Chengbao Yao

Nested fiber ring resonator enhanced Mach–Zehnder interferometer for temperature sensing

We numerically investigate the properties of the nested fiber ring resonator coupled Mach-Zehnder interferometer as a sensor. By introducing the phase bias of 0.5π in the reference arm, the two output intensities exhibit sharp asymmetric line shapes around the resonance wavelength. Utilizing the intensity interrogation, we analyze the effect of parameters on the sensitivity and the detection limit. For the 30 dB signal-noise system, the sensitivity and the detection limit can achieve 4.0866/°C and 7.341×10(-3)°C, respectively; the results indicate that this structure is suitable for high-sensitivity measurements.

Plasmon resonance of silver micro–sphere in fiber taper

We have experimentally studied the plasmon resonance phenomenon of a silver micro-sphere with a diameter of 2.3 μm in cone-shaped air cavity of a hollow fiber taper. To take insight into the plasmon resonance phenomenon, we move the micro-sphere along the fiber and observe the significant shift of the resonance peak. We also explore the light response in both infrared and visible wavelength band by finite difference time domain method. The significant variations of the magnetic and power field distribution are observed. The interesting results imply that the configuration has great potential in optical sensors and color filters.

The lifetime of the triplet excited state and modulation characteristics of all-optical switching in phenoxy-phthalocyanines liquid

We present our experimental results on the measurements of excited state dynamics in 2, 9, 16, 23-phenoxy-phthalocyanine (Pc1) and 2, 9, 16, 23-phenoxy-phthalocyanine-zinc (Pc2) using the pump-probe experiment. The results show that the lifetime of the first triplet excited state of the Pc2 longer than Pc1. The lifetimes of the triplet excited state for Pc2 and Pc1 are 12.8 μs and 10.1 μs at the same intensity, respectively. Moreover, analysis of modulation characteristics of all-optical switching (A-OS) shows that the stronger the light intensity of the pump light is, the smaller the normalized transmittance is, and the lower the A-OS response time is. The consequences of such short lifetimes are also discussed in view of the strong A-OS properties of these molecules.

The optical response of the silver nano-sphere with two spindle-shaped cavities in a sub-wavelength quartz fiber

We propose and experimentally study a fiber-optic filter in hourglass configurations, where a silver nano-sphere is trapped in the quartz fiber and two air spindle-shaped cavities are formed on both sides of it. By using two fiber tapers as the input source and the probe, we measured the transmission and reflection spectra of the configuration. The results show that it is transparent for resonance wavelength and absorptive for other wavelengths, respectively. The 1544 nm and 1557 nm resonance peaks were observed in the single and double hourglass configuration. Such a device can be useful in optical filters and biochemical sensors.

Study of the nonlinear optical absorption and refraction of indium doped zinc oxide (IZO) thin films using Z-scan technique

Indium doped zinc oxide (IZO) thin films were grown on sapphire substrate by radio frequency (RF/DC) magnetron sputtering technique. The structural characterization and surface morphology of IZO thin films were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The XRD results show that the samples exhibit polycrystalline characteristics and still retained wurtzite structure. The surface morphology of the samples reveals the average crystallite sizes are increased as indium content. In addition, the linear optical properties of IZO thin films were studied by UV-VIS spectrometer with wavelength range 200-900 nm. The high transmittances and the band gap values were observed in both thin films. Moreover, the nonlinear optical absorption and refraction of IZO thin films were investigated using nanosecond Z-scan technique. These samples show self-focusing optical nonlinearity and good two-photon nonlinear optical absorption behaviors. Therefore, these studies make the IZO thin films as the applications in nonlinear optical devices.

Slow-light transmission in the metal-dielectric structure based on plasmon-induced transparency

The slow light technology prompts the realization of the all-optical storage, by which one can store the information of different wavelengths at their corresponding locations. The induction of plasmon induced transparency (PIT) provides a reliable and easy implement way to achieve slow light transmission and optical storage on the nanometer scale. Meanwhile, the linewidth and position of the PIT can be adjusted by changing the parameters of materials and structures, rather than just depend on the atom level itself in Electromagnetically induced transparency (EIT). More importantly, it can also be integrated with semiconductor devices on the chip, which is an exciting expectation for optoelectronic integration. PIT technology can pave a new way to optical information processing.

All-optical sensor based on surface plasmon polaritons in multi-layers metal-dielectric structure

We study all-optical sensing characteristics based on long-range surface plasmon resonance in a four-layered metal-dielectric structure immersed in the liquid to be measured. The resonance peaks in the reflection angle spectra depend on different refractive indices from 1.30 to 1.38, which are calculated and compared in three typical wavelengths of 532, 632.8 and 780 nm, respectively. Compared with 532 nm, the incident light of 780 nm results in an unstable sensing stability, but the resolution enhances two times. The sensitivity of this refractive index sensor at an incident angle of 45° is about 236.7 nm/RIU which uses 532-nm laser as the light source.