In this paper, we review recent results on hybrid silicon mode-locked lasers with a focus on low phase noise optical pulse generation. Taking a high level design approach to lowering phase noise, we show the need for long on-chip optical delay lines for mode-locked lasers to reach and overcome material limits. Key results include demonstration of the longest (cavity length 9 cm) integrated on-chip mode locked laser, 14 dB reduction of Lorentzian noise on a 20 GHz radio-frequency (RF) signal, and greater than 55 dB optical supermode noise suppression using harmonically mode locked long cavity laser, 10 GHz passively mode locked laser with 15 kHz linewidth using on-chip all optical feedback stabilization.
Graphene has shown promising perspectives in optical active components due to the large active-control of its permittivity-variation. This paper systematically reviews the recent developments of graphene-based optical modulators, including material property, different integration schemes, single-layer graphene-based modulator, multi-layer and few-layer graphene-based modulators, corresponding figure-of-merits, wavelength/temperature tolerance, and graphene-based fiber-optic modulator. The different treatments for graphene’s isotropic and anisotropic property were also discussed. The results showed graphene is an excellent material for enhancing silicon’s weak modulation capability after it is integrated into the silicon platform, and has great potentials for complementary metal oxide semiconductor (CMOS) compatible optical devices, showing significant influence on optical interconnects in future integrated optoelectronic circuits.
InGaN quantum dots (QDs) have attracted many research interests in recent years for their potentials to realize long wavelength visible emission from green to red, which can pave a way to fabricate the phosphor-free white light emitting diodes (LEDs). In this paper, we reported our recent progresses on InGaN QD LEDs, the discussions were dedicated to the basic physics model of the strain relaxation in self-assembled InGaN QDs, the growth of InGaN QDs with a growth interruption method by metal organic vapor phase epitaxy, the optimization of GaN barrier growth in multilayer InGaN QDs, the demonstration of green, yellow-green and red InGaN QD LEDs, and future challenges.
Recently hybrid plasmonic waveguides have been becoming very attractive as a promising candidate to realize next-generation ultra-dense photonic integrated circuits because of the ability to achieve nano-scale confinement of light and relatively long propagation distance. Furthermore, hybrid plasmonic waveguides also offer a platform to merge photonics and electronics so that one can realize ultra-small optoelectronic integrated circuits (OEICs) for high-speed signal generation, processing as well as detection. In this paper, we gave a review for the progresses on various hybrid plasmonic waveguides as well as ultrasmall functionality devices developed recently.
Plasmonics squeezes light into dimensions far beyond the diffraction limit by coupling the light with the surface collective oscillation of free electrons at the interface of a metal and a dielectric. Plasmonics, referred to as a promising candidate for high-speed and high-density integrated circuits, bridges microscale photonics and nanoscale electronics and offers similar speed of photonic devices and similar dimension of electronic devices. Various types of passive and active surface plasmon polariton (SPP) enabled devices with enhanced deep-subwavelength mode confinement have attracted increasing interest including waveguides, lasers and biosensors. Despite the trade-off between the unavoidable metal absorption loss and extreme light concentration, the ever-increasing research efforts have been devoted to seeking low-loss plasmon-assisted nanophotonic devices with deep-subwavelength mode confinement, which might find potential applications in high-density nanophotonic integration and efficient nonlinear signal processing. In addition, other plasmon-assisted nanophotonic devices might also promote grooming functionalities and applications benefiting from plasmonics.
In this review article, we give a brief overview of our recent progress in plasmon-assisted nanophotonic devices and their wide applications, including long-range hybrid plasmonic slot (LRHPS) waveguide, ultra-compact plasmonic microresonator with efficient thermo-optic tuning, high quality (Q) factor and small mode volume, compact active hybrid plasmonic ring resonator for deep-subwavelength lasing applications, fabricated hybrid plasmonic waveguides for terabit-scale photonic interconnection, and metamaterials-based broadband and selective generation of orbital angular momentum (OAM) carrying vector beams. It is believed that plasmonics opens possible new ways to facilitate next chip-scale key devices and frontier technologies.
This paper reviews the development progress of optical fiber, the producing and application of the specialty optical fiber in the world. Finally it states the leading technology of optical fiber of the world. Specialty optical fibers are series of optical fiber which could satisfy special requirements. Recently, the rapidly growing need from fiber to the home (FTTH), sensors, active optical link, energy conversion and delivery and fiber laser attracts researchers and optical companies to explore more possibilities of optical fiber and some novel specialty optical fibers were invented for the efforts. Bending insensitive optical fiber with the ability of extreme 3 mm bending diameter makes it possible to use the optical fiber as the electric wire in some extremely compact devices. Higher power was achieved in the fiber laser field with the development of rare earth doped fiber. Nanomaterials such as Au particles and ZnO nanostructures were utilized to extend the application in sensors and energy conversion. Pure silica design was commercialized to improve the radiation resistance of sensors based on fiber optics.
In this paper, we reviewed our common phase error (CPE) and intercarrier interference (ICI) compensation methods for coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. We first presented a unified CPE estimation framework combining decision-aided (DA), pilot-aided (PA) and decision feedback (DF) algorithms. The DA method is used to estimate the CPE of the current OFDM symbol based on the decision statistics of the previous symbol. DA+ PA helps increase the phase noise tolerance of DA and reduce the overhead of PA, while DA+ DF reduces the overhead to zero, achieving best performance with one more step of estimation, compensation and demodulation. We also described a modified time-domain blind intercarrier interference (BL-ICI) mitigation algorithm over non-constant amplitude formats. The new algorithm is derived from the BL-ICI algorithm over constant amplitude format for wireless networks. A new power estimation scheme was proposed for the BL-ICI algorithm to adapt to non-constant amplitude format. It has the same order of complexity with frequency domain decision-aided ICI (DA-ICI) compensation method and does not suffer from symbol decision errors. The effectiveness of both CPE and ICI compensation algorithms were demonstrated in a simulated 56-Gbit/s CO-OFDM system with various modulation formats.
This paper reviews recent progresses on optical arbitrary waveform generation (AWG) techniques, which could be used to break the speed and bandwidth bottlenecks of electronics technologies for waveform generation. The main enabling techniques for optically generating optical and microwave waveforms are introduced and reviewed in this paper, such as wavelength-to-time mapping techniques, space-to-time mapping techniques, temporal pulse shaping (TPS) system, optoelectronics oscillator (OEO), programmable optical filters, optical differentiator and integrator and versatile electro-optic modulation implementations. The main advantages and challenges of these optical AWG techniques are also discussed.
This paper investigates the slow light propagation in silicon on insulator wide slot photonic crystal waveguides (PCWs). Two design schemes are presented, relying on the dispersion engineering of hole lattice and slot, respectively. Mode patterns and band diagrams are calculated by 3D-plane wave expansion method. Then, coupling and slow light propagations are modeled using finite difference time domain method in a full Mach-Zehnder interferometer (MZI). Results show high amplitudes interference fringes and high coupling efficiencies. Fabrication and measurement of devices lead to slow light propagation with group indices above 50, while multiple scattering and localized modes near the band edge also observed. This study provides insights for losses in hollow core slot high group index waveguides.
A modal analysis is conducted for analyzing the absorption profile of high power waveguide photodiodes designed for analog optical link. The excitation of guided modes with large filling factor in the absorber is identified as a limiting factor for the performance of waveguide photodiodes at high optical power, including power handling capability, and bandwidth-efficiency product. A waveguide photodiode design, which spatially separates the input waveguide from the absorber in the lateral direction, is analyzed and experimentally demonstrated to suppress the excitation of mode with large filling factor. Photocurrent>60 mA under -4 V bias is measured, with 0.80 A/W responsivity. This design illustrates that high power handling capability can be achieved without compromising the bandwidth-efficiency product.
This paper proposed a novel broadband filter using multi-layer sub-wavelength high-contrast grating (HCG) structure. This filter has wide bandwidth and good sideband suppression. We simulated and analyzed the effects of different numbers of layers and different grating indexes on filtering performance of the broadband filter. According to the simulated results, we designed a multi-layer HCG broadband filter, which has bandwidth of 843 nm and center wavelength of 1550 nm.
An all-optical real-time chromatic dispersion (CD) monitoring technique is proposed and demonstrated for 40 Gbit/s differential phase-shifts keying (DPSK) signal, utilizing the cross modulation effects of semiconductor optical amplifier (SOA). The optical power of the output spectral components, which is from the probe’s frequency up to the signal bandwidth, is used for CD monitoring. This technique provides a wide monitoring range with large variation scale. The impacts of the polarization mode dispersion (PMD) and the optical signal-to-noise ratio (OSNR) on the CD monitoring results are theoretically analyzed and then experimentally investigated, showing that they have slight influence on the monitoring results within a certain range. Furthermore, simulated results for quadrature phase shift keying (QPSK) signal at 80 Gbit/s are also demonstrated, indicating that this technique is suitable for advanced modulated format as well.