Microfiber interferometer integrated with Au nanorods for an all-fiber phase shifter and switch

Light manipulation for all-fiber devices with VCSEL and graphene-based metasurface

Light manipulation for all-fiber devices has played a vital role in controllable photonic devices. A graphene-based metasurface is proposed to realize light manipulation. A row of VCSEL-based optical engines with low crosstalk is used as the control light to modulate the signal transmitted in the microstructured fiber. In this configuration, the proposed device can work independently of the wavelength division multiplexing (WDM) system. With an insertion loss of only 0.28 dB, evanescent wave coupling to graphene layers is polarisation-insensitive. The device could be effectively manipulated for a few days (not less than 72 hours), which possesses the capacity to dynamically modulate the signal light with both low-temperature sensitivity and low-wavelength sensitivity. The 35 nm wavelength interval results in a change of only about 0.1 dB in the output light intensity of the microstructured fiber when the wavelength changes from 1530 nm to 1565 nm. Moreover, the modulation depth is approximately 2 dB when the modulating voltage is 2.2 V, which may open avenues for channel detection techniques and have deep implications in top tuning applications.

Graphene-Assisted Polymer Waveguide Optically Controlled Switch Using First-Order Mode

All-optical devices have a great potential in optical communication systems. As a new material, graphene has attracted great attention in the field of optics due to its unique properties. We propose a graphene-assisted polymer optically controlled thermo-optic switch, based on the Ex01 mode, which can reduce the absorption loss of graphene. Graphene absorbs 980 nm pump light, and uses the heat generated by ohmic heating to switch on and off the signal light at 1550 nm. The simulation results show that, when the graphene is in the right position, we can obtain the power consumption of 9.5 mW, the propagation loss of 0.01 dB/cm, and the switching time of 127 μs (rise)/125 μs (fall). The switching time can be improved to 106 μs (rise) and 102 μs (fall) with silicon substrate. Compared with an all-fiber switch, our model has lower power consumption and lower propagation loss. The proposed switch is suitable for optically controlled fields with low loss and full polarization. Due to the low cost and easy integration of polymer materials, the device will play an important role in the fields of all-optical signal processing and silicon-based hybrid integrated photonic devices.

All-fiber bidirectional optical modulator derives from the microfiber coated with ITO electrode

A cheap, compact, and simply prepared all-fiber bidirectional optical modulator based on the Pockels effect of water and the band population effect was first, to the best of our knowledge, proposed and demonstrated. The transparent conductive oxide indium-tin-oxide (ITO) was coated on the surface of a nonadiabatic microfiber and first used as a modulating electrode on the microfiber. The device was realized by just submerging the microfiber in water. With supplying an electric field perpendicular to the interface between the microfiber and water, the refractive index was modulated in the electric double layer near the tapered region of the microfiber, under the Pockels effect of water. Subsequently, the interference spectrum was modulated. Meanwhile, the intensity of the light was modulated due to the band population effect in the space-charge layer. In this Letter, the proposed all-fiber optical modulator can realize simultaneous bidirectional modulation of the phase and intensity of output light. Experimentally, the maximum phase shift and the extinction ratio were 4.38 nm and 4.87 dB at 1550 nm, respectively. Significantly, the work used the Pockels effect of water and the band population effect to realize an all-fiber optical modulator, showing great potential in the optical phase modulators, optical switches, and electric field sensors.

Compact all-fiber thermo-optic modulator based on a Michelson interferometer coated with NaNdF4 nanoparticles

We propose and investigate an all-fiber thermo-optic modulator based on a side-polished twin-core fiber (TCF) Michelson interferometer (MI) coated with NaNdF₄ nanoparticles. The MI was fabricated by tapering the splicing point between the TCF and a single mode fiber (SMF). A short suspended core fiber (SCF) is spliced to one core of the TCF to introduce a fixed optical phase difference (OPD). The side-polished core is coated with photo-thermal material NaNdF₄. Owing to the ohmic heating of NaNdF₄ nanoparticles under 808 nm pump laser, the effective refractive index of the polished core is changed, resulting in a phase shift of the MI. The MI has a significant modulation phase shift with 2.9 π near the wavelength of 1260 nm and can obtain an optical switching with a rise (fall) time of 152 (50) ms. The proposed device will have a great application potential in optical modulators due to compact structure and strong robustness.

Au Nanoparticles-Doped Polymer All-Optical Switches Based on Photothermal Effects

This article demonstrated the Au nanoparticles-doped polymer all-optical switches based on photothermal effects. The Au nanoparticles have a strong photothermal effect, which would generate the inhomogeneous thermal field distributions in the waveguide under the laser irradiation. Meanwhile, the polymer materials have the characteristics of good compatibility with photothermal materials, low cost, high thermo-optical coefficient and flexibility. Therefore, the Au nanoparticles-doped polymer material can be applied in optically controlled optical switches with low power consumption, small device dimension and high integration. Moreover, the end-pumping method has a higher optical excitation efficiency, which can further reduce the power consumption of the device. Two kinds of all-optical switching devices have been designed including a base mode switch and a first-order mode switch. For the base mode switch, the power consumption and the rise/fall time were 2.05 mW and 17.3/106.9 μs, respectively at the wavelength of 650 nm. For the first-order mode switch, the power consumption and the rise/fall time were 0.5 mW and 10.2/74.9 μs, respectively at the wavelength of 532 nm. This all-optical switching device has the potential applications in all-optical networks, flexibility device and wearable technology fields.

Nanoheater-tuned whispering gallery mode lasing in liquid-filled hollow microcavities

An all-optical tunable whispering gallery mode (WGM) lasing from the liquid-filled hollow glass microsphere (LFHGM) is proposed and experimentally verified. The LFHGM-based microlaser is prepared by injecting ${{\rm NaNdF}_4}/{\rm dye}$NaNdF₄/dye co-doped liquid into the HGM, and WGM resonance is obtained under excitation of a 532 nm pulse laser. Since the high-efficiency absorption of the 793 nm continuous-wave laser by ${{\rm NaNdF}_4}$NaNdF₄ nanocrystals (NCs) can result in photothermal effect-induced effective refractive index change of the microcavity, a secondary 793 nm laser is irradiated into the LFHGM to excite the ${{\rm NaNdF}_4}$NaNdF₄ dispersed in the liquid core, thereby realizing a shift of resonant frequencies. The influence of the doping concentration of ${{\rm NaNdF}_4}$NaNdF₄ NCs on the tuning range and the sensitivity over the power intensity range of $0{-}1.{68}\;{{\rm W/mm}^2}$0-1.68W/mm² are investigated experimentally, obtaining maximum values of 4.95 and ${2}.{95}\;{\rm nm/}({\rm W}\;{{\rm mm}^{ - 2}})$2.95nm/(Wmm^-2). The ability to generate stable lasing in a LFHGM cavity highlights the practical application of the microscale lasers in future all-optical networks.