Photonic crystal fiber (PCF) technology for ultrafast fiber amplifiers traditionally uses air holes as key elements for large mode area (LMA) fiber designs. These air holes are crucial for the performance of high-end LMA PCFs, but makes splicing and interfacing more complex. To reduce this complexity in mid-range amplifiers, we present single-mode polarization-maintaining Yb-doped LMA PCFs without air holes for easier splicing into monolithic all-fiber amplifier designs.
A 30 μm core all-solid spliceable PCF is presented, and amplification of 1064 nm light above 50 W with an optical to optical efficiency of 80 % is demonstrated.
Furthermore, to demonstrate the excellent reliability of PCF based monolithic amplifiers, we demonstrate ultra-longterm performance data of > 35 khrs on a 14 μm core step-index type PCF amplifier with low long-term power degradation slope of < 1.5 % / 10,000 h.
One of the main advantages of photonic crystal fibers (PCFs) is their ability to host novel functional materials in the airholes of the cladding. Here, we demonstrate a unique post-processing method which allows the integration of materials with significantly different thermo-mechanical properties inside the voids of silica PCF. We first present the material properties of silica, As2Se3 and polydimethylsiloxane (PDMS) in terms of their refractive indices and viscosity profile. The latter suggests that the proposed materials are not suitable for direct fiber drawing and thus we present the development of a multi-material As2Se3/PDMS/Silica PCF based on a solution-processed and pressure-assisting method. The integration of both As2Se3 chalcogenide glass films and PDMS was made in ambient conditions using a costeffective approach. The deposition of the high-index chalcogenide glass films revealed distinct resonances in the visible and near-infrared region while the high thermo-optic coefficient of PDMS provides the ability to thermally control the intensity of the antiresonant bands. The proposed method opens new directions towards multimaterial silica-based PCFs for novel tunable devices and sensors.
We present the first demonstration of mid-infrared spectroscopic imaging of human tissue using a fiber-coupled supercontinuum source spanning from 2-7.5 μm. The supercontinuum was generated in a tapered large mode area chalcogenide photonic crystal fiber in order to obtain broad bandwidth, high average power, and single-mode output for good imaging properties. Tissue imaging was demonstrated in transmission by raster scanning over a sub-mm region of paraffinized colon tissue on CaF2 substrate, and the signal was measured using a fiber-coupled grating spectrometer. This demonstration has shown that we can distinguish between epithelial and surrounding connective tissues within a paraffinized section of colon tissue by imaging at discrete wavelengths related to distinct chemical absorption features.
We report on an experimental demonstration of mid-infrared cascaded supercontinuum generation in commercial silica, fluoride, and chalcogenide fibers as a potentially cheap and practical alternative to direct pumping schemes. A pump continuum up to 4.4 μm was generated in cascaded silica and fluoride fibers by an amplified 1.55 μm nanosecond diode laser. By pumping a commercial Ge10As22Se68 single-material photonic crystal fiber with 135.7 mW of the pump continuum from 3.5- 4.4 μm, we obtained a continuum up to 7.2 μm with a total output power after the collimating lens of 54.5 mW, and 3.7 mW above 4.5 μm.
We are establishing a new paradigm in mid-infrared molecular sensing, mapping and imaging to open up the midinfrared spectral region for in vivo (i.e. in person) medical diagnostics and surgery. Thus, we are working towards the mid-infrared optical biopsy (‘opsy’ look at, bio the biology) in situ in the body for real-time diagnosis. This new paradigm will be enabled through focused development of devices and systems which are robust, functionally designed, safe, compact and cost effective and are based on active and passive mid-infrared optical fibers. In particular, this will enable early diagnosis of external cancers, mid-infrared detection of cancer-margins during external surgery for precise removal of diseased tissue, in one go during the surgery, and mid-infrared endoscopy for early diagnosis of internal cancers and their precision removal. The mid-infrared spectral region has previously lacked portable, bright sources. We set a record in demonstrating extreme broad-band supercontinuum generated light 1.4 to 13.3 microns in a specially engineered, high numerical aperture mid-infrared optical fiber. The active mid-infrared fiber broadband supercontinuum for the first time offers the possibility of a bright mid-infrared wideband source in a portable package as a first step for medical fiber-based systems operating in the mid-infrared. Moreover, mid-infrared molecular mapping and imaging is potentially a disruptive technology to give improved monitoring of the environment, energy efficiency, security, agriculture and in manufacturing and chemical processing. This work is in part supported by the European Commission: Framework Seven (FP7) Large-Scale Integrated Project MINERVA: MId-to-NEaR- infrared spectroscopy for improVed medical diAgnostics (317803; www.minerva-project.eu).
Based on the experience gained developing our market leading visible spectrum supercontinuum
sources NKT Photonics has built the first mid-infrared supercontinuum source based on modelocked
picosecond fiber lasers. The source is pumped by a ≈ 2 um laser based on a combination of erbium
and thulium and use ZBLAN fibers to generate a 1.75-4.4 μm spectrum. We will present results
obtained by applying the source for mid-infrared microscopy where absorption spectra can be used
to identify the chemical nature of different parts of a sample. Subsequently, we discuss the possible
application of a mid-IR supercontinuum source in other areas including infrared countermeasures.