Doubling of the emission frequency of CO lasers with an efficiency of 3%

Mode-locked CO laser frequency doubling in ZnGeP2 with 25% efficiency

“…Frequency converted spectrum contained more than 110 emission lines in 2.53 -2.85 μm spectral range. The minimal wavelength 2.53 μm of the frequency converted lines was shorter than 2.65 μm reported in [14] and the most powerful SHG emission line was at the wavelength ∼ 2.6 μm. The excess number of the frequency converted lines to those of the pump spectrum was due to the fact that frequency conversion run simultaneously for both SHG and sum frequency generation of different pairs of the CO laser lines.…”

“…Later ZnGeP 2 was applied for efficient SHG and fourth harmonic generation of different kinds of CO 2 lasers: from continuous wave (CW) to nanosecond pulsed lasers [10,11]. It was also applied for SHG generation of CW and Q-switched CO lasers [12][13][14], sum frequency generation of CO and CO 2 laser emissions [15,16], and far-IR or THz generation [17]. Application of ZnGeP 2 for frequency conversion of IR radiation appears to be advantageous over other nonlinear crystals such as AgGaSe 2 and others [18,19], which stipulated our choice for our experiments on frequency conversion of CO laser radiation.…”

“…The excess number of the frequency converted lines to those of the pump spectrum was due to the fact that frequency conversion run simultaneously for both SHG and sum frequency generation of different pairs of the CO laser lines. The bandwidth of SHG non-critical spectral phase matching was as wide as ∼ 200 cm −1 [14], which resulted in SHG phase matching for all pump lines simultaneously.…”