High density lithium niobate photonic integrated circuits and lasers

Abstract

Photonic integrated circuits are indispensable for data transmission within modern datacenters and pervade into multiple application spheres traditionally limited for bulk optics, such as LiDAR and biosensing1. New applications and higher performance are enabled by the diversification of optical waveguide materials past silicon-on-insulator. Of particular interest are ferroelectrics such as Lithium Niobate, which exhibit a large electro-optical Pockels effect enabling ultrafast and efficient modulation, but are difficult to process via dry etching2. For this reason, etching tightly confining waveguides - routinely achieved in silicon or silicon nitride - has not been possible. Diamond-like carbon (DLC) was discovered in the 1950s 3 and is a material that exhibits an amorphous phase, excellent hardness, and the ability to be deposited in nano-metric thin films. Its use today is pervasive, ranging from applications for hard disk surfaces 4 and medical devices 5 to low friction coatings for automotive components 6. It has excellent thermal, mechanical, and electrical properties, making it an ideal protective coating. Here we demonstrate that DLC is also a superior material for the manufacturing of next-generation photonic integrated circuits based on ferroelectrics, specifically Lithium Niobate on insulator (LNOI). Using DLC as a hard mask, we demonstrate the fabrication of deeply etched, tightly confining, low loss photonic integrated circuits with losses as low as 4 dB/m and Q-factor as high as 10 · 106. In contrast to widely employed ridge waveguides 7,8, this approach benefits from a more than 1 order of magnitude higher area integration density while maintaining efficient electro-optical modulation, low loss, and offering a route for efficient optical fiber interfaces. As a proof of concept, we demonstrate a frequency agile hybrid integrated III-V Lithium Niobate based laser with sub-kHz linewidth and tuning rate of 0.7 Peta-Hertz per second with excellent linearity and CMOS-compatible driving voltage. Our approach can herald a new generation of high density ferroelectric photonic integrated circuits, in particular for applications in coherent laser based ranging 9 and beamforming 10, optical communications 7, and classical 11 and quantum computing networks 12.

Advances in lithium niobate thin-film lasers and amplifiers: a review

“…More recently, this group also demonstrated a frequency-agile LNOI laser by hybrid integrating a DFB laser to LNOI photonic integrated circuits. 141 The maximum measured power in the output fiber of the hybrid laser is 1 mW with an SMSR of 60 dB lasing at 1556.3 nm. Compared to the free-running DFB laser, the frequency noise of the hybrid laser is suppressed by more than 20 dB by exploiting the laser self-injected locking effect, as shown in Fig.…”

“…Reprinted from Ref. 141. (g) The structure schematic of the hybrid integrated III-V/LNOI external cavity laser.…”

“…Moreover, a proof-of-concept frequency-modulated continuous-wave (FMCW) lidar ranging experiment was performed based on this hybrid integrated laser with a resolution of 15 cm. More recently, this group also demonstrated a frequency-agile LNOI laser by hybrid integrating a DFB laser to LNOI photonic integrated circuits 141 . The maximum measured power in the output fiber of the hybrid laser is 1 mW with an SMSR of 60 dB lasing at 1556.3 nm.…”

Stimulated Brillouin scattering by surface acoustic waves in lithium niobate waveguides

“…1(b,c). The waveguide's width and thickness chosen in this study fall within the range of previous experiments on LN waveguides [34][35][36]. We employ the finite element method (FEM) using COMSOL Multiphysics to calculate optical and mechanical modes of our structures.…”

Design and optimization of two-dimensional porous lithium niobate grating birefringent Bloch surface wave sensor with high sensitivity and quality factor

“…The research has mainly explored the influence of different crystal structure doping on the characteristics of LiNbO3, attempting to apply it to sensing detection in pressure, 26 temperature, 27 and electromagnetic fields 28 . Due to the excellent optical performance of LiNbO3, it is now widely used in resonators, 29 optical modulators, 30 and integrated optical devices 31 . Zhang et al.…”