Realization of a High Power MWIR Laser with Coherently Combined Emitters

We propose a technology for coherent combination of 36 high power diode lasers at ~4.9 micron , each with a CW power of ~5W. The underlying principle behind this approach was demonstrated by us earlier [Optics Letter, 30, 3012-3014 (2005)]. Briefly, we will split a beam from a master diode laser into multiple copies using angularly multiplexed gratings, written using light at 532 nm. These copies will then be used to injection-lock an array of diode lasers. Due to time reversal symmetry of Maxwells equations, the injection-locked beams, upon going back through the grating, will combine coherently, with the phase of each one properly adjusted, by using a PZT placed behind each laser. A beam splitter with a reflectivity of 95%, placed between the master laser and the grating, will redirect the combined beam as the output. We will use dye doped PMMA, which has vanishingly small absorption at 4.9 micron, as the holographic substrate. Under Phase I, we will develop a concrete design for the combiner, and demonstrate a proof-of-principle coherent combiner for 4 lasers at 4.9 micron wavelength. A full combiner with 36 lasers will be demonstrated in Phase 2, with a total power of ~144 W.