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This letter reports the tunable liquid microlens using three laminar flows injected into an expansion chamber. Different lens shapes and curvatures can be achieved and tuned through the control of three flow rates. The expansion chamber is designed to improve the fluidic stability and maintain the ideal lens shape for precise microscale optical measurement. The optical aberration is also eliminated by minimizing the diffusive broadening at the interfaces. The collimation and focusing capabilities of three liquid microlenses are demonstrated. The tunable liquid microlens is promising as a tool to realize different optical components that can be integrated onto a microchip.

We report experimental and numerical results on the dynamics of gain-guided solitons in a passively modelocked erbium-doped fiber laser made of purely normal dispersion fibers. We show that formation of the soliton in the laser is a result of mutual interaction and balance among the cavity transmission, fiber Kerr nonlinearity, gain saturation, and filtering over one cavity round trip. © 2007 Optical Society of America OCIS codes: 060.4370, 060.5530, 140.3510. Passively mode-locked fiber lasers have been extensively studied in the past for generating ultrashort pulses. Conventionally, the fiber lasers were operated in the anomalous cavity group-velocity dispersion (GVD) regime, where solitons are automatically generated as a result of the natural balance between the cavity dispersion and the fiber nonlinear Kerr effect. However, the soliton operation of the lasers limits the maximum achievable mode-locked pulse energy. To relax the limitation, the so-called stretched-pulse fiber laser was proposed [1]. Recently, it was shown that self-similar parabolic pulses could also be generated in a stretched-pulse laser with net positive GVD and in the absence of influence of the gain saturation and gain bandwidth limitation [2]. As a self-similar parabolic pulse has linear frequency chirp, such an optical pulse facilitates power scalability and linear pulse width compression. Nevertheless, for any laser as the mode-locked pulse energy increases, eventually the gain effects on the formed pulses can no longer be ignored. Kruglov et al. have shown that the self-similar scaling of a parabolic pulse in an amplifier is determined by the functional form of the gain profile [3]. Limpert et al. discussed the amplifier bandwidth limitation on the power scaling of a parabolic pulse [4]. In fact, the maximum achievable energy of a parabolic pulse is ultimately limited by the finite gain bandwidth of the amplifier [5,6]. It had been shown theoretically that solitary waves could still be formed in positive dispersion amplifiers as a result of the gain filtering effect [7]. In a previous paper, we have experimentally demonstrated that solitary pulses could indeed be generated in an erbium-doped fiber (EDF) laser made of purely normal dispersion fibers, and the formed solitons have a spectral width limited by the effective laser gain bandwidth [8]. Different from the Yb-doped fiber lasers that have superbroad gain and large gain saturation power, an EDF laser has less broad gain and low gain saturation intensity and therefore can easily show the gain limiting effects.Strictly speaking, a pulse circulating in the laser cavity is different from that propagating in a positive dispersion gain medium. In lasers, a pulse is also subject to the action of the cavity components, cavity boundary condition, and the saturable absorption effect that is necessary for the self-started mode locking of a laser. To better understand the gain-guided soliton operation of the fiber lasers, we have further investigated the soliton evolution in the cavity....

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We propose and experimentally demonstrate light beam coupling between a single-mode fiber (SMF) and a highly nonlinear photonic crystal fiber (HN-PCF) based on the fused biconical tapering (FBT) technique. In our experiment, a standard SMF is pre-tapered to match its propagation constant to that of a HN-PCF. In order to remove the condensation in the air holes, the temperature is increased gradually to preheat the fibers. An appropriate level of hydrogen flow is administered to avoid the air-hole collapse. As a result, coupling ratio exceeding 90% between the SMF and HN-PCF is achieved. This technique avoids back Fresnel reflection, mode-field diameter (MFD) mismatch and fiber-core misalignment, bubble generation and air-hole collapse in the interface fusion splice.

We report a novel architecture that can be used to construct optical switch fabrics with very high port count and nanoseconds switching speed. It is well known that optical switch fabrics with very fast switching time and high port count are challenging to realize. Currently, one of the most promising solutions is based on a combination of wavelength-tunable lasers and the arrayed waveguide grating router (AWGR). To scale up the number of ports in such switches, a direct method is to use AWGRs with a high channel count. However, such AWGRs introduce very large crosstalk noise due to the close wavelength channel spacing. In this paper, we propose an architecture for realizing a high-port count optical switch fabric using a combination of low-port count AWGRs, optical ON-OFF gates and WDM couplers. Using this new methodology, we constructed a proof-of concept experiment to demonstrate the feasibility of a 256 x 256 optical switch fabric. To our knowledge, this port count is the highest ever reported for switch fabrics of this type.