Quasi-Phase-Matched Structures for High Average Power Nonlinear Optics

Many scientific and commercial applications of nonlinear optics are frustrated by the lack of suitable nonlinear optical (NLO) crystals. It may be possible to significantly change this situation by altering the basic approach from conventional phase matching to quasi-phase-matching (QPM). QPM involves alternating regions of nonlinear material, such that efficient 3-wave mixing is achieved without conventional phase matching. If a practical implementation of QPM were developed, then harmonic generation (SHG/THG) from CO2 laser radiation and mid-infrared (mid-IR) pumped optical parametric oscillators and amplifiers (OPOs/OPAs) would be able to produce broadly tunable radiation across the infrared (IR) wavelength spectrum. Previous research programs have demonstrated the feasibility of QPM. QPM structures, using crystals with high thermal conductivities and low absorption would be ideal for high average power applications. In addition, the structures typically increase the temperature and angular acceptance bandwidths. Cleveland Crystals would explore the development of two different QPM structures: non-monolithic fabricated structures and "twinned" monolithic crystal structures. Both techniques are high risk, high-payoff technologies. HAP CO2 SHG systems would be studied using numerical/analytic thermo-optical modeling. For both commercial and DOD applications, a CO2 or mid-IR pump laser combined with a QPM structure could provide a selectable-fixed-frequency, limited or broadly tunable, HAP IR laser system. HAP CO2 driven QPM structures could provide the source for various DOD mid-IR systems. The previous demonstrations of feasibility, the opportunity to explore two distinct technical approaches and the large benefit that would derive from building practical QPM structures provide the incentive for this Phase I proposal. The goal of this program would be the development of QPM structures to provide a viable alternative material for DOD's NLO applications. OPTION: None submitted.