Abstract
Chaotic semiconductor lasers have been widely investigated for generating unpredictable random numbers, especially for lasers with external optical feedback. Nevertheless, chaotic lasers ...under external feedback are hindered by external feedback loop time, which causes correlation peaks for chaotic output. Here, we demonstrate the first self-chaotic microlaser based on internal mode interaction for a dual-mode microcavity laser, and realize random number generation using the self-chaotic laser output. By adjusting mode frequency interval close to the intrinsic relaxation oscillation frequency, nonlinear dynamics including self-chaos and period-oscillations are predicted and realized numerically and experimentally due to internal mode interaction. The internal mode interaction and corresponding carrier spatial oscillations pave the way of mode engineering for nonlinear dynamics in a solitary laser. Our findings provide a novel and easy method to create controllable and robust optical chaos for high-speed random number generation.
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.
Nonlinear dynamics in semiconductor lasers have been realized by external optical injection, optical feedback, optoelectronic feedback, and mutual coupling. In this article, an experimental ...demonstration of nonlinear dynamics in a solitary whispering-gallery mode microcavity laser is achieved based on the internal mode interaction. A natural hybrid quadrilateral mode exists in a circular-sided octagonal microcavity, which is coupled by two independent orbital modes formed by the sub-adjacent total reflection. By designing a spatially selective injection area along the field distribution of one quadrilateral mode, the hybrid quadrilateral mode is decoupled into two quadrilateral modes. The frequency offset between two decoupled modes is tuned through the non-uniform injection current. The interaction between the decoupled modes in the isolated-selectively-injected microlaser facilitates abundant nonlinear dynamics including mode locking, four-wave mixing, period-two oscillation and weak chaotic state. Our scheme provides a method for self-generated nonlinear dynamics, and paves the way for mode engineering of tailoring lasing actions in microcavity lasers.
We report the latest development in high-speed directly modulated tunable laser based on simple and compact hybrid square/rhombus-rectangular laser (HSRRL), aiming for low-cost deployment in next ...generation high-throughput optical interconnects, intra-/inter-data center networks, and optical fiber communication system. The HSRRL is composed of a deformed square whispering gallery mode (WGM) microcavity and a Fabry-Pérot (FP) cavity, and the WGM microcavity is used as an end face of the FP cavity with mode selection. A deformable WGM microcavity is designed to obtain a high reflectivity. The HSRRL, fabricated with deep-etching processing steps similar to FP laser without grating or epitaxial regrowth, has achieved 7-mA threshold current, 0.4-mW/mA slope efficiency, above 52-dB side mode suppression ratio (SMSR), and 16.2-GHz modulation bandwidth with injection currents of 34.3 mA and 60 mA for WGM microcavity and FP cavity, respectively. A wavelength tuning from 1537.40 nm to 1570.42 nm is realized by adjusting the injection currents simultaneously. In the tuning range, the laser has an SMSR greater than 40 dB, a linewidth less than 4 MHz, and a 3-dB modulation bandwidth greater than 14 GHz.
Organic single‐crystalline materials have attracted great attention for laser applications. However, the fabrication of laser resonators and pattern of crystals are still intractable problems. ...Organic single crystals have been limited to fundamental property studies despite their superior photonic characteristics. In this work, whispering‐gallery mode (WGM) resonators of BP1T and BP2T crystalline materials have been fabricated through a combination method with improved lithography and dry etching. Crystalline microresonators with different geometries over a large area are top‐down fabricated with submicrometer spatial resolution. WGM lasing oscillation from circular, hexagonal, pentagonal and square resonators is definitively observed. The BP1T and BP2T crystals are characterized with high refractive index, and stable lasing in aqueous solution is demonstrated besides in the air environment. It is expected that organic crystalline materials would be used for the practical applications in a variety of organic electronic and optical devices.
Organic single‐crystalline materials have attracted great attention for laser applications. However, the fabrication of laser resonators and pattern of crystals are still intractable problems. Organic single crystals have been limited to fundamental property studies despite their superior photonic characteristics. In this work, whispering‐gallery mode (WGM) resonators of BP1T and BP2T crystalline materials have been fabricated through a combination method with improved lithography and dry etching. Crystalline microresonators with different geometries over a large area are top‐down fabricated with submicrometer spatial resolution. WGM lasing oscillation from circular, hexagonal, pentagonal and square resonators is definitively observed. The BP1T and BP2T crystals are characterized with high refractive index, and stable lasing in aqueous solution is demonstrated besides in the air environment. It is expected that organic crystalline materials would be used for the practical applications in a variety of organic electronic and optical devices.
Dielectric optical microcavities have been explored as an excellent platform to manipulate the light flow and investigate non‐Hermitian physics in open optical systems. For whispering gallery mode ...optical microcavities, modifying the rotational symmetry is highly desirable for intriguing phenomena such as degenerated chiral modes and directional light emission. However, for the state‐of‐the‐art approaches, namely deforming the cavity geometry by precision lithography or introducing local scatterers near the cavity boundary via micromanipulation, there is a lack of flexibility in fine‐adjusting of chiral symmetry and far‐field emission direction. Here, precise engineering of cavity boundary using electron‐beam‐induced deposition is reported based on rolled‐up nanomembrane‐enabled spiral‐shaped microcavities. The deformation of outer boundary results in delicate tailoring of asymmetric backscattering between the outer and inner rolling edges, and hence deterministically strong mode chirality. Besides, the crescent‐shaped high‐index nanocap leads to modified light tunneling channels and inflected far‐field emission angle. It is envisioned that such a localized deposition‐assisted technique for adjusting the structural deformation of 3D optical microcavities will be highly useful for understanding rich insights in non‐Hermitian photonics and unfolding exotic properties on lasing, sensing, and cavity quantum electrodynamics.
A flexible scheme of tailoring 3D whispering gallery mode resonances is enabled in a spiral nanomembrane microcavity by localized nano‐modification. The deformation of the cavity outer boundary leads to tailored resonant light out‐coupling and asymmetric backscattering between clockwise and counter‐clockwise components. As a result, the directional light emission and mode chirality are efficiently steered in a controllable manner.
A coherent optical frequency comb with a gigahertz line spacing is important in diverse fields, such as calibration of astronomical spectrographs and wavelength division multiplexing optical ...communications. In this paper, we realize octave-spanning 10-GHz optical combs using a directly-modulated 1.55 μm microlaser as a seeding source. A 6.4 ps transform-limited pulse is successfully generated from the directly-modulated laser output through optimal chirp compensation in a fiber. Moreover, after amplifying by an EDFA, the optical pulse width is further reduced to 140 fs by combing the self-phase modulation effect and the anomalous group velocity dispersion in commercial fibers. Finally, a coherent optical comb spanning from 900-2400 nm is produced in a home-made fluorotellurite fiber using the 140-fs pulse boosted to a few Watts as a seeding source. The experimental results demonstrate that optical combs generated from the directly-modulated microlaser have the potential for a fully stabilized frequency comb.
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.
Low relative intensity noise (RIN) was demonstrated experimentally for hybrid square-rectangular lasers (HSRLs). In this paper, RIN of the HSRL is numerically simulated and the laser linewidth is ...investigated theoretically and experimentally. The non-zero delayed self-heterodyne method is utilized to measure the linewidth, and the laser linewidth of 2.9 MHz is obtained experimentally. A two-section single-mode rate equation model including Langevin noise sources is established to study the noise characteristics theoretically. The time-varying mode photon density and frequency are simulated, then the intensity and frequency noise (FN) spectra are calculated. With the rising of bias currents, RIN decreases and approaches the standard quantum limit. Large mode Q -factor, high bias current, and passive square microcavity are effective methods to reduce FN and linewidth of the HSRLs. By inducing a passive square microcavity, we can expect a low linewidth of 37 kHz for the hybrid-cavity laser with Q = 1.17 × 10 4 .
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.
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