Nadezhda Y. Kostyukova

Intracavity-pumped, cascaded AgGaSe 2 optical parametric oscillator tunable from 5.8 to 18 µm

A AgGaSe2 nonlinear crystal placed in a coupled cavity is intracavity pumped by the ~1.85-µm signal pulses of a 1.064-µm pumped Rb:PPKTP doubly-resonant optical parametric oscillator (OPO) operating at a repetition rate of 100 Hz. Using two samples cut for type-I and II phase-matching, the overall idler tunability of the singly-resonant AgGeSe2 OPO covers an unprecedented spectral range from 5.8 to ~18 µm in the mid-IR.

Rb:PPKTP optical parametric oscillator with intracavity difference-frequency generation in AgGaSe 2 .

A 1.064-μm pumped Rb:PPKTP optical parametric oscillator (OPO) generates mid-IR radiation by intracavity mixing the signal and idler in AgGaSe<inf>2</inf>. The ∼6-ns pulses at ∼7 μm have an energy of 565 μJ at 100 Hz.

Exhaled air analysis using wideband wave number tuning range infrared laser photoacoustic spectroscopy

Abstract. The infrared laser photoacoustic spectroscopy (LPAS) and the pattern-recognition-based approach for noninvasive express diagnostics of pulmonary diseases on the basis of absorption spectra analysis of the patient’s exhaled air are presented. The study involved lung cancer patients (N=9), patients with chronic obstructive pulmonary disease (N=12), and a control group of healthy, nonsmoking volunteers (N=11). The analysis of the measured absorption spectra was based at first on reduction of the dimension of the feature space using principal component analysis; thereafter, the dichotomous classification was carried out using the support vector machine. The gas chromatography–mass spectrometry method (GC–MS) was used as the reference. The estimated mean value of the sensitivity of exhaled air sample analysis by the LPAS in dichotomous classification was not less than 90% and specificity was not less than 69%; the analogous results of analysis by GC–MS were 68% and 60%, respectively. Also, the approach to differential diagnostics based on the set of SVM classifiers usage is presented.

Intracavity difference-frequency mixing of optical parametric oscillator signal and idler pulses in BaGa_4Se_7

An overall quantum conversion efficiency of 7.8% is achieved by intracavity mixing the signal and idler of a 1.064 μm pumped Rb:PPKTP optical parametric oscillator in BaGa4Se7. In this way, a pulse energy of ∼0.71  mJ is generated at ∼7  μm for a repetition rate of 100 Hz. Tuning of the mid-IR radiation is demonstrated by heating of the Rb:PPKTP crystal.

Rb:PPKTP optical parametric oscillator with intracavity difference-frequency generation in temperature-tuned OPGaAs

Recently we investigated cascaded schemes for down-conversion to the mid-IR spectral range above 5 μm by implementing the second stage based on a non-oxide nonlinear crystal inside the cavity of a ns optical parametric oscillator (OPO) based on Rb:PPKTP, pumped by a Q-switched Nd:YAG laser [1-3]. Intracavity difference-frequency generation (DFG) [2, 3] turned out to be more efficient compared to intracavity pumped OPO [1], however wavelength tuning is restricted and a broadband dichroic half-wave plate is needed for either type-I or type-II phase-matching in the studied crystals of AgGaSe2 and BaGa4Se7. Low-symmetry cubic semiconductors, such as orientation-patterned GaAs offer greater variety of phase-matching configurations in which intracavity polarization rotation becomes redundant. With a similar spectral coverage of up to ∼18 μm and 2 to 3 times higher effective nonlinearity, OPGaAs exhibits 50 to 100 times higher thermal conductivity, better damage resistivity, and offers the unique possibility of convenient temperature tuning in both stages in non-critical configurations. These advantages point at possible extensions to much higher repetition rates (1–100 kHz). On one hand such low energy regimes will utilize perfectly the limited aperture of the presently available OPGaAs samples but on the other hand will enable the generation of unprecedented average powers in the mid-IR spectral range. In a first demonstration of such intracavity DFG we implement OPGaAs in the same Rb:PPKTP OPO operated at 100 Hz [1-3], using tighter focusing.

Frequency down-conversion of 1 μm laser radiation to the mid-IR using non-oxide nonlinear crystals in a cascaded intracavity configuration

A singly-resonant OPO (SRO) based on AgGaSe2 (AGSe) intracavity pumped at ~1.85 μm by the signal pulses of a Rb:PPKTP doubly-resonant OPO (DRO) provided extremely broad tuning (5.8 to ~18 μm) for the non-resonated idler. In a similar set-up with the same nonlinear crystals, we studied intracavity difference-frequency generation (DFG). Both AGSe and the new monoclinic crystal BaGa4Se7 (BGSe) generated single pulse energies of ~0.7 mJ near 7 μm at an overall conversion efficiency from the 1.064 μm pump of 1.2%. The main advantage of BGSe is its damage resistivity up to the maximum pump levels applied at 100 Hz.

Widely Tunable (2.2 - 10.4 mm) BaGa_4Se_7 Optical Parametric Oscillator Pumped by a Q-switched Nd:YLiF_4 Laser

We report on the first BaGa4Se7 nanosecond optical parametric oscillator pumped by Q-switched Nd:YLiF4 laser at 1053nm. Mid-infrared idler wave tuning from 2.2 µm to 10.4 µm is demonstrated with an angle-tuned type-I (o-ee) y-cut sample.

Breath air measurement using wide-band frequency tuning IR laser photo-acoustic spectroscopy

The results of measuring of biomarkers in breath air of patients with broncho-pulmonary diseases using wide-band frequency tuning IR laser photo-acoustic spectroscopy and the methods of data mining are presented. We will discuss experimental equipment and various methods of intellectual analysis of the experimental spectra in context of above task. The work was carried out with partial financial support of the FCPIR contract No 14.578.21.0082 (ID RFMEFI57814X0082).

Intracavity-Pumped, Cascaded AgGaSe 2 Optical Parametric Oscillator Tunable up to 18 µm

We report on a AgGaSe2 optical parametric oscillator (OPO), intracavity pumped by the 1.85-μm signal pulses of a 1.064-μm pumped Rb:PPKTP OPO. It operates at 100 Hz with idler tunability from ~8 to ...

Widely Tunable in the Mid-IR BaGa 4 Se 7 Optical Parametric Oscillator Pumped at 1064 nm

A BaGa4Se7 optical parametric oscillator shows extremely wide idler tunability (2.7-17 µm) under 1.064-µm pumping. The ~10-ns pulses at ~7.2 µm have an energy of 3.7 mJ corresponding to a quantum conversion efficiency of 40%.