Publications (19)0 Total impact
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Article: Structure of fiber gratings directly written by infrared femtosecond laser
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ABSTRACT: Structural modification m gratings inscribed point-by-point by a femtosecond laser is investigated using quantitative phase microscopy. The gratings present a central region with a depressed refractive index surrounded by an outer corona with increased index. -
Article: Direct writing of fibre Bragg gratings by femtosecond laser
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ABSTRACT: A method for inscribing fiber bragg gratings (FBG) using direct, point-by-point writing by an infrared femtosecond laser was described. The method requires neither phase-masks nor photosensitized fibers and hence offers remarkable technology flexibility. It requires a very short inscription time of less than 60 s per grating. Gratings of first to third order were produced in non-photosensitized, standard telecommunication fiber (SMF) and dispersion shifted fiber (DSF). The gratings produced in this method showed low insertion loss, narrow linewidth and strong, fundamental or high-order resonance. -
Article: High-power picosecond pulse generation from a gain-switched violet diode laser
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ABSTRACT: Generation of picosecond pulses with a peak power in excess of 7W and a duration of 24ps from a gain-switched InGaN diode laser is demonstrated for the first time. -
Article: Gain switching of an external cavity grating-coupled surface emitting laser with wide tunability
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ABSTRACT: The gain-switched, single frequency operation of an external cavity grating-coupled surface emitting laser with a wavelength tuning range of 100 nm was presented. The light in the grating section was coupled out of the laser at a specific angle to the surface of the device. Analysis showed that within the driving current range, lasing in the device only occurred when the external cavity was properly aligned. -
Article: Long period grating directional bend sensor based on asymmetric index modification of cladding
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ABSTRACT: A long period grating (LPG) written in a standard optical fibre was modified by using a femtosecond laser to induce an asymmetric change in the cladding's refractive index. This device produced blue and red wavelength shifts depending on the orientation of applied curvature, with maximum sensitivities of -1.6 nm m and +3.8 nm m, suggesting that this type of LPG may be useful as a shape sensor. -
Article: Vector bending sensors based on fiber bragg gratings inscribed by an infrared femtosecond laser
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ABSTRACT: A direction-sensitive bend sensor in standard single-mode fiber is demonstrated for the first time based on an axially-offset fiber Bragg grating, directly written by an infrared femtosecond laser. -
Article: Directional bend sensor based on an asymmetric modification of the fiber cladding by femtosecond laser
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ABSTRACT: A femtosecond laser was used to modify a part of the cladding of a standard LPG bend sensor. The device produced wavelength shifts depending upon the direction of bend, thus making a shape sensor. -
Article: Pulse tail suppression in laser diode output by tunable notch filter
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ABSTRACT: Efficient suppression of relaxation oscillations in the output signal from an overdriven gain-switched laser diode was demonstrated. Several quantum-well distributed feedback laser diodes from different manufacturers were used for experimental analysis. A five-fold increase in the peak power was achieved for the tail-free operation. It was found that spectral filtering removed the nonlinearly chirped components resulting in pulse shortening by a factor of three. -
Article: Tail-free operation of an overdriven gain-switched DFB laser by spectral filtering
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ABSTRACT: The tail-free operation of an overdriven gain-switched distributed feedback (DFB) laser by spectral filtering was demonstrated. The filtering was realized using a mechanically tunable fiber Bragg grating (FBG). The unfiltered and filtered signals were traced by corresponding oscilloscope. The spectral filtering removed the nonlinearly chirped components resulting in the pulse shortening. The results showed unwanted relaxation in the overdriven DFB laser were supressed by using a steep-edge notch filter. -
Article: Point by point FBG inscription by a focused NIR femtosecond laser
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ABSTRACT: Direct, point-by-point writing of fibre Bragg gratings in standard telecommunication fibre by femtosecond laser irradiation is demonstrated for the first time. -
Article: Propagation of Unequal OTDM Data Channels in 2R Regenerated System
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ABSTRACT: Switching of an optical signal comprising individual OTDM channels of unequal amplitudes in a nonlinear optical loop mirror is investigated. The propagation dynamics of unequal-channel data streams in a switch-guided, dispersion-managed link are also studied Full Text at Springer, may require registration or feeInternational Federation for Information Processing Digital Library; Optical Networks and Technologies;. -
Article: Waveguide inscription in YAG:Cr4+ crystals by femtosecond laser irradiation
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ABSTRACT: We have observed a positive change or refractive index and formation of waveguides in YAG:Cr4+ crystals, exposed to a high-intensity femtosecond laser beam. The technique is potentially suitable for fabrication of waveguide lasers in crystal materials. -
Article: Laser inscription of optical structures in crystals
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ABSTRACT: A method of altering the refractive index of a region of a crystal comprising focusing a pulsed laser beam at a desired position within the crystal and moving the focused beam along a path such that the focussed beam alters the refractive index of the region of the crystal along the path. -
Article: Laser inscribed structures
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ABSTRACT: An optical fiber or waveguide having a core and a cladding, the fiber/waveguide including a modified region or regions with a modified optical property that differs from the surrounding optical fiber/waveguide, wherein the cross sectional area of the modified region(s) is considerably smaller than the cross sectional area of the core of the fiber or waveguide. -
Article: Self-seeded gain-switched operation of an InGaN MQW laser diode
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ABSTRACT: Self-seeded, gain-switched operation of an InGaN multi-quantum-well laser diode has been demonstrated for the first time. An external cavity comprising Littrow geometry was implemented for spectral control of pulsed operation. The feedback was optimized by adjusting the external cavity length and the driving frequency of the laser. The generated pulses had a peak power in excess of 400mW, a pulse duration of 60ps, a spectral linewidth of 0.14nm and maximum side band suppression ratio of 20dB. It was tunable within the range of 3.6nm centered at a wavelength of 403nm. -
Article: Direct femtosecond inscription of fiber Bragg gratings
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ABSTRACT: Direct, point-by-point inscription of fiber Bragg gratings by infrared femtosecond laser is reported. Using this technique, highly reflective gratings can be rapidly inscribed in standard, untreated fiber. Thermal studies demonstrate increased thermal stability compared to the UV-inscribed gratings. -
Article: A long period grating directional bend sensor incorporating index modification of the cladding
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ABSTRACT: Long period gratings written into a standard optical fibre were modified by a femtosecond laser, which produced an asymmetric change to the cladding's refractive index resulting in a directional bend sensor. -
Article: Widely tunable gain-switched operation of external cavity grating-coupled surface emitting laser
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ABSTRACT: Widely tunable gain switching of a grating-coupled surface-emitting laser (GCSEL) has been demonstrated in a simple external cavity configuration for the first time. Pulse duration in range of 40-100ps and wavelength tuning over 100nm have been achieved. High power, tail-free optical pulses have been observed at 980nm. -
Conference Proceeding: Micro-fabrication of advanced photonic devices by means of direct point-by-point femtosecond inscription in silica
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ABSTRACT: We present recent results on experimental micro-fabrication and numerical modeling of advanced photonic devices by means of direct writing by femtosecond laser. Transverse inscription geometry was routinely used to inscribe and modify photonic devices based on waveguiding structures. Typically, standard commercially available fibers were used as a template with a pre-fabricated waveguide. Using a direct, point-by-point inscription by infrared femtosecond laser, a range of fiber-based photonic devices was fabricated including Fiber Bragg Gratings (FBG) and Long Period Gratings (LPG). Waveguides with a core of a couple of microns, periodic structures, and couplers have been also fabricated in planar geometry using the same method.
