Broadband difference frequency generation around phase-match singularity

It is shown that a wide tunability range of greater than 500 nm can be obtained in the 2 μ m band in an 18 mm long periodically poled lithium niobate chip with a single qquasiphase-matching grating period at a constant temperature. This letter demonstrates the difference frequency generation bandwidth. A tunable bandwidth of over 130 nm is experimentally confirmed in the 2 μ m region. This broad bandwidth can be realized by means of the phase-match curve distortion caused by the phase-match singularity. The wavelength conversion temperature dependence is also shown for several quasiphase-matching grating periods. © 2005 American Institute of Physics.