Waveguide‐Integrated Two‐Dimensional Material Photodetectors in Thin‐Film Lithium Niobate

Abstract

Thin‐film lithium niobate on insulator (LNOI) is a promising platform for optical communications, microwave photonics, and quantum technologies. While many high‐performance devices like electro‐optic modulators and frequency comb sources have been achieved on LNOI platform, it remains challenging to realize photodetectors (PDs) on LNOI platform using simple and low‐cost fabrication techniques. 2D materials are excellent candidates to achieve photodetection since they feature strong light‐matter interaction, excellent mechanical flexibility, and potential large‐scale complementary metal–oxide–semiconductor‐compatible fabrication. Herein, this demand is addressed using an LNOI‐2D material platform, and two types of high‐performance LNOI waveguide‐integrated 2D material PDs, namely graphene and tellurium (Te), are addressed. Specifically, the LNOI‐graphene PDs feature broadband operations at telecom and visible wavelengths, high normalized photocurrent‐to‐dark current ratios up to 3 × 106 W−1, and large 3‐dB photoelectric bandwidths of ≈40 GHz, simultaneously. The LNOI‐Te PDs on the other hand provide ultrahigh responsivities of 7 A W−1 under 0.5 V bias for telecom signals while supporting GHz frequency responses. The results show that the versatile properties of 2D materials and their excellent compatibility with LNOI waveguides could provide important low‐cost solutions for system operating point monitoring and high‐speed photoelectric conversion in future LNOI photonic integrated circuits.

Ultrasensitive Bidirectional Photoresponse SnSe2 Photodetector Integration with Thin‐Film Lithium Niobate Photonics

“…The comparison of the response wavelength and responsivity of our PD with those of waveguide PDs based on the SOI/TFLN/Si 3 N 4 platform reported in the literature is shown in Figure 7. [34,35,[55][56][57][58][59][60][61][62][63][64][65][66][67][68] Detailed comparisons can be found in Table S2, Supporting Information. In addition, we compare the performance of our PD with that of PDs based on the SnSe 2 2D material, as shown in Table S3, Supporting Information.…”

“…A few 2D materials and semiconductor materials have been integrated into TFLN for use in PDs, but the responsivity is still low. [34,35] Extracting multiple carriers from a single photon through the charge trapping mechanism to increase the photogain is an effective approach for achieving high responsivity. [36] Broadband light detection is another important developing trend in PD technology that facilitates large-format integration.…”

On-chip two-dimensional material-based waveguide-integrated photodetectors

“…7(e). 186 The graphene-based WI PD exhibited a zero-bias responsivity of 17.27 mA W −1 and a bandwidth of about 40 GHz. Furthermore, the dark current was suppressed to less than 5 nA under the built-in electric field based on the PV effect.…”

“…Most 2DM-based WI PDs employ rectangular waveguides, while the application of ridge waveguides is usually to meet specific requirements, such as avoiding the absorption of mid-infrared light by oxide layers, 184 process limitations in lithium niobate waveguides, 185 and prevention of fracture in thin-layer 2DMs. 186 Next, the performance improvement and development process of 2DM-based PDs integrated with rectangular or ridge waveguides are summarized based on their working principles, types of 2DMs, and waveguide materials.…”

Photodetectors integrating waveguides and semiconductor materials

“…[30][31][32] Thirdly, the reported photodetectors with integrated waveguides mainly include infrared (IR) photodetectors, visible (VIS) photodetectors, and ultraviolet (UV) photodetectors. [33][34][35][36][37][38] Photodetectors integrating waveguides and semiconductor materials effectively extend the length of the interaction of light-sensitive materials. Thus, they are expected to achieve many important and extensive applications in the fields of optical communication, 39 imaging, 40 and sensing.…”