On-chip Si3N4 microcavities composed of multi-mode waveguides can achieve high-quality factor and anomalous dispersion simultaneously, which is necessary for solitons generation. It has been proven to be a promising platform for compact optical (Kerr) frequency comb generation. To further reduce the threshold power for generating a single soliton microcomb, a racetrack Si3N4 microcavity with Euler bends is reported. Compared with traditional racetrack microcavities, Euler bending can significantly suppress the sudden change in bending radius at the waveguide connection, which suppresses mode interactions and reduces propagation losses, resulting in an increase in Q factor value. Based on this racetrack microcavity, using the auxiliary laser heating method, a single soliton frequency comb with a repetition rate of 34 GHz and a 3 dB bandwidth exceeding 18 nm (corresponding to a pulse duration of 143 fs) can be generated using only a 19 mW pump laser (estimated on-chip pump power below 10 mW). The optimized racetrack microcavities can be building blocks for integrated photonics systems.
Based on a high power InGAsP distributed feedback (DFB) semiconductor laser coupling with an ultra-high-Q silicon nitride microring, we proposed a hybrid integration semiconductor laser scheme for realizing high power and narrow linewidth. For such a scheme, the high power DFB laser serves as the light source, whose output is efficiently coupled into the input waveguide port of ultra-high-Q silicon nitride microring through a silicon lens. Under the optical feedback provided by the Rayleigh scattering in the inhomogeneity silicon nitride microring, the laser may be driven into the self-injected locking state, under which the lasing linewidth can be obviously narrowed. The experimental results demonstrate that, adopting such a hybrid integration scheme, the lasing linewidth can be narrowed to 10 kHz and meanwhile the output power is maintained at the level of 20 mW. The hybrid integration semiconductor lasers have application prospects in some fields simultaneously requiring high coherence and high power, such as LiDAR and long-distance coherence communication.
We proposed an integrated semiconductor laser scheme that combines an ultra-high Q silicon nitride microresonator with a DBR semiconductor laser, resulting in a tunable ultra-narrow linewidth laser. The experiment achieves tuning within the wavelength range of 1554.2-1557.15nm (about 370GHz), being almost ten times larger than that of reported DFB scheme. Moreover, the sidemode suppression ratio is low to 52dB with a ultra-narrow linewidth about 6.6kHz. It needs the joint adjustment of DBR operating current, coupling of the high-Q silicon nitride external cavity. These results can be applied in fields such as dense wavelength division multiplexing systems and integration LiDAR System.
In this work, a new scheme based on a Si3N4 microresonator for generating parallel pulsed chaos is proposed, and the performances of the parallel pulsed chaos and its application in imaging are experimentally investigated. Under optical injection with suitable injection parameters, the Si3N4 microresonator can output a continuous wave (CW) chaotic microcomb including nearly 100 comb lines. After passing through an acousto-optic modulator, the CW chaotic microcomb can be transferred into pulsed chaotic microcomb, in which each comb line provides a pulsed chaos. Therefore, parallel pulsed chaos signal can be generated. Taken the parallel pulsed chaos signal as the emitting resource of lidar, the quality of imaging has been analyzed. The experimental results show that clear target imaging can be achieved.
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