Dmitry B. Kolker

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.

Screening of patients with bronchopulmonary diseases using methods of infrared laser photoacoustic spectroscopy and principal component analysis

Abstract. A human exhaled air analysis by means of infrared (IR) laser photoacoustic spectroscopy is presented. Eleven healthy nonsmoking volunteers (control group) and seven patients with chronic obstructive pulmonary disease (COPD, target group) were involved in the study. The principal component analysis method was used to select the most informative ranges of the absorption spectra of patients’ exhaled air in terms of the separation of the studied groups. It is shown that the data of the profiles of exhaled air absorption spectrum in the informative ranges allow identifying COPD patients in comparison to the control group.

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.

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.

3.9-μm Optical parametric oscillator based on MgO:PPLN pumped at 1966 nm using a high-repetition-rate Tm 3+ :Lu 2 O 3 ceramic laser

Mid-infrared coherent sources at 3–4 μm have a wide variety of applications that include, but are not limited to gas sensing, material processing and production control. The MgO-doped periodically poled lithium niobate (MgO:PPLN) crystal is a well-known nonlinear element for quasi-phase-matched optical parametric oscillators (OPOs) typically pumped by 1-μm laser radiation [1]. However, strong multi-phonon absorption losses at wavelengths above 4 μm limit the use of MgO:PPLN for mid-IR OPO applications [2-4].

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.

Wide tunable BaGa 4 Se 7 optical parametric oscillator pumped by Nd:YLF laser

BaGa₄Se₇ optical parametric oscillator (OPO) pumped by compact nanosecond Nd:YLF laser was demonstrated. Wide tuning range from 2.93 up to 9.3 μm is shown for the first time of our knowledge.

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 ...