Coupling light into few-mode optical fibres I: The diffraction limit

Optics Express (Impact Factor: 3.49). 03/2007; 15(4):1443-53. DOI: 10.1364/OE.15.001443
Source: PubMed


Multimode fibres are widely used in astronomy because of the ease of coupling light into them at a telescope focus. The photonics industry has given rise to a broad range of products but these are almost exclusively restricted to single-mode fibres, although some can be adapted for use in fibres that allow several modes to propagate. Now that astronomical telescopes are moving toward diffraction-limited performance through the use of adaptive optics (AO), we address the problem of coupling light into a few-mode fibre (FMF). We find that fibres with as few as ~5 guided modes share important characterisitcs with multimode fibres, in particular high coupling efficiency.We anticipate that future astronomical instruments at an AO-corrected focus will be able to exploit a broad class of photonic devices.

Download full-text


Available from: Anthony John Horton, Sep 30, 2015
16 Reads
  • Source
    • "In its current configuration the spectrograph has limited applications, due to the difficulty of coupling light from a telescope into a single-mode core [1]. However, there have been some interest in using single-mode and very few-mode fibers in telescopes with AO systems and extremely high resolution R~200000 have been demonstrated with this configuration [8]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a proof of concept compact diffraction limited high-resolution fiber-fed spectrograph by using a 2D multicore array input. This high resolution spectrograph is fed by a 2D pseudo-slit, the Photonic TIGER, a hexagonal array of near-diffraction limited single-mode cores. We study the feasibility of this new platform related to the core array separation and rotation with respect to the dispersion axis. A 7 core compact Photonic TIGER fiber-fed spectrograph with a resolving power of around R~31000 and 8 nm bandwidth in the IR centered on 1550 nm is demonstrated. We also describe possible architectures based on this concept for building small scale compact diffraction limited Integral Field Spectrographs (IFS).
    Proceedings of SPIE - The International Society for Optical Engineering 08/2012; DOI:10.1117/12.925254 · 0.20 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We calculate the advances in near-infrared astronomy made possible through the use of fibre Bragg gratings to selectively remove hydroxyl emission lines from the night sky spectrum. Fibre Bragg gratings should remove OH lines at high resolution (R=10,000), with high suppression (30dB) whilst maintaining high throughput (~90 per cent) between the lines. Devices currently under construction should remove 150 lines in each of the J and H bands, effectively making the night sky surface brightness ~4 magnitudes fainter. This background reduction is greater than the improvement adapative optics makes over natural seeing; photonic OH suppression is at least as important as adaptive optics for the future of cosmology. We present a model of the NIR sky spectrum, and show that the interline continuum is very faint (~80 ph/s/m^s/arcsec/micron on the ecliptic plane). We show that OH suppression by high dispersion, i.e. `resolving out' the skylines, cannot obtain the required level of sensitivity to reach the interline continuum due to scattering of light. The OH lines must be suppressed prior to dispersion. We have simulated observations employing fibre Bragg gratings of first light objects, high redshift galaxies and cool, low-mass stars. The simulations are of complete end-to-end systems from object to detector. The results demonstrate that fibre Bragg grating OH suppression will significantly advance our knowledge in many areas of astrophysics, and in particular will enable rest-frame ultra-violet observations of the Universe at the time of first light and reionisation. Comment: Accepted for publication in MNRAS
    Monthly Notices of the Royal Astronomical Society 01/2008; 386(1). DOI:10.1111/j.1365-2966.2008.13021.x · 5.11 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present FLEX, an instrument to demonstrate the power of fibre Bragg grating OH suppression. This ground breaking technology promises great gains in sensitivity for near infrared instrumentation and the time is now right for a pioneer instrument to prove the effectiveness of the technique. Our proposal is for an adaptive optics fed integral field unit for an 8 metre class telescope. We envisage a 61 element IFU with 0.22" sampling and a 2.2" field of view. J and H-band OH suppression units would cleanly suppress the atmospheric emission lines, effectively lowering the sky background by 3 or 4 magnitudes respectively. The capabilities of FLEX will make it ideal for deep Epoch of Reionisation studies, as well as studies of star formation at z~1-4. To enable rapid and economical deployment FLEX would use an existing near infrared spectrograph with R ≈ 1000 and employ facility adaptive optics.
    Proceedings of SPIE - The International Society for Optical Engineering 08/2008; DOI:10.1117/12.788629 · 0.20 Impact Factor
Show more