Generation of mid-infrared radiation in the highly-absorbing nonlinear medium

Summary form only given. There exists a great interest in an efficient source of mid-infrared (MIR) radiation between 3 /spl mu/m and 10 /spl mu/m and there are a number of nonlinear materials such as lithium niobate, GaSe, and others with large nonlinear coefficients in this range. Unfortunately, in all these materials the MIR experience strong absorption which severely limits the range where it can be generated efficiently. For example, in lithium niobate, at 5.4 /spl mu/m the absorption reaches 7 cm/sup -1/ and the efficiency of frequency conversion is reduced by an order of magnitude. We propose a new method for difference frequency generation and parametric generation based on coupling the MIR wave out of the LiNbO/sub 3/ absorbing material into the adjacent linear waveguide before it gets absorbed.