Fig 1

Schematic diagram of optical modulation methods and principles. (a) Schematic diagram of common light modulation methods (all-optical, electro-optic, and thermo-optic modulation). (b) Schematic diagram of crystal modulator. (c) Schematic diagram of all-fiber modulator."

Fig 2

Schematic diagram of common two-dimensional materials."

Fig 3

Schematic diagram of common two-dimensional material hybrid fiber system. In the figure, the light green represents the cladding of the optical fiber, the dark green represents the core of the optical fiber, and the purple represents the transferred or grown two-dimensional materials. "Fiber end-face composite" refers to the two-dimensional materials being transferred or grown on the end-face of a regular optical fiber. "Intra-hole wall composite" refers to the two-dimensional materials being grown or filled within the void of a holey optical fiber. "Tapered composite" refers to the two-dimensional materials being transferred or grown in the tapered region. "Side-polished composite" refers to the two-dimensional materials being transferred or grown on the side-polished plane."

Fig 4

Passive mode-locker and all-optical switch of two-dimensional material hybrid fiber. (a) Absorption of light in graphene. When light is incident on graphene, the electrons from the valence band first absorb the incident photons and are excited into the conduction band. The photogenerated carriers thermalize and cool down within sub-picoseconds until an equilibrium carrier distribution could be finally approached through electron-hole recombination. At high excitation intensity, the photogenerated carriers cause the states near the edge of the conduction and valence bands to fill, which would block further absorption because of the Pauli blocking effect. (b) Transmittance of the MoS2-PCF for αS ≈ 10% and saturation peak intensity of 0.8 MW∙cm−2 50. (c) Schematic of all-fiber mode-locked laser with two-dimensional material hybrid fiber as an SA. Insert shows the side view of MoS2-PCF and the schematic of optical fiber end face coated with graphene film 50. (d) Output pulse train of all-fiber mode-locked laser with MoS2-PCF as an SA (with ~24 ns interval, ~41 MHz repetition rate) 50. (e) Schematic of signal light modulated by switch light in graphene. A signal light is incident on graphene and experiences significant attenuation due to absorption. When a switch light with higher photon energy is introduced, it excites carriers and shifts the absorption threshold of graphene to higher frequency through Pauli blocking of interband transitions, thus resulting in a much lower attenuation of the signal light. (f) Schematic of a graphene-clad microfiber all-optical modulator 54. (g) Schematic of a 1550 nm CW beam modulated by 1064 nm pulse beam in a graphene-clad microfiber. (h) Top: pulses switched out from a 1550 nm CW beam in a graphene-clad microfiber by a 1064 nm pump pulse train. Bottom: time profile of a switched-out pulse 54. (b, c, d) Adapted with permission from Ref. 50, Copyright 2020 Nature Publishing Group. (f, h) Adapted with permission from Ref. 54, Copyright 2014 ACS Publications."

Fig 5

Optical parametric conversion and supercontinuum generation of two-dimensional material hybrid fiber. (a) Greatly enhanced SHG and THG in a MoS2-hollow capillary fiber 50. (b) SHG spectra of a MoS2-HCF, MoS2 on a flat, fused silica substrate (MoS2/silica), and a bare HCF (hollow capillary fiber, HCF) under 1800 nm excitation. In the 25-cm-long MoS2-HCF, SHG can be enhanced by ≈ 300 times compared with monolayer MoS2/silica 50. (c) Schematic of Four Wave Mixing principle. (d) Spectra of cascaded FWMs of graphene-coated microfiber for the detuning of 1 nm (red), 2 nm (blue), and 5 nm (green), respectively 120. (e) Experimental spectra measured for a launched power of 45 W in a long tapered GeO2-doped-core PCF. Insert shows SEM image of the GeO2-doped PCF with a close-up in the core region 137. (f) Systematic of decahedron PCF with MoS2 filled elliptical core 140. (a, b) Adapted with permission from Ref. 50, Copyright 2020 Nature Publishing Group. (d) Adapted with permission from Ref. 120, Copyright 2015 Chinese Laser Press. (e) Adapted with permission from Ref. 137, Copyright 2009 Optica Publishing Group. (f) Adapted with permission from Ref. 140, Copyright 2021, Elsevier."

Fig 6

Polarization of control two-dimensional material hybrid fiber. (a) Schematic model of a polarizer based on graphene hybrid fiber. Only the TE mode can pass through the device and TE or TM mode can be regulated by applying electric field 171. (b) Polar image of output power measured at 980 and 1550 nm 171. (c) The schematic view of the proposed device. The whole structure is configured on the microfiber whose surface is surrounded by the thin layer of graphene at four sides, which is referenced to the four-electrodes structure 150. (d) Attenuation of TE mode and TM mode under different chemical potentials in horizontal direction 150. (e) Attenuation of TE mode and TM mode under different chemical potentials in perpendicular direction 150. (a, b) Adapted with permission from Ref. 171, Copyright 2012 American Chemical Society. (c, d, e) Adapted with permission from Ref. 150, Copyright 2018 IOP publishing."

Fig 7

Two-dimensional material hybrid fiber electro-optic modulation. (a) Schematic of a Gr-PCF-based electro-optic modulator 52. (b) The ionic liquid-gating tunes the graphene's Fermi level and switches on and off the optical absorption in the graphene. When EF = ħω/2, graphene absorbs (does not absorb) light, and the modulator is working in the 'off' ('on') state for light transmission 52. (c) Top, measured optical attenuation of light propagation in the bare PCF (purple dots) and Gr-PCF (cyan dots) with different fiber lengths. Bottom, schematic of light attenuation with multiple reflections during its propagation along the Gr-PCF core 52. (d) Schematic 2D MgO nanoflake integrated optical fiber-based electro-optic modulator 173. (e) Plane of polarization of the linearly polarized beam phase change by 8 after reflection from MgO nanoflakes on a cylindrical fiber end surface in a perpendicular electric field 173. (f) Optical response of an output spectrum in terms of a wavelength shift under the external electric field 173. (a, b, c) Adapted with permission from Ref. 52, Copyright 2019 Nature Publishing Group. (d, e, f) Adapted with permission from Ref. 173, Copyright 2020 Optical Society of America."

Fig 8

Two-dimensional material hybrid fiber thermal-optic modulation. (a) Optical microscope images of the tapered microfiber after graphene transfer 164. (b) Schematic of the experimental setup for measuring the phase shift in MZI 164. (c) Temporal response of the thermol-optical modulator 164. (d) Experimental configuration of thermol-optical modulator based on the MXene-deposited MKR 168. (e) Waveforms of 980 nm pump light (top) and output single light (bottom) and its fitting curve 168. (a, b, c) Adapted with permission from Ref. 164, Copyright 2015 The Optical Society. (d, e) Adapted with permission from Ref. 168, Copyright 2020 Wiley-VCH."