We report a singly resonant optical parametric oscillator (SRO) based on a ZnGeP2 crystal directly-pumped by
a lamp-pumped Q-switched CrTmHo:YAG laser. The IR wavelength was tuneable from 4.7 μm to 7.8 μm via
crystal angle tuning. A maximum optical to optical efficiency of 56% was obtained from pump (2.09 μm) to
total IR at a pump energy of 6.5 mJ. The corresponding idler energy was 1.45 mJ. The SRO was measured to
have a slope efficiency of 64% and a threshold of 1 mJ. The spatial beam quality of the idler, characterized by
the M2 parameter, was 1.38 when the SRO was pumped at 2.5 times threshold. These results show that ZnGeP2
OPOs directly pumped by a CrTmHo:YAG laser can be operated efficiently, while maintaining good IR beam
quality. The wide tuning range and a high pulse energy makes this SRO particularly suitable for spectroscopic
applications, and, tests in the field medical application, e.g., for cutting of soft tissue during surgery or corneal
corrections.
We generate mid-infrared pulsed light tunable between 5.6 &mgr;m and 6.6 &mgr;m using an optical parametric oscillator
(OPO) directly pumped by a Cr,Tm,Ho:YAG, Q-switched laser operating at 2.1 &mgr;m. The Holmium laser uses a
RTP Q-switch to produce pulses shorter than 100 ns and energies of up to 42 mJ in a single spatial transverse
mode at a repetition rate of 5 Hz. To our knowledge this is the first report on a lamp pumped Cr,Tm,Ho:YAG
laser using a RTP crystal as an electro-optical Q-switch.
The OPO is based on a ZnGeP2 (ZGP) crystal cut for type I phase matching. The singly resonant OPO
(SRO) uses a linear cavity consisting of two plane mirrors to minimize the required pump flux to reach threshold.
The SRO has a threshold of 2.4 mJ, a maximum idler pulse energy of 3.1 mJ, and is tunable from 5.6 to
6.6 &mgr;m. Operation in this wavelength range, combined with wide tuning and a high pulse energy makes this
SRO particularly suitable for tests in the field medical application, e.g., for cutting of soft tissue during surgery
or corneal corrections.
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