Directly accessing octave-spanning dissipative Kerr soliton frequency combs in an AlN microresonator

Self-referenced dissipative Kerr solitons (DKSs) based on optical microresonators offer prominent characteristics allowing for various applications from precision measurement to astronomical spectrometer calibration. To date,direct octave-spanning DKS generation has been achieved only in ultrahigh-Q silicon nitride microresonators under optimized laser tuning speed or bi-directional tuning. Here we propose a simple method to easily access the octave-spanning DKS in an aluminum nitride (AlN) microresonator. In the design,two modes that belong to different families but with the same polarization are nearly degenerate and act as a pump and an auxiliary resonance,respectively. The presence of the auxiliary resonance can balance the thermal dragging effect,crucially simplifying the DKS generation with a single pump and leading to an enhanced soliton access window. We experimentally demonstrate the long-lived DKS operation with a record single-soliton step (10.4 GHz or83 pm) and an octave-spanning bandwidth (1100–2300 nm) through adiabatic pump tuning. Our scheme also allows for direct creation of the DKS state with high probability and without elaborate wavelength or power schemes being required to stabilize the soliton behavior.

Narrow-linewidth thermally tuned multi-channel interference widely tunable semiconductor laser with thermal tuning power below 50 mW

A thermally tuned multi-channel interference widely tunable semiconductor laser is designed and demonstrated,for the first time to our knowledge,that realizes a tuning range of more than 45 nm,side-mode suppression ratios up to 56 d B,and Lorentzian linewidth below 160 k Hz.Al Ga In As multiple quantum wells(MQWs)were used to reduce linewidth,which have a lower linewidth enhancement factor compared with In Ga As P MQWs.To decrease the power consumption of micro-heaters,air gaps were fabricated below the arm phase sections.For a 75μm long suspended thermal tuning waveguide,about 6.3 m W micro-heater tuning power is needed for a 2πround-trip phase change.Total micro-heater tuning power required is less than 50 m W across the whole tuning range,which is lower than that of the reported thermally tuned tunable semiconductor lasers.

Design of a single-mode directly modulated orbital angular momentum laser

We propose a design of single-mode orbital angular momentum(OAM) beam laser with high direct-modulation bandwidth. It is a microcylinder/microring cavity interacted with two types of second-order gratings: the complex top grating containing the real part and the imaginary part modulations and the side grating. The side grating etched on the periphery of the microcylinder/microring cavity can select a whispering gallery mode with a specific azimuthal mode number, while the complex top grating can scatter the lasing mode with travelling-wave pattern vertically. With the cooperation of the gratings, the laser works with a single mode and emits radially polarized OAM beams. With an asymmetrical pad metal on the top of the cavity, the OAM on-chip laser can firstly be directly modulated with electrical pumping. Due to the small active volume, the laser with low threshold current is predicted to have a high direct modulation bandwidth about 29 GHz with the bias current of ten times the threshold from the simulation. The semiconductor OAM laser can be rather easily realized at different wavelengths such as the O band, C band, and L band.

Directly modulated active distributed reflector distributed feedback lasers over wide temperature range operation(-40 to 85℃)

We experimentally demonstrated that the distributed feedback(DFB) lasers with the active distributed reflector achieved a 25.8 Gb/s operation over a wide temperature range of -40 to 85℃. The DFB lasers can achieve additional feedback from an active distributed reflector with accurately controlled phase, and single-mode yields are not related to the position of cleave. The threshold currents of the fabricated laser are 6 mA and 20 mA at -40℃ and 85℃, respectively. The side mode suppression ratio of the fabricated laser is above 50 dB at all temperatures. Transmissions of 25.8 Gb/s after 10 km single-mode fibers with clear eye openings and less than 0.8 dB power penalty over a wide temperature range have been demonstrated as well.