Hollow-core Photonic Bandgap Fiber Research Articles

An in-line fiber-optic modal interferometer for simultaneous measurement of twist and ambient temperature

A novel and simple sensor based on fiber-optic modal interferometer fabricated by a segment of low elliptical hollow-core photonic bandgap fiber for simultaneous temperature and twist measurements is demonstrated. Meanwhile the sensor can also measure the twist angle and determine the twist direction simultaneously. The mode distribution of EHC-PBGF is demonstrated both in theory and experiments. There is an obvious difference of two transmission dips on the temperature and twist. The twist sensitivities of Dip 1 and Dip 2 are obtained to be −31.95 and −585.8pm/(rad/m), respectively. The temperature sensitivities are 12.99pm/°C for Dip 1 and 5.09pm/°C for Dip 2, respectively. Two parameters of twist and temperature can be distinguished and measured simultaneously by using a sensing matrix. Meanwhile the structure is found to be weakly sensitive to the axial strain. It has the advantage of avoiding the crosstalk of strain in the applications.

Towards high sensitivity gas detection with hollow-core photonic bandgap fibers.

This paper investigates the effect of modal interference on the performance of hollow-core photonic bandgap fiber (HC-PBF) gas sensors. By optimizing mode launch, using proper length of sensing HC-PBF, and applying proper wavelength modulation in combination with lock-in detection, as well as appropriate digital signal processing, an estimated lower detection limit of less than 1 part-per-million by volume (ppmv) acetylene is achieved.

Cladding defects in hollow core fibers for surface mode suppression and improved birefringence.

We demonstrate a novel polarization maintaining hollow-core photonic bandgap fiber geometry that reduces the impact of surface modes on fiber transmission. The cladding structure is modified with a row of partially collapsed holes to strip away unwanted surface modes. A theoretical investigation of the surface mode stripping is presented and compared to the measured performance of four 7-cells core fibers that were drawn with different collapse ratio of the defects. The varying pressure along the defect row in the cladding during drawing introduces an ellipticity of the core. This, combined with the presence of antiresonant features on the core wall, makes the fibers birefringent, with excellent polarization maintaining properties.

Dispersion in a Gas Filled Hollow Core Photonic Crystal Fiber

Hollow core photonic bandgap fibers provide a new geometry for the realization and enhancement of many nonlinear optical effects. Such fibers offer novel guidance and dispersion properties that provide an advantage over conventional fibers for various applications. Dispersion, which expresses the variation with wavelength of the guided-mode group velocity, is one of the most important properties of optical fibers. Photonic crystal fibers (PCFs) offer much larger flexibility than conventional fibers with respect to tailoring of the dispersion curve. This is partly due to the large refractive-index contrast available in the silica/air microstructures, and partly due to the possibility of making complex refractive-index structure over the fiber cross section. In this paper the fundamental physical mechanism has been discussed determining the dispersion properties of PCFs, and the dispersion in a gas filled hollow core photonic crystal fiber has been calculated. We calculate the dispersion of air filled hollow core photonic crystal fiber, also calculate the dispersion of N2 gas filled hollow core photonic crystal fiber and finally we calculate the dispersion of He gas filled hollow core photonic crystal fiber.

Dispersion in a Gas Filled Hollow Core Photonic Crystal Fiber

Hollow core photonic bandgap fibers provide a new geometry for the realization and enhancement of many nonlinear optical effects. Such fibers offer novel guidance and dispersion properties that provide an advantage over conventional fibers for various applications. Dispersion, which expresses the variation with wavelength of the guided-mode group velocity, is one of the most important properties of optical fibers. Photonic crystal fibers (PCFs) offer much larger flexibility than conventional fibers with respect to tailoring of the dispersion curve. This is partly due to the large refractive-index contrast available in the silica/air microstructures, and partly due to the possibility of making complex refractive-index structure over the fiber cross section. In this paper the fundamental physical mechanism has been discussed determining the dispersion properties of PCFs, and the dispersion in a gas filled hollow core photonic crystal fiber has been calculated. We calculate the dispersion of air filled hollow core photonic crystal fiber, also calculate the dispersion of N2 gas filled hollow core photonic crystal fiber and finally we calculate the dispersion of He gas filled hollow core photonic crystal fiber.

Stored Energy, Transmission Group Delay and Mode Field Distortion in Optical Fibers

The relationship between transmission group delay and stored energy in optical fibers is discussed. We show by numerical computations that the group delay of an optical pulse of finite bandwidth transmitted through a piece of a low loss optical fiber of unit length is proportional to the energy stored by the standing wave electromagnetic field. The stored energy-group delay ratio typically approaches unity as the confinement loss converges to zero. In case of a dispersion tailored Bragg fiber, we found that the stored energy-group delay ratio decreased while the confinement loss increased compared to those of the standard quarterwave Bragg fiber configuration. Furthermore, a rapid variation in the group delay versus wavelength function due to mode-crossing events (in hollow core photonic bandgap fibers for instance) or resonances originating from slightly coupled cavities, surface or leaking modes in index guiding, photonic bandgap, or photonic crystal fibers always results in a rapid change in the mode-field distribution, which seriously affects splicing losses and focusability of the transmitted laser beam. All of these factors must be taken into consideration during the design of dispersion tailored fibers for different applications.

High Power Diode-Seeded Fiber Amplifiers at 2 μm—From Architectures to Applications

We review recent advances in the development of high power short- and ultrashort pulsed Thulium-doped fiber amplifier (TDFA) systems seeded by semiconductor laser diodes at wavelengths around 2 μm. The diode-seeding and the master oscillator power amplifier (MOPA) design allow for the construction of extremely versatile laser systems that can operate over wide ranges of peak power, pulse energy and repetition rate in the ultrashort picosecond to the long nanosecond pulsed regimes. We present a record peak power of 130 kW and pulse energy of 5 μJ in picosecond mode, while demonstrating user-defined pulse-shaping capabilities at millijoule pulse energy levels in the nanosecond regime from essentially the same amplifier system. The system architecture as well as important design and power scaling considerations are discussed in detail. Additionally, we highlight recent results in the application of these MOPA systems and their high performance TDFA stages in such diverse application areas as next generation telecommunication networks, mid-infrared supercontinuum generation and mid-infrared gas detection in hollow-core photonic bandgap fibers.

Mode division multiplexing over 19‐cell hollow‐core photonic bandgap fibre by employing integrated mode multiplexer

A photonic integrated mode coupler based on Silicon-on-Insulator (SOI) is employed for mode division multiplexing (MDM) over a 193m 19-cell hollow-core photonic bandgap fiber (HC PBGF) with a 3dB bandwidth > 120nm. Robust LP01 and LP11 modes, and two degenerate LP11 modes (LP11a and LP11b) MDM x 20Gbaud QPSK transmissions are both experimentally verified.

High peak-power monolithic femtosecond ytterbium fiber chirped pulse amplifier with a spliced-on hollow core fiber compressor.

We demonstrate a monolithic Yb-fiber chirped pulse amplifier that uses a dispersion matched fiber stretcher and a spliced-on hollow core photonic bandgap fiber compressor. For an output energy of 77 nJ, 220 fs pulses with 92% of the energy contained in the main pulse, can be obtained with minimal nonlinearities in the system. 135 nJ pulses are obtained with 226 fs duration and 82 percent of the energy in the main pulse. Due to the good dispersion match of the stretcher to the hollow core photonic bandgap fiber compressor, the duration of the output pulses is within 10% of the Fourier limited duration.

Fiber fluorescent spectroscopy

In this paper we present the current history of fluorescent spectroscopy research conducted in our team. Results obtained by single-photon fluorescence spectroscopy are presented, together with a description of potential PCF fiber solutions for multi-photon type of excitation. Single-photon research contained of two methods – the classical endoscope imaging as well as fluorescence lifetime analysis. The proposed PCF fibers are optimized for possible use as a fluorescent sensors, which will require the usage of femtosecond light pulses. Full Text: PDF References Z. Kulas, E. Bereś – Pawlik, T. Kręcicki, SPIE – cop., 59590 (2005) E. Bereś – Pawlik, A. Grobelny, Z. Pałasz, T. Kręcicki, Polish Patent PL 207002 (2010) Z. Kulas, E. Bereś – Pawlik, T. Kręcicki,"Numerical analysis of endoscopic autofluorescence imaging for cancerous tissue detection", J. Non-Cryst Solids 32, 2468-2475 (2006) CrossRef E. Bereś – Pawlik, A. Grobelny, Z. Pałasz, T. Kręcicki, Polish Patent PL 207002 (2010) Z. Kulas, PhD Thesis, I28/2012/P-002, Wroclaw University of Technology (2012) U. S. Dinish, P. Gulati, V. M. Murukeshan, L. K. Seah, "Diagnosis of colon cancer using frequency domain fluorescence imaging technique", Optics Communications 271, 291-301 (2006) CrossRef F. V. Bright, Ch. A. Munson, "Time-resolved fluorescence spectroscopy for illuminating complex systems", Analytica Chimica Acta 500, 71-104 (2003) CrossRef Gyungseok Oh, Euiheon Chung, Seok H. Yun, "Optical fibers for high-resolution in vivo microendoscopic fluorescence imaging", Optical Fiber Technology 19, 760-771 (2013) CrossRef E. Bereś – Pawlik, K. Gąsiorek, Z. Kulas, M. Rząca, "Optical Fiber Sensors for Point Investigation οf Cancer Tissues ", Acta Physica Polonica A 116, 254-256 (2009) DirectLink K. Gąsiorek, M.S. Thesis, Wrocław University of Technology (2006) W. Sokół, M.S. Thesis, Wroclaw University of Technology (2013) B. B. Collier, M. J. McShane, "Time-resolved measurements of luminescence", Journal of Luminescence 144, 180-190 (2013) CrossRef T. Dou et al., "Dispersion control with reflection grisms of an ultra-broadband spectrum approaching a full octave", Opt. Express 18, 27900-27909 (2010) CrossRef S. F. Elahi, T. D. Wang, "Future and advances in endoscopy", J. Biophotonics. 4, 471–481 (2011). CrossRef H. Stawska, E. Bereś-Pawlik, Dispersion properties of double-clad hollow-core photonic bandgap fibers based on a circular lattice cladding, in Proc. 22nd International Conference on Optical Fiber Sensors, OFS-22, 84217F-1 – 84217F-4 (15-19 Oct. 2012, Beijing, China) E. Bereś-Pawlik, H. Stawska, Ł. Kłonowski, Detecting cancerous tissues in human body by means of fiber fluorescent spectroscopy, ICTON (2013)

Model Analysis of Underwater Acoustic Sensing with Hollow-Core Photonic Bandgap Fiber

Recently, using hollow-core photonic bandgap fiber (HC-PBF) for underwater acoustic sensing has been tested experimentally. Besides its unique characteristics and advantages over conventional single mode fiber (SMF), it provides higher responsivity to acoustic pressure. A robust deep water ray tracing model for multipath acoustic signals propagation and the elastic model of HC-PBF are both required to study the effects of underwater enviroment on the propagating acoustic signal for sensing with HC-PBF hydrophones. The combination of the two models allows studying the frequency response, sensitivity, detection range, and maximum operating depth of the HC-PBF hydrophones. The models analysis and simulations show the considerations that must be taken into account for the design and field operation of the HC-PBF hydrophones. In this paper, a complete package to study, design, optimize, and analyze the simulation results of the interferometric HC-PBF hydrophones is proposed.

Phase sensitivity of fundamental mode of hollow-core photonic bandgap fiber to internal gas pressure.

The response of the commercial HC-1550-02 hollow-core photonic bandgap fiber (HC-PBF) to gas pressure applied internally to the hollow-core was experimentally investigated. The transmission spectrum of the HC-PBF was hardly affected by the pressure, while the accumulated phase of the fundamental optical mode showed a normalized pressure sensitivity of 1.044 × 10(-2) rad/(Pa∙m), which is over two orders of magnitude higher than that to the external pressure. Numerical simulation showed that the observed high sensitivity to pressure is due to the pressure-induced refractive index change of air inside the hollow-core. This research could find potential applications in high sensitivity static and dynamic pressure measurement and optical phase manipulation.

High-power beam transport through a hollow-core photonic bandgap fiber

We investigate the use of a seven-cell hollow-core photonic bandgap fiber for transport of CW laser radiation from a single-mode, narrow-linewidth, high-power fiber laser amplifier. Over 90% of the amplifier output was coupled successfully and transmitted through the fiber in a near-Gaussian mode, with negligible backreflection into the source. 100W of power was successfully transmitted continuously without damage and 160W of power was transmitted briefly before the onset of thermal lensing in the coupling optics.

First Demonstration of a 2-<inline-formula> <tex-math notation="TeX">$\mu{\rm m}$ </tex-math> </inline-formula> OTDR and Its Use in Photonic Bandgap <inline-formula> <tex-math notation="TeX">${\rm CO}_{2}$ </tex-math> </inline-formula> Sensing Fiber

We report the first demonstration of an optical time domain reflectometer (OTDR) designed for the emerging wavelength band of 2 μm. A dynamic range of 30 dB with a spatial resolution of 5 m is achieved. The characterization of three different fibers using the 2-μm OTDR is described. Two solid core fibers (SMF with a cutoff at 1.7 μm and SMF 28e) have been probed to ascertain their transmission loss values, while measurements in a 19-cell hollow core photonic bandgap fiber show the presence of carbon dioxide gas in the fiber core and allow the contribution that it makes to the fiber loss to be quantified.

Characterization and application of chirped photonic crystal fiber in multiphoton imaging

Fiber delivery of ultrashort pulses is important for multiphoton endoscopy. A chirped photonic crystal fiber (CPCF) is first characterized for its transmission bandwidth, propagation loss, and dispersion properties. Its extremely low dispersion (~150 fs(2)/m) enables the delivery of sub-30 fs pulses through a ~1 m-long CPCF. The CPCF is then incorporated into a multiphoton imaging system and its performance is demonstrated by imaging various biological samples including yew leaf, mouse tendon, and human skin. The imaging quality is further compared with images acquired by a multiphoton imaging system with free-space or hollow-core photonic band-gap fiber (PBF) delivery of pulses. Compared with free-space system, the CPCF delivered system maintains the same ultrashort pulsewidth and the image qualities are comparable. Compared with the PBF delivery, CPCF provides a 35 times shorter pulsewidth at the sample location, which results in a ~12 and 50 times improvement in two-photon excitation fluorescence (TPEF) and second harmonic generation (SHG) signals respectively. Our results show that CPCF has great potential for fiber delivery of ultrashort pulses for multiphoton endoscopy.

Study of Birefringence and Mode Field for Hollow-Core Photonic Bandgap Fiber

Since the Appearance of Hollow-Core Photonic Bandgap Fiber (HC-PBF), it was Widely Concerned for its Excellent Characteristics. in Order to Study the Characteristics of the HC-PBF that can be Used in Resonator Fiber Optic Gyros (R-Fogs), the Model Structure of a Polarization-Maintaining HC-PBF was Built and its Performance was Simulated by Using the Finite Element Method (FEM). its Mode Field Distribution and Birefringence Characteristics were Obtained. the Influences of the Air Core and Cladding Structures on the Mode Field Distribution and Birefringence were Simulated and Analyzed Further. the Result Showed that there are both Core Mode and Surface Mode in the Structure we Built. by Adding Scattering Points into the Fiber Core, the Surface Mode can be Significantly Suppressed. by Matching the Size of Core and Air Holes around the Core, a Birefringence up to 8*10-4 were Obtained.

Plasmonic hollow-core photonic band gap fiber for efficient sensing of biofluids

We report a new family of hollow-core photonic crystal fibers with embedded metal wires for sensitive refractive index measurement of fluids. These fibers operate on the principle of resonant coupling of the guided core mode with the surface plasmon mode generated at the surface of metal wires embedded in the photonic crystal structure. A maximum sensitivity of 2151 nm RIU−1 (nanometer per refractive index unit) can be achieved even for refractive index values lower than 1.26. The fiber is simple in design and can be fabricated with a certain modification to the conventional hollow-core photonic band gap fiber manufacturing technique. The proposed design is useful for detecting a small change in refractive index of the sample and may be implemented to estimate the bulk permittivity of the core fluid.

Frequency translation via four-wave mixing Bragg scattering in Rb filled photonic bandgap fibers

We demonstrate frequency translation at microwatt pump power levels in Rubidium vapor confined to a hollow-core photonic bandgap fiber using four-wave mixing Bragg scattering. The 5S(1/2)→5D(3/2) two-photon transition in 85Rb is employed for the four-wave mixing process. Using continuous-wave pump beams at 780 and 795 nm, a weak signal beam at 776 nm is translated to a wavelength of 762 nm with a 21% conversion efficiency at pump powers of 300 μW.

Detection H2S mixed with natural gas using hollow-core photonic bandgap fiber

An optical fiber gas sensor using hollow-core photonic bandgap fiber as a gas cell is proposed to detect H2S mixed with natural gas. This sensor is advantageous for eliminating instability of light source, impact of thermal zero drift, and zero shift of photoelectric device. The gas sensing probe of configuration is using two shorter pieces of hollow-core photonic bandgap fiber (HC-PBF) with the same overall length instead of one long piece of HC-PBF to improve the system response. The experimental dates indicate that a minimum detectivity of 10ppm for the system configuration was estimated.

Competition between stimulated Raman and Brillouin scattering processes in CF_4 gas

CF₄ gas has a relatively high Raman cross section and a relatively small Raman shift and is an excellent candidate for a gas-filled hollow-core photonic bandgap (HC-PBG) fiber Raman wavelength converter. Here we investigate experimentally the onset and competition between stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) processes in high-pressure CF₄ gas. We focus 532 nm laser pulses into a high-pressure gas cell and measure the SBS and SRS response. The thresholds for both processes decrease with pressure, as expected. However, with short focusing geometries, the SBS threshold is lower than the SRS threshold, and with long focusing geometries, it is the opposite. We further show that with HC-PBG fiber geometry SRS dominates.