The relationship between the SERS signal intensity properties and the soaking times in a given concentration of
4-aminothiophenol (4-ATP) solution is experimentally investigated. The results show that the relationship depends on
the specific position of the SERS excitation wavelength within the LSPR spectrum of the SERS substrates. In the case of
LSPR peak wavelength of the SERS substrate located at the right side of ideal excitation wavelength arrangement, the
SERS intensity no longer increases monotonically with the soaking time, which is different from the previous result
Double-clad rare-earth-doped fiber laser is a new generation of high power solid-state lasers. The numerical simulation is
an important approach in the configuration design and parameter optimization for the high power fiber lasers (HPFLs).
In this paper, we report our user-friendly high-power fiber laser simulation software system, which integrates the design,
analysis and optimization functions together. The numerical simulations of the software are with the HPFL model based
on the rate-equation theory. By using the theoretical model, for specific laser cavity configuration, doped fiber
parameters and pump conditions, the distributions of the population inversion, forward and backward pump, and
circulating lasing intensity along the doped fiber can be calculated, and thus, the main output characteristics, such as
cavity gain, output power and laser efficiency, can be achieved accordingly. On the basis of the simulation results, the
software supplies the functions developed for designs and optimizations of the pump configuration, doped fiber length
and the reflectivity of output mirror. By combining the calculated mode-field distribution in doped fibers with the
mechanism of curvature loss to suppress the higher-order modes, the software also supplies the function for optimizing
the beam quality. With graphical user interface (GUI), all the functions of the software are provided function tools in
menu options, especially for those which may be used frequently, toolbar buttons, shortcut keys and pop-up menus are
also provided. The software is with single-document interface (SDI) and coded in C++ in the integrated development
environment of Visual C++ 6.0. We believe it would be very helpful for the investigation and development of HPFLs.
Based on the investigation of the high-pressure nitrogen-filling and leaking characteristics of the HC-PCF, a new making
technique for the all-fiber high-pressure HC-PCF gas cell is present. An HC-PCF nitrogen-filled cell with a pressure of
17.1 atm and an insertion loss of 9.3 dB is manufactured with the technique.
Erbium-doped fiber (EDF) lasers with active coupling cavities have recently shown to enable the production of multiwavelength oscillations with various novel functions. This paper reviews the advances of such lasers. The lasers may be designed to produce multiwavelength oscillations in both C and L bands, either as a combined band or as two separate bands. In the C band, the laser can operate in a multiwavelength regime with controllable output powers and tunable wavelengths for any one individual lasing line. Wavelength-switching is also possible; switching responses of about 100 Hz are typical. In the L band, the laser exhibits multiwavelength bistable phenomena. The bistable hysterisis behaviors for a dual-wavelength laser evolve in antiphase with respect to each other. The width of the bistable region can be controlled; it could be designed to be as wide as a few hundred milliwatts. The two wavelengths can be switched from one to the other, with typical switching times of 4 to 15 ms. By suitably controlling the bistability, simultaneous multiwavelength oscillations in the L band alone, or in combination with the C band, can be obtained. A new wavelength-tuning and switching mechanism can be achieved by using such bistabilities. With this scheme, widely tunable and switchable lasers in fiber ring and linear configurations have been constructed with two commercially available tunable ordinary fiber Bragg gratings (FBGs). The lasers can be tuned over the whole L-band although the tunable range of each of the FBGs is only about 15 nm.
Optical bistability in an L-band dual-wavelength erbium-doped fiber laser with linear overlapping cavities is investigated. The hysterisis bistabilities of the two lasing wavelengths evolve in antiphase. It has a large bistable region which may be controlled and adjusted by the EDF length and the cavity losses. Simultaneous dual-wavelength oscillations in the L-band are also achieved.