Terahertz (THz) absorption spectra have been applied to measure the compositions of amino acid samples. Because the concentration information about a specific composition is involved in its spectrum, keeping the spectrum length and dynamic range as wide as possible is essential for precise measurements. It is well known that a spectrum is always contaminated by apparatus noises. In this paper, we present a criterion for noise cutting based on wavelet transform, which usually extends the range determined by traditional threshold criterion. Finally, the improvement on measurement precision shows the validity of the new criterion.

The functions of the chemicals are closely related with their compositions and structures. In this paper, we report the characterization of different lignin in the midribs of tobacco leaves using terahertz (THz) time-domain spectroscopy in the frequency range of 0.3 to 2 THz. These lignins are extracted from tobacco leaves grown in different regions. Lignin in midribs of tobacco leaves from the south region and the north region show distinctively different refractive indexes and absorption coefficients at THz frequency. The differences at THz range are found to be correlated with their chemical compositions, which are obtained by way of X-ray microanalysis. This clearly verifies that it is possible to employ THz time-domain spectroscopy as a tool for identifying the functions of the chemicals and analyzing their chemical compositions.

In order to measure the relative change of muscle oxygenation non-invasively, dynamically and directly, a portable monitor based on near infrared spectroscopy (NIRS) was developed. The monitor consists of several function modules, including 735 nm, 805 nm and 850 nm integrated three-wavelength light emitting diode (LED) light source, LED driver, integrated detector, amplifier and filter, A/D sampling circuit, single-chip microcomputer and laptop. The distance between light source and detector is 3 cm and the photon migration depth in tissue is approximately 1.5 cm. The monitor is portable with low dark noise and good long-term stability. The relative change of muscle oxygenation measured by the monitor was in accordance with the real physiology status in the cuff ischemia experiment, verifying the performance of the monitor for living muscle. Two inflexions referring to an accelerated fall and a leveling-off phase in the muscle oxygenation index, respectively, were observed in in vivo incremental intensity exercises. Significant correlation was found between the first inflexion and the ventilatory threshold which was identified by the gas exchange measurement. These results demonstrated that the monitor can be used to detect the local lactate threshold of the measured muscle and reflect the changes of oxygen index in local muscle for in vivo exercises. The monitor may provide a meaningful approach to evaluate the subject’s oxidative capacity effectively.

A novel and simple non-return-to-zero differential phase shift keying (NRZ-DPSK) wavelength division multiplexing (WDM) system, which can simultaneously demultiplex and demodulate multiple wavelengths, is proposed and investigated in this paper. The phase-to-intensity demodulation principle is based on detuned filtering, which is achieved by using a single commercial array waveguide grating (AWG) in our scheme. By properly choosing appropriate AWG channels at the transmitter, the AWG at the receiver can act as both the demultiplexer and the demodulator of the DPSK signals. Simulations at 10, 20, and 40 Gbit/s show good flexibility and performance for the proposed system.

Optical buffer is a key component in all optical information processing systems. Slow light at room temperature via four-wave mixing (FWM) in semiconductor optical amplifier (SOA) is experimentally investigated. Time delay of 0.40 ns is achieved for a sinusoidal modulation signal at 0.1 GHz, corresponding to a delay bandwidth product (DBP) of 0.04. Factors that affect the experimental results are discussed. It is found out that the variable optical delay via FWM in SOA can be controlled either electrically by changing the SOA bias or optically by varying the pump power or pump-probe detuning.

Research on fiber laser combination is discussed briefly in this paper. High-power double clad-fiber laser beam combination technology is introduced and different kinds of fiber laser beam combination and coherent combination technologies are evaluated. Tapered fused bundle (TFB) couplers are used in laser combine for higher power. In this paper, the theory and progress in TFB coupling are introduced. The experiment on our selffabricated TFB is presented. The efficiency of the fiber coupler exceeded 70% and increased as the input power went up. A maximum total output power of 689W was obtained, with an efficiency of 74%. The fiber coupler displayed stability during the course of the experiment, without any cooling provided.

This paper first presents the fundamental principles of the microwave photonic filters. As an example to explain how to implement a microwave photonic filter, a specific finite impulse response (FIR) filter is illustrated. Next, the Q value of the microwave photonic filters is analyzed theoretically, and methods around how to gain high Q value are discussed. Then, divided into FIR filter, first-order infinite impulse response (IIR) filter, and multi-order IIR filter, several novel microwave photonic filters with high Q value are listed and compared. The technical difficulties to get high Q value in first-order IIR filter and multi-order IIR filter are analyzed concretely. Finally, in order to gain higher Q value, a multi-order IIR microwave photonic filter that easily extends its order is presented and discussed.

A novel algorithm for the synthesis of fiber gratings is presented. For the first time we propose an effective optimal approach to construct a coupling coefficient function by employing 4th-order Runge-Kutta (R-K) analysis method for calculating the reflection spectra of fiber gratings. The numerical results show that with this proposed method, some required optical filters have been yielded with better features compared with other methods such as Gel’Fand-Levitan-Marchenko (GLM) algorithm. In addition, the performance of different interpolation functions particularly utilized in our algorithm, including linear-type, spline-type, and Hermit-type, are discussed in detail.

Fiber grating is an optical passive device which has been greatly developed in recent years. The largest application for fiber Bragg grating (FBG) is the fiber sensor. Cross-sensitivity of fiber grating sensor is the most important problem which has restricted the development of the fiber sensor. In this paper, we explain how the crosssensitivity problem is produced based on the basic principle, and we suggest a modification for the traditional dual-wavelength matrix calculation method, which is used to solve the cross-sensitivity problem. The modified calculation method has a higher accuracy than the traditional one.

A novelty dispersion ultra-flattened Bragg photonic crystal fiber (PCF) has been fabricated in this paper. The fiber is composed of compound cores and periodical claddings with 11 coaxial rings. It has flattened dispersion of 8.5
1.3 ps$(nm$km)-1 in the communication wavelength range of 1460-1625 nm. Its dispersion slope alters from-0.0428 to 0.0392 ps$nm-2$km-1. The low attenuation of 0.52 dB/km and low bending loss of 0.09 dB at 1550 nm of the fiber are also achieved. The Bragg PCF has enormously potential application in the fields of dense wavelength division multiplexing systems because of its superior dispersion properties and easy splicing performances.

We numerically studied supercontinuum generation in a tapered photonic crystal fiber with flattened dispersion properties. The fiber was weakly tapered to have normal dispersion at wavelengths around 1.55 μm after a certain distance. We pumped 4 ps pulses with low peak power and found that flatly broadened, wideband supercontinuum was generated in telecommunication windows. Furthermore, we also demonstrated the effects of tapered length and pulse width of the pump pulse on supercontinuum generation.

We simultaneously observed both the fast proton generation and terahertz (THz) radiation in the laser pulse interaction with a thin-foil target. The maximum proton energy of ~2.3 MeV and an intense THz radiation were observed at the pulse duration of ~30 fs. We also measured the proton beam and UV harmonics from a thin-foil target by changing the laser pulse duration. In the case of the ~500 fs, peaks of UV harmonics up to fourth order appeared. This unique combination of the multiple beams will provide useful applications such as pump-probe experiments.

Silicon nitride microring resonators were demonstrated as chemical sensors. The microring devices, with diameter of 100 μm, were fabricated using complementary metal oxide semiconductor (CMOS)-compatible technology, and a high Q factor of 15000 was realized with free spectrum range (FSR) of 2 nm. The structures were further packaged to perform as chemical sensors, and their functionality was proved using deionized water (DI water) and ethanol as detecting mediums. Lastly, the packaged chips were used to detect glucose solutions with various concentrations, and a detection capability of refractive index change of 10-3 refractive index unit (RIU) was obtained.

Fabrication of microscale and nanoscale silicon waveguide devices requires patterning silicon, but until recently, exploitation of the technology has been restricted by the difficulty of forming ever-small features with minimum linewidth fluctuation. A technique was developed for fabricating such devices achieving vertical sidewall profile, smooth sidewall roughness of less than 10 nm, and fine features of 40 nm. Subsequently, silicon microring resonator and silicon-grating coupler were realized using this technique.

The purpose of this report is to present an experimental study of the effects of light propagation through atmospheric turbulence. Free space optical communication is a line-of-sight technology that transmits a modulated beam of visible light through the atmosphere for broadband communication. The fundamental limitations of free space optical communications arise from the environment through which it propagates. However these systems are vulnerable to atmospheric turbulence, such as attenuation and scintillation. Scintillation is due to the air index variation under the temperature effects. These factors cause an attenuated receiver signal and lead to higher bit error rate (BER). An experiment of laser propagation was carried out to characterize the light intensity through turbulent air in the laboratory environment. The experimental results agree with the calculation based on Rytov for the case of weak to intermediate turbulence. Also, we show the characteristics of irradiance scintillation, intensity distribution and atmospheric turbulence strength. By means of laboratory simulated turbulence, the turbulence box is constructed with the following measurements: 0.5 m wide, 2 m long and 0.5 m high. The simulation box consists of three electric heaters and is well described for understanding the experimental set up. The fans and heaters are used to increase the homogeneity of turbulence and to create different scintillation indices. The received intensity scintillation and atmosphere turbulence strength were obtained and the variation of refractive index, with its corresponding structure parameter, is calculated from the experimental results.

At present, the maximal transmission distance between the optical line terminal (OLT) and optical network unit (ONU) of an Ethernet passive optical network (EPON) system is 20 km. However, this distance should be extended to 50 km or even longer in some applications such as fiber to the village (FTTV). A method for extending the transmission distance of an EPON system is proposed in this paper, in which the optical power amplifier and the adjustment of dynamic bandwidth allocation (DBA) are the key technologies.

As the extension of service provider network, the home network is the last section of the service delivery process, so it must have the characteristics of the operator network, that is, stable performance, manageable, maintainable, quality of service, security, and extendable. In this paper, with the integration of the new access network technology Ethernet passive optical network (EPON) and the remote network management protocol, TR-069 protocol, addressed by the Digital Subscriber Line (DSL) Forum, a remote management framework of home network based on EPON is presented. Then, a prototype system is also provided to realize the functions of TR-069 protocol on residential gateway.

To improve the limitations of Ethernet over Coax (EoC) technology in the bidirectional reformation of the hybrid fiber-coaxial (HFC) network, this paper proposes the concept of Ethernet passive electronic network (EPEN) based on multi-point control protocol (MPCP) and the hybrid access scheme of Ethernet passive optical network (EPON) and EPEN. This paper describes the network architecture of EPEN, and introduces the implementation scheme and design of the EPEN system. At present, the project group has been working on the core technology research and key software and hardware design of the EPEN system, on which we have accomplished the hardware design and debugging, the embedded software coding and debugging, the EPEN network management protocol design and software coding. However, there is still a lot to do to achieve networking capability, management, security, quality of service (QoS) and some other functions.

When a glass substrate was irradiated by three different temporal shapes of laser sources, namely, linetime-shape laser, triangle-time-shape laser, and parabolatime-shape laser, the mathematical models were proposed, and the temperature distribution and the resulting thermal stress were calculated by the finite-element-method (FEM) software ANSYS. With these three types of lasers having the same output laser energy, the resulting thermal stress induced in the glass substrate was analyzed. The results showed that, with the same output laser energy, the thermal stress produced in glass heated by line-time-shape laser is higher than that produced in glass heated by the other two shapes of lasers.

A number of spectroscopic techniques make use of ultra violet (UV) absorbance and luminescence measurements to characterize materials, for use in medical/pharmaceutical applications, for forensic and sensor applications, and for remote detection or monitoring, especially for hazardous environments. Furthermore, many high-power applications in medicine and industry are looking forward to using UV wavelengths. The UV fiber’s mechanical reliability has become one of the most crucial performances with longer length fiber being used. This paper reviews the researched evolvement of the normal single mode fiber’s mechanical reliability. Based on the standard measure method of the normal fiber, the mechanical reliability of the UV fiber has been researched. The measurement results show the difference of mechanical reliability between the different doping composition UV fibers.

Properties of atom-like emitters in cavities are successfully described by cavity quantum electrodynamics (cavity-QED). In this work, we focus on the issue of the steady-state and spectral properties of the light emitted by a driven microcavity containing a quantum well (QW) with the excitonic interactions using simulation of fully quantum-mechanical treatment. The system is coherently pumped with laser, and it is found that depending on the relative values of pumping rate of stimulated emission, either one or two peaks close to the excitation energy of the QW or to the natural frequency of the cavity are shown in the emission spectrum. Furthermore, the nonclassical proprieties of the emitted photon have been investigated. This excitonic system presents several dynamical and statistical similarities to the atomic system, in particular for the bad-cavity and good-cavity limits. The results show that the photon emission can be significantly amplified due to the coupling strength between a single emitter and radiation field in the microcavity, and it is concluded that the present semiconductor microcavity system may serve as a QW laser with low threshold.

The AlxGa1-xN/AlyGa1-yN multiple quantum well (MQW) structure for deep ultraviolet emission has been grown on sapphire by metal organic chemical vapor deposition (MOCVD). High resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), and cathodoluminescence (CL) are used to characterize the structural and optical properties of MQWs, respectively. Clear step flows can be observed in the AFM image indicating a two-dimensional growth model. There are many cracks on the surface of the MQW structure because of the high tensile stress. HRXRD shows multiple satellite peaks to the 2nd order. The HRXRD simulation shows that the MQW period is about 11.5 nm. The emission peak of AlxGa1-xN/AlyGa1-yN MQWs is about 295 nm in the deep ultraviolet region from the CL spectra.