Eye-safe Emission Research Articles

Study of the phase formation of transparent magnesium aluminosilicate glass-ceramic materials

Current trends in the development of materials for optics and laser technology were analyzed. The prospects of creating passively Q-switched Yb-Er glass lasers with eye-safe emission wavelengths based on glass-ceramic magnesium aluminosilicate materials for compact pulsed lasers were established. The main types of transparent glass-ceramic materials were analyzed and the main criteria for the synthesis of transparent nanostructured glass-ceramic materials with a crystalline phase content of approximately 70–80 vol.% were substantiated. Compositions of magnesium aluminosilicate glasses were synthesized and the differences of compositions with different types of optical transparency were determined, taking into account their thermal prehistory. The mechanism of phase formation and the differences of MgO, Al2O3, MgO/Al2O3 and RO2 in their composition, which determine the character of crystallization, optical transparency and density under the conditions of heat treatment with a duration of 0.5 and 6 hours, were studied. The developed magnesium aluminosilicate glasses can be used as a basis for the creation of protective and functional high-strength nanostructured glass-ceramic materials based on spinel or cordierite with adjustable optical transparency for optics and laser technology.

Broadband Profiled Eye-Safe Emission of LMA Silica Fiber Doped with Tm3+/Ho3+ Ions.

LMA (Large Mode Area) optical fibers are presently under active investigation to explore their potential for generating laser action or broadband emission directly within the optical fiber structure. Additionally, a wide mode profile significantly reduces the power distribution density in the fiber cross-section, minimizing the power density, photodegradation, or thermal damage. Multi-stage deposition in the MCVD-CDT system was used to obtain the structural doping profile of the LMA fiber multi-ring core doped with Tm3+ and Tm3+/Ho3+ layer profiles. The low alumina content (Al2O3: 0.03wt%) results in low refractive index modification. The maximum concentrations of the lanthanide oxides were Tm2O3: 0.18wt % and Ho2O3: 0.15wt%. The double-clad construction of optical fiber with emission spectra in the eye-safe spectral range of (1.55-2.10 µm). The calculated LP01 Mode Field Diameter (MFD) was 69.7 µm (@ 2000 nm, and 1/e of maximum intensity), which confirms LMA fundamental mode guiding conditions. The FWHM and λmax vs. fiber length are presented and analyzed as a luminescence profile modification. The proposed structured optical fiber with a ring core can be used in new broadband optical radiation source designs.

Efficient continuous-wave eye-safe Nd:YVO4 self-Raman laser at 1.5 µm.

Due to a high Raman threshold and serious thermal effect, a challenge is to achieve efficient continuous-wave (CW) operation of a crystalline Raman laser at 1.5 µm. Based on effective thermal management and the self-Raman effect, we demonstrate, to our knowledge, the first efficient CW operation of a Nd:YVO4 Raman laser at 1.5 µm. We achieve 685 mW of CW eye-safe emission at 1524.5 nm by the use of a 20-mm-long composite Nd:YVO4 and 300-µm pump beam radius, with a diode-to-Stokes conversion efficiency of 4.8%. Lasers operating at ∼1.5µm have found many important applications in various areas such as optical communication, laser radar, laser ranging, remote sensing, and spectral research.

Eye safe emission in Tm3+/Ho3+ and Yb3+/Tm3+ co-doped optical fibers fabricated using MCVD-CDS system

The RE-co-doped silica optical fibers emitting in the eye-safe spectral range are still attractive for new applications like LIDAR, pollution monitoring, navigation, and free-space optical communication. High gain and beam quality of fiber sources based on large mode area (LMA) active fibers can be fabricated by the well-known Modified Chemical Vapor Deposition (MCVD) technology improved by the chelate doping system. Considering silica matrix, the most interesting co-dopants in the region above 1400 nm are thulium and holmium. In the paper Tm3+/Ho3+ and Yb3+/Tm3+ co-doped silica optical fibers (refractive index and rare earth distribution profile, luminescence) are presented. Their respective emission spectra has been measured over the range 1550–2150 nm for Tm3+/Ho3+ (exc. at 796 nm) and 1600–2100 nm for Yb3+/Tm3+ (exc. at 976 nm). A wide luminescent spectrum has been recorded from RE co-doping of silica glass during the MCVD process and we were able to achieve the appropriate and uniform concentration for getting the conditions of energy transfer. The fabrication and characterization of Tm3+/Ho3+ and Yb3+/Tm3+ co-doped optical fibres are presented. The analysis of luminescence spectrum changes vs. fibre length has shown that there is Amplified Spontaneous Emission (ASE) at 1960 nm in Yb3+/Tm3+ co-doped optical fibre. The possibilities of obtaining novel constructions of RE co-doped optical fibers for eye-safe emission region will be also shown.

The mobile Water vapor Aerosol Raman LIdar and its implication in the framework of the HyMeX and ChArMEx programs: application to a dust transport process

Abstract. The increasing importance of the coupling of water and aerosol cycles in environmental applications requires observation tools that allow simultaneous measurements of these two fundamental processes for climatological and meteorological studies. For this purpose, a new mobile Raman lidar, WALI (Water vapor and Aerosol LIdar), has been developed and implemented within the framework of the international HyMeX and ChArMEx programs. This paper presents the key properties of this new device and its first applications to scientific studies. The lidar uses an eye-safe emission in the ultraviolet range at 354.7 nm and a set of compact refractive receiving telescopes. Cross-comparisons between rawinsoundings performed from balloon or aircraft and lidar measurements have shown a good agreement in the derived water vapor mixing ratio (WVMR). The discrepancies are generally less than 0.5 g kg−1 and therefore within the error bars of the respective instruments. A detailed study of the uncertainty of the WVMR retrieval was conducted and shows values between 7 and 11%, which is largely constrained by the quality of the lidar calibration. It also proves that the lidar is able to measure the WVMR during daytime over a range of about 1 km. In addition the WALI system provides measurements of aerosol optical properties such as the lidar ratio (LR) or the particulate depolarization ratio (PDR). An important example of scientific application addressing the main objectives of the HyMeX and ChArMEx programs is then presented, following an event of desert dust aerosols over the Balearic Islands in October 2012. This dust intrusion may have had a significant impact on the intense precipitations that occurred over southwestern France and the Spanish Mediterranean coasts. During this event, the LR and PDR values obtained are in the ranges of ~45–63 ± 6 and 0.10–0.19 ± 0.01 sr, respectively, which is representative of dust aerosols. The dust layers are also shown to be associated with significant WVMR, i.e., between 4 and 6.7 g kg−1.

Laser operation of diode-pumped Er,Yb co-doped YAG ceramics at 16 μm

1.6 μm eye-safe emission of a diode pumped Er,Yb co-doped YAG ceramic laser is firstly demonstrated. Operation of the ceramic laser under different ceramic sample lengths, co-doping concentrations and control temperatures were experimentally investigated. A maximum output power of 222 mW was achieved at an absorbed pump power of 8.1 W, corresponding to a conversion efficiency of 2.74%. Laser emission at 1.05 μm for transition of the Yb(3+) ions was also studied on the same ceramic samples. The results clearly show the existence of resonantly energy transfer from the Yb(3+) ions to Er(3+) ions.

Resonantly pumped eyesafe erbium lasers

The viability of high-power and high-energy, direct eyesafe emission from bulk erbium lasers has recently been demonstrated. In this paper, we present a review of eyesafe erbium lasers that are resonantly pumped by both fiber and diode lasers. High brightness pumping with a 1.53-/spl mu/m erbium fiber laser has yielded 60 W of continuous wave (CW) output, 10 W of repetitively Q-switched output, and as much as 16 mJ of pulse energy. Diode laser pumping has yielded 38 W of quasi-CW output and >40 mJ of Q-switched output.