Highly efficient, high average power, narrowband, pump-tunable BWOPO.

We demonstrate a continuously tunable mid-infrared source that produces narrowband radiation at 1981 nm and 2145 nm based on a tunable Yb-based hybrid MOPA pump and a backward-wave optical parametric oscillator (BWOPO). The BWOPO employs a PPRKTP crystal with 580 nm domain periodicity. The BWOPO has a record-low oscillation threshold of 19.

Range-resolved detection of boundary layer stable water vapor isotopologues using a ground-based 1.98 µm differential absorption LIDAR.

This paper presents a first demonstration of range-resolved differential absorption LIDAR (DIAL) measurements of the water vapor main isotopologue H O and the less abundant semi-heavy water isotopologue HDO with the aim of determining the isotopic ratio. The presented Water Vapor and Isotope Lidar (WaVIL) instrument is based on a parametric laser source emitting nanosecond pulses at 1.98 µm and a direct-detection receiver utilizing a commercial InGaAs PIN photodiode.

Long-wave infrared multi-wavelength optical source for standoff detection of chemical warfare agents.

We have designed and built a wavelength-tunable optical source for standoff detection of gaseous chemicals by differential absorption spectrometry in the long-wave infrared. It is based on a nanosecond 2 µm single-frequency optical parametric oscillator, whose idler wave is amplified in large aperture Rb:PPKTP crystals. The signal and idler waves are mixed in crystals to produce single-frequency tunable radiation in the 7.

Actively Q-switched tunable single-longitudinal-mode 2 µm Tm:YAP laser using a transversally chirped volume Bragg grating.

A pulsed, single longitudinal mode, wavelength-tunable Tm:YAP laser is reported. We demonstrate 1 kHz stable operation with 230 µJ, 50 ns pulses and a spectrum linewidth narrowed below 4 pm (FWHM) close to the Fourier transform limit by use of a volume Bragg grating and a YAG etalon. The output wavelength was tuned from 1940 to 1960 nm owing to a transverse chirp of the period of the Bragg grating.

Wavelength tunable, single-longitudinal-mode optical parametric oscillator with a transversally chirped volume Bragg grating.

We report on single-longitudinal-mode (SLM) operation of a low-threshold optical parametric oscillator, with a 17 nm tunability near 2 µm. The oscillator uses a MgO:PPLN crystal in Type 0 quasi-phase-matching configuration, pumped by a 1.064 µm SLM laser.

Quartz Enhanced Photoacoustic Spectroscopy Based on a Custom Quartz Tuning Fork.

We have designed and fabricated a custom quartz tuning fork (QTF) with a reduced fundamental frequency; a larger gap between the prongs; and the best quality factor in air at atmospheric conditions ever reported, to our knowledge. Acoustic microresonators have been added to the QTF in order to enhance the sensor sensitivity. We demonstrate a normalized noise equivalent absorption () of 3.

Spectrotemporal dynamics of a picosecond OPO based on chirped quasi-phase-matching: erratum.

This erratum is to correct an error made in our paper [Opt. Lett.40, 280 (2015)OPLEDP0146-959210.

Atmospheric boundary layer CO remote sensing with a direct detection LIDAR instrument based on a widely tunable optical parametric source.

We report on the capability of a direct detection differential absorption lidar (DIAL) for range resolved and integrated path (IPDIAL) remote sensing of CO in the atmospheric boundary layer (ABL). The laser source is an amplified nested cavity optical parametric oscillator (NesCOPO) emitting approximately 8 mJ at the two measurement wavelengths selected near 2050 nm. Direct detection atmospheric measurements are taken from the ground using a 30 Hz frequency switching between emitted wavelengths.

Wide and fast dispersion tuning of a picosecond OPO based on aperiodic quasi-phase matching using an axially chirped volume Bragg grating.

We report on a widely tunable synchronously pumped picosecond optical parametric oscillator (OPO) combining an aperiodically poled MgO-doped LiNbO crystal as a broadband gain medium and an axially chirped volume Bragg grating as a spectral filtering dispersive element. Translation of the Bragg grating along the beam axis enables wavelength tuning over 215 nm around 3.82 μm and provides spectral narrowing.

Rapidly tunable optical parametric oscillator based on aperiodic quasi-phase matching.

A new optical parametric oscillator (OPO) architecture with high tuning speed capability is demonstrated. This device exploits the versatility offered by aperiodic quasi-phase matching (QPM) to provide a broad parametric gain spectrum without changing the temperature, angle, or position of the nonlinear crystal. Rapid tuning is then straightforwardly achieved using a fast intracavity spectral filter.

Dual-wavelength source from 5%MgO:PPLN cylinders for the characterization of nonlinear infrared crystals.

We conceived a unique fully parametric source based on two independent cylindrical OPOs simultaneously pumped by the same Nd:YAG laser. Each OPO delivers more than 2 mJ and is continuously tunable between 1.41 µm and 4.

Tunable optical parametric amplification of a single-frequency quantum cascade laser around 8 μm in ZnGeP2.

We demonstrate optical parametric amplification in ZnGeP(2) (ZGP) of the radiation emitted by a single-frequency continuous-wave quantum cascade laser (QCL) in the range 7.8-8.4 μm.

Microsecond fiber laser pumped, single-frequency optical parametric oscillator for trace gas detection.

We report on the first microsecond doubly resonant optical parametric oscillator (OPO). It is based on a nested cavity OPO architecture allowing single longitudinal mode operation and low oscillation threshold (few microjoule). The combination with a master oscillator-power amplifier fiber pump laser provides a versatile optical source widely tunable in the 3.

Application of self-regulation theory and motivational interview for improving oral hygiene: a randomized controlled trial.

Aim: Because patient adherence to oral hygiene is essential for periodontal treatment success, the aim of the study was to assess whether a motivational interview addressing the five dimensions of Leventhal's theory performed better than conventional basic instruction on improving compliance with plaque control among patients with periodontitis.

Materials And Methods: A randomized controlled clinical trial design was used in which a group of patients underwent a motivational interview in addition to classical consultation. A control group received only the standard consultation.

Picosecond tunable mode locking of a Cr2+:ZnSe laser with a nonlinear mirror.

We report on a nonlinear mirror (NLM) scheme that enables, for the first time to the best of our best knowledge, tunable mode locking of a Cr2+:ZnSe laser in the picosecond regime. The NLM-used as the output coupler of the laser cavity-consists of a periodically poled lithium niobate (PPLN) crystal with a fan-out grating coupled with a dichroic mirror and a wedged dispersive YAG plate. The Cr2+:ZnSe laser, pumped by a CW thulium-doped fiber laser, delivers 85 ps pulses at a repetition rate of 220 MHz with a 300 mW average power.

Management of thermal effects in high-repetition-rate pulsed optical parametric oscillators.

We report on the investigation of thermal effects in high-repetition-rate pulsed optical parametric oscillators emitting in the mid-IR. We find that the thermal load induced by the nonresonant idler absorption plays a critical role in the emergence of thermally induced bistability. We then demonstrate a significant improvement of the conversion efficiency (more than 30%) when a proper axial temperature gradient is applied to the nonlinear crystal by use of a two-zone temperature-controlled oven.

Second order coherence of broadband down-converted light on ultrashort time scale determined by two photon absorption in semiconductor.

We study the photon correlation properties of broadband parametric down-converted light. The measurement of the photon correlation is carried out thanks to a modified Hanbury Brown-Twiss interferometer based on two photon absorption in GaAs detector. Since this method is not affected by the phase matching conditions of the detecting apparatus (so called "final state post-selection"), the detection bandwidth can be extremely large.

Picosecond synchronously pumped ZnGeP2 optical parametric oscillator.

We report on the experimental operation of a picosecond, singly resonant, synchronously pumped optical parametric oscillator (SPOPO) based on a ZnGeP(2) (ZGP) crystal. The ZGP SPOPO is pumped with the idler radiation from a diffraction-grating-tuned periodically poled lithium niobate SPOPO emitting a continuous picosecond pulse train (Delta tau approximately 8 ps, f=76 MHz). The noncritically 90 degree phase-matched ZGP SPOPO is tuned in the 3.

High-energy single-longitudinal mode nearly diffraction-limited optical parametric source with 3 MHz frequency stability for CO2 DIAL.

We report on a 2.05 microm nanosecond master oscillator power amplifier optical parametric source for CO2 differential-absorption lidar. The master oscillator consists of an entangled-cavity nanosecond optical parametric oscillator based on a type II periodically poled lithium niobate crystal that provides highly stable single-longitudinal-mode radiation.

Fresnel phase matching: exploring the frontiers between ray and guided wave quadratic nonlinear optics.

Fresnel phase matching is a convenient and universal way to phase match nonlinear three-wave mixing by total internal reflection in isotropic materials like common semiconductors. This technique makes use of the large relative phase lag between the interacting waves at total internal reflection, and was suggested by the nonlinear optics pioneers in the 70's; it has been worked out by several teams since then but, quite unexpectedly, has never succeeded in producing enough parametric gain to achieve optical parametric oscillation. We show that this failure stems mostly from a basic law of nonlinear reflection, which leads to a spatial walk-off between the pump and the generated parametric waves, resulting in unexpected destructive interference patterns between the waves while bouncing back and forth between the interfaces.

Passively mode-locked slow pump optical parametric oscillators.

We predict that employing a Bragg grating to simultaneously phase match and induce large temporal walk-off between the signal and slow propagating pump in a nonlinear crystal can be conducive to development of passively mode locked optical parametric oscillators in which cw near-infrared pump is efficiently converted into short middle-infrared pulses.

Generation of mid-infrared radiation by self-difference frequency mixing in chromium-doped zinc selenide.

We report what we believe to be the first demonstration of mid-infrared generation (approximately 9 microm) by self-difference frequency generation in Fresnel birefringence quasi-phase-matched Cr:ZnSe laser slabs.

Relaxation of the single-mode emission conditions in extended-cavity semiconductor lasers with a self-organizing photorefractive filter.

Commercial 1.55-microm extended-cavity semiconductor lasers provide single-mode operation that can be continuously tuned over a range larger than 100 nm without mode hopping. But such performance requires delicate factory adjustment and high mechanical stability of the external cavity.