Petrus J.M. van der Slot

Mid-Infrared ZGP optical parametric oscillator directly pumped by a lamp-pumped, Q-switched Cr,Tm,Ho:YAG laser

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.

One-Watt level mid-IR output, singly resonant, continuous-wave optical parametric oscillator pumped by a monolithic diode laser

We report more than 1.1 Watt of idler power at 3373 nm in a singly resonant optical parametric oscillator (SRO), directly pumped by a single-frequency monolithic tapered diode laser. The SRO is based on a periodically poled MgO:LiNbO3 crystal in a four mirror cavity and is excited by 8.05 W of 1062 nm radiation. The SRO pump power at threshold is 4 W. The internal slope-efficiency and conversion efficiency reach 89% and 44% respectively. The signal and idler waves are temperature tuned in the range of 1541 to 1600 nm and 3154 to 3415 nm respectively. To the best of our knowledge, this is the highest output obtained for a diode pumped optical parametric oscillator (OPO), and the first time a SRO is directly pumped by a monolithic tapered diode laser.

Ellipsometry with randomly varying polarization states

We show that, under the right conditions, one can make highly accurate polarization-based measurements without knowing the absolute polarization state of the probing light field. It is shown that light, passed through a randomly varying birefringent material has a well-defined orbit on the Poincar sphere, which we term a generalized polarization state, that is preserved. Changes to the generalized polarization state can then be used in place of the absolute polarization states that make up the generalized state, to measure the change in polarization due to a sample under investigation. We illustrate the usefulness of this analysis approach by demonstrating fiber-based ellipsometry, where the polarization state of the probe light is unknown, and, yet, the ellipsometric angles of the investigated sample (Ψ and Δ) are obtained with an accuracy comparable to that of conventional ellipsometry instruments by measuring changes to the generalized polarization state.