Generation and manipulation of infrared light using quasi-phasematched devices: ultrashort-pulse, aperiodic-grating and guided-wave frequency conversion


Nonlinear optical frequency conversion is often used to extend the useful wavelength range of available laser sources - and has been employed commercially for decades. However, in many cases, inadequate properties of conventional nonlinear materials have prevented the application of frequency conversion to low power laser sources. Recent advances in nonlinear materials, particularly those making use of the quasi-phasematching (QPM) technique, have enabled the generation of an increasing range of wavelengths with improved efficiencies. Peri­ odically (or aperiodically) poled lithium niobate (PPLN) is the most successful of the QPM- based materials, not only offering high efficiencies and wavelength versatility, but also enabling nonlinear frequency conversion interactions which are impossible with conventional materials.
In this thesis, I will describe several experiments which demonstrate frequency conversion using sub-picosecond (<10e-12 seconds) pulses with bulk PPLN as the nonlinear material. Both second harmonic generation (SHG) and tunable optical parametric generation (OPG) are described. Significantly greater efficiencies and/or lower thresholds are achieved with PPLN than are possible with conventional materials.
Then, I will describe an entirely new nonlinear optical process. This interaction, which relies on aperiodic QPM structures, is capable of simultaneous frequency conversion and compression of optical pulses. First, I detail the theoretical background for this interaction. Second, I describe experiments which show efficient conversion from 1560 to 780 nm while compressing pulses from 17 ps to 110 fs.
Finally, I will describe results of experiments employing annealed proton exchanged (APE)-PPLN waveguides for frequency conversion with even greater efficiencies. The 380-pJ-threshold OPG device that I demonstrated has a threshold which is two orders of magnitude below that of our bulk PPLN OPG device and four orders of magnitude below that of any other published OPG result in any material system in any geometry.


Mark Alan Arbore


June, 1998