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Supercontinuum generation has been extensively studied in optical waveguides pumped with femtosecond pulses, while there are few reports using picosecond pump pulses with a small spectral power variation. In this paper, we numerically demonstrate the supercontinuum generation in a dispersion-engineered silicon nitride waveguide pumped with 10-ps pulses at 1550 nm wavelength. A supercontinuum from 656 to 3867 nm (2.5 octaves) is enabled by uniquely tailored dispersion. The spectrum has a power variation of < 15 dB and shows a very flat pedestal varying by < 5 dB. The spectra generated from different dispersion profiles are compared and analyzed, which verifies the unique role of dispersion tailoring in flattened supercontinuum generation. To the best of our knowledge, it is the first study on such broad and flat supercontinuum generation on a chip using picosecond pump pulses, which would be highly desirable for many applications. [ABSTRACT FROM AUTHOR]

Manipulating radio frequency (RF) signals in integrated photonic devices has recently emerged as a new paradigm for wireless communications, enabling high-frequency signal processing and broadband frequency agility in miniaturized photonic platforms. These advances are crucial for space and airborne applications which are weight and size sensitive. Recent progress in on-chip stimulated Brillouin scattering (SBS) using high gain has shown great potentials for RF photonic signal processing, owing to its inherent advantages of high resolution, high reconfigurability, and flexible programmability. On-chip SBS serves as a versatile and high-performance toolbox to process and manipulate the amplitude and phase of RF signals in the optical domain. In this paper, we provide a brief overview of recent advances achieved using SBS in planar waveguides, with a focus on applications requiring phase control of RF signals, including phase shifters, delay lines, and separate carrier tuning. We introduce a power-efficient scheme based on the concept of phase amplification to improve Brillouin-based phase processing capability. [ABSTRACT FROM AUTHOR]

In this paper, terahertz (THz) generation in nonlinear plasmonic waveguides is proposed and thoroughly investigated. The proposed plasmonic waveguide is composed of metal–insulator–metal nanostructure filled with lithium niobate. The THz generation is conducted by means of difference-frequency generation of surface plasmon-polariton (SPP) modes. The SPP modes are designed to be tightly confined inside the plasmonic waveguide, while the generated THz waves diffract rapidly to propagate outside the plasmonic waveguide. It then follows that the THz absorption is minimized. It is shown that viable THz generation can be achieved, despite the SPP losses, by properly choosing the SPP wavelengths and the waveguide dimension. Our numerical evaluations show viable THz generation over the entire frequency band from 1 to 10 THz. The proposed structure introduces a new modality of having the SPP modes totally confined inside a nanoscale waveguide, while most of the generated THz waves are (and thus interacting) with the surrounding medium of the waveguide. These properties promise potential applications in nanocommunication systems and body-centric nanonetworks. [ABSTRACT FROM AUTHOR]

Wide-stripe design for high-power laser diodes (LDs) permits multilateral-mode optical field distribution and the formation of an unstable filament pattern within the active waveguide. This is a serious drawback leading to a decrease in the emitted beam quality. The filaments cause spatial and time fluctuations in the LDs near- and far-field (FF) characteristics due to their random nature. The multimode optical field induces a widening of the FF pattern (known as FF blooming effects) as the drive current increases due to an increasing number of lateral modes. In this paper, the gain shaping in the LDs active region by ion implantation is proposed as a way to induce beam stability improvement. The optical resonator of the presented LDs consists of a series of interlaced narrow high- and low-gain stripes. The low-gain stripes are pumped only by spreading the current from neighboring stripes. The calculations show that under such conditions, one of the higher lateral modes can be excited at laser threshold due to the best spatial fit to the stripe’s periodicity. This should restrict the FF blooming effect. The predictions are confirmed by measurements of the LDs based on the multistripe design. A reduction of the optical field intensity fluctuations has also been observed. [ABSTRACT FROM AUTHOR]

In this paper, the gain, phase, and refractive index dynamics of photonic crystal quantum-dot semiconductor optical amplifiers (PC-QDSOAs) are investigated for the first time. For this purpose, we establish a comprehensive nonlinear state space model with 1088 state variables to simulate the carrier dynamics of the inhomogeneously broadened InAs/GaAs QD active region embedded in a flat-band slow-light photonic crystal waveguide. The gain and phase recovery responses are monitored during the amplification of an ultrashort pump pulse. Simulation results show that changes in refractive index in the PC-QDSOA active region are much stronger than the index changes in the conventional QDSOAs. In addition, the gain and phase recovery time in PC-QDSOAs are similar to those in the conventional QDSOAs based on ridge waveguide structures. Also, we found that the injected current and the consumed power in PC-QDSOAs can be two orders of magnitude less than those values in the conventional QDSOAs. [ABSTRACT FROM AUTHOR]