Carlos Gordon

On-Chip Multiple Colliding Pulse Mode-Locked Semiconductor Laser

We report for the first time to the best of our knowledge, an on-chip multiple colliding pulse mode-locked semiconductor laser source. The device structure is fully integrated, replacing cleaved facet mirrors by using multimode interference reflectors; this allows us to precisely control the location of the saturable absorbers within the cavity length, which is critical to achieve the multiple colliding regime. In this paper, we succeeded to achieve this regime generating a repetition rate at four times the fundamental round-trip frequency, demonstrating a repetition rate within the millimeter wave frequency range, at 100 GHz using a 25 GHz resonator cavity length. We also demonstrate the advantage of having the signal on-chip including a boost semiconductor optical amplifier in order to increase the output optical power. This novel structure was fabricated on a generic InP photonic integrated technology through a multi-project wafer run.

Mode-locked laser with pulse interleavers in a monolithic photonic integrated circuit for millimeter wave and terahertz carrier generation

This Letter presents a photonics-based millimeter wave and terahertz frequency synthesizer using a monolithic InP photonic integrated circuit composed of a mode-locked laser (MLL) and two pulse interleaver stages to multiply the repetition rate frequency. The MLL is a multiple colliding pulse MLL producing an 80 GHz repetition rate pulse train. Through two consecutive monolithic pulse interleaver structures, each doubling the repetition rate, we demonstrate the achievement of 160 and 320 GHz. The fabrication was done on a multi-project wafer run of a generic InP photonic technology platform.

Numerical modeling and parameterization of on-chip colliding pulse mode-locked lasers

The successful numerical modeling and parameterization of on-chip colliding pulse mode-locked lasers by using the simulation tool FreeTWM based on Matlab is reported. We have been able to reproduce the performance of on-chip colliding pulse mode-locked lasers with different repetition rates within the millimeter wave frequency range. We have achieved the successful simulation of a first device working around 37 GHz and the second device working around 70 GHz due to the fact that the collision in the saturable absorber located in the middle of the resonator multiply by two the fundamental frequency of 18.5 GHz and 35 GHz, respectively. The Free TWM software is a promising candidate for the simulation and optimization of on-chip colliding pulse mode-locked lasers. So, we will avoid spending time and money on fabrication process of many samples in order to obtain an optimized device.

Millimeter-wave signal generation for a wireless transmission system based on on-chip photonic integrated circuit structures

We demonstrate and compare two different photonic-based signal sources for generating the carrier wave in a wireless communication link operating in the millimeter-wave range. The first signal source uses the optical heterodyne technique to generate a 113 GHz carrier wave frequency, while the second employs a different technique based on a pulsed mode-locked source with 100 GHz repetition rate frequency. The two optical sources were fabricated in a multi-project wafer run from an active/passive generic integration platform process using standardized building blocks, including multimode interference reflectors which allow us to define the structures on chip, without the need for cleaved facet mirrors. We highlight the superior performance of the mode-locked sources over an optical heterodyne technique. Error-free transmission was achieved in this experiment.

Comparison of photonic integrated circuits for millimeter-wave signal generation between dual-wavelength sources for optical heterodyning and pulsed mode-locked lasers

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.

InGaAs/InP-based Echelle mirror multiplexer using dual Rowland circle gratings for DFB QCL arrays in the mid-long infrared range

In this work we introduce the design, optimization, simulation and experimental characterization results of a 30-to-1 wavelength multiplexer for a Distributed Feedback Quantum Cascade Laser (DFB QCL) laser array operating in the 7- 8.5 μm (mid-long) infrared (IR) range based on an Echelle mirror using a dual Rowland circle grating scheme. This design is proposed in order to achieve a continuous tuning range overcoming the limited tunability of individual QCLs. The design is based on a DFB-QCL array with wavelength spacing of 0.05 μm, aiming to reducing coupling between the slab waveguides to a minimum. We discuss the design parameters such as the order of diffraction, the operation wavelength range in the slab waveguides and the position of both the input and output waveguides are optimized for obtaining higher output power in the overall wavelength range of the multiplexer device than in a single Rowland circle grating scheme, providing an improvement in channel transmission. Other design characteristics, such as the structure scalability and reduction in size for these devices are considered and studied, including the input/output waveguide optimization as a function of parameters such as waveguide width, etching depth and wavelength. A systematic process is presented for all steps in the design of these devices, comparing both simulated and experimental results, placing them as suitable options when compared to other IR multiplexer schemes in terms of size and transmission.

Virtual Environments to Stimulate Skills in the Early Childhood Education Stage

This article describes the development of games within virtual reality environments oriented to early childhood education children between 3 and 5 years old. These games are developed according to the Cone of Learning and have been developed with a Unity 3D graphic engine. They are very attractive and allow children’s learning through playing. They also stimulate the skills and abilities required to be developed and strengthened during this learning stage. The proposed games allow the teacher to select several difficulty levels on each game in order to stimulate the child to accomplish more complex tasks during this initial stage. At the end, the areas intended to be covered are presented according to the goals set.

Theoretical and experimental development of on-chip colliding pulse mode-locked lasers

We report the successful theoretical and experimental optimization of the absorber length of on-chip colliding pulse mode-locked lasers working at 50 GHz repetition rate. The fundamental approach is that the active-passive integration provides freedom to choose the desired gain section to saturable absorber length ratio in order to obtain stable mode-locked regimes. We have developed four on-chip colliding pulse mode-locked semiconductor laser devices with saturable absorber lengths ranging from 20 μm to 50 μm in steps of 10 μm with fundamental repetition rate at 25 GHz and twice this frequency at 50 GHz due to the fact that the colliding pulse mode-locked structure doubles the fundamental frequency. The agreement in the theoretical and experimental demonstration is that the smallest SA considered (20 μm) exhibits the shortest pulse width, which provides a transform limited time bandwidth product. The theoretical study was carried out by using the simulation tool called FreeTWM which is a free travelling wave model software designed for the study of the dynamics of multi-section semiconductor lasers, while the experimental analysis was executed on the samples fabricated in a multi-project wafer run provided by SMART Photonics foundry service.

On-chip selectable-frequency comb generation by passive harmonic mode locking

A monolithic integrated 2.8-mm colliding-pulse mode-locked laser is demonstrated to emit optical combs with switchable mode spacing for millimeter-wave generation. By selecting the DC-bias condition, the laser is forced to operate in harmonic mode locking regimes. Optical frequency combs with mode spacing of 2nd (30 GHz), 3rd (45 GHz), 4th (60 GHz) and 6th (90 GHz) harmonics are presented. The autocorrelation trace of 2nd harmonic exhibits a 1.03-ps pulsewidth. The beat note of 4th harmonic has an RF linewidth of 520 kHz.