@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}
}
@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{TrinhEllisBlandHawthornetal.2013,
  author    = {Trinh, Christopher Q. and Ellis, Simon C. and Bland-Hawthorn, Joss and Lawrence, Jon S. and Horton, Anthony J. and Leon-Saval, Sergio G. and Shortridge, Keith and Bryant, Julia and Case, Scott and Colless, Matthew and Couch, Warrick and Freeman, Kenneth and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Gers, Luke and Glazebrook, Karl and Haynes, Roger and Lee, Steve and O'Byrne, John and Miziarski, Stan and Roth, Martin M. and Schmidt, Brian and Tinney, Christopher G. and Zheng, Jessica},
  title     = {Gnosis - the first instrument to use fiber bragg gratings for OH suppression},
  series = {The astronomical journal},
  volume    = {145},
  journal   = {The astronomical journal},
  number    = {2},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0004-6256},
  doi       = {10.1088/0004-6256/145/2/51},
  pages     = {13},
  year      = {2013},
  abstract  = {The near-infrared is an important part of the spectrum in astronomy, especially in cosmology because the light from objects in the early universe is redshifted to these wavelengths. However, deep near-infrared observations are extremely difficult to make from ground-based telescopes due to the bright background from the atmosphere. Nearly all of this background comes from the bright and narrow emission lines of atmospheric hydroxyl (OH) molecules. The atmospheric background cannot be easily removed from data because the brightness fluctuates unpredictably on short timescales. The sensitivity of ground-based optical astronomy far exceeds that of near-infrared astronomy because of this long-standing problem. GNOSIS is a prototype astrophotonic instrument that utilizes "OH suppression fibers" consisting of fiber Bragg gratings and photonic lanterns to suppress the 103 brightest atmospheric emission doublets between 1.47 and 1.7 mu m. GNOSIS was commissioned at the 3.9 m Anglo-Australian Telescope with the IRIS2 spectrograph to demonstrate the potential of OH suppression fibers, but may be potentially used with any telescope and spectrograph combination. Unlike previous atmospheric suppression techniques GNOSIS suppresses the lines before dispersion and in a manner that depends purely on wavelength. We present the instrument design and report the results of laboratory and on-sky tests from commissioning. While these tests demonstrated high throughput (approximate to 60\%) and excellent suppression of the skylines by the OH suppression fibers, surprisingly GNOSIS produced no significant reduction in the interline background and the sensitivity of GNOSIS+IRIS2 is about the same as IRIS2. It is unclear whether the lack of reduction in the interline background is due to physical sources or systematic errors as the observations are detector noise dominated. OH suppression fibers could potentially impact ground-based astronomy at the level of adaptive optics or greater. However, until a clear reduction in the interline background and the corresponding increasing in sensitivity is demonstrated optimized OH suppression fibers paired with a fiber-fed spectrograph will at least provide a real benefit at low resolving powers.},
  language  = {en}
}