Sub-kHz linewidth, hybrid III-V/silicon wavelength-tunable laser diode operating at the application-rich 1647-1690 nm

Actively tunable laser action in GeSn nanomechanical oscillators

Mechanical forces induced by high-speed oscillations provide an elegant way to dynamically alter the fundamental properties of materials such as refractive index, absorption coefficient and gain dynamics. Although the precise control of mechanical oscillation has been well developed in the past decades, the notion of dynamic mechanical forces has not been harnessed for developing tunable lasers. Here we demonstrate actively tunable mid-infrared laser action in group-IV nanomechanical oscillators with a compact form factor. A suspended GeSn cantilever nanobeam on a Si substrate is resonantly driven by radio-frequency waves. Electrically controlled mechanical oscillation induces elastic strain that periodically varies with time in the GeSn nanobeam, enabling actively tunable lasing emission at >2 μm wavelengths. By utilizing mechanical resonances in the radio frequency as a driving mechanism, this work presents wide-range mid-infrared tunable lasers with ultralow tuning power consumption.

Hybrid laser diode with ultrawide wavelength-tunable range using curved directional couplers

Wavelength-tunable laser diode with a wide tuning range is required for optical communication systems and optical sensing. External cavity laser diodes with silicon-photonic wire waveguides and ring resonators have small footprint because of high refractive index contrast between Si. However, power coupling efficiency κ of conventional straight directional coupler between ring and bus waveguides have large wavelength dependence, which lowers tunable range. In this study, we demonstrate a hybrid wavelength-tunable laser diode using curved directional couplers, whose wavelength dependence on κ is low. The wavelength-tunable range record of 120.9 nm has been achieved. In addition, curved directional couplers are tolerant of waveguide width fabrication error.

Research on Narrow Linewidth External Cavity Semiconductor Lasers

Narrow linewidth external cavity semiconductor lasers (NLECSLs) have many important applications, such as spectroscopy, metrology, biomedicine, holography, space laser communication, laser lidar and coherent detection, etc. Due to their high coherence, low phase-frequency noise, high monochromaticity and wide wavelength tuning potential, NLECSLs have attracted much attention for their merits. In this paper, three main device structures for achieving NLECSLs are reviewed and compared in detail, such as free space bulk diffraction grating external cavity structure, waveguide external cavity structure and confocal Fabry–Perot cavity structure of NLECSLs. The Littrow structure and Littman structure of NLECSLs are introduced from the free space bulk diffraction grating external cavity structure of NLECSLs. The fiber Bragg grating external cavity structure and silicon based waveguide external cavity structure of NLECSLs are introduced from the waveguide external cavity structure of NLECSLs. The results show that the confocal Fabry–Perot cavity structure of NLECSLs is a potential way to realize a lower than tens Hz narrow linewidth laser output.

Research on Silicon-Substrate-Integrated Widely Tunable, Narrow Linewidth External Cavity Lasers

Widely tunable, narrow linewidth external cavity lasers on silicon substrates have many important applications, such as white-light interferometry, wavelength division multiplexing systems, coherent optical communication, and optical fiber sensor technology. Wide tuning range, high laser output power, single mode, stable spectral output, and high side-mode suppression ratio external cavity lasers have attracted much attention for their merits. In this paper, two main device-integrated structures for achieving widely tunable, narrow linewidth external cavity lasers on silicon substrates are reviewed and compared in detail, such as MRR-integrated structure and MRR-and-MZI-integrated structure of external cavity semiconductor lasers. Then, the chip-integrated structures are briefly introduced from the integration mode, such as monolithic integrated, heterogeneous integrated, and hybrid integrated. Results show that the silicon-substrate-integrated external cavity lasers are a potential way to realize a wide tuning range, high power, single mode, stable spectral output, and high side-mode suppression ratio laser output.

Electrically pumped widely tunable O-band hybrid lithium niobite/III-V laser

Significant improvements in the lithium niobate on insulator (LNOI) platform are pushing LNOI-based laser sources to the forefront of integrated photonics. Here, we report the first, to the best of our knowledge, electrically pumped hybrid lithium niobate/III-V laser by butt coupling an InP-based optical gain chip with a LNOI photonic integrated circuit (PIC). In the PIC, a Vernier filter consisting of two LNOI microring resonators is employed to select the lasing wavelength. A wavelength tuning range of more than 36 nm is achieved in the O band. The hybrid laser has a maximum on-chip optical power of 2.5 mW and threshold current density of 2.5kA/cm². A side mode suppression ratio better than 60 dB is achieved.

Hybrid-integrated diode laser in the visible spectral range

Generating visible light with wide tunability and high coherence based on photonic integrated circuits is of high interest for applications in biophotonics, precision metrology, and quantum technology. Here we present, to our knowledge, the first demonstration of a hybrid-integrated diode laser in the visible spectral range. Using an AlGaInP optical amplifier coupled to a low-loss Si₃N₄ feedback circuit based on microring resonators, we obtain a spectral coverage of 10.8 nm around 684.4 nm wavelength with up to 4.8 mW output power. The measured intrinsic linewidth is 2.3±0.2kHz.