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ABSTRACT: Due to their broadband saturable absorption and fast response, carbon nanotubes have proven to be an excellent material for the modelocking of fiber lasers and have become a promising device for the implementation of novel laser configurations. However, it is imperative to address the issue of their long-term reliability under intense optical pulses before they can be exploited in widespread commercial applications. In this work, we study how carbon nanotubes degrade due to oxidation when exposed to high-intensity continuous-wave light and we demonstrate that by sealing the carbon nanotubes in a nitrogen gas, the damage threshold can be increased by over one order of magnitude. We then monitor over 24 hours the performance of the carbon nanotube saturable absorbers as the passive modelocking device of an erbium-doped fiber laser with intracavity powers ranging from 5 mW to 316 mW. We observe that when the carbon nanotubes are sealed in nitrogen environment, oxidation can be efficiently prevented and the laser can operate without any deterioration at intracavity powers higher than 300 mW. However, in the case where carbon nanotubes are unprotected (i.e. those directly exposed to the air in the environment), the nanotubes start to deteriorate at intracavity powers lower than 50 mW.
Optics Express 02/2013; 21(4):4665-4670. · 3.59 Impact Factor
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ABSTRACT: In this paper, we demonstrate a nonlinear optical device based on a fiber taper coated with a carbon nanotube (CNT)/polymer composite. Using this device, four wave mixing (FWM) based wavelength conversion of 10 Gb/s Non-return-to-zero signal is achieved. In addition, we investigate wavelength tuning, two photon absorption and estimate the effective nonlinear coefficient of the CNTs embedded in the tapered fiber to be 1816.8 W<sup>-1</sup>km<sup>-1</sup>.
Optics Express 02/2013; 21(3):3651-3657. · 3.59 Impact Factor
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ABSTRACT: We theoretically and numerically explain the power saturation and the additional phase noise brought by the fiber optical parametric amplifier (FOPA). An equation to calculate an approximation to the saturated signal output power is presented. We also propose a scheme for alleviating the phase noise brought by the FOPA at the saturated state. In simulation, by controlling the decisive factor dispersion difference term Δk of the FOPA, amplitude-noise and additional phase noise reduction of quadrature phase shift keying (QPSK) based on the saturated FOPA is studied, which can provide promising performance to deal with PSK signals.
Optics Express 11/2012; 20(24):27254-64. · 3.59 Impact Factor
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ABSTRACT: Graphene exhibits wavelength-independent, saturable optical absorption with fast response time, and large modulation depth. Thus, it is an attractive material for the saturable absorption of fiber lasers. In this paper, we report a simple method for the in-situ monitoring of the deposition of few-layers graphene in an optical fiber end by mechanical exfoliation. Saturable absorbers with different number of graphene layers (from 4 layers of graphene to few 10 s of layers) are prepared and low threshold, self-starting passive mode-locked operation of a fiber laser with sub-picosecond pulse duration is demonstrated.
Applied Physics Letters 10/2011; · 3.84 Impact Factor
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08/2011; , ISBN: 978-953-307-496-2
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ABSTRACT: There is an increasing demand for all-fiber passively mode-locked lasers with pulse repetition rates in the order of gigahertz for their potential applications in fields such as telecommunications and metrology. However, conventional mode-locked fiber lasers typically operate at fundamental repetition rates of only a few megahertz. In this paper, we report all-fiber laser operation with fundamental repetition rates of 4.24 GHz, 9.63 GHz and 19.45 GHz. This is, to date and to the best of our knowledge, the highest fundamental repetition rate reported for an all-fiber laser. The laser operation is based on the passive modelocking of a miniature all-fiber Fabry-Pérot laser (FFPL) by a carbon nanotube (CNT) saturable absorber. The key components for such device are a very high-gain Er:Yb phosphosilicate fiber and a fiber compatible saturable absorber with very small foot print and very low losses. The laser output of the three lasers was close to transform-limited with a pulsewidth of approximately 1 ps and low noise. As a demonstration of potential future applications for this laser, we also demonstrated supercontinuum generation with a longitudinal mode-spacing of 0.08 nm by launching the laser operating at 9.63 GHz into 30 m of a highly nonlinear dispersion shifted fiber.
Optics Express 03/2011; 19(7):6155-63. · 3.59 Impact Factor
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ABSTRACT: Mode-locked fiber lasers are currently undergoing a significant evolution towards higher pulse energies and shorter pulse durations. A key enabler in this progress has been the discovery of novel saturable absorbers (SA) such as carbon nanotubes (CNT) and graphene. The exceptional properties of CNTs as SA have been extensively studied in recent years. Graphene, a one atom thick planar sheet of carbon atoms arranged into a hexagonal lattice, has been recently proposed as an alternative to CNTs in several photonics applications. Here, we propose a method for the integration of graphene into a fiber ferrule using an optical deposition technique, which has been also employed for the deposition of CNT directly on the core of a fiber edge and in tapered fibers. We investigate and compare the optical properties of CNT-SA and graphene-SA fabricated by this optical deposition technique. Soliton-like, mode-locked lasing is confirmed using an erbium doped optical fiber in an all-fiber ring cavity laser configuration.
Optics Express 10/2010; 18(22):23054-61. · 3.59 Impact Factor
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ABSTRACT: In this paper, we propose a saturable absorber (SA) device consisting on an in-fiber micro-slot inscribed by femtosecond laser micro fabrication, filled by a dispersion of Carbon Nanotubes (CNT). Due to the flexibility of the fabrication method, efficient and simple integration of the mode-locking device directly into the optical fiber is achieved. Furthermore, the fabrication process offers a high level of control over the dimensions and location of the micro-slots. We apply this fabrication flexibility to extend the interaction length between the CNT and the propagating optical field along the optical fiber, hence enhancing the nonlinearity of the device. Furthermore, the method allows the fabrication of devices that operate by either a direct field interaction (when the central peak of the propagating optical mode passes through the nonlinear media) or an evanescent field interaction (only a fraction of the optical mode interacts with the CNT). In this paper, several devices with different interaction lengths and interaction regimes are investigated. Self-starting passively modelocked laser operation with an enhanced nonlinear interaction is observed using CNT-based SAs in both interaction regimes. This method constitutes a simple and suitable approach to integrate the CNT into the optical system as well as enhancing the optical nonlinearity of CNT-based photonic devices.
Optics Express 05/2010; 18(11):11008-14. · 3.59 Impact Factor
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ABSTRACT: In this chapter, we have proposed and demonstrated the optical deposition method of CNTs. After brief introduction of this chapter (section 1), we explained the general characteristics, optical properties, and optical devices based on CNTs in section 2. From
02/2010; , ISBN: 978-953-7619-82-4
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ABSTRACT: We present a method to fabricate graded-index multimode polymer optical fibers doped with carbon nanotubes (CNTs). Such fiber structures provide the means to fully utilize the exceptional optical properties of the CNTs. The core region of the fiber is composed of CNTs and polymethyl methacrylate (PMMA) with the addition of diphenyl sulfide (DPS), which acts as the dispersion stabilizer of CNTs in PMMA as well as the dopant to increase the refractive index of the core. Utilizing 2.5 cm of the fiber as a saturable absorber, passively mode-locked lasing with duration of 3.0 ps and repetition rate of 30.3 MHz was demonstrated.
Optics Letters 10/2009; 34(20):3077-9. · 3.40 Impact Factor
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ABSTRACT: Optical devices based on carbon nanotubes (CNTs) have been realized with several fabrication methods in different structures, such as free-space, fiber-end, waveguide, and fiber structures. Most of waveguide- and fiber-type devices utilize evanescent coupling between the guided light and CNT layers, and offer very high optical damage threshold and high third-order nonlinearity. However, the conventional fabrication methods require complicated processes and waste much of CNTs. In this work, we propose and demonstrate CNT deposition around microfibers induced by injecting light through the fibers. This method can area-selectively deposit desired number of CNTs around microfibers, and can be realized by a simple process and setup. We also demonstrate a passively mode-locked fiber laser using a CNT-deposited microfiber as a passive mode-locker.
Optics Express 09/2009; 17(20):18364-70. · 3.59 Impact Factor
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ABSTRACT: We report a wavelength-swept fiber laser with high speed and wide tuning range, and its application to fiber sensors. The laser is based on the dispersion tuning technique, which does not require any optical tunable filter in the laser cavity. By directly modulating the semiconductor amplifier and adjusting the dispersion in the cavity, a wide wavelength tuning range of 178.7 nm and a fast tuning rate of over 200 kHz are obtained. The wavelength-swept laser source is applied to a dynamic fiber Bragg grating sensing system. Dynamic measurement of a 150 Hz sinusoidal strain is demonstrated with a measuring speed as fast as 40 kHz.
Optics Express 06/2009; 17(10):8310-8. · 3.59 Impact Factor
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ABSTRACT: Carbon nanotubes (CNTs) emerged as an attractive material for nonlinear optical devices. Their quasi-one-dimensional structure provided their unique nonlinear characteristics. However, one of their drawbacks is the handling method. We have proposed and demonstrated optical manipulation of CNTs to deposit them onto cores of optical fiber ends with a simple technique. Although the method is very simple, it requires precise control of the optical power. The method does not posses controllability of the CNT-layer properties. In this paper, we employed optical reflectometry to solve these problems. A 15 microm diameter circular region was area-selectively coated by CNTs using highly uniform solution. The preferentially-deposited CNTs were directly, for the first time, observed by a field emission scanning electron microscope (FE-SEM).
Optics Express 04/2009; 17(7):5711-5. · 3.59 Impact Factor
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ABSTRACT: The one-pump optical fiber parametric amplification (FOPA) has been well known to be a means for realizing wideband amplification when the group-delay dispersion (beta(2)) is small at the pump wavelength. In this paper, we report one-pump FOPA in short Bismuth-Oxide-based highly nonlinear fiber (Bi-HNLF) that has large normal dispersion at 1550nm, both theoretically and experimentally, for the first time to the best of our knowledge. We found that, due to the large beta(4) along with large beta(2), FOPA in the Bi-HNLF is very narrowband, and its gain peak wavelength is tunable in proportional to the pump wavelength. We achieved the gain bandwidth as narrow as 0.75nm and gain peak as high as 58dB in the experiment using a 2m-long Bi-HNLF.
Optics Express 10/2008; 16(18):13871-7. · 3.59 Impact Factor
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ABSTRACT: Fueled by their high third-order nonlinearity and nonlinear saturable absorption, carbon nanotubes (CNT) are expected to become an integral part of next-generation photonic devices such as all-optical switches and passive mode-locked lasers. However, in order to fulfill this expectation it is necessary to identify a suitable platform that allows the efficient use of the optical properties of CNT. In this paper, we propose and implement a novel device consisting of an optofluidic device filled with a dispersion of CNT. By fabricating a microchannel through the core of a conventional fiber and filling it with a homogeneous solution of CNTs on Dimethylformamide (DMF), a compact, all-fiber saturable absorber is realized. The fabrication of the micro-fluidic channel is a two-step process that involves femtosecond laser micro-fabrication and chemical etching of the laser-modified regions. All-fiber high-energy, passive mode-locked lasing is demonstrated with an output power of 13.5 dBm. The key characteristics of the device are compactness and robustness against optical, mechanical and thermal damage.
Optics Express 10/2008; 16(20):15425-30. · 3.59 Impact Factor
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ABSTRACT: Carbon nanotubes (CNT) are an attractive material for photonic applications due to their nonlinear optical properties, such as the nonlinear saturable absorption and high third order nonlinearity. However their utilization has been hindered by the lack of flexibility on the device design which rises from the current methods of Carbon nanotube deposition within the optical system. A suitable approach to solve this problem is to embed the CNTs in an optical material from which complex devices such as optical waveguides or optical fibers can be fabricated. Here, we propose a novel method to fabricate Carbon nanotube-doped poly-methyl-methacrylate (PMMA) composites in which the Carbon nanotubes are dispersed in the methyl-methacrylate (MMA) monomer solution prior to and during the polarization process. This method allows the bundle separation and dispersion of the CNT in a liquid state without the need for solvents, hence simplifying the method and facilitating the fabrication of volume CNT-PMMA. Volume fabrication makes this technique suitable for the fabrication of CNT-doped polymer fibers. In this paper, we also analyzed the merits of adding dopants such as diphenyl sulfide (DPS) and benzyl benzoate (BEN) to the CNT-PMMA composite and we observed that DPS plays the role of CNT dispersion stabilizer that can improve the device performance. The CNT-PMMA composite was employed to implement passive mode-locked laser.
Optics Express 07/2008; 16(15):11337-43. · 3.59 Impact Factor
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ABSTRACT: We report numerical simulation about thermal stabilities of silicon slot waveguide. A polymer cladding, which has negative thermo-optic(TO) coefficient, was used to compensate positive TO coefficient of silicon and silicon-dioxide(SiO 2). We found athermal waveguide can be realized with air slot, and even with SiO 2 slot.
07/2008;
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ABSTRACT: Carbon nanotubes (CNTs) offer vast possibilities for future ultra-fast photonic devices. One of the biggest challenges to realize the devices is handling of carbon nanotubes. To achieve efficient handling, we have proposed and demonstrated the optical deposition of CNTs onto optical fiber ends. We found that a sphere-shaped super-structure made of carbon nanotubes can be fabricated by changing the light intensity. Chemical functionalization was not necessary in contrast to the conventional techniques of fabricating super-structures. We demonstrated physical manipulation of the sphere, and realized a passively mode-locked fiber laser employing the sphere.
Optics Express 03/2008; 16(4):2528-32. · 3.59 Impact Factor
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ABSTRACT: An all-fiber passive laser mode locking is realized with a vertically aligned single-walled carbon nanotube film that can be transferred onto an arbitrary substrate using only hot water. A D-shaped fiber is employed as the substrate for the evanescent field interaction of propagating light with the nanotubes. The scheme highlights the efficient interaction achieved by the nanotube alignment as well as the dramatically simplified device preparation process. The demonstrated pulsed laser output has 2.9 nm of spectral full width at half-maximum and a 20.8 MHz repetition rate.
Optics Letters 07/2007; 32(11):1399-401. · 3.40 Impact Factor
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ABSTRACT: 17.2 GHz, the highest fundamental-mode repetition rate to our knowledge, of a carbon nanotube-based passively mode-locked laser is realized at 1570 nm by employing purified single-walled carbon nanotubes as saturable absorbers. The ultrashort linear laser cavity configured with a approximately 9 mm length is designed and demonstrated with our extremely miniaturized nanotube mode locker and a mirror-coated semiconductor optical amplifier as gain medium. The demonstrated pulsed laser has the inferred temporal pulse width of 14 ps and a 3 dB spectral bandwidth of 0.73 nm.
Optics Letters 03/2007; 32(4):430-2. · 3.40 Impact Factor
