The integral field mode is optimised for use in the H- and K-bands, but is available with most of the spectroscopy grisms . The throughput and performance at L and M will be limited by diffraction losses.
Unfortunately, with the IJ grism we are unable to focus the instrument – use with the IJ grism is therefore NOT recommended. We have a similar focus problem with the JH grism, though the situation is less severe. Users may use the JH grism with the IFU, provided the reduced resolution is acceptable.
Note also that because the spectra are initially staggered on the array, the resulting wavelength coverage given by the “scrunched” or spectrally-aligned data is slightly less than with normal long-slit spectroscopy. In other words, about 4% (~35 pixels) is chopped off the red and blue ends of each spectrum.
The spectral resolution with the IFU is equivalent to a 2-pixel slit. See the long-slit spectroscopy pages for further details.