Influence of Al-doped ZnO and Ga-doped ZnO substrates on third harmonic generation of gold nanoparticles

Principal role of substrate types on the nonlinear optical properties of Au NP was investigated. Third harmonic generation (THG) studies were carried out for Au NP deposited on the Al-doped ZnO (AuNP/AZO) and Ga-doped ZnO (AuNP/GZO) substrates at fundamental wavelength of 20 ns Er:glass laser (generating at 1540 nm wavelength) during photostimulation by the 532 nm 15 ns laser pulses. Sizes of Au NP were 5 nm, 10 nm, 20 nm, and 30 nm. The output signal was registered at 513 nm. The photoinduced power density was increased from 0 up to 800 MW/cm². So in our work we explore the role of the substrate on the optically stimulated non-linear optical properties during simultaneous photo stimulation near the inter-band transition. The results were studied depending on the type of substrate and the sizes of the deposited nanoparticles. The analysis was done within a framework of interaction between the photoinduced light and SPR wavelengths. Control of the photoinduced temperature was done.     

Advanced multifunctional optical switch for multimode optical fiber networks

In this work, an advanced multifunctional optical switch based on multimode fibers is proposed. It can work as a 3 × 1 optical multiplexer/combiner, a 2 × 2 optical switch, a variable optical attenuator and a variable optical power splitter. All these functionalities can be developed in the same device without any hardware modification, only by using the proper ports and control electronics.The proposed switch has been developed for being used in the visible and near infrared wavelength range: 450–650 nm for optical fiber automobile applications, 650–850 nm for home broadband applications; and 850–1300 nm for multimode fiber access networks. Up to three different types of twisted nematic liquid crystal cells have been designed and fabricated for fulfilling these different wavelength ranges as part of the proposed device.The multifunctional switch has been implemented and experimentally tested. Crosstalk usually better than ? 15 dB at 532 nm, 660 nm and 850 nm, in any state has been measured. Switching is achieved at voltage levels of 4 Vrms. Fiber to fiber insertion losses when operating as a 2 × 2 optical switch, range from 10 to 15 dB within 200 nm wavelength range; with a non-optimized optics for collimation and coupling.     

Spectroscopy and efficient laser emission of Yb3+: LuAG single crystal grown by μ-PD

A LuAG shaped rod crystal, doped with Yb³⁺, has been grown by μ-PD technique. The crystal diameter was about 3 mm and the length around 130 mm. A complete spectroscopic investigation in the temperature range 10–300 K is reported and data has been utilized to model the laser behavior. In the laser experiment the Yb:LuAG sample was placed in an X cavity and pumped longitudinally obtaining an efficient CW laser emission. The Yb:LuAG laser yielded a maximum output power of 23 mW with a slope efficiency of 32% and a threshold around 35 mW, at lasing wavelength of 1030 nm. No significant depolarization effects were observed, indicating a crystal growth with negligible stress. The output beam profile was investigated, yielding M² ≈ 1.0 in both directions, further confirming the good optical quality of the sample.     

Design and experiment of spectrometer based on scanning micro-grating integrating with angle sensor

A compact, low cost, high speed, non-destructive testing NIR (near infrared) spectrometer optical system based on MOEMS grating device is developed. The MOEMS grating works as the prismatic element and wavelength scanning element in our optical system. The MOEMS grating enables the design of compact grating spectrometers capable of acquiring full spectra using a single detector element. This MOEMS grating is driven by electromagnetic force and integrated with angle sensor which used to monitored deflection angle while the grating working. Comparing with the traditional spectral system, there is a new structure with a single detector and worked at high frequency. With the characteristics of MOEMS grating, the structure of the spectrometer system is proposed. After calculating the parameters of the optical path, ZEMAX optical software is used to simulate the system. According the ZEMAX output file of the 3D model, the prototype is designed by SolidWorks rapidly, fabricated. Designed for a wavelength range between 800 nm and 1500 nm, the spectrometer optical system features a spectral resolution of 16 nm with the volume of 97 mm × 81.7 mm × 81 mm. For the purpose of reduce modulated effect of sinusoidal rotation, spectral intensity of the different wavelength should be compensated by software method in the further. The system satisfies the demand of NIR micro-spectrometer with a single detector.     

An all-fiber high resolution fiber grating concentration sensor

An all-fiber high resolution optical fiber grating concentration sensor has been studied theoretically and experimentally. A long period grating is used as the sensor head and a wavelength matched fiber Bragg grating is used as an interrogator to convert wavelength into intensity encoded information for interrogation. A concentration resolution of 0.104 g/L for NaCl solution is realized in experiment. The all-fiber sensor system, with the sensor head and the interrogator being all optical fiber components, is suitable for far-distance monitoring. The sensor system is with multifunction and can be used for temperature monitoring. A temperature resolution of 0.013 °C has realized in experiment.     

Tunable dual-wavelength fiber laser based on an opto-VLSI processor and four-wave mixing in a photonic crystal fiber

A stable wavelength and wavelength spacing tunable dual-wavelength fiber laser based on an Opto-very-large-scale-integration (Opto-VLSI) processor and four-wave mixing (FWM) in a high-nonlinear photonic crystal fiber is experimentally demonstrated. The results show that the line width of the tunable dual-wavelength fiber laser is 0.02 nm, and the wavelength spacing can be tuned from 0.8 nm to 4 nm with a 0.15 nm step. Under the influence of the FWM, the uniformity is below 0.6 dB and the measured side mode suppression ratio (SMSR) is above 45 dB.     

A high-finesse fiber optic Fabry–Perot interferometer based magnetic-field sensor

A high-finesse extrinsic Fabry–Perot interferometric sensor for the measurement of weak dc magnetic fields is demonstrated. The Fabry–Perot cavity is formed by aligning the fiber end-face and the TbDyFe rod end-face, and each end-face is coated by a mirror with a micro-lens. The length of the TbDyFe rod is changed by the variation of an applied dc magnetic field, leading a change of the Fabry–Perot cavity length. By interrogating the white-light interferometric spectrum, the wavelength of the resonant peak is tracked and the length of the Fabry–Perot cavity is obtained. The sensor exhibits a high sensitivity of 1510 nm/mT with a magnetic resolution of 25 nT.     

Supercontinuum generation using a passive mode-locked stretched-pulse bismuth-based erbium-doped fiber laser

A Supercontinuum (SC) generation in photonic crystal fiber (PCF) is demonstrated using an amplified picosecond stretched-pulses from a passive mode-locked Bismuth-based Erbium-doped fiber laser (Bi-EDFL). The Bi-EDFL employs of a piece of a highly nonlinear 49 cm long Bismuth-based Erbium-doped fiber (Bi-EDF), an optical isolator and a polarization controller in a cavity to generate a mode-locked stretched-pulse via a nonlinear polarization rotation technique. It operates at 1560 nm with a repetition rate of 42 MHz and a pulse width of 131 fs. The SC lights, which extends from 1250 nm to 1910 nm as well as in the visible green wavelength region are obtained with a 100 m long PCF and the amplified pump power of 30 dBm.     

Inherently gain flattened S-band erbium doped fiber amplifier based on dual core resonant leaky fiber

A co-axial dual core resonant leaky optical fiber (DCRLF) is designed for inherent gain equalization of S-band erbium doped fiber amplifier (EDFA). Resonance tail of leakage loss of the fiber into the S-band region is utilized to flatten the gain. We have numerically studied the effect of various design parameters and their fabrication tolerances on gain flattening. We show 23.5 dB flat gain with ± 0.9 dB ripple over 30 nm bandwidth (1490–1520 nm) using 120 mW pump. The study should be useful in designing optical fiber amplifiers for optical communication system employing wavelength division multiplexing.     

Wavelength conversion based on high nonlinear microstructured fiber

A wavelength conversion based on high nonlinear microstructured fiber is demonstrated. Core diameter and pitch of the microstructured fiber used in this wavelength conversion method are 2.05 μm and 5.0 μm, respectively. Diameter of the air-holes in the fiber cladding is 4.50 μm, the nonlinear coefficient of the microstructured fiber is 112.2 W^?1 km^?1 and it is 60 times higher than that of a conventional dispersion-shift fiber, the length of the fiber is 100 m. Four-wave-mixing effect is improved in the high nonlinear microstructure fiber and then the efficiency of the wavelength conversion is improved also. 10 Gbps Not-Return-to-Zero (NRZ) modulation format and 10 Gbps Return-to-Zero (RZ) modulation format are converted effectively by our method. This study can provide a new alternative solution for high effective all-light wavelength conversion in high speed optical communication systems with multi-wavelengths and all-light optical networks.     

Flat and compact switchable dual wavelength output at 1060 nm from ytterbium doped fiber laser with an AWG as a wavelength selector

A dual-wavelength ytterbium doped fiber laser with a narrowest spacing of 0.53 nm and widest spacing of 12.2 nm at 1064 nm is presented in this paper. An arrayed waveguide grating (AWG) together with an optical channel selector (OCS) have also been incorporated in the proposed setup that works as a switchable mechanism giving 23 different wavelength tunings. Producing an average output power of ?8 dB m and side mode suppression ratio (SMSR) of 59.65 dB, this dual-wavelength fiber laser is quite stable with an output power variance as low as 0.47 dB giving it an advantage due to its switching ability and stable dual-wavelength output powers.     

Dual-wavelength narrow-linewidth fiber laser based on F-P fiber ring filter

A dual-wavelength fiber laser with a narrow-linewidth, based on a P-F fiber filter has been proposed. Polarization-maintaining fiber Bragg grating (PM-FBG) and a F-P fiber filter are introduced based on the traditional fiber laser. PM-FBG is used as the wavelength selection device. The fiber F-P filter consists of two optical couplers and a section of un-pumped erbium-doped fiber (EDF). Due to the delay of cavity and the loss generated by the EDF, the filter has comb spectral response. The incorporation of the fiber F-P filter leads to the suppression of undesirable modes. At the room temperature, under 980 nm LD pumped, the maximum output of the two wavelengths is respectively ?2.259 dBm and 0.568 dBm, with the 3-dB bandwidth separately 0.1 nm and 0.14 nm, realizing the narrow linewidth and dual-wavelength output.     

Tunable multi-wavelength fiber laser based on a polarization-maintaining erbium-doped fiber and a polarization controller

A stable and tunable multi-wavelength fiber laser with a polarization-maintaining erbium-doped fiber (PM-EDF) and a polarization controller (PC) is proposed and demonstrated. A homemade PM-EDF incorporated in the ring cavity is used as the gain medium. Simultaneous multi-wavelength oscillation is achieved at room temperature. The theory of the PM-EDF and PC to suppress the wavelength competition is described in detail. The 3 dB bandwidth is less than 0.01 nm. The power fluctuation and wavelength shift are measured to be less than 0.5 dB and 0.05 nm over 32 min. The wavelength tuning between single-, double-, triple-, and four-wavelength is realized.     

Picosecond laser cutting and drilling of thin flex glass

We investigate the feasibility of cutting and drilling thin flex glass (TFG) substrates using a picosecond laser operating at wavelengths of 1030 nm, 515 nm and 343 nm. 50 μm and 100 μm thick AF32^®Eco Thin Glass (Schott AG) sheets are used. The laser processing parameters such as the wavelength, pulse energy, pulse repetition frequency, scan speed and the number of laser passes which are necessary to perform through a cut or to drill a borehole in the TFG substrate are studied in detail. Our results show that the highest effective cutting speeds (220 mm/s for a 50 μm thick TFG substrate and 74 mm/s for a 100 μm thick TFG substrate) are obtained with the 1030 nm wavelength, whereas the 343 nm wavelength provides the best quality cuts. The 515 nm wavelength, meanwhile, can be used to provide relatively good laser cut quality with heat affected zones (HAZ) of <25 μm for 50 μm TFG and <40 μm for 100 μm TFG with cutting speeds of 100 mm/s and 28.5 mm/s, respectively. The 343 nm and 515 nm wavelengths can also be used for drilling micro-holes (with inlet diameters of ⩽75 µm) in the 100 μm TFG substrate with speeds of up to 2 holes per second (using 343 nm) and 8 holes per second (using 515 nm). Optical microscope and SEM images of the cuts and micro-holes are presented.     

Analysis of multimode BDK doped POF gratings for temperature sensing

We report a temperature sensor based on a Bragg grating written in a benzil dimethyl ketal (BDK) doped multimode (MM) polymer optical fiber (POF) for the first time to our knowledge. The thermal response was further analyzed in view of theory and experiment. In theory, with the order of the reflected mode increasing from 1st to 60th order, for MM silica fiber Bragg grating (FBG) the temperature sensitivity will increase linearly from 16.2 pm/°C to 17.5 pm/°C, while for MM polymer FBG the temperature sensitivity (absolute value) will increase linearly from ?79.5 pm/°C to ?104.4 pm/°C. In addition, temperature sensitivity of MM polymer FBG exhibits almost 1 order larger mode order dependence than that of MM silica FBG. In experiment, the Bragg wavelength shift will decline linearly as the temperature rises, contrary to that of MM silica FBG. The temperature sensitivity of MM polymer FBG is ranged from ?0.097 nm/°C to ?0.111 nm/°C, more than 8 times that of MM silica FBG, showing great potential used as a temperature sensor.     

Fiber curvature sensor based on spherical-shape structures and long-period grating

A novel curvature sensor based on optical fiber Mach–Zehnder interferometer (MZI) is demonstrated. It consists of two spherical-shape structures and a long-period grating (LPG) in between. The experimental results show that the shift of the dip wavelength is almost linearly proportional to the change of curvature, and the curvature sensitivity are −22.144 nm/m⁻¹ in the measurement range of 5.33–6.93 m⁻¹, −28.225 nm/m⁻¹ in the range of 6.93–8.43 m⁻ and −15.68 nm/m⁻¹ in the range of 8.43–9.43 m⁻¹, respectively. And the maximum curvature error caused by temperature is only −0.003 m⁻¹/°C. The sensor exhibits the advantages of all-fiber structure, high mechanical strength, high curvature sensitivity and large measurement scales.     

The influence of Au thickness on the structural,optical and electrical properties of ZnO/Au/ZnO multilayer films

Transparent and conductive ZnO/Au/ZnO (ZAZ) multilayer films were deposited on glass substrates by magnetron sputtering without intentional substrate heating. The thickness of Au interlayer was set at 1, 2 and 3 nm.The observed structural, optical and electrical properties were dependent on the thickness of the Au interlayer. For all of the ZAZ films, the diffraction peaks in the XRD pattern were identified as the (002) and (103) planes of a ZnO films and the (111) plane of an Au interlayer. The ZAZ films with a 2 nm thick Au interlayer showed a higher figure of merit than the other ZAZ films prepared in this study, and they also demonstrated the relatively high work function of 5.13 eV.From these results, we concluded that a ZAZ film with a 2 nm thick Au interlayer is an alternative candidate for use as a transparent electrode in OLEDs and various flat panel displays.     

Tunable single-longitudinal-mode operation of a sandwich-type YAG/Ho:YAG/YAG ceramic laser

We present a 2.09 μm single-longitudinal-mode sandwich-type YAG/Ho:YAG/YAG ceramic laser pumped by a Tm-doped fiber laser for the first time. A pair of F-P etalons was used to achieve tunable single-longitudinal-mode operation. The maximum single-longitudinal-mode output power of 530 mW at 2091.4 nm was obtained with an absorbed pump power of 8.06 W, corresponding to an optical conversion efficiency of 6.6% and a slope efficiency of 12.7%. Wavelength tunable was achieved by tuning the angle of etalons and the wavelength could be tuned from 2091.1 nm to 2092.1 nm, corresponding to a tuning frequency of 68 GHz. The M² factor was measured to be 1.23.     

Numerical analysis of a broadband spectrum generated in a standard fiber by noise-like pulses from a passively mode-locked fiber laser

This paper covers a numerical analysis of supercontinuum spectrum generation in a piece of standard fiber by using as the pump noise-like pulses produced by a passively mode-locked fiber laser. An experimental study was also carried out, yielding results that support the numerical results. In the numerical study we estimated that the spectral extension of the generated supercontinuum reaches ~ 1000 nm, and that it presents a high flatness over a region of ~ 220 nm (1630 nm-1850 nm) when we use as the pump noise-like pulses with a wide optical bandwidth (~ 50 nm) and a peak power of ~ 2 kW. Experimentally, the output signal spectrum extends from ~ 1530 nm to at least 1750 nm and presents a high flatness over a region of 1640 nm to 1750 nm for the same value of numerical input power, 1750 nm being the upper limit of the optical spectrum analyzer. The numerical analysis presented here is thus an essential part to overcome the severe limitation in measuring capabilities and to understand the phenomena of supercontinuum generation, which is mainly related to Raman self-frequency shift. Finally, this work demonstrates the potential of noise-like pulses from a passively mode-locked fiber laser for broadband spectrum generation.     

Low-threshold all-fiber 1000 nm supercontinuum source based on highly non-linear fiber

We present an highly efficient all-fiber compact supercontinuum source that exhibits a nearly flat spectrum from 1.1 μm to 2.1 μm. This broadband infrared optical source is made-up of a highly non-linear fiber pumped by a 1.55 μm self-Q-switched Er-Brillouin nanosecond pulsed fiber laser, which in turn is pumped by a low-power 1480 nm laser diode. In this work we highlight the great potential of highly non-linear fiber for supercontinuum generation with respect to conventional dispersion-shifted fiber by demonstrating a significant 10 dB power enhancement in the short wavelength side of the supercontinuum.