Two-dimensional (2-D) materials are of tremendous interest to integrated photonics given their singular optical characteristics spanning light emission, modulation, saturable absorption, and nonlinear optics. To harness their optical properties, these atomically thin materials are usually attached onto prefabricated devices via a transfer process. In this paper, we present a new route for 2-D material integration with planar photonics. Central to this approach is the use of chalcogenide glass, a multifunctional material which can be directly deposited and patterned on a wide variety of 2-D materials and can simultaneously function as the light guiding medium, a gate dielectric, and a passivation layer for 2-D materials. Besides claiming improved fabrication yield and throughput compared to the traditional transfer process, our technique also enables unconventional multilayer device geometries optimally designed for enhancing light-matter interactions in the 2-D layers. Capitalizing on this facile integration method, we demonstrate a series of highperformance glass-on-graphene devices including ultra-broadband on-chip polarizers, energyefficient thermo-optic switches, as well as graphene-based mid-infrared (mid-IR) waveguideintegrated photodetectors and modulators.

Passive Q-switching of an ytterbium-doped fiber (YDF) laser with few-layer topological insulator (TI) is, to the best of our knowledge, experimentally demonstrated for the first time. The few-layer TI: Bi 2 Se 3 (2-4 layer thickness) is fabricated by the liquid-phase exfoliation method, and has a low saturable optical intensity of 53 MW/cm 2 measured by the Z-scan technique. The optical deposition technique is used to induce the few-layer TI in the solution onto a fiber ferrule for successfully constructing the fiber-integrated TI-based saturable absorber (SA). By inserting this SA into the YDF laser cavity, stable Q-switching operation at 1.06 μm is achieved. The Q-switched pulses have the shortest pulse duration of 1.95 μs, the maximum pulse energy of 17.9 nJ and a tunable pulse-repetition-rate from 8.3 to 29.1 kHz. Our results indicate that the TI as a SA is also available at 1 μm waveband, revealing its potential as another wavelength-independent SA (like graphene).

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In this paper, both nonlinear saturable absorption and two-photon absorption (TPA) of few-layer molybdenum diselenide (MoSe2) were observed at 1.56 μm wavelength and further applied to mode-locked ultrafast fiber laser for the first time to our knowledge. Few-layer MoSe2 nanosheets were prepared by liquid-phase exfoliation method and characterized by x ray diffractometer, Raman spectroscopy, and atomic force microscopy. The obtained fewlayer MoSe2 dispersion is further composited with a polymer material for convenient fabrication of MoSe2 thin films. Then, we investigated the nonlinear optical (NLO) absorption property of the few-layer MoSe2 film using a balanced twin-detector measurement technique. Both the saturable absorption and TPA effects of the few-layer MoSe2 film were found by increasing the input optical intensity. The saturable absorption shows a modulation depth of 0.63% and a low nonsaturable loss of ∼3.5%, corresponding to the relative modulation depth of 18%. The TPA effect occurred when the input optical intensity exceeds ∼260 MW∕cm 2. Furthermore, we experimentally exploit the saturable absorption of few-layer MoSe2 film to mode lock an all-fiber erbium-doped fiber laser. Stable soliton mode locking at 1558 nm center wavelength is achieved with pulse duration of 1.45 ps. It was also observed that the TPA process suppresses the mode-locking operation in the case of higher optical intensity. Our results indicate that layered MoSe2, as another two-dimensional nanomaterial, can provide excellent NLO properties (e.g., saturable absorption and TPA) for potential applications in ultrashort pulse generation and optical limiting.