Indium Phosphide Photonic Integrated Circuit Research Articles

Differential Absorption Lidar Transmitter Based on an Indium Phosphide Photonic Integrated Circuit for Carbon Dioxide Sensing

We demonstrate carbon dioxide sensing using a random-modulation continuous-wave differential absorption lidar transmitter based on an indium phosphide photonic integrated circuit. We have designed and characterized the photonic circuit that has been fabricated through an open access generic integration platform based on standard building blocks. It consists of three four-section distributed Bragg reflector lasers, two fast photodiodes, two electro-absorption modulators and five semiconductor optical amplifiers integrated together with several couplers and waveguides. The circuit contains two interrelated subsystems, one for performing the differential absorption lidar measurement, and the other for stabilizing the emission wavelength of the different lasers. We characterize the individual integrated devices, especially lasers, photodiodes and modulators. The carbon dioxide sensing is done by measuring a gas cell in a fiber setup emulating a lidar configuration. Our promising results pave the way to miniaturized differential absorption lidar systems, while highlighting some of the main challenges to overcome.

Dual Laser Indium Phosphide Photonic Integrated Circuit for Integrated Path Differential Absorption Lidar

An indium phosphide photonic integrated circuit (PIC) was demonstrated for integrated path differential absorption lidar of atmospheric carbon dioxide (CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). The PIC consists of two widely tunable sampled grating distributed Bragg reflector (SGDBR) lasers, directional couplers, a phase modulator, a photodiode, and semiconductor optical amplifiers (SOAs). One SGDBR laser, the leader, is locked to the center of an absorption line at 1572.335 nm using the on-chip phase modulator and a bench-top CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Herriott reference cell. The other SGDBR laser, the follower, is stepped in frequency over ±15 GHz around 1572.335 nm to scan the target CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> absorption line. The follower laser is offset locked to the leader laser with an optical phase lock loop. An SOA after the follower laser generates a pulse at each frequency step to create a train of pulses that samples the target CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> absorption line. The PIC components and subsystem are characterized and evaluated based on target performance requirements. The leader laser demonstrated a 236-fold improvement in frequency stability standard deviation when locked compared to free running and the follower laser frequency stability standard deviation compared to the leader laser was 37.6 KHz at a 2 GHz programmed offset.

Indium Phosphide Photonic Integrated Circuit Transceiver for FMCW LiDAR

We present a photonic integrated circuit (PIC) transceiver for frequency modulated continuous wave (FMCW) LiDAR applications. The transmitter consists of a widely tunable sampled grating distributed Bragg reflector laser (SGDBR) and a frequency discriminator which combines multimode interference couplers, a tunable asymmetric Mach–Zehnder Interferometer (a-MZI), and balanced photodiodes. The frequency discriminator converts frequency fluctuations of the laser to amplitude fluctuations of the photodiode currents. This provides an error signal for feedback into the laser cavity for frequency stabilization. Frequency modulation is obtained by a phase shifter in the a-MZI which tunes the quadrature point of the filter and the frequency where the error is zero. An on-chip receiver couples power from the transmitter to self-heterodyne with the time-delayed echo of a distant object. The generated beat frequency of the self-heterodyne measurement gives the echo signals time-of-flight to obtain the distance and velocity of the reflecting object. The theory of the components is described, and characterization of the transmitter and receiver is presented.

InP AAC for data compression applications

The authors propose a 2 × 2 asymmetric adiabatic coupler (AAC) indium phosphide (InP) photonic integrated circuit (PIC), suitable for tunable power applications such as all-optical data processing. The device was idealised as the key building block in Haar transform network used for image compression, allowing to perform the necessary separate addition and subtraction of incoming input signals at its output ports. The tunable behaviour of the coupler was demonstrated experimentally for addition/subtraction and splitting (with experimental coupling ratios of 77:23/14:86 and 50:50, respectively) through phase control. The use of the developed InP PIC enables a low footprint structure design together with the high-quality active components (lasers, photodetectors and phase modulators) of Fraunhofer Gesellschaft Heinrich Hertz Institute design toolkit. The proposed study provides a full experimental characterisation of the AAC, exploring its tuning properties and enabling further usage in a plethora of applications in high processing computing and data communications.

Indium Phosphide Photonic Integrated Circuits for Free Space Optical Links.

An indium phosphide (InP)-based photonic integrated circuit (PIC) transmitter for free space optical communications was demonstrated. The transmitter consists of a sampled grating distributed Bragg reflector (SGDBR) laser, a high-speed semiconductor optical amplifier (SOA), a Mach-Zehnder modulator, and a high-power output booster SOA. The SGDBR laser tunes from 1521 nm to 1565 nm with >45 dB side mode suppression ratio. The InP PIC was also incorporated into a free space optical link to demonstrate the potential for low cost, size, weight and power. Error-free operation was achieved at 3 Gbps for an equivalent link length of 180 m (up to 300 m with forward error correction).

Quantum entropy source on an InP photonic integrated circuit for random number generation

Random number generators are essential to ensure performance in information technologies, including cryptography, stochastic simulations and massive data processing. The quality of random numbers ultimately determines the security and privacy that can be achieved, while the speed at which they can be generated poses limits to the utilisation of the available resources. In this work we propose and demonstrate a quantum entropy source for random number generation on an indium phosphide photonic integrated circuit made possible by a new design using two-laser interference and heterodyne detection. The resulting device offers high-speed operation with unprecedented security guarantees and reduced form factor. It is also compatible with complementary metal-oxide semiconductor technology, opening the path to its integration in computation and communication electronic cards, which is particularly relevant for the intensive migration of information processing and storage tasks from local premises to cloud data centres.

Data readout system utilizing photonic integrated circuit

We describe a novel optical solution for data readout systems. The core of the system is an Indium-Phosphide photonic integrated circuit performing as a front-end readout unit. It functions as an optical serializer in which the serialization of the input signal is provided by means of on-chip optical delay lines. The circuit employs electro-optic phase shifters to build amplitude modulators, power splitters for signal distribution, semiconductor optical amplifiers for signal amplification as well as on-chip reflectors. We present the concept of the system, the design and first characterization results of the devices that were fabricated in a multi-project wafer run.