155-μm distributed feedback laser monolithically integrated with amplifier array

We present a laterally coupled 1.55-μm distributed feedback laser monolithically integrated with multistage multimode interferences and semiconductor optical amplifiers, using low-bias currents and providing an output power of ∼100  mW with a quasi-single spatial-mode far-field pattern and low divergence angle of 3.5° in the horizontal direction. The fabrication techniques are based on side-wall gratings and quantum-well intermixing and offer a simple, flexible, and low cost alternative to conventional methods

Photonic integrated circuits based on quantum well intermixing techniques

The passive sections of a monolithic device must have a wider bandgap than the active regions to reduce losses due to direct interband absorption. Such bandgap engineering is usually realized by complicated regrown butt-joint or selective-area growth techniques. We, however, have developed a simple, flexible and low-cost alternative technique – quantum well intermixing (QWI) – to increase the bandgap in selected areas of an integrated device post-growth. To verify the QWI process, we have fabricated the following demonstrators: a 40 GHz semiconductor mode-locked laser producing pulses as short as 490 fs; a 10 GHz passively mode-locked extended cavity laser integrated with surface-etched distributed Bragg reflector (DBR) which can be tuned in both wavelength and pulse repetition rate; four 10 GHz 1.55 μm AlGaInAs/InP mode-locked surfaced-etched DBR lasers integrated combiner, a semiconductor optical amplifier and modulator where the four channels can be operated separately or simultaneously; a CWDM source with 12 nm wavelength separation based on an AlGaInAs/InP integrated distributed feedback laser array; and a 1.55 μm DFB laser monolithically integrated with power amplifier array. In all these applications, QWI has the advantage of eliminating crystal regrowth and the associated stringent tolerance requirements that are required in traditional integration schemes

THz Repetition Frequency Mode-Locked Laser Using Novel Sampled Gratings

Conventional sampled grating distributed-Bragg-gratings (C-SGDBRs) are widely used in tunable DBR lasers [1], and more recently have been used to precisely control the wavelength spacing in arrays of DBR lasers for use in WDM systems [2], and as the reflectors in THz repetition frequency (Fr) semiconductor mode locked lasers (SMLLs) [3]. However, the effective coupling coefficient, κ, of a C-SGDBR (Fig. 1(a)) is necessarily reduced substantially from that of a uniform grating because much of the sampled grating period has no grating. Here, for the first time, we apply a combination of π-phase shifted gratings, previously demonstrated in fiber lasers [4], with the C-SGDBR technique to THz repetition frequency SMLLs. Using a single electron beam lithography (EBL) step we have demonstrated a 620 GHz side-wall SGDBR MLL with an increased effective κ

Integrated Phase-locked Laser Diodes at 1.55μm

Two types of integrated phased locked laser diodes operating at 1.55 μm were demonstrated, using either a distributed feedback laser seeding source or a self-locking multi-mode interference array. Both exhibited far field patterns that reflected mutual coherence between the light from the output waveguides

Improvement of indoor VLC network downlink scheduling and resource allocation

Indoor visible light communications (VLC) combines illumination and communication by utilizing the high-modulation-speed of LEDs. VLC is anticipated to be complementary to radio frequency communications and an important part of next generation heterogeneous networks. In order to make the maximum use of VLC technology in a networking environment, we need to expand existing research from studies of traditional point-to-point links to encompass scheduling and resource allocation related to multi-user scenarios. This work aims to maximize the downlink throughput of an indoor VLC network, while taking both user fairness and time latency into consideration. Inter-user interference is eliminated by appropriately allocating LEDs to users with the aid of graph theory. A three-term priority factor model is derived and is shown to improve the throughput performance of the network scheduling scheme over those previously reported. Simulations of VLC downlink scheduling have been performed under proportional fairness scheduling principles where our newly formulated priority factor model has been applied. The downlink throughput is improved by 19.6% compared to previous two-term priority models, while achieving similar fairness and latency performance. When the number of users grows larger, the three-term priority model indicates an improvement in Fairness performance compared to two-term priority model scheduling

The Impacts of North American BSE Discoveries on U.S. and Canadian Cattle Prices

Demand and Price Analysis, Research and Development/Tech Change/Emerging Technologies,

Laterally-Coupled Dual-Grating Distributed Feedback Lasers for Generating Mode-Beat Terahertz Signals

We present a laterally-coupled AlGaInAs/InP DFB laser emitting two longitudinal modes simultaneously within the same cavity and integrated with EAM. A stable 0.82 THz beating signal was observed over a wide range of bias parameters

Novel Sampled Grating Design for High Precision, Multiple Wavelength DFB Laser Arrays

No abstract available

1.55 µm AlGaInAs/InP sampled grating laser diodes for mode-locking at THz frequencies

We report mode locking in lasers integrated with semiconductor optical amplifiers, using either conventional or phase shifted sampled grating distributed Bragg reflectors(DBRs). For a conventional sampled grating with a continuous grating coupling coefficient of ~80 cm-1, mode-locking was observed at a fundamental frequency of 628 GHz and second harmonic of 1.20 THz. The peak output power was up to 142 mW. In the phase shifted sampled grating design, the grating is present along the entire length of the reflector with π-phase shift steps within each sampled section. The effective coupling coefficient is therefore increased substantially. Although the continuous grating coupling coefficient for the phase shifted gratings was reduced to ~23 cm-1 because of a different fabrication technology, the lasers demonstrated mode locking at fundamental repetition frequencies of 620 GHz and 1 THz, with a much lower level of amplified spontaneous emission seen in the output spectra than from conventional sampled grating devices. Although high pulse reproducibility and controllability over a wide operation range was seen for both types of grating, the π-phase-shifted gratings already demonstrate fundamental mode-locking to 1 THz. The integrated semiconductor optical amplifier makes sampled grating DBR lasers ideal pump sources for generating THz signals through photomixing

Fully integrated multi-optoelectronic synthesizer for THz pumping source in wireless communications with rich backup redundancy and wide tuning range

We report a monolithic photonic integrated circuit (PIC) for THz communication applications. The PIC generates up to 4 optical frequency lines which can be mixed in a separate device to generate THz radiation, and each of the optical lines can be modulated individually to encode data. Physically, the PIC comprises an array of wavelength tunable distributed feedback lasers each with its own electro-absorption modulator. The lasers are designed with a long cavity to operate with a narrow linewidth, typically <4 MHz. The light from the lasers is coupled via an multimode interference (MMI) coupler into a semiconductor optical amplifier (SOA). By appropriate selection and biasing of pairs of lasers, the optical beat signal can be tuned continuously over the range from 0.254 THz to 2.723 THz. The EAM of each channel enables signal leveling balanced between the lasers and realizing data encoding, currently at data rates up to 6.5 Gb/s. The PIC is fabricated using regrowth-free techniques, making it economic for volume applications, such for use in data centers. The PIC also has a degree of redundancy, making it suitable for applications, such as inter-satellite communications, where high reliability is mandatory