@article{ZajnulinaBoehmBlowetal.2015,
  author    = {Zajnulina, Marina and B{\"o}hm, Michael and Blow, K. and Rieznik, A. A. and Giannone, Domenico and Haynes, Roger and Roth, Martin M.},
  title     = {Soliton radiation beat analysis of optical pulses generated from two continuous-wave lasers},
  series = {Chaos : an interdisciplinary journal of nonlinear science},
  volume    = {25},
  journal   = {Chaos : an interdisciplinary journal of nonlinear science},
  number    = {10},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {1054-1500},
  doi       = {10.1063/1.4930316},
  pages     = {6},
  year      = {2015},
  abstract  = {We propose a fibre-based approach for generation of optical frequency combs (OFCs) with the aim of calibration of astronomical spectrographs in the low and medium-resolution range. This approach includes two steps: in the first step, an appropriate state of optical pulses is generated and subsequently moulded in the second step delivering the desired OFC. More precisely, the first step is realised by injection of two continuous-wave (CW) lasers into a conventional single-mode fibre, whereas the second step generates a broad OFC by using the optical solitons generated in step one as initial condition. We investigate the conversion of a bichromatic input wave produced by two initial CW lasers into a train of optical solitons, which happens in the fibre used as step one. Especially, we are interested in the soliton content of the pulses created in this fibre. For that, we study different initial conditions (a single cosine-hump, an Akhmediev breather, and a deeply modulated bichromatic wave) by means of soliton radiation beat analysis and compare the results to draw conclusion about the soliton content of the state generated in the first step. In case of a deeply modulated bichromatic wave, we observed the formation of a collective soliton crystal for low input powers and the appearance of separated solitons for high input powers. An intermediate state showing the features of both, the soliton crystal and the separated solitons, turned out to be most suitable for the generation of OFC for the purpose of calibration of astronomical spectrographs.},
  language  = {en}
}
@article{MunzkeBoehmReich2015,
  author    = {Munzke, Dorit and B{\"o}hm, Michael and Reich, Oliver},
  title     = {Gaseous Oxygen Detection Using Hollow-Core Fiber-Based Linear Cavity Ring-Down Spectroscopy},
  series = {Journal of lightwave technology},
  volume    = {33},
  journal   = {Journal of lightwave technology},
  number    = {12},
  publisher = {Inst. of Electr. and Electronics Engineers},
  address   = {Piscataway},
  issn      = {0733-8724},
  doi       = {10.1109/JLT.2015.2397177},
  pages     = {2524 -- 2529},
  year      = {2015},
  abstract  = {We demonstrate a method for the calibration-free and quantitative analysis of small volumes of gaseous samples. A 10 m hollow-core photonic bandgap fiber is used as the sample cell (volume = 0.44 mu L) and is placed inside a linear resonator setup. The application of cavity ring-down spectroscopy and in consideration of rather small coupling losses, this leads to an increased effective optical path length of up to 70 m. This implies a volume per optical interaction path length of 6.3 nL.m(-1). We used tunable diode laser spectroscopy at 760 nm and scanned the absorption for oxygen sensing. The optical loss due to sample absorption is obtained by measuring the ring-down time of light propagating inside the cavity. The resultant absorption coefficient shows a discrepancy of only 5.1\% comparing to the HITRAN database. This approach is applicable for sensitive measurements if only submicroliter sample volumes are available.},
  language  = {en}
}
@article{ZajnulinaBoggioBoehmetal.2015,
  author    = {Zajnulina, Marina and Boggio, Jose M. Chavez and B{\"o}hm, Michael and Rieznik, A. A. and Fremberg, Tino and Haynes, Roger and Roth, Martin M.},
  title     = {Generation of optical frequency combs via four-wave mixing processes for low- and medium-resolution astronomy},
  series = {Applied physics : B, Lasers and optics},
  volume    = {120},
  journal   = {Applied physics : B, Lasers and optics},
  number    = {1},
  publisher = {Springer},
  address   = {New York},
  issn      = {0946-2171},
  doi       = {10.1007/s00340-015-6121-1},
  pages     = {171 -- 184},
  year      = {2015},
  abstract  = {We investigate the generation of optical frequency combs through a cascade of four-wave mixing processes in nonlinear fibres with optimised parameters. The initial optical field consists of two continuous-wave lasers with frequency separation larger than 40 GHz (312.7 pm at 1531 nm). It propagates through three nonlinear fibres. The first fibre serves to pulse shape the initial sinusoidal-square pulse, while a strong pulse compression down to sub-100 fs takes place in the second fibre which is an amplifying erbium-doped fibre. The last stage is a low-dispersion highly nonlinear fibre where the frequency comb bandwidth is increased and the line intensity is equalised. We model this system using the generalised nonlinear Schrodinger equation and investigate it in terms of fibre lengths, fibre dispersion, laser frequency separation and input powers with the aim to minimise the frequency comb noise. With the support of the numerical results, a frequency comb is experimentally generated, first in the near infra-red and then it is frequency-doubled into the visible spectral range. Using a MUSE-type spectrograph, we evaluate the comb performance for astronomical wavelength calibration in terms of equidistancy of the comb lines and their stability.},
  language  = {en}
}