Potential of P1 organic crystal for compact SHG green laser

• P1 organic crystal in which CT axis leans against x-axis enables phase matching properties.
• SH power for type I non-collinear phase matching was measured by using a small crystal.
• These P1 crystals are high-promising for single-pass or intra-cavity green SHG device.

The potential of P1 organic crystal for compact green SHG laser is reported. One sample of P1 nonlinear optical (NLO) organic material, (-)-1-(4-dimethylaminophenyl)-2-(-hydeoxypropyopylamino)-cyclobutene-3,4-dione, was investigated by using a non-collinear phase matching method. The effective NLO coefficients (deff) for type I were estimated using the size of 3×2×0.190 mm3. The maximum of the deff is theoretically estimated to be - 440 pm/V at the incident angle φ1=148° and φ2=152°. The deff in another angle that the light can be incident into the crystal, is experimentally estimated to be 90 pm/V, as a result the second harmonic wave generates 4.8 mW at 532 nm for a fundamental power of 62.8 W with the interaction length of 0.195 mm, compared to a theoretical value of 103.9 pm/V. The experimentally obtained value is extremely large deff in the range that is transparent in the green light and more than 10 times of PPKTP used as SHG material of compact green laser. The deff of P1 organic crystal, DAD, was discussed compared to the reports of Zyss et al., and the application to SHG green laser is discussed compared to PPKTP of inorganic crystal.