Daryl Ho

Record power, ultra-broadband supercontinuum source based on highly GeO 2 doped silica fiber

We demonstrate highly germania doped fibers for mid-infrared supercontinuum generation. Experiments ensure a highest output power of 1.44 W for a broadest spectrum from 700 nm to 3200 nm and 6.4 W for 800 nm to 2700 nm from these fibers, while being pumped by a broadband Erbium-Ytterbium doped fiber based master oscillator power amplifier. The effect of repetition frequency of pump source and length of germania-doped fiber has also been investigated. Further, germania doped fiber has been pumped by conventional supercontinuum source based on silica photonic crystal fiber supercontinuum source. At low power, a considerable broadening of 200-300 nm was observed. Further broadening of spectrum was limited due to limited power of pump source. Our investigations reveal the unexploited potential of germania doped fiber for mid-infrared supercontinuum generation. These measurements ensure the potential of germania based photonic crystal fiber or a step-index fiber supercontinuum source for high power ultra-broad band emission being by pumped a 1060 nm or a 1550 nm laser source. To the best of our knowledge, this is the record power, ultra-broadband, and all-fiberized supercontinuum light source based on silica and germania fiber ever demonstrated to the date.

Hollow core anti-resonant fiber with split cladding.

An improved design for hollow core anti-resonant fibers (HAFs) is presented. A split cladding structure is introduced to reduce the fabrication distortion within design tolerance. We use numerical simulations to compare the Kagome fibers (KFs) and the proposed split cladding fibers (SCFs) over two normalized transmission bands. It reveals that SCFs are able to maintain the desired round shape of silica cladding walls, hence improving the confinement loss (CL) compared to the KF and is comparable to that of the nested antiresonant nodeless fiber (NANF) with the same core size. In addition, the SCF allows stacking multiple layers of cladding rings to control the CL. The influences of the number of cladding layers and the cladding gap width on the CL of the SCFs have been studied. SCF with three cladding rings is fabricated by the stack-and-draw technique. A measured attenuation spectrum matches well with the calculation prediction. The measured near field mode patterns also prove the feasibility of our fiber design.

Optical orbital angular momentum amplifier based on an air-core erbium doped fiber

We present for the first time wideband operation of an optical orbital angular momentum amplifier with topological charge |l|=1. An air-core erbium-doped fiber is fabricated and up to 15.7dB gain is obtained with a cladding-pumped configuration.

Stress-Loss Correlation and Dispersion Control in Highly GeO 2 -Doped Fibers

We report a fabrication route to achieve highly GeO2-doped silica fibers with GeO2 molar concentration as high as 74% using the conventional modified chemical vapor deposition (MCVD) process. The dependence of background loss on fiber frozen-in stress in these highly doped fibers is investigated. A central dip of refractive index in the core is found to introduce stress variation, and contribute to the background loss. Dispersion control and supercontinuum generation in 2.1-2.8-μm region using the 74-mol% fiber are also presented.

High power, ultra-broadband supercontinuum source based on highly GeO2 doped silica fiber

We demonstrate a 74 mol % GeO2 doped fiber for mid-infrared supercontinuum generation. Experiments ensure a highest output power for a broadest spectrum from 700nm to 3200nm from this fiber, while being pumped by a broadband 4 stage Erbium fiber based MOPA. The effect of repetition rate of pump source and length of Germania-doped fiber has also been investigated. Further, Germania doped fiber has been pumped by conventional Silica based photonic crystal fiber supercontinuum source. At low power, a considerable broadening of 200-300nm was observed. Further broadening of spectrum was limited due to limited power of pump source. Our investigations reveal the unexploited potential of Germania doped fiber for mid-infrared supercontinuum generation. This measurement ensures a possibility of Germania based photonic crystal fiber or a step-index fiber supercontinuum source for high power ultra-broad band emission being pumped a 1060nm or a 1550nm laser source. To the best of our knowledge, this is the record power, ultra-broadband, and all-fiberized SC light source based on Silica and Germania fiber ever demonstrated to the date.

Benchtop Mini Preform Fabrication for Specialty Optical Fibers

We propose and demonstrate a benchtop version of the mini preform and hence short length fiber fabrication system. The system is compact, low cost, fast and flexible compared to the standard fabrication systems. We mimic the recipe used in standard Modified Chemical Vapour Deposition (MCVD) preform fabrication process. Incorporating with solution doping technique, we have fabricated several short length rare earth doped silica fibers, including Ytterbium and Erbium. The results obtained serve as a good indication on the composition of the rare earth elements to be used in the standard processes. The technique is promising and suitable for rapid specialty optical fiber prototyping.

Birefringent Bragg Grating in C-Shaped Optical Fiber as a Temperature-Insensitive Refractometer

We demonstrate a simple-to-fabricate refractometer based on the inscription of fiber Bragg gratings in a special C-shaped optical fiber. The C-shaped fiber was drawn into shape using a quarter cladding removed preform of a commercial standard single-mode fiber by simple machining. The sensor did not suffer from cross-sensitivity of the refractive index with ambient temperature fluctuations, commonly occurring with many optical fiber refractometers. A refractive index sensitivity of 1300 pm per refractive index unit (RIU) was achieved without employing any additional sensitization techniques such as tapering or etching.

Ultra-wideband Operation of a Tunable Thulium Fibre Laser offering Tunability from 1679–1992 nm

We demonstrate a tuneable thulium-doped fibre laser incorporating in-house fabricated Tm/Ge co-doped fibre capable of accessing the sub 1700nm wavelength band. An ultra-wide operating bandwidth of over 310nm is realized using an external cavity grating.

Double layer hollow core anti-resonant fiber for small core and low loss characteristics

We study the function of second cladding layer of the tube lattice fiber (TLF) and experimentally demonstrate the important role of the second layer in the reduction of both confinement loss (CL) and bending loss.

Asymmetric large mode area fibres

Asymmetric core is an alternative approach for mode scalability and better heat dissipation, thus being expected for suppressed mode instability. This talk will present stretched core fibres in aspects of its mode area scalability and mode instability.