Tunable and efficient ultraviolet generation with periodically poled lithium niobate

Abstract

On-chip ultraviolet (UV) sources are of great interest for building compact and scalable atomic clocks, quantum computers, and spectrometers. However, few material platforms are suitable for integrated UV light generation and manipulation. Of these materials, thin-film lithium niobate offers unique advantages such as sub-micron modal confinement, strong nonlinearity, and quasi-phase matching. Despite these characteristics, its utilization in the UV has remained elusive because of the substantial sensitivity of standard quasi-phase matching to fabrication imperfections, the photorefractive effect, and relatively large losses in this range. Here, we present efficient (197 ± 5%/W/cm2) second harmonic generation of UV-A light in a periodically poled lithium niobate nanophotonic waveguide. We achieve on-chip UV powers of ∼30 µW and linear wavelength tunability using temperature. These results are enabled with large cross section waveguides, which leads to first-order UV quasi-phase-matching with relatively long poling periods (>1.5 µm). By varying the poling period, we have achieved the shortest reported wavelength (355 nm) generated through frequency doubling in thin-film lithium niobate. Our results open up new avenues for UV on-chip sources and chip-scale photonics through compact frequency-doubling of common near-IR laser diodes.

Single-mode squeezed-light generation and tomography with an integrated optical parametric oscillator

“…Our approach uses a periodically poled thin-film lithium niobate (TFLN) ( 21 , 22 ) and leverages its strong χ (2) nonlinearity, electro-optic effect, and low-loss linear optical characteristics for the photonic circuit. Integrated TFLN devices have shown remarkable promise, offering a toolbox of capabilities such as efficient light generation spanning from mid-infrared to near-ultraviolet ( 23 – 27 ), dispersion engineering ( 28 – 30 ), electro-optic modulation and tuning ( 31 , 32 ), OPO ( 13 , 14 ), waveguide squeezers for efficient pulse squeezing ( 33 ) and with similar level of integration including on-chip pump generating section and homodyne measurement subsystem ( 34 ), and frequency combs ( 35 , 36 ). Here, we harness the full capabilities of this emerging platform, demonstrating a monolithic integrated quantum system for the generation and tomography of squeezed light.…”

Wavelength-accurate and wafer-scale process for nonlinear frequency mixers in thin-film lithium niobate

“…1b). Therefore, to guarantee devices operating at desired wavelengths, fabrication uncertainties are compensated for by sweeping the poling period across many devices to guarantee phase-matching over a wide wavelength range 27,28 . This, however, results in a low yield and makes it very difficult to fabricate more complex nonlinear devices (Fig.…”

“…Thermal tuning leveraging the thermo-optic effect in TFLN is the conventional approach to control the operating wavelength of QPM device 28,32,33 . In our approach, we use a large heater to increase the temperature of Wafer B by ∆T max = 120 K above room temperature and measure the wavelength of SHG signal (Fig.…”

“…Thus, for applications requiring accuracy in the operating wavelength-such as for interfacing with atom-like single-photon emitters that have fixed emission wavelengths (e.g. silicon-vacancy center in diamond at 737 nm with ∼ 80 GHz demonstrated tuning range 26 )-the conventional approach is to sweep the design parameters to guarantee at least one device that meets specifications 27,28 . While this is viable for standalone devices and small photonic circuits, the number of trial circuits that must be fabricated to guarantee one meets specifications scales geometrically with the number of frequency mixing devices in each circuit even if one assumes unity yield on all other components in the circuit.…”