Andrey A. Boyko

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.

LaserBreeze gas analyzer for noninvasive diagnostics of air exhaled by patients

A laser gas analyzer has been designed for determining the composition of exhaled air by means of photoacoustic spectroscopy. The analyzer, based on a broadband optical parametric oscillator and photoacoustic detector, provides high-precision rapid analysis of the multicomponent composition of human exhaled air for dynamic estimation of the efficiency of treating bronchus and lung diseases.

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.

Mercury thiogallate nanosecond optical parametric oscillator continuously tunable from 4.2 to 10.8 μm

We demonstrate an optical parametric oscillator based on two HgGa2S4 crystals with an extremely wide tuning range from 4.2 to 10.8 μm. The HgGa2S4 optical parametric oscillator was pumped by a Q-switched nanosecond Nd : YLF laser at 1.053 μm. The absorption spectrum of ammonia was presented to demonstrate the feasibility of the developed optical parametric oscillator system for spectroscopic measurements and gas detection.

Continuously wavelength tuned optical parametric oscillator based on fan-out periodically poled lithium niobate

A PC-controlled optical parametric oscillator (OPO) based on fan-out periodically poled lithium niobate (MgO : PPLN) structures was developed. Continuous wavelength tuning (2.40–3.85 μm) was realized via linear displacements of fan-out MgO : PPLN structures using a PC-controlled precision motorized translation stage. The total wavelength scanning time in the range of 2.40–3.85 μm was ≤1 min. The OPO was developed as a source of tunable radiation for use in a laser photo-acoustic gas analyzer. Studies of the methane absorption spectrum showed a good coincidence of the experimental and theoretical data.

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.

LiGaSe2 optical parametric oscillator pumped by a Q-switched Nd:YAG laser

Optical parametric oscillation is demonstrated for the first time with the chalcogenide nonlinear crystal LiGaSe2 pumped by a nanosecond Nd:YAG laser. Angle tuning provides coverage of the 4.8–9.9 µm spectral range in the mid-IR by idler pulses.

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.