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A highly coherent and flat optical frequency comb (OFC) based on an optoelectronic oscillator (OEO) is presented using a dual-mode microcavity laser. In this scheme, the microcavity laser is applied as a light source and a photonic microwave filter simultaneously. The dual-mode is phase-locked in the self-injection OEO configuration. Meanwhile, a 10-tones OFC with a frequency spacing of 28.8 GHz is generated without an external microwave source. The generated OFC is further broadened through a parametric frequency mixer by the dispersion compensation and nonlinear expansion technique. Forty-three optical tones with a 5-dB power variation spanning over 10 nm are obtained. [ABSTRACT FROM AUTHOR]

An approach to achieving a highly selective and stable dual-passband microwave photonic filter (MPF) is presented. The dual-passband MPF is realized based on the phase-to-intensity modulation conversion by stimulated Brillouin scattering (SBS). The core of the proposed scheme is a two-tone pump generation by a directly modulated microcavity laser instead of two individual lasers or electro-optic modulators (EOMs), which makes the system relatively simple and stable. The center frequency of the MPF can be tuned from 0 to 20 GHz by adjusting the modulation frequency of the microcavity laser, where the center frequencies of the two passbands are related. The 3-dB bandwidth and the out-of-band rejection ratio of each passband are about 38 MHz and lager than 28.5 dB, respectively. The frequency stability of the MPF is also verified experimentally. [ABSTRACT FROM AUTHOR]

All-optical switching and multiple logic gates are experimentally demonstrated using AlGaInAs/InP hybrid square-rectangular lasers. Controllable bistability induced by saturable absorption in the square microcavity is achieved around the threshold with the square cavity in an open circuit state. Based on the bistability, all-optical switching operation is realized by injecting set/reset optical signals with the wavelengths around the lasing mode of 1529.9 nm and another high-Q mode at 1560 nm. Furthermore, mode competitions between three resonant modes around 1541 nm with an interval of 1.2 nm are used to realize all-optical multiple logic gates of NOT, NOR, and NAND functions under low-power optical pulses, with injecting currents to the square and rectangular sections. The static extinction ratio of 34, 40 and 24 dB are obtained for NOT, NOR, and NAND gates, respectively, and the dynamic extinction ratio over 10 dB of NOT function at 15 Gb/s, NOR and NAND functions at 2 Gb/s are demonstrated. With the merits of multifunctional operations, large optical injection wavelength tolerant ranges, low power consumption, small footprint and suitability for on-chip integration, the device offers a potential solution for all-optical signal processing in photonic integration circuits. [ABSTRACT FROM AUTHOR]

Dual-mode microcavity semiconductor lasers are investigated for potential applications in photonic microwave and optical frequency comb (OFC) generation. By regulating whispering-gallery modes (WGMs) in square microcavities, dual-mode lasing is achieved with frequency intervals ranging from tens to hundreds of gigahertz. In the square microcavities, the fundamental and first-order transverse WGMs have spatially separated field distributions, which allow stable dual-transverse-mode lasing with mode intervals inversely proportional to the cavity areas. Dual-transverse-mode square microcavity lasers are experimentally demonstrated with frequency intervals ranging from ∼35 to ∼150 GHz. Photonic microwaves and OFCs are successfully generated based on the dual-mode square microcavity lasers. To enhance the transverse-mode intervals, circular-side square microcavity lasers with a square hole in the center are proposed and demonstrated, and dual-transverse-mode lasing with a frequency interval up to ∼0.56 THz is obtained. Furthermore, a square-Fabry–Pérot coupled-cavity microlaser is demonstrated to increase the output power and introduce an additional degree for manipulating the lasing modes. Dual-mode lasing is realized with a frequency interval of ∼0.5 THz, a single mode optical fiber coupled power of ∼3 mW, and a wavelength tuning range of ∼10 nm. [ABSTRACT FROM AUTHOR]

The optoelectronic oscillators (OEOs) based on a 1.55-μm direct-modulated AlGaInAs/InP square microcavity laser without optical injection are demonstrated for narrow-linewidth photonic microwave signal generation. The square microcavity laser with a side length of 16 μm under an injection current of 14 mA is used in the experiment. High-quality photonic microwave signals with 3-dB linewidths around 30 Hz are obtained by the first harmonics of the single-loop and dual-loop OEOs. Single-sideband phase noise at 10 kHz frequency offset is as low as −116 dBc/Hz for the microwave signal. With the dual-loop OEO, the side-mode suppression ratios up to 55 dB are obtained for the first harmonics, and tunable microwave signals from 1.85 to 10.24 GHz are realized with narrow linewidths and low-phase noises. [ABSTRACT FROM AUTHOR]

Whispering-gallery mode (WGM) microlasers are potential light sources for monolithic photonic integration circuits and optical interconnects. In this study, stable single-mode hybrid square-rectangular lasers (HSRLs) are reported, based on mode coupling between WGM and Fabry–Pérot (FP) modes. Mode selection mechanisms are explained based on numerical results of the resonant reflection of the square microcavity and energy distributions of coupled mode in the two cavities, and the reduction of effective linewidth enhancement factor is expected as two cavities are modulated individually. HSRLs with different sizes are fabricated by contact photolithography and dry-etching techniques. For a hybrid laser with a square-side length a = 15 μm and the FP cavity length and width of L = 300 μm and d = 2 μm, stable single-mode operation with a side-mode suppression ratio up to 47 dB is obtained, and a small-signal modulation bandwidth of 13.3 GHz is realized by modulating the current of the FP cavity. The dynamic characteristics are further investigated for the hybrid laser. Furthermore, threshold currents and tunable behaviors are compared for HSRLs with a = 10, 15, and 20 μm and d = 1.5 and 2 μm. [ABSTRACT FROM PUBLISHER]

Square microcavity lasers with a cut-corner are proposed and demonstrated for realizing unidirectional emission single-mode lasers. The mode characteristics of the square resonator with a cut-corner are investigated by 2-D finite-element method simulation. Far filed patterns with single petal and double petals are obtained numerically for symmetric and anti-symmetric modes, respectively. Square microcavity lasers with a cut-corner are fabricated using planar photolithography and inductively coupled-plasma etching techniques. A continuous-wave single-mode operation with a side mode suppression ratio of 31 dB is achieved at an injection current of 25 mA for a 20 \mu \textm -side-length square microcavity laser with a cut-corner width of 10 \mu \textm . The far field patterns agreement with the simulated symmetric and anti-symmetric modes are observed at different injected currents. [ABSTRACT FROM AUTHOR]