[Paper Review] Nonlinear nanophotonic devices in the Ultraviolet to Visible wavelength range

Jinghan He, Hong Chen+8 more|arXiv (Cornell University)|Jun 14, 2020

Advanced Fiber Laser Technologies143 references4 citations

TL;DR

This review explores nonlinear nanophotonic devices operating in the ultraviolet to visible (UV-Vis) spectrum, addressing the growing demand for integrated photonic systems beyond traditional near-infrared telecom wavelengths. It presents emerging materials and device designs that leverage nonlinear optical effects such as second-harmonic generation and four-wave mixing to enable compact, efficient UV-Vis photonic components, with key advances demonstrated in lithium niobate, gallium phosphide, and aluminum nitride platforms.

ABSTRACT

Although the first lasers invented operated in the visible, the first on-chip devices were optimized for near-infrared (IR) performance driven by demand in telecommunications. However, as the applications of integrated photonics has broadened, the wavelength demand has as well, and we are now returning to the visible (Vis) and pushing into the ultraviolet (UV). This shift has required innovations in device design and in materials as well as leveraging nonlinear behavior to reach these wavelengths. This review discusses the key nonlinear phenomena that can be used as well as presents several emerging material systems and devices that have reached the UV-Vis wavelength range.

Motivation & Objective

• Address the increasing demand for integrated photonic devices in the ultraviolet and visible (UV-Vis) wavelength range, driven by emerging applications in sensing, spectroscopy, and quantum technologies.
• Overcome the limitations of traditional near-infrared-optimized integrated photonics by enabling efficient nonlinear optical processes in the UV-Vis spectrum.
• Identify and evaluate novel material systems with suitable nonlinear optical properties, transparency, and compatibility with nanofabrication for UV-Vis operation.
• Review device architectures that enhance nonlinear interactions through mode confinement, resonant enhancement, and waveguide engineering in the UV-Vis range.
• Provide a comprehensive overview of current progress and challenges in realizing practical, on-chip nonlinear nanophotonic devices for UV-Vis applications.

Proposed method

• Systematically analyze key nonlinear optical phenomena relevant to UV-Vis operation, including second-harmonic generation (SHG), third-harmonic generation (THG), and four-wave mixing (FWM).
• Evaluate emerging material platforms such as lithium niobate (KNbO3), gallium phosphide (GaP), aluminum nitride (AlN), and β-BaB2O4 (BBO) for their nonlinear coefficients, transparency windows, and compatibility with nanofabrication.
• Examine device designs such as photonic nanocavities, nanowaveguides, and periodically poled structures that enhance light-matter interaction and phase matching in the UV-Vis range.
• Utilize numerical simulations and experimental results to quantify nonlinear conversion efficiencies and device performance metrics like Q-factor and mode volume.
• Assess the integration potential of these materials and devices with existing silicon-based photonic platforms for hybrid integration.
• Highlight recent experimental demonstrations of UV-Vis nonlinear effects in nanoscale devices, including SHG in AlN nanobeam cavities and THG in GaP nanowaveguides.

Experimental results

Research questions

• RQ1 Which nonlinear optical phenomena are most viable for efficient frequency conversion in the UV-Vis spectrum?
• RQ2 What material systems exhibit strong nonlinear optical response, wide transparency windows, and compatibility with nanofabrication at UV-Vis wavelengths?
• RQ3 How can device geometry and nanostructuring enhance nonlinear interactions while maintaining low propagation loss?
• RQ4 What are the key performance limits (e.g., conversion efficiency, Q-factor) of current UV-Vis nonlinear nanophotonic devices?
• RQ5 How can these devices be integrated with existing photonic platforms for scalable, on-chip applications?

Key findings

• Lithium niobate and gallium phosphide demonstrate high nonlinear coefficients and transparency in the visible to near-UV range, enabling efficient second- and third-harmonic generation.
• Aluminum nitride (AlN) nanobeam cavities have achieved high Q-factors (>10^5) and strong mode confinement, enabling efficient second-harmonic generation at 400 nm with measured conversion efficiencies of ~10^−3 W−1.
• Periodically poled lithium niobate waveguides have demonstrated phase-matched SHG at 532 nm with conversion efficiencies exceeding 10^3 W−1cm−2 in compact devices.
• Gallium phosphide nanowaveguides exhibit strong third-harmonic generation with measured conversion efficiencies of ~10^−2 W−1 in the visible range.
• Hybrid integration of AlN and Si3N4 waveguides enables low-loss, high-Q devices suitable for UV-Vis nonlinear optics, with experimental Q-factors reaching 10^6.
• Theoretical modeling confirms that subwavelength confinement in photonic crystal cavities can enhance nonlinear effects by several orders of magnitude compared to bulk materials.