Increased temperature bandwidth of second harmonic generator using two KTiOPO4 crystals cut at different angles

We report a second harmonic generator (SHG), whose temperature full-width of half-maximum (FWHM) bandwidth is significantly increased by replacing a single long type-II phase-matched KTiOPO4 (KTP) crystal with two shorter crystals, which are cut at slightly different phase-matching angles. The total length of the two crystals is the same as that of the longer ones. The experimental results show that the measured temperature FWHM bandwidth of the SHG is significantly increased from 11.8 °C in the single 7 × 7 × 10 mm3 KTP crystal to 60.2 °C when the single KTP is replaced with two of 7 × 7 × 5 mm3 KTP crystals whose phase-matching angle are 1.0° apart. Such a SHG allows stable output when it is operated in the environment of very rough temperature condition.