In this paper, we develop a technique for realizing multi-centimeter-long lithium niobate on insulator (LNOI) waveguides with a propagation loss as low as 0.027 dB/cm. Our technique relies on patterning a chromium thin film coated on the top surface of LNOI into a hard mask with a femtosecond laser followed by chemo-mechanical polishing for structuring the LNOI into the waveguides. The surface roughness on the waveguides was determined with an atomic force microscope to be 0.452 nm. The approach is compatible with other surface patterning technologies, such as optical and electron beam lithographies or laser direct writing, enabling high-throughput manufacturing of large-scale LNOI-based photonic integrated circuits.

We report the fabrication of crystalline microresonators of high quality (Q) factors with a controllable wedge angle on lithium niobate on insulator (LNOI). Our technique relies on a femtosecond laser assisted chemo-mechanical polish, which allows us to achieve ultrahigh surface smoothness as critically demanded by high Q microresonator applications. We show that by refining the polish parameters, Q factors as high as 4.7 × 10⁷ can be obtained and the wedge angle of the LNOI can be continuously tuned from 9° to 51°.

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.

High-quality lithium niobate (LN) thin-film microresonators provide an ideal platform for on-chip nonlinear optical applications. The strict phase-matching condition should be satisfied for an efficient nonlinear optical process, which requires dispersion engineering with an LN microresonator. However, this is challenging in single microresonator, resulting from the fabrication error. Here, we demonstrate strong nonlinear effects in a photonic molecule (PM) structure composed of two strongly coupled lithium niobate microdisks. The size mismatch of the microdisks enables phase matching by employing coupling-induced frequency splitting to compensate for the material and geometric dispersion. With a continuous wave excitation, rich nonlinear optical phenomena including cascaded four-wave mixing and stimulated Raman scattering were observed around the second harmonic signal. Meanwhile, an ultra-high four-wave mixing absolute conversion efficiency of 14% as obtained when the second harmonic signal power is at microwatts level. The LN PM is of great potential for applications in nonlinear integrated photonics.

Three-dimensional (3D) printing has allowed for the production of geometrically complex 3D objects with extreme flexibility, which is currently undergoing rapid expansion in terms of materials, functionalities, as well as areas of application. When attempting to print 3D microstructures in glass, femtosecond laser-induced chemical etching (FLICE)—which is a subtractive 3D printing technique—has proved itself a powerful approach. Here, we demonstrate the fabrication of macro-scale 3D glass objects of large heights up to ~3.8 cm with an identical lateral and longitudinal feature size of ~20 μm. The remarkable accomplishment is achieved by revealing an unexplored regime in the interaction of ultrafast laser pulses with fused silica, which results in depth-insensitive focusing of the laser pulses inside fused silica.

We demonstrate the fabrication of single-mode optical waveguides on lithium niobate on an insulator (LNOI) by optical patterning combined with chemomechanical polishing. The fabricated LNOI waveguides had a nearly symmetric mode profile of ~2.5 µm mode field size (full-width at half-maximum). We developed a high-precision measurement approach by which single-mode waveguides were characterized to have propagation loss of ~0.042 dB/cm.