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We have demonstrated spectral beam combining of two high power fiber lasers and obtained more than 40 W output power from the system. The system consists of two 30 W fiber lasers, a diffraction grating and a resonator. Both fiber lasers have broadband fiber Bragg gratings on the rear sides and share the diffraction grating and output coupler on the output sides. The wavelengths of the fiber lasers are determined by the optical dispersion provided by the grating and the collimating lens, as well as the fiber spacing. A model that analyzes dependence of laser line-width on beam quality of an SBC system is given in this paper. We also model a novel configuration that can significantly improve beam quality. The experimental results have shown that control of fiber laser line-width is the key to achieving high power SBC lasers. In addition, a new approach using three gratings is proposed and has been proven by the experiment. The new approach consists of three gratings, in which one grating is used by the SBC cavity to lock wavelengths while the other two combine the collimated beams without beam quality reduction. This approach has successfully improved beam quality M 2 from 11 to 2.0.

We study oscillatory properties of solutions for nonlinear impulsive hyperbolic differential equations and find new necessary and sufficient conditions for oscillations are established. Вивчено властивостi коливань розв’язкiв нелiнiйних гiперболiчних диференцiальних рiвнянь з iмпульсами i знайдено новi необхiднi та достатнi умови для iснування коливань.

Partial response (PR) signaling with maximum likelihood (ML) detection is now a well-entrenched technology in magnetic disk drive systems. Indeed, read channel products using Extended Partial Response (EPR) systems are ubiquitous in commercially available disk drive products. Efforts are now underway to implement even more advanced detection methods that combine EPR systems with trellis coding techniques to provide higher recording densities or to operate with a lower SNR for a given bit error rate (EPR). This paper describes one such method, which is referred to as TC-E/sup 2/PRML. TC-E/sup 2/PRML is based on the idea of jointly designing the coding and the equalization functions to achieve improved utilization of the available SNR and bandwidth of the head/media combination. Its SNR performance is superior to that of the previous generation PRML or EPRML channels over the linear densities of current and future interest (PW50/T>3.0).

Simultaneous lasing at multiple wavelength of solid-state lasers has been reported by a number of researchers, which may be used in double wavelength lidar, nonlinear optical study and laser medical treatment. One way to achieve multiple wavelength lasing is through utilizing the different energy levels of the active ion. Another way is by doping more that one active ions into one single host crystal. In addition, combining different laser crystals together should also be able to achieve multiple wavelength lasing and may provide a broader flexibility in choosing different wavelength combinations. One thing should be noticed is that the absorption spectrum of lasers with multiple active ions or multiple host materials will become a multiple absorption spectrum. This will be a problem when using laser diodes (LD) as a pumping source because of the narrow bandwidth of LD emission which can only match well with one absorption peak. We used two of the frequently used laser crystals: Nd/sup 3+/ doped YAG and YLF and mounted them together using two bonding methods within a single cavity. By using a LD pumping source which is a off-resonant absorption or wind-pumping system, we achieved simultaneous CW output at wavelength of 1064 nm and 1047 nm, among which output at wavelength of 1047 nm is about 25 % out of the total 30 W under 150 W LD input power. Different bonding methods are compared which shows that the use of a simple optical adhesive is effective at low and middle power presenting no deterioration.

A multi-wavelength surface plasmon resonance (Dr-SPR) sensor consisting of three excitation wavelengths at 665 nm, 980 nm, and 1480 nm has been demonstrated. The use of three excitation wavelengths not only provides three penetration depths of 186 nm, 570 nm, and 1395 nm but also enables depth-resolving capability. To verify its depth-resolving capability, three silica bead sizes of 150 nm, 540 nm, and 1860 nm were used to form bead monolayers with different thicknesses on the sensor chip surface. It is found that the Dr-SPR produces the maximum response when the bead size matches the penetration depth. The demonstration provides a unique technique to characterize penetration depths of SPR using multiple excitation wavelengths. It also opens a variety of applications in which particles can be used as a biomedical/biochemical marker and tracked by the Dr-SPR.

Numerical analysis for the high-power double-clad fiber lasers is presented and experimental results using different microscope objectives for focusing into a Nd-doped rectangular double-clad fiber also performed. The numerical analysis includes dependence of output power on output mirror reflectivity, absorbed pump power, loss, and fiber length and pump power distribution for the cases of one-end and two-end pumps with 20 dB/km loss. Calculated conversion efficiencies are 76.36%, 69.73%, and 63.84% for lossless, two-end pump, and one-end pump fiber lasers, respectively. Slope efficiencies from absorbed pump power/output powers measured using microscope objectives are 16.8%/182 mW, 53.8%/351 mW, 24.9%/1240 mW, and 13.9%/ 649 mW for magnifications of 5x, 10x, 20x, and 40x, respectively.

Simultaneous multiple wavelength cw laser operations were achieved in two types of composite laser rods composed of Nd 3+ :YAG and Nd 3+ :YLF crystals, which were laser diode (LD) pumped within a single virtual-point-source cavity. Up to 30 W total output from wavelength of both 1064 nm and 1047 nm was obtained under 150 W LD input power, among which about 25% was from 1047 nm wavelength. Different bonding methods were compared which shows that the use of an optical adhesive is effective and presents no deterioration at low and middle power level. Simultaneous multiple wavelength operation at 1064-nm and 1053 nm was also studied.

The absorption characteristics of circular, offset, and rectangular double-clad fibers are investigated with simple and comprehensible 2D models. In the model, the pump modes in the first-cladding are divided into absorbable and unabsorbable modes. For circular fiber, a concept of absorbable power ratio is defined to characterize the effective absorption. For offset and rectangular fibers, almost all pump modes are absorbable, it is possible to achieve very high absorption efficiency. Such 2D models have been verified by 3D ray tracing simulations. The influences of offset distance for offset fibers, as well as cross sectional shapes for rectangular one on absorption are also discussed. The propagation losses of pump light in rectangular double-clad fibers are characterized both experimentally and theoretically. The measures to reduce pump loss in use of rectangular double-clad fibers are proposed. At last, the two ends of an Nd-doped rectangular double-clad fiber are bundled together to achieve efficient matching with a 10 W fiber coupled LD. With such a configuration, about 5.4 W pump light is launched into the first-cladding and 2.8 W laser output is obtained. A slope efficiency of 58 percent with respect to launched pump power has been achieved.

A piezoelectric microcantilever probe is designed for the scanning probe microscope working in tapping mode, and the dynamic characteristics of the piezoelectric microcantilever probe are tested by experiments. The results indicate that due to the resonance effect, induced voltage and sensitivity of microcantilever are not only associated with force magnitude, but also with the force frequency. When the frequency is close to the first natural frequency 97.04 Hz, the output voltage rapidly increases and reaches a maximum value 62.0 mV. The peak voltage value and its position change as the structure size changes. In dynamic mode, the peak voltage is an order of magnitude higher than that in the static mode, and the dynamic mode is more sensitive. Selecting a reasonable size for the device can help to improve the first-order natural frequency and improve the response speed of piezoelectric microcantilever probe during nanomicro detecting.

For the piezoelectric microcantilever, a device is designed for the IPC-208B type scanning probe microscope. We analyzed the structure size's effect on the piezoelectric cantilever device, and find that the deformation displacement of the cantilever tip depends mainly on the length, while the output voltage of piezoelectric layer depends on the aspect ratio of cantilever itself. We choose the device structure as the length and width dimensions of 200 μm × 40 μm, piezoelectric thickness of 2.0 μm, and electrode layer of 0.2 μm for the experimental analysis. We conclude that the device voltage sensitivity is 0.43 mV/nN, and tip displacement sensitivity up to 4.6 nm/nN, which shows that the output voltage is in the mV-level, is easy to meet the input requirements of testing circuit. The differentiable range can be in nanometer scale, which meets the SPM work requirements, and the device performance is considerable.

In this paper, we designed the SPM micro-cantilever device with the nano- ZnO piezoelectric film, modeled and analyzed the micro-cantilever structure with ANSYS tools and comparatively analyzed the ZnO film performance in the static and dynamic mode. The results showed that: when the design size and force amplitude are same, the output voltage is 0.893 mV, deformation displacement is 32 nm, sensitivity is 0.893 mV/nN and natural frequency is 45.48 KHz in the static mode. In the dynamic mode, when the excitation frequencies close to the device first order natural frequency, the output voltage is an order of magnitude more than the voltage under the static induction and has higher sensitivity. The simulation results provide a valuable basis on producing the micro-cantilever with nano- ZnO piezoelectric film which meets the SPM system requirements.

The PZT piezoelectric film was prepared for tapping mode SPM cantilever with four-coupled structure Si , Pt layer + PZT layer + Pt layer + deposition layer. The sample has the length of 200 μm, width of 40 μ m , silicon substrate thickness of 2.0 μ m , the upper and lower electrode thickness of 0.2 μ m . We analyzed the effect of the piezoelectric, sensitivity, frequency etc by changing the structure size of PZT piezoelectric thin film, and we obtained better parameters for structure and performance by the experimental comparison. The results show that: When the force is 10 nN, the thickness of output voltage in the PZT layer is about 2.0 μ m up to maximum, sensitivity is 0.16 mV/nN and the operating frequency is 64.97 kHz. It is convenient to detect and distinguish SPM when deformation displacement rate remained below 500 nm and the output voltage of the device is above 1.0 mV. The device performance is stable and suitable for the SPM system testing requirements.

This addendum to the above-named article is made to address the issue that A/P Wang Yinfeng has applied to be promoted from A/P to Full Professor by using the above-named paper. Professor J. D. Fan, the proceedings editor for the Sixth International Conference on New Theories, Discoveries and Applications of Superconductors and Related Materials, has mentioned that there are severe contradictions between faculty members in the College of Math & Physics, Chongqing University (CQU), and it is quite clear that Liu Anping is the major person who illegally plagiarized other’s results of research as his publications, and included three other people as co-authors, including Professor Wang Yinfeng, the major leader of the college. Professor J. D. Fan supports any measures and action that IJMPB Journal Office might take against Liu Anping et al., and IJMPB Journal Office will retract the above-named paper from the journal, and prohibit the above-named offending authors from publishing any papers in IJMPB and all other World Scientific copyright publications for 3–5 years.

We propose a novel approach of making large effective area laser fiber with higher threshold for the stimulated Brillouin scattering (SBS) using Al/Ge co-doping in the fiber core. The increased SBS threshold is achieved by reducing the acoustic-optic overlap integral while keeping the optical refractive index profile with a step structure. The manipulation of the overlap integral is done by adjusting the relative doping level between Al(2)O(3) and GeO(2) in the core. The mechanism is validated by detailed examples of numerical modeling. An Yb-doped double clad fiber with the core co-doped with Al(2)O(3) and GeO(2) was fabricated by the OVD process. Measured acoustic velocity profile using a scanning acoustic microscope verified that the acoustic velocity in the fiber core changes with the design. An amplifier utilizing the fiber demonstrated that the proposed fiber yielded 6 dB higher SBS threshold than a fiber without using the co-doping scheme.

A novel all-glass Yb-doped double-clad fibre laser that emits over 1 W of single-transverse-mode output at 978 nm is described. This device is efficiently pumped with 2.5 W of launched power from a single 200 µm broad-area laser diode at 915 nm.

Using a 1-W high-brightness laser diode as the pump source, we investigated the output characteristics of an intracavity frequency-doubled Nd:YVO(4)/KTP laser. Highly efficient operation was realized based on an optimized cavity design. The second-harmonic output power at 532 nm was measured to be 286.5 mW at an incident pump power of 881.4 mW, corresponding to an optical-to-optical efficiency of 32.5%.

We built a 32-laser-diode-formed virtual point source pumping system and achieved different pump light distributions from central intense to central uniform and central depressed. Continuous wave TEM(00) operations of a Nd:YAG laser were performed under these pump light distributions and their thermal lensing effects were estimated. Results show that the operation under central depressed pump light distribution has the lowest thermal lensing effect and can provide the highest output power, which agrees with the results derived from the theoretical calculation with the heat conduction equation.

The propagation losses of pump light in rectangular double- clad fibers are investigated both experimentally and theoretically. The dependence of propagation losses on the incidence of pump light as well as fiber lengths are measured using a simple method. It is found that for the same material compositions, the effective numerical apertures (NAs) of rectangular fibers is less than those of circular fibers and the pump light propagation loss in rectangular fibers is larger. The difference of propagation losses between both fibers is rationalized with a geometrical optics analysis. © 1996 Society of Photo-Optical Instrumentation Engineers.

Using a 32-diode-pumped virtual point source, we investigated the output characteristics of a cw Nd:YAG laser of both a linear cavity and a ring cavity. CW output power of 81 W was obtained from the linear-cavity laser under 291 W pumping power and 22 W cw output power was obtained from the ring-cavity laser under 149 W pumping power.

The two ends of an Nd-doped rectangular double-clad fibre are bundled together to achieve efficient matching with a 10 W fibre coupled LD. With such a configuration, ~5.4 W pump light is launched into the first-cladding, and 2.5 W laser output is obtained. A slope efficiency of 51% with respect to launched pump power has been achieved.