In this paper, we characterize the femtosecond laser filament-fringes in titanium. In order to fabricate regular arrays of filaments, we place either a pinhole or a beam shaper in the optical path of the femtosecond laser beam that originates linear diffraction of the laser beam. Soda-lime glass is used as Kerr medium to produce the filaments. As a consequence, the intensity distribution of the laser beam is modulated and fringe type of filament distributions is evident. The suitable control over the size of the diaphragms (pinhole or beam shaper) leads us to adjust the shape, orientation, and number of filaments in each irradiated spots in titanium sample. By properly adjusting the diameter of a pinhole that was placed in the optical path, we are successful in forming a single filament in titanium. By using these single filaments, we fabricated high aspect ratio periodic holes in the titanium surface by moving the translation stage in both horizontal and vertical directions. The period of the holes in the horizontal direction is controlled by varying the scanning speed, whereas the period in the vertical direction is controlled by varying the vertical scanning step. We strongly believe that, filamentation technology described in this paper will have applications in forming a variety of micro/nano-structures in various materials.
In this paper, we report on the formation of micro/nano-fluidic channels inside fused silica glass using single-beam femtosecond laser. The micro/nano-fluidic channels are fabricated by controlling the irradiation conditions of the femtosecond laser pulses, especially, pulse energy and scanning speed. We examine the production of this kind of channels both in air and water. In both cases, laser beam is focused inside the glass bar and shined horizontally with very low scanning speeds. In case of water, the glass sample is placed inside distilled water, which way is expected to reduce the surface roughness of the channels. The quality of the channels fabricated under different environment is compared as well. We further investigate the influence of various laser parameters on the production of channels. We also evaluate the fluid flowing ability of the fabricated micro/nano-fluidic channels of various diameters, fabricated under different environment and irradiation conditions.
This work reports femtosecond laser based fabrication of long period fiber gratings (LPFG). Index modulation in the
core of single mode fiber (SMF) is written employing femtosecond pulse filamentation technique. Highly repeatable
filamentary voids written in line-by-line femtosecond laser inscription technique enables steady and noise free growth of LPFGs. The sharp transmission valley (with a narrow full width at half maximum of 5 nm) of long period grating offers better resolution for refractive index (RI) measurement of a solution. The LPFGs inscribed by femtosecond laser
radiation show RI sensing sensitivity of 29.199 nm/RIU which is three times higher than the sensitivity of LPFGs written
by UV radiation (sensitivity: 11.179 nm/RIU). The position of transmission dip of a grating can be tailored relatively
easily simply by varying the period of index modulation.
We demonstrate the formation of self-organized nanogratings on a titanium surface under the irradiation of a single-beam femtosecond laser. Self-formed, periodic nanogratings are printed on a titanium surface by varying the average pulse energy, pulse width, and number of laser pulses in each spot. The direction of the nanogratings is perpendicular to the direction of the laser polarization. The nanograting period shows obvious dependence on the average pulse energy, pulse width, and number of laser pulses. The period of the self-organized nanogratings shows an increasing trend with the increase of laser energy and pulse width, and a decreasing trend with an increase of number of applied laser pulses. We qualitatively explain the formation mechanism of the self-organized nanogratings and their dependence on various laser parameters.
In this paper, we demonstrate the formation of self-organized periodic nanogratings on the titanium surface under the
irradiation of a single-beam femtosecond laser. We vary various laser parameters such as the laser fluence and the
number of laser pulses in each spot to fabricate self-organized nanogratings on the titanium surface. We investigate that
the direction of the nanogratings is perpendicular to the direction of laser polarization. We also report on the dependence
of the nanogratings' period, produced on titanium surface, on the laser fluence and the number of irradiated laser pulses
in each spot. Nanogratings' period show increasing trend with the increase of the laser fluence, whereas show decreasing
trend with the increase of the number of applied laser pulses. Furthermore, we briefly explain the formation mechanism
of the self-organized periodic nanogratings, produced on the titanium surface. The reasons behind the dependence of
nanogratings' period on the laser fluence and the number of laser pulses are explained as well. The self-organized
nanogratings are mainly produced due to the interaction of the
high-intensity incident laser beam and the laser induced
plasma waves. Above certain threshold energy, phase explosion takes place, which in turn causes the formation of selforganized
nanogratings on the titanium surface.
This paper reports on the colorizing of the stainless steel surface by controlling the irradiation conditions of a single-beam
femtosecond laser. We change the color of the stainless steel surface by femtosecond laser induced periodic self-organized
nanogratings or microgratings on the sample surface. Colorizing of metal surface by periodic microholes,
produced by femtosecond laser, is achieved for the first time. The laser modified stainless steel surfaces show different
colors under different incident or azimuthal angles of the incident light, which changes in color indicate the dependence
of the metal color on the angles (incident and azimuthal) of the incident light. We report, for the first time, the changes
of metal color due to the change of the azimuthal angles of the incident light. Furthermore, the changes in the color of
the laser modified metal surfaces are mainly due to the excitation of surface plasmon polaritons (SPPs) on the metal
surface. The resonant angle of SPPs is different for different wavelength of light. As a result, under different incident or
azimuthal angles different wavelength of light is trapped on the surface depending on the resonance for that particular
wavelength; light of other wavelengths react naturally and contributes for the color change of the stainless steel surfaces.
Finally, we discovered that the nanostructures produced inside the self-organized nanogratings and microholes play
important roles for the propagation of the SPPs in parallel with the nanogratings and mcroholes, which nanostructures
are responsible for a complex SPPs excitation on the sample surface.
A potential method for precise and fast dicing of display glass plates is proposed in this study. This technique facilitates
the micromachining of cavities in both front and rear surfaces for a single pass of laser beam. The influences of focusing
depth, input pulse energy, and scanning speed of the laser beam are investigated to study the morphology of the front and
rear surface cavities. A commercial femtosecond laser with pulse duration of 172 fs, center wavelength of 780 nm, and
repetition rate of 1 kHz is used for introducing the cavities.
When diffractive gratings are used to split a beam of ultrashort laser pulses, due to its broad spectral bandwidth, the spots split will be distorted because of chromatic dispersion. Our ambition is to construct a novel pulse splitter system that is possible to compensate for chromatic dispersion during fanning-out of laser beam by diffractive gratings. Moreover, the proposed design can reduce the size of the splitter system and obtain higher diffraction efficiencies.
Polarization Division Multiplexing (PDM) transmission system is simulated. Two types of PDM system are simulated in order to find important variables for transmission. Both 10 Gbit/s and 40 Gbit/s case are examined for comparison. Signal modulations are NRZ and RZ. PDM systems are sensitive for transmission length and polarization-related loss, especially Polarization Mode Dispersion (PMD). RZ signal has more degradation than NRZ.
In this paper, we propose OBS ring network structure and OBS access protocol for burst collision resolution. Our collision free scheme can save wavelengths for transmission and effectively transport bursty and asymmetric traffic. It shows better throughput performance than OBS ODD RR-R, RR-P, and RR-NP protocols.
Dynamic traffic grooming in optical mesh networks is one of the most important and practical problems for designing WDM networks. Most of previous work solves it by applying the Dijsktra's algorithm on an auxiliary graph. Although those algorithms can give very good performance since they have a global view of the whole network, they are very time-consuming and thus cannot be applied in large networks. Therefore, we propose a heuristic algorithm to reduce the required computations by minimizing the size of the graph. We compare our algorithm with existing algorithms by extensive simulations. The results demonstrate that our algorithm can significantly reduce the computational complexity and outperform existing algorithms by large margins since it can easily avoid resource-inefficient lightpaths.
The system performance of data- and telecommunication equipment must keep up with the increasing network speed. Optical interconnections technology is a promising alternative for high-throughput systems. We demonstrate the optical backplane system using a waveguide-embedded optical backplane and two processing boards. The transmitter and receiver modules were prepared for optical printed circuit boards (PCBs), which consists of the metal optical bench, the driver chips, vertical-cavity surface-emitting lasers (VCSELs), photodiodes, and a tapered polymeric waveguide. We report high-speed transmission of 27–1 pseudorandom bit sequence (PRBS) nonreturn to zero (NRZ) data up to 10 Gbits/s through the optical backplane system. The results demonstrate that the optical backplane system can be practical and valuable for the future high-throughput systems by using metal optical bench and precisely machined optical plug-adaptor structure to achieve stable board-to-board interconnection.
The performance of data and telecommunication equipment must keep up with the increasing network speed. Optical interconnection technology is a promising alternative for high throughput systems. The Optical backplane system was demonstrated with waveguide-embedded optical backplane, transmitter board and receiver board. The transmitter and receiver module were prepared for optical PCB, which consists of the metal optical bench, the driver chips, VCSELs, photodiodes and a tapered polymeric waveguide. And parallel optical transmitter and a receiver module were attached onto the processing boards for the interconnection with optical backplane board. The tapered polymeric waveguides are fabricated using the hot embossing technique. And the propagation loss of the waveguide was approximately 0.1dB/cm at 850nm. The waveguide-embedded optical backplane boards were fabricated by using conventional PCB lamination process. The data transmission characteristics of the processing board have been investigated. In our optical backplane system, we demonstrated up to 10Gb/s 27-1 PRBS NRZ data transmission from the transmitter board to the receiver board through optical backplane. The BERs were less than 10-12 under 8Gb/s data rate, which is sufficient level for telecommunications.
Using tightly focused femtosecond laser pulses, we produced optical waveguide and devices in the transparent materials. This technique has the potential to generate not only channel waveguide but three-dimensional optical devices. In this paper, an optical splitter and U-grooves, which are used for fiber alignment, are simultaneously fabricated in a fused silica glass by using near-IR femtosecond laser pulses. The fiber aligned optical splitter has a low insertion loss, less than 4 dB, including intrinsic splitting loss of 3 dB and excess loss due to the passive alignment of a single-mode fiber. Finally, the utility of the femtosecond laser writing technique is demonstrated by fabricating gratings at the surface and inside the silica glass, respectively.
This paper presents the micro-machining results on optical devices by using Ti:sapphire femtosecond pulsed laser. It has been used successfully for the micro-machining of U-grooves in planar lightwave circuit (PLC) splitter, wedged filber and lensed fiber. U-grooves in PLC splitter is helpful to simplification of the alignment procedure between optical fiber and waveguide in the PLC chip. The insertion loss and the optical return loss of packaged 1 x 8 optical splitter modules which have been presented were less than 11.0 dB and more than 55 dB, respectively. These results also mean that the packaging technique using the passive alignment is excellent and femtosecond pulsed laser micro-machining technique could provide a new PLC packaging technology. The wedged fiber for reduction of reflection loss and the lensed fiber increasing coupling efficiency are also fabricated by laser system. A comparison of direct polishing method with that of laser micro-machining shows that laser technique is more favorable.
We show that permanent optical waveguides can be formed in glasses by photoinduced refractive index change with an ultrashort pulse laser. Waveguides are written by translating the glass sample along the optical axis of a strongly focused laser beam. Both straight and curved waveguides are written in a silicate glass using 800 nm Femtosecond laser pulses. The utility of the Femtosecond writing technique is demonstrated by fabricating optical devices. Y coupler was fabricated in a silica glass using femtosecond laser pulses. Waveguide propagation characteristics and optical losses are also determined.
The paper presented a new thermally expanded core(TEC) lensed fiber using a standard single-mode fiber(SMF), which was fabricated with a lens at fiber tip using mechanical polishing after expanding the core diameter of a single-mode fiber into about 20μm. This TEC lensed fiber shows that it has the working distance of 60μm and high coupling efficiency (>75%).
This paper introduces a novel feed-forward type burst mode optical receiver, which has automatically gain controllable preamplifier and high sensitive peak detector using a 0.18mm CMOS technology. The important feature of the receiver is that it operates with a reset signal that is self-generated inside the receiver not applied externally. The designed receiver can be used in the Ethernet PON (Passive Optical Network) system and has a sensitivity of -28dBm and a overload of -8dBm at 1.25Gb/s optical input signal.
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