5†µm CW Ce3+-doped chalcogenide glass fiber laser with 17% slope efficiency.

Efficient room temperature mid-infrared laser action in a Ce3+-doped chalcogenide fiber was demonstrated. The fiber had a doped selenide glass core in an undoped sulfide glass cladding. The pump source was a CW Fe2+:ZnSe laser emitting at 4.14 µm. The optimized fiber length allowed obtaining up to 7 mW of 5.06 µm output with 17% slope efficiency at room temperature.

Passively Q-switched 5-µm Ce3+-doped selenide glass laser using Fe:CdTe and Fe:CdSe as saturable absorbers.

The first, to the best of our knowledge, mid-infrared Q-switched Ce3+-doped glass laser is demonstrated. As saturable absorbers, Fe2+:CdSe and Fe2+:CdTe are used for the first time. When Q-switched by Fe:CdSe, the laser operates in a multi-pulse regime with an individual pulse width of 110 ns, centered at λ = 5.20 µm. With Fe:CdTe as saturable absorber, 1-3 giant pulses of 30 ns pulse width are generated at λ = 5.13 µm.

Resonantly pumped Ce3+ mid-infrared lasing in selenide glass.

In high purity Ce3+-doped selenide glass pumped by a 4.08 µm Fe:ZnSe laser, 5.1-5.5 µm laser oscillations were observed. This is the first evidence of laser action corresponding to the 2F7/2→2F5/2 transition of Ce3+ ions.

Efficient Fe:CdTe laser producing 0.35 J pulses in the 5 µm spectral range.

High-energy laser operation of a Fe2+-doped single-crystal CdTe is demonstrated at the temperature of 77 K. Pumped with 250 µs pulses of a 4.08 µm Fe:ZnSe laser, the Fe:CdTe laser produced a record output of 0.35 J, with a slope efficiency of 44%. A further up-scaling by employing high-energy pump sources is feasible, thus facilitating material-processing applications. The laser was tunable from 4.86 to 5.37 µm. In a nonselective cavity, the laser's central wavelength was 5.03 µm at 77 K, and shifted to 5.23 µm at 215 K. At the later operation point, reachable using a Peltier element, the laser still produced 0.15 J of output energy with an efficiency of 22%.

2 mJ room temperature Fe:CdTe laser tunable from 5.1 to 6.3 µm.

We report a room temperature (RT) operation of a Fe:CdTe laser pumped by a Q-switched 2.94 µm Er:Y3Al2(AlO4)3 laser. The Fe:CdTe laser produced 2 mJ of output energy at λ=5.55 µm with slope efficiency of 16% with respect to absorbed pump energy. With the use of an intracavity prism, the spectral tuning was demonstrated in the 5.1-6.3 µm range, being the longest wavelength tuning achieved for Fe2+:II-VI lasers. The lifetime of the upper laser level was measured to be 530 ns at RT.

Compact, highly efficient, 2.1-W continuous-wave mid-infrared Fe:ZnSe coherent source, pumped by an Er:ZBLAN fiber laser.

In this Letter, we report a compact and robust coherent source, operating in mid-infrared (IR) and based on the Fe:ZnSe chalcogenide gain medium, optically pumped by an Er:ZBLAN fiber laser. The output power of 2.1 W with a 59% slope efficiency with respect to the absorbed pump power at liquid nitrogen cooling is achieved. We show that strong re-absorption at a high pump power and iron ion doping concentrations leads to a continuous tuning of central wavelength from 4012 to 4198 nm. The robustness of a high-power Er:ZBLAN fiber laser combined with prominent spectroscopic properties of Fe:ZnSe media pave the way for the development of a reliable tunable continuous-wave mid-IR sources for scientific and industrial purposes.

Nanosecond-pulsed RT-operating at ~4 µm Fe:ZnSe laser pumped inside the cavity of a LD side-pumped Er:YLF laser.

Characteristics of an Fe:ZnSe laser with a new pump scheme were presented. An Fe:ZnSe crystal was placed inside the cavity of the Er:YLF laser pumped by a bar of laser diodes (LD) emitting at 975 nm. The high power 2.66 µm wave ~50 ns pulses were generated inside the cavity due to passive Q-switching of the Er:YLF laser by an Fe:ZnSe saturated absorber. These pulses pumped the Fe:ZnSe laser. As a result, the pulses with an energy of ~2 µJ at a wavelength around 4 µm and time duration of about 50 ns were generated. The laser operated in periodic-pulsed pump regime at room temperature with a repetition rate up to 200 Hz. The Q-switching pulse repetition rate during the pump pulse ran up to 2.5 kHz.

High-energy thermoelectrically cooled Fe:ZnSe laser tunable over 3.75-4.82 µm.

The characteristics of an Fe:ZnSe laser thermoelectrically cooled to 220 K are described. Output energy of 7.5 J and optical-to-optical efficiency of 30% have been demonstrated in single-shot operation at 4.3 µm with a 2.94 µm Er:YAG pump laser. By using an intracavity prism, continuous tuning from 3.75 to 4.82 µm has been obtained at output energy up to 3.1 J.

Continuous-wave broadly tunable high-power Cr:CdS laser.

We report spectroscopic characteristics and laser properties of the mid-infrared active laser medium Cr2+:CdS. Temperature-dependent absorption, luminescence and lifetime measurements of the 5E exited state allow determination of peak emission cross section value of 1.35 × 10-18 cm2 in σ-polarization at room temperature. Lifetime values vary from 7.6 µs at 8 K to 0.48 µs at 320 K, corresponding to 22 % quantum yield at 285 K. Under Tm-fiber laser pumping, the continuous-wave output reached 1.8 W at 2.5 µm with 35.5 % slope efficiency. With a single CaF2 prism, the CW Cr2+:CdS laser could be tuned from 2.240 to 3.285 µm.

Evaluation of magnetocardiography indices in patients with cardiac diseases.

The purpose of this work was to reveal pathological electrophysiological changes in patients with different cardiological diseases by means of magnetocardiographic (MCG) mapping. MCG mapping was performed with a 7-channel magnetocardiograph without a magnetically shielded room. We divided the 159 subjects studied into seven groups: 44 healthy controls, 42 patients with coronary artery disease (CAD), 11 patients affected with myocardiac infarction (MI), 11 with hypertension (HT), 14 with silent ischemia (SI), 13 with heart failure (HF), 14 with fibrillation (FB), and 10 patients after stunning of coronary arteries (ST). All patients were examined using a standard 12-lead electrocardiogram (ECG), biochemical analyses, and loading tests (bicycle-ergometry); some were also studied by holter monitoring, echocardiography, electrophysiological test, and coronary angiography. Morphological and correlation analyses of MCG maps were performed. Moreover, a number of quantitative MCG indices, which reflect the distribution of the excitation in the heart, were proposed. We observed that some indices demonstrated efficiency in recognition of pathologic activity for 5 diseases: CAD, MI, HT, HF, SI and FB.