We report an environmentally insensitive, all-fiberized, polarization-maintained (PM), self-starting, mode-locked Tm fiber laser cavity enabled by a single-wall carbon nanotube (SWNT) saturable absorber. This produces dissipative solitons at 1876 nm, with a repetition rate of 19.2 MHz, and a maximum average power of 21.5 mW, corresponding to a pulse energy of 1.1 nJ. The output pulse has a duration of 4.2 ps and can be compressed to 391 fs using a grating-based compressor. To the best of our knowledge, this is the first demonstration of an all-fiberized, all-PM, dissipative-soliton, mode-locked thulium fiber laser using a SWNT saturable absorber.
We report an all-fiberized, dissipative-soliton, mode-locked thulium fiber laser enabled by a single-wall carbon nanotube saturable absorber operating at 1790 nm for deep-penetration three-photon microscopy in bio-medical imaging applications. The laser provides output pulses with a maximum pulse energy of 1.3 nJ and a minimum pulse duration of 310 fs after compression. With a new pump recycling design, a low pump threshold of 110 mW is observed. Consequently, a compact mode-locked thulium fiber laser cavity using a single-mode pump laser diode is successfully realized.
We present a highly efficient method for generating multiple beam spots through the multimode interference within Single Mode Fiber – Square Core Fiber (SMF-SCF) structures. By adjusting the length of SCF, we can achieve diverse beam spot configurations in a square lattice, such as 4×4, 3×3 and 2×2, providing unparalleled flexibility. Through simulations and experimental validations at a wavelength of 1060 nm, our study unveils significant potential for applications in photonics and laser technology.
We introduce a new approach for the generation of high-power multi-spot fiber lasers, employing square core fiber segments to enhance the efficiency of material processing. Utilizing an all-fiber strategy with Single Mode Fiber– Square Core Fiber (SMF-SCF) structures, our approach exemplifies notable progress in beam shaping technologies. Through laser drilling experiments on metals, the effectiveness of this technique is demonstrated, promising diverse applications in advanced manufacturing and industrial processes.
We report the development of a high-power, fiber-laser-pumped, sub-nanosecond pulsed 260 nm DUV laser and demonstrate its use for bacterial disinfection. The source generates up to 5.8 W of average power at 260 nm (585 ps pulses at a repetition rate of 1.6 MHz, corresponding to a pulse energy of 3.6 μJ and a peak power of 6.9 kW). The results represent the highest DUV output power from an all-fiberized fiber laser pumped frequency conversion source to date. We demonstrate the application of the laser system to bacterial inactivation. A survival rate of less than 1 in 100000 is demonstrated for E. Coli bacteria after exposure to a DUV dose of 7 mJ/cm2.
We describe an approach capable of generating structured light beams from a compact laser source based on the coherent combination of multiple tailored Gaussian beams emitted from a multicore fiber (MCF) amplifier. We report a proof-of-concept structured light generation experiment, using a cladding-pumped 7-core MCF amplifier as an integrated parallel amplifier array and a spatial light modulator to actively control the amplitude, polarization and phase of the signal light input to each fiber core. We demonstrate the generation of various structured light beams including high-order linearly polarized spatial fiber modes, cylindrical vector beams and helical phase front optical vortex beams.
KEYWORDS: Signal processing, Terahertz radiation, All optical signal processing, Data processing, Modulation, Metamaterials, Absorption, Picosecond phenomena, Networks, Ultrafast phenomena
Energy-efficient ultrafast all-optical signal processing may contribute to solving growing bandwidth and energy challenges in optical telecommunications. However, conventional solutions for all-optical data processing rely on nonlinear optical materials with inherent minimum power requirements and trade-offs between bandwidth and speed. In contrast, the coherent interaction of light-with-light in an absorber of nanoscale thickness can facilitate high-contrast modulation of one optical signal with another, ultimately with few-femtosecond response times and at arbitrarily low (even single photon) intensities.
We report here on the first demonstration of a fiberized metamaterial device for all-optical signal processing based upon coherent modulation of absorption. The integrated metadevice is based on a plasmonic metamaterial of nanoscale thickness fabricated on the core area of a single-mode optical fibre, and designed to operate over the 1530 – 1565 nm telecoms wavelength range. We demonstrate signal processing operations analogous to logical NOT, XOR and AND functions at effective rates from tens of kbit/s up to 40 Gbit/s with energy consumption as low as 2.5 fJ/bit, as well as selective absorption and transmission of picosecond pulses and the generation of 1 ps ‘dark pulses’. We anticipate that such metadevices, with THz bandwidth, may provide solutions for quantum information networks as well as orders-of-magnitude improvements in speed and energy consumption over existing nonlinear approaches to all-optical signal processing in coherent information networks.
Orbital angular momentum (OAM) beams, have attracted great attention in recent years. An OAM beam with a phase singularity is characterized by a helical phase front which provides an additional degree of freedom for wide amount of classical and quantum optical applications. However, despite many attempts to generate and manipulate OAM beams, a robust, reliable and scalable technique to directly address generation, multiplexing and low-loss transmission of the distinct OAM beams is still in great demand. Here, we review the development of all-fiber, ring core photonics lantern mode multiplexer to generate high quality OAM beams up to the second order within a broad spectral range of >550 nm. Our device is a 5-mode mode selective photonic lantern (MSPL) with an annular refractive index profile which is fully compatible with well-established ring core and vortex transmission fibers. Through the excitation of pairs of degenerate linearly polarized (LP) modes of the MSPL, we demonstrate the generation of high quality OAM beams up to the second order. In addition, we demonstrate multiplexing of two OAM modes (OAM+1+ OAM-2) to verify complex beam pattern generation of our all fiber devices. Furthermore, by splicing the end-facet of the photonic lantern to a ring core fiber, we achieve low-loss coupling of OAM modes while maintaining high contrast spiral phase patterns. These results demonstrate the potential of photonic lanterns for generating complex optical beams.
Space division multiplexing (SDM) utilizing few-mode fibers or multicore fibers supporting multiple spatial channels, is currently under intense investigation as an efficient approach to overcome the current capacity limit of high-speed long-haul transmission systems based on single mode optical fibers. In order to realize the potential energy and cost savings offered by SDM systems, the individual spatial channels should be simultaneously multiplexed, transmitted, amplified and switched with associated SDM components and subsystems. In this paper, recent progress on the implementation of various SDM amplifiers and its related SDM components is presented.
We demonstrate a 60μm core diameter single-trench Yb free Er-La-Al doped fiber having 0.038 ultra-low-NA, using conventional MCVD process in conjunction with solution doping process. Numerical simulations ensure an effective single mode, the effective area varies from 1,820μm2 to 1,960μm2 for different thicknesses of trenches and resonant rings. This fiber has been fabricated with conventional fabrication process, which can dramatically reduce the fabrication cost, hence suitable for mass production. Moreover, all solid structure ensures easy cleaving and splicing. Experimental measurements demonstrate a robust effective single mode operation. Furthermore, this fiber in 4%-4% laser cavity shows a record efficiency of 46% with respect to absorbed power.
We investigated various types of optical fiber sensor based on novel structure of photonic crystal fibers (PCFs) including Ge-doped ring defect PCF and Suspended ring core PCF. Furthermore, a new type of fiber named C-type fiber is utilized as a fiberized sensor unit in/outlet. This configuration enabled to package the entire sensor unit in fiber form as well as could overcome prior limitations in PCF-based optical sensors such as too small holes for efficient measurand entry and sophisticated fabrication processes. The experiment and simulation results proved that the designed sensor can improve both sensitivity and response time compare to conventional PCF based sensors.
This paper reviews our recent work on novel large-mode area fibers for high power lasers and amplifiers. An ultra-low- NA fiber and single-trench fiber have been proposed for mode area scaling of the fundamental mode. In case of single-trench fiber design, resonant coupling of the higher order modes has been exploited to achieve effective single mode operation in fiber with large effective mode area. Our proposed fiber designs are easy to fabricate using conventional low-loss fiber fabrication techniques, and moreover, being all solid structure, they ensure easy cleaving and splicing. A monolithic and compact high power fiber laser/amplifier device with a good output beam quality can be achieved using Single-trench fiber design.
We propose a novel fiber design single-trench fiber (STF) for large mode area fiber laser and amplifier. Fiber offers cylindrical symmetry and also offer higher refractive index of core compared to cladding. This avoids the need of stack and draw process and refractive index compensation of core doped with index raising rare earth and co-dopants ions, which are an indispensable condition in most of other fiber designs. That is why, this fiber design can be fabricated with conventional modified chemical vapour deposition process in conjunction with solution doping process, which can dramatically reduce the fabrication cost, hence suitable for mass production. Fiber offers very high loss (>10dB/m) and low power fraction in core (<50%) to the higher order modes for low loss of fundamental mode (<0.1dB/m) and high power fraction in core (>80%) thanks to the resonant coupling between core and ring modes. We fabricated a preform for 30μm core STF using MCVD process in conjunction with solution doping process in a single step, without using any micro-structuration and pixilation of core. Experiments ensure the robust single mode behaviour irrespective of launching condition of input beam.
Furthermore, this fiber used in three stages MOPA provides 80kW peak pulses with repetition rate of 500 kHz, average power up to 10W, with M2 ~ 1.14. Moreover, all solid structure ensures easy cleaving and splicing. In nutshell, an ultra-low cost, monolithic, compact, and an effective single mode fiber amplifier device can be achieved using single-trench fiber.
A review of passive devices and sensors manufactured from optical fiber microwires at the Optoelectronics Research
Centre (University of Southampton) is presented.
This paper reviews sensing applications of optical fibre microwires and nanowires. In addition to the usual benefits of
sensors based on optical fibres, these sensors are extremely compact and have fast response speeds. In this review
sensors will be grouped in three categories according to their morphology: linear sensors, resonant sensors and tip
sensors. While linear and resonant sensors mainly exploit the fraction of power propagating outside the microwire
physical boundary, tip sensors take advantage of the extreme light confinement to sense chemicals within minute areas.
We propose and experimentally demonstrate an effective method to reduce far-field speckle noise in multimode fiber
with a short cylindrical piezoelectric transducer (PZT) vibrating in radial direction. In this study, the fiber was coiled as
tightly as possible around the mandrel of the PZT and periodic stretching effect was caused by the radial oscillations of
the actuator. This technique can be adapted at a high modulation frequency, so the speckle patterns can be time-averaged.
The output of the optical fiber was intensively observed by a CCD camera. By counting all the pixels
corresponding to relative intensity graded 256 levels in selected area and by calculating the mean value and standard
deviation of the intensity, we can measure the speckle contrast and vibration effect in quantitative measurands. It was
clearly observed that the characteristics of the speckle pattern in vibration-ON-state were signinficantly reduced than that
of vibration-OFF-state by comparing the proposed measurands as well as direct CCD images. We expect that the
proposed speckle reduction technology would find viable applications in realization of fiber laser, laser marking, optical
trapping and projection display systems.
Interactions between acoustic waves and optical modes both propagating along an optical fiber are reviewed for applications in tunable photonic sensory devices. Fiber design parameters in Brillouin scattering sensors, and acoustooptic tunable filters are discussed.
A new index-guiding-holey-fiber is proposed for flexible modal birefringence control by introducing a fourlayered defect with central air hole, silica pedestal, germanosilicate ring, and silica clad. Effects of these parameters over birefringence are reported.
We have experimentally demonstrated a new compact surrounding refractive-index sensor using MMF-CSF-MMF structure. For refractive index range of 1.30 to 1.42, resolution of 9.68×10-3 /nm and linear dynamic range of 20.5dB were obtained at λ=1310nm.
We report a novel all-fiber, maskless lithograpic technology to form various concentric grating patterns for micro zone plate on azo polymer film. The proposed technology is based on the interference pattern out of the cleaved end of a coreless silica fiber (CSF)-single mode fiber (SMF) composite. The light guided along SMF expands into the CSF segment to generate various circular interference patterns depending on the length of CSF. Interference patterns are experimentally observed when the CSF length is over a certain length and the finer spacing between the concentric rings are obtained for a longer CSF. By using beam propagation method (BPM) package, we could further investigated the concentric interference patterns in terms of intensity distribution and fringe spacing as a function of CSF length. These intereference patterns are directly projected over azo polymer film and their intensity distrubution formed surface relief grating (SRG) patterns. Compared to photoresist films azo polymer layers produce surface relief grating (SRG), where the actual mass of layer is modulated rather than refractive index. The geometric parameters of the CSF length as well as diameter and the spacing between the cleaved end of a CSF and azo polymer film, were found to play a major role to generate various concentric structures. With the demonstration of the circular SRG patterns, we confirmed that the proposed technique do have an ample potential to fabricate micro fresnel zone plate, that could find applications in lens arrays for optical beam formings as well as compact photonic devices.
KEYWORDS: Temperature sensors, Cladding, Fiber optics sensors, Fabry–Perot interferometers, Single mode fibers, Sensors, Optical fibers, Temperature metrology, Fiber optics, Control systems
Novel all-fiber optic temperature sensors based on hollow optical fibers (HOFs) are presented. The HOFs with an air hole diameter of 8um at the center are fabricated through elaborate controls of MCVD and fiber drawing process. Two types of all-fiber temperature sensors are described. One is an all-fiber temperature sensor composed of a short HOF serially concatenated between a pair of long-period fiber gratings using a B/Ge-codoped core single mode fiber (SMF). The broadband pass-band tuning range of 84.3nm, covering both S and C band, is observed in the range from 25 to 215°C. Transmission peak is linearly shifted showing negative slope of -0.44nm/°C at 1500nm region. Its design, fabrication arts, and device integration are explained with characteristics of output filter spectrum and temperature tuning. The other is an in-line fiber etalon temperature sensor using a short HOF segment fusion-spliced between standard SMFs. This device is characterized in terms of wavelength shift according to temperature for HOFs with and without Ge-doped ring core. Temperature sensitivity of 3.38×10-5/°C and dynamic range of 20dB are observed over the range from 25 to 330°C at 1550nm. It is confirmed that the experimental results for both fiber optical sensors show a good agreement with theoretical analysis.
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