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.
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.
Nonlinear dynamics of mutually injected twin-microring semiconductor lasers are studied numerically and experimentally. For the twin-microring laser, a bridge waveguide directly connecting two ...identical microrings is utilized to realize mutual optical injection or mode coupling. The coupling coefficient is related to the waveguide parameter and influences the mutual injection process dramatically. By adjusting the frequency offset between two microrings, four-wave mixing, injection locking, periodic, and multi-period oscillation states are observed from the experimental lasing spectra. The plentiful nonlinear dynamical states are induced by the mode interaction between the two microrings and can be well explained by the rate equations with mutual optical injection.
A four‐channel directly modulated square‐rectangular laser array was demonstrated in 1.3 μm wavelength range with the wavelength interval about 5 nm. The laser array shows stable single mode ...operation with the side‐mode suppression ratio (SMSR) over 30 dB, 3‐dB modulation bandwidth above 11.8 GHz and an open‐eye diagram is obtained at data rates of 10 Gb/s, and the relative intensity noise (RIN) about −138 dB/Hz up to 5 GHz for all channels.
In this work, we investigate an alternative directly modulated laser solution with applications to multiwavelength 25 Gb/s systems. The presented solution is based on a hybrid ...square/rhombus-rectangular laser (HSRRL), which consists of a Fabry–Pérot (FP) cavity and a square/rhombus microcavity (SRM). This structure is implemented and demonstrates single-mode lasing over a wide wavelength tuning range (30.8 nm). Single-mode operation is achieved with a side-mode suppression ratio (SMSR) greater than 30 dB and a linewidth of 10 MHz. Furthermore, with an electrical 3 dB bandwidth of 10 GHz. It is possible to directly modulate at 25 Gb/s with promising performance. These devices are simple and they are expected to meet the cost and power requirements of current networks.
All-optical flip-flop has been demonstrated experimentally based on our optical bistable hybrid square-rectangular lasers. In this paper, dual-mode rate equations are utilized for studying the ...optical bistability in the two-section hybrid-coupled semiconductor laser. A phenomenological gain spectrum model is constructed for considering the mode competition in gain section and saturable absorption effect in the absorptive section in a wide wavelength range. The mechanisms of the optical bistability are verified in the aspect of the distribution of carriers and photons in the two-section hybrid-coupled cavity. In addition, we find that with the adjustment of the device parameters, both of the width and biasing current for achieving the bistability can be tuned for a wide range. Furthermore, a dynamic response of all-optical flip-flop is simulated, using a pair of set/reset optical triggering pulses, in order to figure out the laws for faster transition time with lower power consumption.
We demonstrated a narrow linewidth semiconductor laser based on a deep-etched sidewall grating active distributed Bragg reflector (SG-ADBR). The coupling coefficients and reflectance were numerically ...simulated for deep-etched fifth-order SG-ADBR, and a reflectance of 0.86 with a bandwidth of 1.04 nm was obtained by the finite element method for a 500-period SG-ADBR. Then the fifth-order SG-ADBR lasers were fabricated using projection i-line lithography processes. Single-mode lasing at 1537.9 nm was obtained with a high side-mode suppression ratio (SMSR) of 65 dB, and a continuous tuning range of 10.3 nm was verified with SMSRs greater than 53 dB. Furthermore, the frequency noise power spectral density was characterized, from which a Lorentzian linewidth of 288 kHz was obtained.
A narrow linewidth optical frequency comb (OFC) based on a directly modulated microcavity laser with external optical feedback is investigated numerically and demonstrated experimentally. Based on ...the numerical simulations with rate equations, the evolution of the optical and electrical spectra is presented for the direct-modulated microcavity laser with increased feedback strength, and the linewidth property is improved at suitable feedback conditions. The simulation results also show good robustness for the generated OFC in terms of feedback strength and phase. Moreover, the OFC generation experiment is performed by combining with the dual-loop feedback structure to suppress the side mode, and an OFC with a side-mode suppression ratio of 31 dB is realized. Thanks to the high electro-optical response of the microcavity laser, a 15-tone OFC with a frequency interval of 10 GHz is obtained. Finally, the linewidth of each comb tooth is measured to be around 7 kHz under the feedback power of 47 µW, which indicates an enormous compression of approximately 2000 times compared with the free-running continuous-wave microcavity laser.
We propose and demonstrate a circular-side octagonal microcavity (COM) semiconductor laser with a spatially distributed current injection for manipulating the lasing modes. There are two types of ...high-quality-factor whispering-gallery (WG) modes with distinct field patterns in a COM: the four-bounced quadrilateral modes and the eight-bounced octagonal modes. By designing two separated p-electrodes, the COM laser is divided into two regions that are pumped independently to select specific modes for lasing. The two types of WG modes lase simultaneously when the two regions are injected with equivalent currents. Degeneracy removal of the quadrilateral modes is observed in both simulation and experiment when the two regions are injected with inequivalent currents. The quadrilateral modes are suppressed when one of the two regions is un-injected or biased with a negative current, and single-octagonal-mode lasing is realized. The results show that the lasing modes can be efficiently manipulated with the spatially distributed current injection considering the distinct field patterns of different WG modes in the microcavities, which can promote the practical application of the microcavity lasers.
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