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Mid-infrared supercontinuum generation with high spectral flatness in dispersion flattened tellurite all-solid hybrid microstructured optical fibers
摘要： Tellurite all-solid hybrid microstructured optical fibers are proposed for chromatic dispersion control. An ultra-flattened chromatic dispersion profile with variation as small as ± 0.2 ps/km/nm over the wavelength range from 2.5 to 3.7 μm can be obtained. The fibers with flattened chromatic dispersion profiles have high potential for broadband mid-infrared supercontinuum generation. Fabrication of the fiber is successfully performed and by pumping the fabricated fiber at 2 μm, a broad and highly coherent supercontinuum with high spectral flatness is generated.
关键词： mid-infrared,supercontinuum generation,microstructured optical fibers,tellurite fibers,chromatic dispersion
更新于2025-09-23 15:19:57
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Broadband Multi-Species Trace Gas Detection by Up-Converting Mid-Infrared Supercontinuum Light into the Near-Infrared
摘要： Recent advancement in compact, stable, and broadband mid-infrared supercontinuum (SC) sources has provided attractive scientific and industrial applications in metrology, sensing, and communications [1]. The wide spectral coverage in the so-called molecular fingerprint region is the main advantage of such SC sources, opening up new opportunities for efficient multi-species trace gas detection at short time scale. Presently, there is a lack of sensitive, low-cost, uncooled MIR photodetectors. The alternative approach involves up-converting mid-infrared light into the near-infrared region via non-linear conversion, leveraging the benefits of sensitive and cost-effective CCD detectors [2]. Here, we present the development of a multi-species trace gas sensor utilizing a mid-infrared SC source in combination with a multipass absorption cell and an up-conversion-based spectrometer. The customized SC source (NKT Photonics) has a total power of 450 mW covering the 1.5 – 4.5 μm spectral window. The astigmatic Herriott multipass cell (AMAC-76, Aerodyne Research) provides an effective optical pathlength of 76 meters improving the detection sensitivity. Details of the up-conversion-based spectrometer (NLIR) have been recently published. [3]. Note that in the present upconversion system the intracavity laser at 1064 nm is generated by pumping the Nd:YVO4 gain medium at 808 nm instead of 880 nm. In order to enhance the long term stability for single species detection, the amplitude drift of the SC source is minimized by counterbalancing the SC intensity with a non-absorbing reference. Multispecies broadband absorbance spectra have been obtained for, amongst others, mixtures of ethane and acetaldehyde at ppm levels in nitrogen as shown in Fig. 1 (a). A non-negative least squares global fitting method has been applied to extract the concentration of individual sub-component. To check system linearity by different gas concentrations, the absorbance with various mixing ratios were measured at a pressure of 900 mar for 60 s. A linear fit of these measurements that agreed with the calculated ones is depicted in Fig. 1 (b) for ethane. The sensor is capable of detecting sub-ppmv gas concentrations (e.g. ~300 ppbv ethane) in a wide range of spectrum (over 600 cm-1) with a ~5 cm-1 spectral resolution. Broadening the spectrum to a wider range by using chirped crystals in the up-converter system and further experiments are under progress. More details and the results for the on-going experiments will be presented at the conference.
关键词： multi-species,mid-infrared supercontinuum,up-conversion,broadband,trace gas detection
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Chalcogenide Glass Polarization-Maintaining Photonic Crystal Fiber for Mid-Infrared Supercontinuum Generation
摘要： Chalcogenide-glass-based optical fibers are excellent photonic platforms for nonlinear applications in the mid-IR region due to their wide transmission window, tunable dispersion and high optical nonlinearity. There is particular interest in combining the chalcogenide fiber platform with polarization-preserving properties as this will allow polarization-dependent measurements while minimizing detrimental effects and thus enable new applications in interferometric techniques, gas sensing, integrated-optic devices and optical coherence tomography. In this work, for the first time to our knowledge, we demonstrate mid-IR supercontinuum (SC) generation in a highly birefringent polarization maintaining photonic crystal fiber (PM-PCF). The PM-PCF was drawn using the casting method from As38Se62 glass which features a transmission window from 2-10 μm and a high nonlinear refractive index up to 1.13×10-17 m2/W [1,2]. To introduce strong birefringence, an asymmetric arrangement of air holes was used as shown in Fig. 1(a). The PCF cross section consists of 36 circular air holes in 3 rings with 2 larger air holes adjacent to the core. The (approximate) core diameter (i.e. distance between two large air holes) is ~8.1 μm and the outer diameter of the PCF is 125 μm. The group velocity dispersion and group birefringence for the fundamental mode (computed from the SEM image) are shown in Fig. 1(b). The fiber has a zero-dispersion wavelength around 4.5 μm and, at this wavelength, a large birefringence of 6×10-4 such that strong polarization maintaining properties are expected. In our experiments, a 25cm long PM-PCF was pumped with 250 fs pulses at 4 μm (i.e. the normal dispersion regime) using the same experimental setup for MIR SC generation as previously described in Ref. [3]. Figure 1(c) shows the generated SC spectra with different output power. For a pump power of 135 mW, we obtained a SC spectrum from 3.1-6.02 μm with an average output power of 11 mW. Pumping close to the zero dispersion wavelength with the pump at 4.53 μm yielded comparable spectral broadening but at much lower input pump power of 62 mW as shown in Fig. 1(d). In this case, we were able to measure the polarization dependence of the SC spectra by changing the coupling angle through rotation of the fiber. These results demonstrate the potential of chalcogenide PM-PCF for polarized SC generation, and work is underway to optimize the spectral generation and polarization dependency using detailed numerical modelling.
关键词： Polarization-maintaining,Photonic crystal fiber,Chalcogenide glass,Mid-infrared,Supercontinuum generation
更新于2025-09-12 10:27:22