Miniaturized transmission grating laser at 1.55 μm with 128-nm tuning range

We report a transmission grating-based external-cavity diode laser operating at around 1.55 μm. The laser wavelength is tunable over a range of 128 nm, covering the entire S- and C-bands of optical telecommunications. A transmission grating in Littrow geometry yields a compact and stable laser without the drawback of beam direction variation while tuning the wavelength. High output power, wide tuning range, and high spectral purity make the laser suitable for the purposes of optical telecommunications, metrology, and spectroscopy. To optimize the laser performance, we have studied the transmission grating sensitivity to fabrication errors. The effects of variations on the grating parameters have been studied numerically and experimentally. Transverse magnetic polarization was found, in general, to be less sensitive to such variations than transverse electric polarization.