Jun Long Lim

Agency for Science, Technology and Research (A*STAR) | A*Star · Institute for Infocomm Research (I2R)

Tube internal erosion, which corresponds to its wall thinning process, is one of the major safety concerns for tubes. Many sensing technologies have been developed to detect a tube wall thinning process. Among them, fiber Bragg grating (FBG) sensors are the most popular ones due to their precise measurement properties. Most of the current works foc...

The microhole collapsing effect technique is a relatively simple fabrication process that produces Photonic Crystal Fiber (PCF) refractometer using modal interferometry in the range of 10^−5 refractive index resolution. The repeatable method preserves the same 125 μm structural integrity of the optical fiber for various applications such as multi-p...

In this report, we carry out simulation and experimental investigations of directional coupler structures with different separations between the glycerin selectively infiltrated channel and silica core of a large mode area Photonic Crystal Fiber (PCF). We assess their coupling characteristics and the corresponding temperature sensing capabilities....

In this paper, we investigate and experimentally demonstrate the influences of distance between the silica core and the glycerin core of a selectively glycerin-infiltrated photonic crystal fiber (PCF) on the mode characteristics, as well as the temperature sensitivity. By comparing the simulation and experiment results of three single-void glycerin...

We report the development of a fully fiber-integrated pulsed master oscillator power fibre amplifier (MOPFA) source at 780 nm, producing 3.5 W of average power with 410 ps pulses at a repetition rate of 50 MHz. The source consists of an intensity modulated 1560 nm laser diode amplified in an erbium fiber amplifier chain, followed by a fiber coupled...

In this letter, the microfluidic optical fiber devices composed of microchannel are modeled and thoroughly analyzed. The microchannel intersecting the fiber core allows direct infusion of surrounding substances for detection. The simulation results suggest that the dimension of the microchannel can significantly affect the detection sensitivity of...

In this report, we present the design of a holey fiber structure with six air holes in the cladding and a transverse microfluidic channel intersecting the silica core for the purpose of liquid detection. The simulation results suggest an improved refractive index sensitivity of the proposed structure compared to that of a single mode fiber with a s...

Research on photonic crystal fiber-based interferometric sensors is rapidly developing for many applications, such as temperature, refractive index, and biosensing etc. We report the exploration and progress of various configurations of PCF-based interferometric sensors.

A 4-pointed gold nanostar is proposed to form the array on a fiber facet to achieve a greatly enhanced near field intensity for Surface-Enhanced Raman Scattering (SERS) detection. The proposed gold nanostar array has a Surface Plasmon Resonance (SPR) peaked at a wavelength of ∼650 nm with up to 45 times electric field intensity enhancement compared...

Suspended-core fiber (SCF) represents a promising class of microstructured optical fibers for sensing applications. In this work, we present a thorough modal analysis of the SCF based modal interferometer which is constructed by splicing 50 mm of SCF to single mode fiber at both ends. The measured transmission spectrum exhibits three-beam interfere...

A review of photonic crystal fiber sensors with microbubble is presented. The work concentrate in three sensing fields: the first reports on temperature sensing; the second describes on strain sensing; the last part focuses on refractive index sensing and bio-sensing. The method of fabricating the microbubble is also briefly discussed.

We present hybrid propagation in a photonic liquid crystal fiber (PLCF) fabricated by selective infiltration of photonic crystal fiber (PCF) air channels with a nematic liquid crystal (LC). Temperature tuning of the position of the photonic bandgaps is also demonstrated.

We report on the fabrication and characterization of a highly sensitive temperature sensor by selectively filling the nematic liquid crystal (NLC) 6CHBT into a single void within the photonic crystal fiber (PCF) structure. The temperature response of the device is experimentally characterized, showing good linearity, repeatability, and sensitivity...

A directional coupler structure formed by a nematic liquid crystal (NLC)-filled photonic crystal fiber (PCF) represents a promising configuration in sensing applications. Because of large refractive index difference between the NLC and silica material, the mode coupling between the NLC waveguide and the silica core is more complicated than the situ...

A highly temperature sensitive directional coupler is demonstrated experimentally by selectively filling nematic liquid crystal into a single void of the photonic crystal fiber. The temperature response of the device exhibits good linearity.

We present a cascaded fiber device based on photonic crystal fiber (PCF) interferometers for refractive index (RI) sensing. The PCF modal interferometers have microbubbles at both sides of the splice regions. The microbubbles act as thick diverging lens that scatter light for efficient excitation of higher order cladding modes and attenuation of th...

A high sensitive fiber-optic refractive index tip sensor based on a simple inline hollow glass micro-sphere is presented. The inline hollow glass micro-sphere can be automatically constructed at the splicing joint break time when splicing a hollow core photonic crystal fiber to an SMF. Simultaneously, the micro-sphere is tipped on the SMF end. It i...

We demonstrated a fiber sensor for simultaneous measurement of refractive index and temperature by cascading one long period grating and one modal interferometer. Cladding mode interference between them was also investigated here.

We propose and demonstrate a novel and simple dual-parameter measurement scheme based on a cascaded optical fiber device of long-period grating (LPG) and photonic crystal fiber (PCF) modal interferometer. The temperature and refractive index (RI) can be measured simultaneously by monitoring the spectral characteristics of the device. The implemente...

In this paper, we report and demonstrate a novel miniaturized intrinsic Fabry-Perot interferometer (IFPI) based on a simplified hollow core fiber ended with a hollow silica sphere tip. The hollow core fiber is spliced to single mode fiber and subsequently applied with fusion arc at the end, forming a hollow sphere with a thin silica wall. The refle...

In this paper we present an interferometer based on photonic crystal fiber (PCF) tip ended with a solid silica-sphere for refractive index sensing. The sensor is fabricated by splicing one end of the holey PCF to a single mode fiber (SMF) and applying arc at the other end to form a solid sphere. The sensor has been experimentally tested for refract...

Photonic crystal fibers (PCFs) offer innovative design and optical properties. In this paper, we measured the temperature dependence of a polarization-maintaining PCF based interferometer. The sensor head was fabricated by splicing PMPCF to single mode fiber (SMF) and temperature sensitivity of 15.4 pm/°C was obtained. The temperature measurements...

We fabricate and demonstrate a refractometer based on photonic crystal fiber (PCF) modal interferometer. The streptavidin and biotin are used as analyte and receptor in the experiment. The fabrication of the sensor is carried out via micro-hole collapsing with straightforward fusion arc splicing technique. Both sides of a short length of PCF (∼3 mm...

We report on the fabrication of a miniaturized photonic crystal fiber (PCF) tip sensor for sensitive liquid refractive index measurement. The PCF tip sensor has a hybrid configuration of Fabry-Perot (FP) and modal interferometer. A short length (less than 1 mm) of PCF is spliced to a standard single mode fiber. An air bubble is created in the splic...

We report the fabrication of a highly sensitive refractometer based on photonic crystal fiber (PCF) interferometry. Using fusion arc splicing technique, a short length of PCF (~3 mm) was spliced to conventional single mode fibers (SMF) on both sides. The voids of the PCF were completely collapsed in the splice region, which acted as mode splitter a...

Using a surface-emitted THz parametric oscillator, an MgO:LiNbO3-based frequency up-conversion detector and a special optical design for fast frequency tuning and achromatic THz-wave detection, we realized a room-temperature-operated THz frequency-domain spectrometer (THz-FDS).

The motivation of the project was to develop a powerful and compact Terahertz system that would replace decade old Terahertz systems that were expensive and bulky. The Terahertz Parametric Oscillator (TPO) was one of it and it operated under room temperature, making it a popular Terahertz source. Coherent and strong Terahertz wave was generated by...