Zhihe Huang

Temperature sensor based on surface plasmon resonance within selectively coated photonic crystal fiber

We demonstrate a temperature sensor based on surface plasmon resonances supported by photonic crystal fibers (PCFs). Within the PCF, to enhance the sensitivity of the sensor, the air holes of the second layer are filled with a large thermo-optic coefficient liquid and some of those air holes are selectively coated with metal. Temperature variations will induce changes of coupling efficiencies between the fundamental core mode and the plasmonic mode, thus leading to different loss spectra that will be recorded. In this paper, variations of the dielectric constants of all components, including the metal, the filled liquid, and the fused silica, are considered. We conduct numerical calculations to analyze the mode profile and evaluate the power loss, demonstrating a temperature sensitivity as high as 720 pm/°C.

Temperature sensing using the bandgap-like effect in a selectively liquid-filled photonic crystal fiber.

A compact temperature sensor based on a selectively liquid-filled photonic crystal fiber (PCF) is proposed using controlled hole collapse in PCF post-processing. The first ring around the core is filled with liquid of higher refractive index than the matrix, while the outer rings of holes are filled with air. The bandgap (BG)-like effect of the high refractive index ring is analyzed. Absorption loss spectra of the fiber are found to be quite sensitive to the refractive index of liquid when the liquid is lossy. Using the BG-like effect, a fiber temperature sensor is fabricated by selectively injecting a mixture of dimethyl sulfoxide and aqueous gold colloids with a high thermo-optic coefficient to the PCF. Temperature sensitivity up to -5.5 nm/°C is experimentally confirmed.

Comparison of fiber lasers based on distributed side-coupled cladding-pumped fibers and double-cladding fibers.

We compare both analytically and numerically the distributed side-coupled cladding-pumped (DSCCP) fiber lasers and double cladding fiber (DCF) lasers. We show that, through optimization of the coupling and absorbing coefficients, the optical-to-optical efficiency of DSCCP fiber lasers can be made as high as that of DCF lasers. At the same time, DSCCP fiber lasers are better than the DCF lasers in terms of thermal management.

Power scalability of a single-stage Yb-doped superfluorescent fiber source

A high-power all-fiber broadband superfluorescent source is fabricated by using a distributed side-coupled cladding-pumped Yb-doped fiber. It is found experimentally that besides the optical feedback, the active fiber parameters have a significant effect on the power scaling. By optimizing the fiber length, a record amplified spontaneous emission output of 186.3 W is achieved, and the slope efficiency with respect to launched pump power is 78%. The bandwidths are larger than 20 nm. Furthermore, the power scalability of the superfluorescent source is analyzed numerically. The parasitic laser oscillation can be suppressed further with a large core to cladding ratio.

A Kilowatt All-Fiber Cascaded Amplifier

A kilowatt all-fiber cascaded amplifier is demonstrated with a distributed side-coupled cladding-pumped Yb-doped fiber for the first time, to the best of our knowledge. Two-stage cascaded amplification is realized in the amplifier, with a total output power of 1.009 kW and an optical-to-optical efficiency of 76.8% with respect to launched pump power. The output beam quality of the cascaded amplifier is also measured, and the M2 factor is ~2.1. The results illuminate that the cascaded amplifier should be beneficial to the power scalability of fiber laser systems.

Surface plasmon resonance sensor based on supercontinuum source

Current research on Surface plasmon polaritons (SPPs) is widely spread to surface adsorption, surface roughness and other related phenomena. It has also been used in the chemical and biological high-precision detection fields. More and more high-precision sensors have been created. Supercontinuum (SC) is a laser source with advantages as broad and flat spectra, high brightness and good coherent characters. By researching the SC laser source based surface plasmon resonance (SPR) effect, we can get a more comprehensive reflection of the SPR effect from factors as the light intensity reflectivity and the phase change. The SC laser source based SPR effect is a subject with important theoretical and practical significance. The testing principles and testing methods of the SPR effect in the installations with the Au-coated prism structure were studied. Using a SC laser, the wavelength-scanning and angle-scanning methods can be carried out in one system. The SC laser source based SPR effect in the installations with the Au-coated prism structure was tested. The SPR effect sensors based on SC were designed and realized. The theoretical results matched with the experimental results. Through the relation between the refractive index and the resonance wavelength, we could demarcate different substances.

High-efficiency high-power all-fiber oscillator with counter-pumping configuration

A 525 W all-fiber counter-pumping oscillator is demonstrated with a distributed side-coupled cladding-pumped Yb-doped fiber, which outputs at 1080 nm with a slope efficiency as high as 78.7%. The beam quality is also measured.

Study on coupling between two strongly-coupled highly multi-mode fibers

The optical coupling between two strongly-coupled highly multi-mode fibers is studied. The coupling process is measured in experiment. The effects of the differences between two fiber cores on the coupling process are revealed.

Home-made high efficiency side-pumped fiber amplifiers

The side-coupled cladding-pumped fiber has many advantages in terms of system design, ease of pump injection, signal extraction and power scalability over traditional double cladding fiber. We demonstrate a 290-W all home-made side-coupled cladding-pumped fiber laser with the slope efficiency of 67.8%. To the best of our knowledge, the slope efficiency is the highest for the published high power fiber laser based on the DSCCP fiber. The slope efficiency of the home-made side-coupled cladding-pumped fiber amplifier is mainly limited by the background loss, pump light coupling and pump light absorption. The results show that the power ratio of signal light to residual pump light is near 20 dB. The pump light is not absorbed enough that the slope efficiency can be further improved by optimizing the amplifier structure.

102 W Distributed Side-Coupled Cladding-Pumped Yb-Doped Superfluorescent Fiber Source

An all-fiberized broadband superfluorescent source based on a distributed side-coupled cladding-pumped Yb-doped fiber is demonstrated. A recorded 102-W combined output power is obtained by the excellently angle-cleaved termination. The bandwidth is larger than 10 nm.