Showing papers by "Sulaiman Wadi Harun published in 2015"

A Stable Dual-wavelength Thulium-doped Fiber Laser at 1.9 μm Using Photonic Crystal Fiber.

Abstract: A stable dual-wavelength thulium-doped fiber laser operating at 1.9 μm using a short length of photonic crystal fiber (PCF) has been proposed and demonstrated. The photonics crystal fiber was 10 cm in length and effectively acted as a Mach-Zehnder interferometry element with a free spectral range of 0.2 nm. This dual-wavelength thulium-doped fiber laser operated steadily at room temperature with a 45 dB optical signal-to-noise-ratio.

A Study of Relative Humidity Fiber-Optic Sensors

Abstract: A humidity sensor made of tapered plastic optical fiber (POF) coated with agarose gel or hydroxyethylcellulose/polyvinylidenefluoride (HEC/PVDF) detects humidity from the change in the refractive index (RI) of its coating. The RI of the deposited agarose gel or HEC/PVDF coating changes when it swells after absorbing water molecules from the surrounding. Similarly, when a tapered POF seeded with ZnO nanostructure is exposed to ambient humidity, a rapid surface adsorption of water molecules into the ZnO surface occurs. Therefore, the effective RI of its coating, which consists of the thin ZnO nanostrtucture and air, changes with humidity variation. For all of these sensors, the change in the RI of the coating affects the ability of the fiber to modulate light, thereby altering the output light intensity. In this paper, the performances of the three coating materials used with tapered fibers to construct humidity sensors are investigated. The results of the experiments show that agarose gel, HEC/PVDF, and ZnO-based optical fiber sensors are both sensitive and efficient for humidity sensing.

Tunable S-Band Q-Switched Fiber Laser Using Bi 2 Se 3 as the Saturable Absorber

Abstract: This paper describes a successful demonstration of S-band region wavelength output generated via a tunable Q-switch fiber laser with the topological insulator (TI) Bi2Se3 as a saturable absorber (SA). The modulation depth of the TI was measured as 11.1%, whereas the utilized 980-nm laser source operated at 100 mW pump power. By inserting the TI-SA between two ferrules and utilizing a tunable bandpass filter (TBPF), a stable and tunable Q-switching operation was achieved over the S-band wavelength region from 1493.6 to 1508.9 nm, wherein pulsewidth was 7.6 $\mu{\rm s} $ , and the tunable repetition rate ranged from 26.1 to 36.6 kHz. The Q-switched pulses had maximum pulse energy of 6.1 nJ, as measured from 2.5% of the cavity output. The results provide evidence that a TI-based SA is suitable for pulsed laser operation in the S-band wavelength region and offers potential for further development as an ultrabroadband photonics device.

Tapered Plastic Optical Fiber Coated With Al-Doped ZnO Nanostructures for Detecting Relative Humidity

Abstract: A relative humidity (RH) sensor is demonstrated using a tapered plastic optical fiber (POF) that is coated with Al-doped ZnO nanostructures. A simple etching method was used to fabricate the tapered POF that operates based on intensity modulation technique. The tapered fiber was then coated with Al-doped ZnO nanostructures using sol-gel immersion method with different mol% of Al nitrate that acts as a dopant. The 1 mol% of Al nitrate that used in the synthesis process exhibited better performance compared with the other doping concentrations. Then, results obtained for both undoped ZnO and 1 mol% of Al-doped ZnO were compared and investigated. The performance of 1 mol% of Al-doped ZnO demonstrated better linearity and sensitivity of 97.5% and 0.0172 mV/%, respectively, whereas the undoped ZnO yielded linearity and sensitivity of 93.3% and 0.0029 mV/%, respectively. The proposed sensor provides numerous advantages, such as simplicity of design, low cost of production, higher mechanical strength, and is easier to handle compared with silica fiber optic. Results show that tapered POF with Al-doped ZnO nanostructures enables the increase in sensitivity of fiber for detection of changes in RH.

Q-switched erbium doped fiber laser based on single and multiple walled carbon nanotubes embedded in polyethylene oxide film as saturable absorber

Abstract: A passive, stable and low cost Q-switched Erbium-doped fiber laser (EDFL) is demonstrated using both single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), which are embedded in polyethylene oxide (PEO) film as a saturable absorber (SA). The film is sandwiched between two FC/PC fiber connectors and integrated into the laser cavity for Q-switching pulse generation operating at wavelength of 1533.6 nm. With SWCNTs, the laser produces a stable pulse train with repetition rate and pulse width ranging from 9.52 to 33.33 kHz and 16.8 to 8.0 μs while varying the 980 nm pump power from 48.5 mW to 100.4 mW. On the other hand, with MWCNTs, the repetition rate and pulse width can be tuned in a wider range of 6.12–33.62 kHz and 9.5– 4.2 μs, respectively as the pump power increases from 37.9 to 120.6 mW. The MWCNTs produce the pulse train at a lower threshold and attain a higher repetition rate compared to the SWCNTs. This is due to thicker carbon nanotubes layer of the MWCNTs which provides more absorption and consequently higher damage threshold. The Q-switched EDFL produces the highest pulse energy of 531 nJ at pump power of 37.9 mW with the use of MWCNTs-PEO SA.

Experimental realization and performance evaluation of refractive index SPR sensor based on unmasked short tapered multimode-fiber operating in aqueous environments

Abstract: In this work, we fabricate and characterize an SPR sensor based on unmasked short tapered multimode fiber. The entire taper region is coated with gold without masking offering a simpler approach towards the sensor fabrication. The sensor was tested by immersion in sensing solutions of different refractive indices and the transmittance is measured using a spectrometer system. The sensor performance in terms of sensitivity, detection accuracy, and robustness can be controlled by adjusting the taper physical parameters such as waist diameter, waist length, and transition length. We realize a compact, sensitive, cost-effective and robust SPR sensor suitable for aqueous media sensing by reducing the waist diameter up to 25–45 μm with a total taper length of 3–5 mm coated with a thin gold film of around 55 nm. The demonstrated sensor exhibits a sensitivity of 1600–2000 nm/RIU and a full width at half maximum (FWHM) of 140–220 nm.

Reversible thermo-pneumatic valves on centrifugal microfluidic platforms.

Abstract: Centrifugal microfluidic systems utilize a conventional spindle motor to automate parallel biochemical assays on a single microfluidic disk. The integration of complex, sequential microfluidic procedures on these platforms relies on robust valving techniques that allow for the precise control and manipulation of fluid flow. The ability of valves to consistently return to their former conditions after each actuation plays a significant role in the real-time manipulation of fluidic operations. In this paper, we introduce an active valving technique that operates based on the deflection of a latex film with the potential for real-time flow manipulation in a wide range of operational spinning speeds. The reversible thermo-pneumatic valve (RTPV) seals or reopens an inlet when a trapped air volume is heated or cooled, respectively. The RTPV is a gas-impermeable valve composed of an air chamber enclosed by a latex membrane and a specially designed liquid transition chamber that enables the efficient usage of the applied thermal energy. Inputting thermo-pneumatic (TP) energy into the air chamber deflects the membrane into the liquid transition chamber against an inlet, sealing it and thus preventing fluid flow. From this point, a centrifugal pressure higher than the induced TP pressure in the air chamber reopens the fluid pathway. The behaviour of this newly introduced reversible valving system on a microfluidic disk is studied experimentally and theoretically over a range of rotational frequencies from 700 RPM to 2500 RPM. Furthermore, adding a physical component (e.g., a hemispherical rubber element) to induce initial flow resistance shifts the operational range of rotational frequencies of the RTPV to more than 6000 RPM. An analytical solution for the cooling of a heated RTPV on a spinning disk is also presented, which highlights the need for the future development of time-programmable RTPVs. Moreover, the reversibility and gas impermeability of the RTPV in the microfluidic networks are validated on a microfluidic disk designed for performing liquid circulation. Finally, an array of RTPVs is integrated into a microfluidic cartridge to enable sequential aliquoting for the conversion of dengue virus RNA to cDNA and the preparation of PCR reaction mixtures.

A Switchable Figure Eight Erbium-Doped Fiber Laser Based on Inter-Modal Beating By Means of Non-Adiabatic Microfiber

Abstract: A switchable multiwavelength figure eight fiber laser effect of multimode interference is proposed and experimentally demonstrated. A narrow bandpass filter of multiple specific wavelengths was created by incorporating a tapered non-adiabatic microfiber of 70 mm length and 2 μm diameter in a Sagnac loop mirror. Spatial mode beating arose due to the modal interference in the non-adiabatic microfiber, and resulted in a comb filter able to suppress mode competition. The proposed laser generated single longitudinal modes having a 3-dB linewidth of less than 0.16 pm, which represents an upper limit measurement imposed by the restrictions of the optical analyzer resolution, and possessed an optical signal-to-noise ratio of 58 dB at 82 mW pumping power. Moreover, nonlinear polarization rotation and strain switching mechanisms are demonstrated for generating single, dual, and triple wavelength over more than 20 nm span. In addition, a description is provided on a new technique of packaging non-adiabatic microfiber that diminishes issues relating to degradation of the microfiber over time and external perturbation.

A passively Q-switched ytterbium-doped fiber laser based on a few-layer Bi2Se3 saturable absorber

Abstract: In this work, we demonstrate a simple Q-switched pulsed ring ytterbium-doped fiber laser based on a few-layer TI:Bi2Se3 saturable absorber (SA). Few-layer bismuth selenide within a suspension was induced onto a fiber ferrule at room temperature via an optical deposition method, resulting in a simple SA for the laser. Stable Q-switched pulsed lasing was achieved at a low pump threshold of 122.2 mW at 974 nm. The pulse repetition rate ranged from 18.97 to 45.41 kHz, and the narrowest pulse width and the maximum pulse energy were 13.1 μs and 5.88 nJ respectively. Results indicated that TI:Bi2Se3 was also compatible with the 1 μm waveband, and hence could be considered a potential broadband SA for passively mode-locked and Q-switched optical fiber lasers.

Performance analysis of an all-optical OFDM system in presence of non-linear phase noise

Abstract: The potential for higher spectral efficiency has increased the interest in all-optical orthogonal frequency division multiplexing (OFDM) systems. However, the sensitivity of all-optical OFDM to fiber non-linearity, which causes nonlinear phase noise, is still a major concern. In this paper, an analytical model for estimating the phase noise due to self-phase modulation (SPM), cross-phase modulation (XPM), and four-wave mixing (FWM) in an all-optical OFDM system is presented. The phase noise versus power, distance, and number of subcarriers is evaluated by implementing the mathematical model using Matlab. In order to verify the results, an all-optical OFDM system, that uses coupler-based inverse fast Fourier transform/fast Fourier transform without any nonlinear compensation, is demonstrated by numerical simulation. The system employs 29 subcarriers; each subcarrier is modulated by a 4-QAM or 16-QAM format with a symbol rate of 25 Gsymbol/s. The results indicate that the phase variance due to FWM is dominant over those induced by either SPM or XPM. It is also shown that the minimum phase noise occurs at -3 dBm and -1 dBm for 4-QAM and 16-QAM, respectively. Finally, the error vector magnitude (EVM) versus subcarrier power and symbol rate is quantified using both simulation and the analytical model. It turns out that both EVM results are in good agreement with each other.

Enhanced Erbium–Zirconia–Yttria–Aluminum Co-Doped Fiber Amplifier

Abstract: An efficient optical amplifier is demonstrated using an improved erbium–zirconia–yttria–aluminum co-doped fiber (Zr-EDF) as the gain medium. With a combination of both Zr and Al, we could achieve a high erbium doping concentration with an absorption loss of around 80.0 dB/m at 980 nm. The Zr-EDF is obtained from a fiber preform, which is fabricated in a ternary glass host, i.e., a zirconia–yttria–aluminum co-doped silica fiber, using a modified chemical vapor deposition, in conjunction with a solution doping process. At the optimum length of 1 m, the Zr-EDF amplifier produces a flat gain of 38 dB within a wavelength region between 1530 and 1565 nm with a gain variation of less than 3 dB when the input signal power and 980 nm pump power are fixed at $-$ 30 dBm and 130 mW, respectively. The highest gain of 40.3 dB is obtained at 1560 nm wavelength. Compared with the previous Zr-EDF amplifier, the proposed Zr-EDFA shows improved gain, particularly at longer wavelengths. The gain is enhanced by about 15.8 dB at a wavelength of 1560 nm for an input signal of $-$ 30 dBm.

Tunable dual-wavelength thulium-doped fiber laser at 1.8 μm region using spatial-mode beating

Abstract: This study describes a proposal and experimental demonstration of a tunable thulium-doped fiber laser with a multi-wavelength output operating at 1.8 μm. The introduction of a multi-mode non-adiaba...

Relative Humidity Sensor Employing Optical Fibers Coated with ZnO Nanostructures

Abstract: We demonstrate two simple relative humidity sensors using a tapered Plastic Optical Fiber (POF) and silica microfiber. The POF is tapered by chemical etching method whereby the fiber is immersed into acetone and polished by a sand paper to reduce the fiber’s waist diameter from 1 mm to about 0.4 - 0.5 mm. The silica microfibers were fabricated using flame brushing techniques. Both tapered fibers are then coated with zinc oxide (ZnO) nanostructures using sol-gel immersion on ZnO seeded and non-seeded fiber methods before it is used to sense relative humidity. It is found that the tapered POF coated with seeded ZnO performed better compared to tapered silica microfiber. The tapered POF coated with seeded ZnO based sensor has linearity and sensitivity of 94.41 % and 0.176 mV/%, respectively.

Generation of switchable domain wall and Cubic–Quintic nonlinear Schrödinger equation dark pulse

Abstract: A switchable domain-wall (DW) and Cubic–Quintic nonlinear Schrodinger equation (CQNLSE) dark soliton pulse generation are demonstrated in Erbium-doped fiber laser (EDFL) for the first time. The DW pulse train operates at 1575 nm with a fundamental repetition rate of 1.52 MHz and pulse width of 203 ns as the pump power is increased above the threshold pump power of 80 mW. The highest pulse energy of 2.24 nJ is obtained at the maximum pump power of 140 mW. CQNLSE pulse can also be realized from the same cavity by adjusting the polarization state but at a higher threshold pump power of 104 mW. The repetition rate and pulse width of the CQNLSE dark pulses are obtained at 1.52 MHz and 219 ns, respectively. The highest energy of 0.58 nJ is obtained for the CQNLSE pulse at pump power of 140 mW.

Passively dual-wavelength Q-switched ytterbium doped fiber laser using Selenium Bismuth as saturable absorber

Abstract: This paper describes a demonstration of a passively dual-wavelength Q-switched ytterbium-doped fiber laser using a selenium bismuth-based saturable absorber. By utilizing a short-length photonic crystal fiber in a ring cavity and performing adjustments to the polarization state of an incorporated polarization controller (PC), we obtained a stable dual-wavelength Q-switched output at 1037.14 and 1037.69 nm, with maximum pulse energy of 0.65 nJ, shortest pulse width of 8.46 μs, and pulse repetition rate from 15.37 to 59.24 kHz. The Q-switched laser output consistently achieved high-power stability with a 0.8 dB maximum fluctuation over a period of 20 min.

Fabrication of polymer microfiber by direct drawing

Abstract: We report the fabrication of polymer microfiber with high surface smoothness and length uniformity using molten polymethyl methacrylate (PMMA) by direct drawing technique. PMMA microfibers with diameters ranging from 6 to 12 m and lengths up to few centimeters have been drawn by this method. The microfibers' losses are obtained at 0.37, 0.27, and 0.19 dB/mm for the microfibers with diameters of 6, 8, and 12 m, respectively. (c) 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:820-823, 2015

Sideband-controllable soliton pulse with bismuth-based erbium-doped fiber

Abstract: A sideband-controllable soliton mode-locked erbium-doped fiber laser is successfully demonstrated utilizing the nonlinear polarization rotation technique. The sidebands can be produced or suppressed by performing simple polarization light tuning with a polarization controller. It is believed that the elimination of the sidebands is due to the dispersive waves that are filtered out by the polarization-dependent isolator in the resonator. With the elimination of the Kelly sidebands, the obtained 3 dB bandwidth is 10.6 nm and the attainable pulse duration is 0.86 ps. In this experiment, it is proven that the existence of Kelly sidebands limits the attainable pulse duration.

Inline Mach–Zehnder interferometer with ZnO nanowires coating for the measurement of uric acid concentrations

Abstract: A simple optical fiber sensor is proposed and demonstrated using a dumbbell shaped inline Mach–Zehnder interferometer (MZI), which is coated with ZnO nanowires for measuring different concentrations of uric acid in de-ionized water. It is found that the interference spectrum of the sensor is red-shifted when the concentration of uric acid rises from 0 to 500 ppm. The peak-wavelength shift linearly increases with the increment in uric acid concentration. The sensitivity of the MZI sensor coated with ZnO is recorded at 0.001 nm/ppm with a good slope of linearity of more than 99% for a limit of detection (LOD) of 5.74%. On the other hand, the sensitivity of MZI-sensor without ZnO coating is 0.0005 nm/ppm with a slope of linearity of more than 99% and an LOD of 8.55%. It can be deduced that the sensitivity of the MZI-coated with ZnO is higher than the one without. This is due to the presence of the ZnO nanowires that trap water molecules within their mesh thereby improving the sensor’s response. These results show that the proposed sensor is applicable and useful for measuring the concentration of biochemical such as uric acid, glucose and fructose.

Detection of different concentrations of uric acid using tapered silica optical sensor coated with zinc oxide (zno)

Abstract: The working principle of measurement of output power from silica optical sensor for the detection of different concentrations of uric acid is demonstrated. The fabricated sensors used single mode silica optical fibers (SOF) which were tapered using flame brushing technique to achieve a waist diameter of 32 µm and tapering length of 2 mm. The tapered fiber were then coated with ZnO nanostructures using sol–gel immersion method. The concentration of the uric acid is measured in volume parts per million (ppm) for a concentration change from 0 ppm to 500 ppm by tapered SOF coated with ZnO and non-coated sensors. The peak voltage increases linearly for coated and non-coated from 214 mV to 268 mV and 270 mv to 344 mV, respectively. Sensitivity was measured with 0.11 mV/ppm and 0.15 mV/ppm, respectively. In addition, the results show that the linearity of the sensors is 94.56% and 97.78%, respectively. Simple in fabrication and low in cost, this sensor can detect concentration changes of uric acid in a fast and convenient way with high stability and sensitivity. Thus, this sensor will be very promising in chemical and biomedical applications.

Intensity based optical fiber sensors for calcium detection

Abstract: Two optical fiber sensors are proposed and demonstrated for monitoring calcium concentration in a liquid solution. The first sensor utilizes a bundle plastic optical fiber (POF) as a probe. The system comprises fiber optic transmitter, fiber optic probe which consists of 1000 cores as a receiver, mirror reflection, photodiode detector, lock-in amplifier and computer.The measurementis based on the peak voltage of the output which increases with the calcium concentration of the solution varying from 0 to 2.5. It is found that the peak voltage of the detector increases with the calcium concentration due to the scattering effects which allow more photons to be collected by the receiver. The sensitivity of the bundled POF based sensor is obtained at 4.321mW with a resolution of 0.05. The second sensor employs a silica microfiber as a probe. The system consists of an amplified spontaneous emission (ASE) light source, microfiber probe and optical spectrum analyzer (OSA). The transmitted light intensity is observed to decrease with the increase in calcium concentration due to the change in the refractive index of the solution. The sensitivity of the second sensor is obtained at 2.4dB/ with a resolution of 0.8. Both sensors show a good stability and high sensitivity. They are simple in design and low in fabrication cost, which are appropriate for chemical, biomedical, pharmaceutical and process control applications. © 2015, National Institute of Optoelectronics. All rights reserved.

Tapered fiber coated with hydroxyethyl cellulose/polyvinylidene fluoride composite for relative humidity sensor

Abstract: A new evanescent wave based sensor is proposed and demonstrated using a silica fiber interferometer coated with Hydroxyethyl Cellulose/Polyvinylidene Fluoride ( HEC/PVDF) composite. The performance of the sensor is investigated for two different types of interferometer structure: inline Mach Zehnder Interferometer (MZI) with dumbell structure and non-adiabatic etched fiber. The measurement is based on interferometric technique where the transmission spectrum of the reflected light is investigated for changes in relative humidity. For instance, the resonant dip wavelength for MZI dumbbell shape increases from 1555.76 to 1556.34 nm as the RH increases from 10 to 80%. While, for etched SMF the resonant dip wavelength increases from 1554.58 to 1554.85 nm as the RH increases from 10 to 80%. Both sensors demonstrated a linear shift especially within a range from 20 to 45%. It is found that the MZI-based sensor has a sensitivity of 0.0123 nm/% with a linearity of 99.88% and limit of detection of 0.44%. On the other hand, the etched SMF structure also shows change in the resonant wavelength with the increase in RH. The tapered fiber based sensor has a sensitivity of 0.0074 nm/% with linearity of 98.85% and limit of detection of 0.65%. The lower limit of detection for dumbbell structure shows that the system is more efficient than etched SMF structure. The proposed sensor has a high potential for RH measurement as it has easy to fabricate, low fabrication cost, and compact size.

Harmonic Dark Pulse Emission in Erbium-Doped Fiber Laser

Abstract: A harmonic dark pulse generation in an erbium-doped fiber laser is demonstrated based on a figure-of-eight configuration. It is found that the harmonic dark pulse can be shifted from the fundamental to the 5th order harmonic by increasing the pump power with an appropriate polarization controller orientation. The fundamental repetition rate of 20 kHz is obtained at the pump power of 29 mW. The highest pulse energy of 42.6 nJ is obtained at the fundamental repetition rate. The operating frequency of the dark pulse trains shifts to 2nd, 3rd, 4th and 5th harmonic as the pump powers are increased to 34 mW, 50 mW, 59 mW and 137 mW, respectively.

Dual wavelength single longitudinal mode Ytterbium-doped fiber laser using a dual-tapered Mach-Zehnder interferometer

Abstract: This paper describes a dual wavelength single longitudinal mode (SLM) demonstration for a proposed ytterbium-doped fiber laser. A dualtapered Mach-Zehnder interferometer (MZI) was inserted into the laser ring cavity setup to ensure a stable dual wavelength and SLM operation. The consequent dual wavelength lasing operation had a wavelength spacing of 0.94 nm and a side mode suppression ratio (SMSR) of 50 dB, with the linewidth of this setup measured as 294.15 kHz. A stability test allowed for a measurement of max power fluctuation as less than 0.8 dB for each wavelength and which was indicative of a stable dual wavelength operation.

PMMA microfiber coated with al‐doped ZnO nanostructures for detecting uric acid

Abstract: A biosensor is demonstrated using the fabricated polymethyl methacrylate (PMMA) microfiber, which is coated with Al-doped ZnO nanostructure using a sol-gel process, used as the probe. The change in the transmitted light intensity from the PMMA microfiber-based sensor with the increase in uric acid concentration is investigated. It is observed that the light power linearly decreases with the increase in uric acid concentration. As the uric acid concentration increases from 0 to 500 ppm, the transmitted light intensity reduces from −31.54 to −36.54 dBm. It is found that the sensor has a sensitivity of 0.010 dB/ppm with a good linearity of more than 99%. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2455–2457, 2015