Yange Liu

Highly birefringent elliptical-hole photonic crystal fiber with squeezed hexagonal lattice

We propose a novel polarization-maintaining index-guiding photonic crystal fiber (PCF). It is composed of a solid silica core and a cladding with squeezed-hexagonal-lattice elliptical air holes. Using a full-vector finite-element method, we study the modal birefringence of the fundamental modes in such PCFs. Numerical result shows that very high modal birefringence with a magnitude of the order of 10(-2) around 1550 nm has been obtained. Furthermore, large normal dispersion appears over a wide range of wavelengths in both orthogonal polarizations.

Switchable dual-wavelength ytterbium-doped fiber laser based on a few-mode fiber grating

The authors propose and demonstrate a simple switchable dual-wavelength Ytterbium-doped fiber laser based on a few-mode fiber grating. The laser can be designed to operate in stable dual-wavelength or wavelength-switching modes, due to the polarization hole burning enhanced by the few-mode fiber grating. The lasing lines may be controlled only by a polarization controller. Stable operation is achieved at room temperature when the wavelength separation is 0.9 nm.

Stable room-temperature multi-wavelength lasing realization in ordinary erbium-doped fiber loop lasers.

A suppressant effect for mode competition of multi-wavelength lasing oscillations induced by deeply saturated effect in an ordinary erbium-doped fiber ring laser (EDFRL) was observed and experimentally investigated. Results show that the effect is helpful to obtain stable multi-wavelength lasing at room temperature in the EDFRL, which offers a new and simple approach to achieve stable multi-wavelength EDF lasing. Stable two- and three- wavelength lasing oscillations were achieved based on the effect in the ordinary EDFRL for the first time to our best knowledge. The multi-wavelength lasing oscillations were so stable integrated over smaller than 1 ms that the maximum power fluctuation over more than 30 minutes of observation was less than 0.1 dB and 0.5 dB for two-wavelength lasing with a spacing of 1.28 nm and 0.76 nm, respectively.

Simultaneous four-wavelength lasing oscillations in an erbium-doped fiber laser with two high birefringence fiber Bragg gratings.

A novel multiwavelength erbium-doped fiber laser configuration is proposed and demonstrated. The laser can produce simultaneous four-wavelength lasing oscillations with a minimum wavelength spacing of only 0.36 nm in C-band via using two fiber Bragg gratings written in high birefringence fiber, while ensuring fairly stable room-temperature operation. The laser can also achieve switching modes among four wavelengths by simple adjustment of two polarization controllers in the cavities. Theconfiguration is based on the polarization hole burning and overlapping cavities principle. The laser has the advantages of simple all-fiber configuration, low cost, high stability and operating at room temperature.

L-Band switchable dual-wavelength erbium-doped fiber laser based on a multimode fiber Bragg grating

In this letter, a simple, switchable dual-wavelength erbiumdoped fiber laser operating in L-band is successfully proposed and demonstrated. The two wavelengths are specified by a Bragg grating formed in multimode fiber and the wavelength separation is 1.7 nm. The multimode section including the multimode fiber grating selects not only the lasing wavelengths but also the polarization states of the lasing lines. Stable dualwavelength operation can be achieved due to the spatial mode beating effect induced by a single-mode /multimode/ single-mode fiber combination structure. By simple adjustment of a polarization controller, the proposed laser can operate in stable dual-wavelength or switch between two wavelengths, all at room temperature.

Fiber-optic in-line magnetic field sensor based on the magnetic fluid and multimode interference effects

A compact magnetic field sensor has been proposed based on multimode interference effects. It consists of typical multimode interferometer (MMI) immersed into the magnetic fluid (MF) which is formed by a section of square no-core fiber (NCF) spliced between two single-mode fibers. The transmission spectral characteristics of this MMI have been analyzed, and the spectral magnetic response of the proposed sensor has been investigated by immersing the NCF into the MF environment. The transmission response of the interference maxima exhibits a sensitivity of −0.01939 dB/Oe in the relatively linear range. Due to its low cost and compactness, this sensor would find potential applications in the measurement of magnetic field.

Broadband all-optical modulation using a graphene-covered-microfiber

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.

Electrically tunable Sagnac filter based on a photonic bandgap fiber with liquid crystal infused

We demonstrate an electrically tunable Sagnac filter based on a photonic bandgap fiber that is realized by infusing liquid crystal into a solid-core air-hole photonic crystal fiber. The filter enables an electrical tuning with a range of about 26 nm for one single interference minimum in the transmission bandgap from 1330 to 1650 nm wavelength. The tuning efficiency is averaged to 0.53 nm/V.

Unique characteristics of a selective-filling photonic crystal fiber Sagnac interferometer and its application as high sensitivity sensor.

We demonstrate a Sagnac interferometer (SI) based on a selective-filling photonic crystal fiber (SF-PCF), which is achieved by infiltrating a liquid with higher refractive index than background silica into two adjacent air holes of the innermost layer. The SF-PCF guides light by both index-guiding and bandgap-guiding. The modal birefringence of the SF-PCF is decidedly dependent on wavelength, and the modal group birefringence has zero value at a certain wavelength. We also theoretically and experimentally investigate in detail the transmission and temperature characteristics of the SI. Results reveal that the temperature sensitivity of the interference spectrum is also acutely dependent on wavelength and temperature, and an ultrahigh even theoretically infinite sensitivity can be achieved at a certain temperature by choosing proper fiber length. An ultrahigh sensitivity with -26.0 nm/°C (63,882 nm/RIU) at 50.0 °C is experimentally achieved.

Bragg grating resonances in all-solid bandgap fibers

Bragg gratings are fabricated in all-solid photonic bandgap fibers by forming a longitudinal periodic index modulation over the high-index rod lattice in the cladding. Due to its unique index-modulation pattern and the modal properties of the fiber, resonance couplings to the LP(01) supermodes (also known as high-index rod modes) are observed. The corresponding peak is located at the long-wavelength side of the Bragg wavelength and presents the highest depth. The asymmetric index profile over the high-index rods, which is induced by side UV illumination, leads to broadening of the supermode resonance peaks and variation with fiber orientation in the bend response of the fiber grating.