We demonstrate all-optical modulation based on ultrafast saturable absorption in graphene-covered-microfiber. By covering the microfiber surface with polydimethylsiloxane supported graphene film along the fiber length, a greatly enhanced interaction between the propagating light and the graphene can be obtained via the strong evanescent field of the microfiber. The strong light-graphene interaction results in high-speed, broadband all-optical modulation with maximum modulation depths of 5 dB and 13 dB for single-layer and bi-layer graphene, respectively. Such a graphene all-optical modulator is easy to fabricate, is compatible with optical fiber systems and has high potential in photonics applications such as all-optical switching and all-optical communications.
Graphene saturable absorbers (GSAs) have been widely applied in ultra-fast mode-locked fiber lasers. Thanks to the broadband advantage of graphene, we theoretically and experimentally demonstrate the variation of the modulation depth of GSA by employing the effect of cross absorption modulation. This method provides an easy and efficient way to modulate the characteristics of GSA. By varying the modulation power, we realize an all-fiber fundamental mode-locked fiber laser and a harmonic mode-locked fiber laser with tunable output pulse width. Results show that the output pulse widths of the two fiber lasers can be tuned more than 40%, and the lasers have high wide application potential on nonlinear optical bio-imaging and offer an advantageous front end for extreme-power laser technologies.
We experimentally demonstrate an operation switchable Erbium-doped fiber laser by employing graphene saturable absorber (GSA) on microfiber. With the introducing of a polydimethylsiloxane layer, a graphene can be considered as a parallel plate on microfiber and induces different propagation losses to TE and TM modes. By the use of such polarization sensitive GSA on microfiber, Erbium doped fiber laser with switchable operation states such as continuous wave, stable Q-switching, Q-switched mode-locking, and continuous-wave mode-locking, can be achieved by simply tuning the polarization states in the laser cavity. Our results show that covering graphene on microfibers could be a promising method for fabricating all fiber SA, and may have high potential in wide applications.
We report a miniature fiber-optic water vector flow sensor based on an array of silicon Fabry-Perot interferometers (FPIs). The flow sensor is composed of four silicon FPIs, one in the center with the other three equally distributed around it. The center FPI is heated by a cw laser at 980 nm, which is guided through the lead-in single mode fiber. The temperature structure established within the sensor head due to laser heating is a function of the flow vector (speed and direction), which can be deduced from the wavelength shifts of the four FPIs. Theoretical analysis has been conducted to illustrate the operating principle and experimental demonstration has been provided.
The paradox between a large dynamic range and a high resolution commonly exists in nearly all kinds of sensors. Here, we propose a fiber-optic thermometer based on dual Fabry-Perot interferometers (FPIs) made from the same material (silicon), but with different cavity lengths, which enables unambiguous recognition of the dense fringes associated with the thick FPI over the free-spectral range determined by the thin FPI. Therefore, the sensor combines the large dynamic range of the thin FPI and the high resolution of the thick FPI. To verify this new concept, a sensor with one 200 μm thick silicon FPI cascaded by another 10 μm thick silicon FPI was fabricated. A temperature range of -50°C to 130°C and a resolution of 6.8×10-3°C were demonstrated using a simple average wavelength tracking demodulation. Compared to a sensor with only the thick silicon FPI, the dynamic range of the hybrid sensor was more than 10 times larger. Compared to a sensor with only the thin silicon FPI, the resolution of the hybrid sensor was more than 18 times higher.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.