Thin-film lithium niobate electro-optic isolator fabricated by photolithography assisted chemo-mechanical etching.

We report an electro-optic isolator fabricated on thin-film lithium niobate by photolithography-assisted chemo-mechanical etching that shows an isolation of 39.50 dB and an overall fiber-to-fiber loss of 2.6 dB.

On-Chip Integrated Yb3+-Doped Waveguide Amplifiers on Thin Film Lithium Niobate.

We report the fabrication and optical characterization of Yb3+-doped waveguide amplifiers (YDWA) on the thin film lithium niobate fabricated by photolithography assisted chemo-mechanical etching. The fabricated Yb3+-doped lithium niobate waveguides demonstrates low propagation loss of 0.13 dB/cm at 1030 nm and 0.1 dB/cm at 1060 nm. The internal net gain of 5 dB at 1030 nm and 8 dB at 1060 nm are measured on a 4.0 cm long waveguide pumped by 976 nm laser diodes, indicating the gain per unit length of 1.25 dB/cm at 1030 nm and 2 dB/cm at 1060 nm, respectively. The integrated Yb3+-doped lithium niobate waveguide amplifiers will benefit the development of a powerful gain platform and are expected to contribute to the high-density integration of thin film lithium niobate based photonic chip.

High-Production-Rate Fabrication of Low-Loss Lithium Niobate Electro-Optic Modulators Using Photolithography Assisted Chemo-Mechanical Etching (PLACE).

Integrated thin-film lithium niobate (LN) electro-optic (EO) modulators of broad bandwidth, low insertion loss, low cost and high production rate are essential elements in contemporary interconnection industries and disruptive applications. Here, we demonstrated the design and fabrication of a high performance thin-film LN EO modulator using photolithography assisted chemo-mechanical etching (PLACE) technology. Our device shows a 3-dB bandwidth over 50 GHz, along with a comparable low half wave voltage-length product of 2.16 Vcm and a fiber-to-fiber insertion loss of 2.6 dB. The PLACE technology supports large footprint, high fabrication uniformity, competitive production rate and extreme low device optical loss simultaneously, our result shows promising potential for developing high-performance large-scale low-loss photonic integrated devices.

On-chip microdisk laser on Yb3+-doped thin-film lithium niobate.

We demonstrate an on-chip Yb3+-doped lithium niobate (LN) microdisk laser. The intrinsic quality factors of the fabricated Yb3+-doped LN microdisk resonator are measured up to 3.79×105 at a 976 nm wavelength and 1.1×106 at a 1514 nm wavelength. The multi-mode laser emissions are obtained in a band from 1020 to 1070 nm pumped by a 984 nm laser and with the low threshold of 103µW, resulting in a slope efficiency of 0.53% at room temperature. Furthermore, both the second-harmonic frequency of pump light and the sum frequency of the pump light and laser emissions are generated in the on-chip Yb3+-doped LN microdisk, benefiting from the strong χ(2) nonlinearity of LN. These microdisk lasers are expected to contribute to the high-density integration of a lithium niobate on insulator-based photonic chip.

On-chip ultra-narrow-linewidth single-mode microlaser on lithium niobate on insulator.

We report an on-chip single-mode microlaser with a low threshold fabricated on erbium doped lithium-niobate-on-insulator (LNOI). The single-mode laser emission at 1550.5 nm wavelength is generated in a coupled microdisk via the inverse Vernier effect at room temperature, when pumping the resonator at 977.7 nm wavelength. A threshold pump power as low as 200 µW is demonstrated due to the high quality factor above 106. Moreover, the measured linewidth of the microlaser reaches 348 kHz without discounting the broadening caused by the utilization of optical amplifiers, which is, to our knowledge, the best result in LNOI microlasers. Such a single-mode microlaser lithographically fabricated on chip is in high demand by the photonics community.

An Ultra-High-Q Lithium Niobate Microresonator Integrated with a Silicon Nitride Waveguide in the Vertical Configuration for Evanescent Light Coupling.

We demonstrate the hybrid integration of a lithium niobate microring resonator with a silicon nitride waveguide in the vertical configuration to achieve efficient light coupling. The microring resonator is fabricated on a lithium niobate on insulator (LNOI) substrate using photolithography assisted chemo-mechanical etching (PLACE). A fused silica cladding layer is deposited on the LNOI ring resonator. The silicon nitride waveguide is further produced on the fused silica cladding layer by first fabricating a trench in the fused silica while using focused ion beam (FIB) etching for facilitating the evanescent coupling, followed by the formation of the silicon nitride waveguide on the bottom of the trench. The FIB etching ensures the required high positioning accuracy between the waveguide and ring resonator. We achieve Q-factors as high as 1.4 × 107 with the vertically integrated device.

A Microfluidic Mixer of High Throughput Fabricated in Glass Using Femtosecond Laser Micromachining Combined with Glass Bonding.

We demonstrate a microfluidic mixer of high mixing efficiency in fused silica substrate using femtosecond laser-induced wet etching and hydroxide-catalysis bonding method. The micromixer has a three-dimensional geometry, enabling efficient mixing based on Baker's transformation principle. The cross-sectional area of the fabricated micromixer was 0.5 × 0.5 mm2, enabling significantly promotion of the throughput of the micromixer. The performance of the fabricated micromixers was evaluated by mixing up blue and yellow ink solutions with a flow rate as high as 6 mL/min.