Multiple distributed feedback operation at 1.55 μm with uniform output powers in a single laser diode

Abstract
We demonstrate in a single laser diode the simultaneous operation on different wavelengths around 1.55 μm while preserving the spectral distributed feedback selection mechanism for each wavelength. The grating that exists all along the cavity is a multiwavelength grating obtained by the linear transfer of superimposed multiple holographic exposures. Such a grating acts as a reflectivity comb, the action of each reflector being uniformly distributed all along the cavity. Thanks to a clever incorporation of a phase shift, the lasing wavelengths are deterministically placed on the Bragg modes. The equal strengths of the different spatial frequencies of the grating translate into uniform optical output powers on the simultaneous lasing modes.