Albert F. Nieuwenhuis

High-efficiency mid-infrared ZnGeP2 optical parametric oscillator directly pumped by a lamp-pumped, Q-switched CrTmHo:YAG laser

We report a singly resonant optical parametric oscillator (SRO) based on a ZnGeP(2) crystal directly pumped by a lamp-pumped Q-switched CrTmHo:YAG laser. The IR was tunable from 4.7 to 7.8 microm via crystal angle tuning. A maximum optical to optical efficiency of 56% was obtained from the pump (2.09 microm) 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 M(2) parameter, was 1.38 when the SRO was pumped at 2.5 times threshold. These results show that ZnGeP(2) optical parametric oscillators directly pumped by a CrTmHo:YAG laser can be operated efficiently, while maintaining good IR beam quality.

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.

Incoherently pumped continuous wave optical parametric oscillator broadened by non-collinear phasematching

In this paper, we report on a singly resonant optical parametric oscillator (OPO) pumped by an amplified spontaneous emission (ASE) source. The pump focusing conditions allow non-collinear phasematching, which resulted in a 230 nm (190 cm(-1)) spectral bandwidth. Calculations indicate that such phasematching schemes may be used to further broaden OPO spectral bandwidths.

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.

Redox cycling without reference electrodes

The reference electrode is a key component in electrochemical measurements, yet it remains a challenge to implement a reliable reference electrode in miniaturized electrochemical sensors. Here we explore experimentally and theoretically an alternative approach based on redox cycling which eliminates the reference electrode altogether. We show that shifts in the solution potential caused by the lack of reference can be understood quantitatively, and determine the requirements for accurate measurements in miniaturized systems in the absence of a reference electrode.

Application of mid-infrared attenuated total reflectance spectroscopy using broadly tunable OPOs

A singly resonant optical parametric oscillator based on MgO:PPLN is used as a tunable light source for attenuated total reflectance spectroscopy. Because of high emitted power spectral densities, diluting the sample can be avoided.