Re: Proč výkonný laser?

Jan Roháč,2025-07-28 12:25:14

To je přesně důvod, proč jsem přestal Osla číst. Jsem tady po delší době a koukám, že je to stále horší. V dnešní době, kdy má i úplný neangličtinář přímý přístup k vědeckým zdrojům, nevidím důvod, proč bych měl číst přežvýkané vědecké články, zabalené do lokálního, propagandistického, umaštěného papíru.

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Re: Proč výkonný laser?

Josef Hrncirik,2025-07-31 15:50:19

10.1016/j.optlastec.2023.110455
The experimental setup is shown in Fig. 1. The BGSe-OPO was pumped by a 1064 nm master oscillator power amplifier (MOPA). The master oscillator is a 808 nm pulsed LD pumped Nd:YAG laser with a plane-parallel cavity structure, which has been reported [30]. The Nd:YAG laser operated at pulse repetition frequency (PRF) of 1 kHz with an electro-optic (EO) Q-switch. The p-polarized beam from the master oscillator passes through the pulsed LD side-pumped Nd:YAG module and a quarter-wave plate (QWP) twice. Then the amplified s-polarized beam is reflected by a polarizing beam splitter (PBS). The pump module was composed of five pulsed 808 nm LD arrays, each with a maximum power of 900 W, and a Nd:YAG rod (0.6 at % doped) with diameter of Φ5 mm and length of 148 mm. The pump power was measured by a thermopile power meter (Newport, 919P-050–26) and the temporal pulse waveform was detected by an InGaAs photodiode (Thorlabs, DET08C). When pump current is set to 40 A, the Nd:YAG MOPA system reached an output power of ∼ 7 W with a pulse width of 5.52 ns.
A half-wave plate (HWP1) and a Brewster polarizer were combined as an energy controller to adjust the pump energy. The 1064 nm pump beam has a large divergence angle after the Brewster window because of the thermal lens effect of the side-pumped Nd:YAG module. A BaF2 based lens, which has a focal length of 500 mm, is utilized to compensate the beam divergence. Then the 1064 nm pump beam passed through an optical isolator (Thorlabs, IO-10-1064VHP) to avoid the possible damage to the Nd:YAG laser from the reflected pump. Additionally, the second half-wave plate (HWP2) was inserted before the BGSe-OPO to adjust the polarization for type I phase-matching. The pump beam before BGSe-OPO had a diameter of ∼ 2.13 mm.
The BGSe-OPO has a linear cavity configuration, consisting two BaF2 planar mirrors M3 (1.064 μm AR and 1.35–1.65 μm & 3.65–4.50 μm HR) and M4 (3.65–4.50 μm AR and 1.064 μm & 1.35–1.65 μm HR). The cavity length was set to 40 mm. The pump double-pass single resonant oscillator (DP-SRO) configuration is used to increase the conversion efficiency and reduce the threshold [31]. The type I phase-matching BGSe crystal used in the experiment has dimensions of 8 mm × 8 mm × 15 mm, cut at θ = 53.6° and φ = 0°. By rotating the crystal, the angle between the optical axis and the pump wave vector could be continuously changed in x-z plane to achieve angular tuning. The crystal was grown by Bridgman-Stockbarger method in Technical Institute of Physics and Chemistry, Chinese Academy of Sciences [24]. Both side of the BGSe crystal was well polished and AR coated for 1.064 μm, 1.3–1.6 μm and 3–5 μm. The transmittance of the AR coated BGSe crystal was measured to be about 84.86 % at 1064 nm. There is no significant change on the transmittance when the temperature raised from 20 °C to 70 °C, so the variation of pump absorption during temperature tuning is negligible. The crystal was mounted in a water-circulating copper sink whose temperature is controlled by a thermostat water bath (Coolum instruments, HX-105). The temperature control accuracy is ± 0.1 °C. The wavelength of the generated mid-IR idler was calculated according to the energy conservation relationship 1/λp = 1/λs + 1/λi and the signal wavelength, which was measured by a spectrometer (Yokogawa, AQ6375). The idler power was measure by a thermal power sensor (Ophir, 3A-FS), covering with a BaF2 mirror (3.65–4.50 μm AR and 1.064 μm & 1.35–1.65 μm HR) to block the near infrared pulse.
maximum output power was measured to be 483 mW under an incident pump power of 5.5 W, corresponding to a pump-to-idler conversion efficiency of 8.78 %. As evident from the plot, the mid-IR idler power increases almost linearly with a slope efficiency of 15.4 %. No trend of saturation was observed under the maximum pump intensity in the experiment. Current literature on high repetition rate 1064 nm laser pumped BGSe-OPO is summarized in Table 1. The 1064 nm laser pumped BGSe-OPO at kHz level repetition rate is first reported in this work. Furthermore, optical damage was observed on the front facet coating of the BGSe when continue enhancing pump power beyond 5.7 W. This corresponds to pump fluence of 0.175 J/cm2 or intensity of 31.7 MW/cm2. In a pump double pass OPO configuration, the peak on-axis values of the pump intensity could be estimated to twice of the incident pump intensity [10]. Accordingly, the laser induced damage threshold is fluence of 0.35 J/cm2 or intensity of 63.4 MW/cm2. The laser induced damage threshold is lower than the results of lower pulse repetition rate laser pumping [19], [32]. It could result from that the laser induced damage threshold decrease with the increase of pulse repetition rate [25]
Fig. 5(c) shows the relationship between average output power and wavelength for angle tuned BGSe-OPO. Typical enhancement of idler power can be observed at normal incidence, corresponding to idler wavelength of 4.18 μm. When the pump beam propagates through BGSe crystal at normal incidence, Fresnel reflection on the facet will provide additional feedback for BGSe-OPO. The general decreasing trend of the idler power at longer wavelengths could be attributed to the reducing of λi-1 dependent parametric gain. On the other hand, the transmittance of BGSe coating decrease with the increase of incidence angle, which would lead to the raise of cavity loss. As a result, it will show a decline in the idler power when the rotation angle of BGSe is large. Similarly, the idler power shows an increasing trend in the shorter wavelength range of 3.77–4.06 μm. Then this trend is gradually canceled by the continual growth of cavity loss resulted from the increasing incidence angle. Besides, the dips around 4.28 μm and 4.71 μm are due to the transmittance drops of output coupler of OPO. Comparing the tuning characteristics of angle tuned BGSe-OPO and temperature tuned BGSe-OPO in this work, it could be found that the angle tuned BGSe-OPO could perform agile tuning across a wide mid-IR range. On the other hand, the temperature tuned BGSe-OPO is free from the cavity loss caused by crystal rotation. So, the temperature tuned BGSe-OPO shows a relatively flatter tunable output curve, which is more conducive to practical applications.
The beam quality factors M2 of idler at normal incidence were measured by the 84/16 knife -edge method. A BaF2 based lens with focus length of 200 mm was used to compress the divergence angle of the idler beam. The beam sizes at different distances are shown in Fig. 7(a). The M2 was measured to be 14.84 and 17.15 in horizontal (X) and vertical (Y) directions. The deterioration of the beam quality in Y direction could result from the heterogeneity of the BGSe along the crystallographic axis b, which is parallel to the Y direction in the experimental configuration. To evaluate the stability of the BGSe-OPO, the pump and the idler powers were recorded for 30 min with an interval of 1 s, shown in Fig. 7(b) and Fig. 7(c). The root mean square (RMS) fluctuation of the mid-IR idler power was less than 1 %, approximate to it of pump power. The periodic oscillation of pump power stems from the variation of LD temperature, which would affect the LD wavelength and the absorbed pump power of Nd:YAG. It is believed that the stability of the Nd:YAG MOPA system pumped BGSe-OPO can be further improved by suppressing the fluctuation of LD temperature.
Malý kalibr jedovatého selenidu hrozně kadící irradiance scales as 1/M4
na propalování sovětských sputniků určitě nebude stačit.



Buy an article and perish! MAGA!! https://opg.optica.org/ol/abstract.cfm?URI=ol-45-16-4595
"High energy mid-infrared laser pulse output from a BaGa4Se7 crystal-based optical parametric oscillator," Opt. Lett. 45, 4595-4598 (2020)
Report a high energy, narrow spectral linewidth mid-infrared laser pulse output from a laser-pumped (BGSe) crystal-based optical parametric oscillator (OPO). Output pulse energy of 21.5 mJ was obtained at 3816 nm, with spectral width of 12 nm and pulse width of 11.4 ns,

corresponding to peak power as high as 1.89 MW.

A BGSe crystal with aperture size of 10x10 mm and length of 16 mm was applied as the nonlinear crystal in a pump fed back OPO for achieving such high pulse energy output from the simple oscillator scheme.

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Re: Re: Proč výkonný laser? Dyť se TO přehřeje!

Josef Hrncirik,2025-07-31 16:03:42

Barium chalcogenides for nonlinear optics in the mid-IR: Properties and applications

https://doi.org/10.1016/j.omx.2024.100319

Jak ví dno z říti fig.1 trans mission neščastného BGSE je v použitém IR buzení i modulaci jen cca 65% tj. 35% je Vy užito k ničení krystalu přátelskou palbou!

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Re: Cooooooooo?

Waldemar Nováček,2025-07-26 15:15:35

to nepatřilo sem

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Žádným optickým zobrazením nelze na terči dosáhnout jasu zdroje (emitujícího krystalu); (MW na srat cm2)

Josef Hrncirik,2025-08-01 11:47:44

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