable interest for such diverse applications as
very high speed optical time division multiplexing sources (40-160 GHz), all-optical signal processing, and low noise
sampling for signal monitoring of optical networks.
In a large number of these applications, MLLs may be subjected to optical feedback generated by unwanted reflections
in optical systems which may greatly degrade laser performance. A number of experimental studies have been performed
to evaluate the sensitivity of MLLs to optical feedback showing an increase of phase noise [1-5]. Quantum-dash (Qdash)
based Fabry Perot lasers have been shown to exhibit an improved tolerance to feedback [6].
In this work, optical feedback tolerance is investigated for a monolithic quantum-dash-based passive mode-locked laser
emitting at 1.58 μm. The two-section device generates ~5 ps pulses at a repetition rate of 17 GHz. The onset of the
coherence collapse (CC) regime is experimentally determined by measuring the broadening of the longitudinal modes in
the optical spectrum. Depending on bias condition, the CC regime is reached for values of feedback ranging from -35 dB
to -29 dB at which emitted pulses were slighly broadened. The radio-frequency (RF) linewidth was simultaneously
assessed and a drastic reduction of the RF linewidth with increasing feedback strength is evidenced. This indicates a
reduction of the phase noise, thus implying a low "high frequency" timing jitter. We in particular observed an RF
linewidth narrowing down to a value of less than 1 kHz under optical feedback.
We propose in this communication an experimental study of the relaxation oscillations behavior in mode-locked
lasers. The semiconductor self-pulsating laser diode is composed by two gain sections, without saturable absorber.
It is made of bulk structure and designed for optical telecommunication applications. This specific device
allows two different regimes of optical modulation: the first one corresponds to the resonance of the relaxation
oscillations and the second one, to the mode-locking regime at FSR value. This singular behavior leads us to
characterize the self-pulsations which are coexisting in the laser and to describe two regimes of output modulation:
the first one appears thanks to the resonance of the oscillation relaxation and the other one corresponds to the
FSR of the Fabry-Perot laser at 40 GHz.
F. Lelarge, R. Brenot, B. Rousseau, F. Martin, G. Patriarche, F. Poingt, L. LeGouezigou, O. Le Gouezigou, C. Dernazaretian, E. Derouin, O. Drisse, F. Pommereau, A. Accard, M. Caligaro, D. Make, J.-G. Provost, P. Resneau, B. Dagens, F. van-Dijk, M. Krakowski, G. H. Duan
We report on the recent advances in InP-based Quantum Dashes (Qdashes) material for 1.55μm optoelectronic devices.
We achieve highly uniform, reproducible and wavelength-controlled Qdashes, with a length ranging from 50nm to
500nm depending on the growth conditions. These Qdashes lead either to high modal gain distributed feedback (DFB)
lasers or low chirp semiconductor optical amplifier (SOA). Moreover, we demonstrate that Qdashes are compatible with
buried ridge stripe and shallow ridge technology and lead to very reliable lasers. Directly modulated lasers with 10GHz
bandwidth are demonstrated in continuous wave mode operation. 10Gb/s transmission over 25km in semi-cooled
operation is achieved using DFB buried lasers. Qdashes optimization leads to SOA with internal gain of 10 dB and a -3dB optical bandwidth of 120 nm at 50°C, paving the way for semi-cooled CWDM optical sources. Furthermore, low
chirp Qdashes SOA are evaluated as optical boosters after a modulated source. Although we still observe overshoots on
the amplified signal, the chirp, even in their saturation regime, is low enough to allow for 50 km of transmission at
10Gb/s.
Guang-Hua Duan, F. Lelarge, B. Dagens, R. Brenot, A. Accard, A. Shen, F. van Dijk, D. Make, O. Le Gouezigou, L. Le Gouezigou, J.-G. Provost, F. Poingt, J. Landreau, O. Drisse, E. Derouin, B. Rousseau, F. Pommereau
This paper summarizes recent advances on InAs/InP mode-locked quantum dashes (QD) lasers, and their applications for
all-optical clock recovery, short pulse generation and millimeter wave generation. We demonstrate that QD FP lasers,
owing to the small confinement factor and the 3D quantification of electronic energy levels, exhibit a beating linewidth
as narrow as 15 kHz. Such an extremely narrow linewidth, compared to their QW or bulk counterparts, leads to the
excellent phase noise and time jitter characteristics when QD lasers are actively mode-locked. We report also on an
actively mode-locking tunnel injection quantum dash Fabry-Perot laser diode at 42.7GHz, generating nearly Fourier
transform limited pulses with a pulse width of 2ps over 16nm.
Quantum dot (QD) materials offer attractive performances for the development of lasers and amplifiers at 1.55μm. The
3-D quantification of the energy levels in QD leads to several advantages, such as high optical gain and efficiency, low
sensitivity to temperature variations, low noise and low linewidth enhancement factor. We shall present in this paper the
growth and basic properties of QD materials for lasers and amplifiers, and device performances with particular interest
for optical communications and microwave transmission.
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