  The astronomical J-band (1.25 micrometres) is a relatively untapped wave-band
in long-baseline infrared interferometry. It allows access to the photosphere
in giant and super-giant stars relatively free from opacities of molecular
bands. The J-band can potentially be used for imaging spots in the 1350 nm
ionised iron line on slowly rotating magnetically-active stars through
spectro-interferometry. In addition, the access to the 1080 nanometres He I
line may probe outflows and funnel-flows in T-Tauri stars and allow the study
of the star-disk interaction.
  We present the progress in the development of a six-inputs, J-band
interferometric beam combiner based on the discrete beam combiner (DBC)
concept. DBCs are periodic arrays of evanescent coupled waveguides which can be
used to retrieve simultaneously the complex visibility of every baseline from a
multi-aperture interferometer. Existing, planned or future interferometric
facilities combine or will combine six or more telescopes at the time, thus
increasing the snapshot uv coverage from the interferometric measurements. A
better uv coverage will consequently enhance the accuracy of the image
reconstruction.
  The component we are currently developing is manufactured in borosilicate
glass using the technique of multi-pass ultrafast laser inscription (ULI),
using a mode-locked Yb:KYW laser at the wavelength of 1030 nm, pulse duration
of 300 fs and repetition rate of 1 MHz. After annealing, the written components
showed a propagation loss less than 0.3 dB/cm and a negligible birefringence at
a wavelength of 1310 nm, which makes the components suitable for un-polarized
light operation. A single mode fiber-to-component insertion loss of 0.9 dB was
measured. Work is currently in progress to characterize the components in
spectro-interferometric mode with white light covering the J-band spectrum.
