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International audience; We demonstrate broadband supercontinuum generation in an all-normal dispersion polarization maintaining photonic crystal fiber and we report the observation of a cross-phase modulation instability side band that is generated outside of the supercontinuum bandwidth. We demonstrate this sideband is polarized on the slow axis and can be suppressed by pumping on the fiber’s fast axis. We theoretically confirm and model this nonlinear process using phase-matching conditions and numerical simulations, obtaining good agreement with the measured data

Mid-infrared (MIR) fibre-optics may play a future role in in vivo diagnosis of disease, including cancer. Recently, we reported for the first time an optical fibre based broadband supercontinuum (SC) laser source spanning 1.3 to 13.4 μm wavelength to cover the spectral 'fingerprint region' of biological tissue. This work has catalysed the new field of fibre MIR-SC and now very bright sources equivalent to a 'few synchrotrons' have been demonstrated in fibre. In addition, we have made record transparency MIR fibre for routeing the MIR light and reported first-time MIR photoluminescence (with long lifetime) in small-core, rare earth ion doped, MIR fibre - an important step towards MIR fibre lasing at > 4 μm wavelength for pumping fibre MIR-SC. First time fibre MIR-SC spectroscopic imaging of colon tissue is described at wavelengths in the ‘fingerprint region’.

Mid-IR supercontinuum sources are a new type of source for the 2-4.5 µm spectrum, but their weight, size and power consumption has previously made them unsuitable for mobile sensing. We demonstrate a highly compact supercontinuum source with a weight of

Mid-InfraRed (MIR) broadband SuperContinuum (SC) sources are desirable for applications such as polution monitoring, spectroscopy, and IR countermeasures due to their high spatial coherence and high power density over a broad bandwidth [1]. Conventional silica fibers cannot facilitate this need due to their intrinsic IR transmission edge at 2.4 μm, so instead soft glasses are used for MIR SC sources. The soft glass ZBLAN is in particular interesting as it has low loss out to 4.5 μm [Fig. 1(a)]. Additionally, it has a material Zero Disperison Wavelength (ZDW) around 1.6 μm that with proper fiber design allows to generate a broadband SC using direct pumping with commercially available Erbium (Er) mode-locked fiber lasers at 1550 nm. Formation of SC is manipulated both in the UV and IR by changing the fiber dispersion and nonlinearity using tapers. This has been much studied in various silica fiber designs and is now also becoming used in ZBLAN [2], and other soft glasses such as chalcogenide [3] and tellurite [4]. The aim of this nummerical work is to show how pumping tapered commercially available ZBLAN fibers with an Er mode-locked fiber laser can generate a broadband SC approaching the ZBLAN long wavelength transmision edge. The taper employed here is a 20 cm long symmetric taper with a down- and up-taper length of 2 cm and a 16 cm long waist [see inset in Fig. 1(c)] and can be easily fabricated on a conventional Vytran taper stage.Ten meters of uniform ZBLAN Step Index Fiber with NA=0.3 (max. commercially available), core diameter Dc=7 μm, and ZDW=1.5 μm, is pumped with TFWHM=10 ps and P0=10 kW pulses from an Er mode-locked laser with a 40 MHz repetition rate and 4W average power. The resulting MIR SC seen in Fig. 1(b) is based on Modulation Instability breakup of the pump pulse, which generates solitons that undergo Soliton Self Frequency Shift (SSFS). The -30 dB SC IR edge is at 3.06 μm. The increasing dispersion (D) for Dc=7 μm [see Fig. 1(b)] decreases the rate of SSFS, which is why the IR edge is still far away from the ZBLAN transmission edge. This is overcome by tapering the fiber with taper start at 8 m down to Dc=5.5 μm. At the taper waist a region of normal dispersion now appears in between the solitons, which generates MIR Dispersive Waves (DWs) between the second and third ZDW and also accelerates a large number of solitons towards the IR, as we will detail in the presentation. This moves the IR edge to 4.36 μm, close to the ZBLAN transmission edge.In Fig. 1(c) we show the integrated power above 3.06 μm and the -30 dB IR edge versus the taper waist between 5 and 7 μm for a fixed taper start at 8 m (optimum found through extensive modelling to be presented). Both indicate that a taper waist of 5.5 μm provides the maximum power of 45 mW above 3.06 μm.The ZBLAN taper in [2] resembling this work is based on very high NA fiber and is 6m long, which can only be made on the draw tower. The resulting SC in [2] covers 1.5-3 μm, where our spectrum covers 0.8-4.4 μm and uses only realistic fiber and laser parameters and a short taper, which can be fabricated on a taper station.

A Supercontinuum (SC) is a broad spectrum generated from a narrow light source through non-linear effects. This thesis describes SC generation based on 1064 nm ps pulses in PCF fibres. We investigate how the SC spectrum can be modified and intensity noise reduced by feeding back part of the SC. It is also described how the bandwidth of the SC can be expanded by optimizing the structure of the PCF. Finally SC generation in short (5-10 cm) tapered PCFs is explored and it is shown that these can be used to generate a SC which has very short wavelengths, low amplitude noise and very short output pulses.

Limited availability of tests to diagnose cancer in its early stages has contributed to an unfortunate prevalence of late-stage diagnoses and metastatic spread. For this reason, emerging technologies that promise early diagnosis constitute a key focus of research. Mid-infrared imaging (MIR), with its ability to enable in vivo medical diagnosis, is particularly interesting. In fact, the European Commission provides support for a major effort to develop the technology through its Framework Seven (FP7) project called MINERVA (MId- to-NEaR- infrared spectroscopy for improVed medical diAgnostics).

The advent of photonic crystal fibers (PCFs) has paved the road for commercial high-power supercontinuum light sources. The air-hole structuring in the PCF manipulates the properties of light and gives a tremendous degree of design freedom, which has enabled pushing the properties of PCFs to limits that can never be achieved with standard step index fibers. For example, one can move the zero dispersion wavelength (ZDW) into the visible [1] and make them endlessly single moded [2]. For efficient supercontinuum generation it is of great importance that the pump wavelength is close to the ZDW. We demonstrate how the spectral blue-edge can be manipulated by careful fiber design and tapering of the PCF enabling supercontinuum generation spanning all the way from 380 nm to 2.4μm [3]. We discuss the limiting factors of the supercontinuum bandwidth. Furthermore, we discuss how the fiber tapering influences the intensity noise of the supercontinuum source [4].Supercontinuum sources based on silica fibers are limited to the material loss edge at 2.4 μm. However, for wavelengths beyond 2.4 μm the attenuation of light in silica fibers is greatly increased making them useless for the mid-infrared region. Instead, other fiber materials such as fluoride-based glasses (ZBLAN) and chalcogenide glasses can be used for mid-infrared supercontinuum generation. We will show supercontinuum generation in ZBLAN fibers covering 1.5-4.5 μm [5] and super-continuum generation in microstructured chalcogenide fibers out to 9 μm. We discuss the prospects for extending the supercontinuum generation beyond 10 μm and highlight useful applications such as cancer detection and food analysis.