Eye-safe Laser Wavelength Research Articles

Comparative studies of long-wave laser-induced breakdown spectroscopy emissions excited at 1.064 µm and eye-safe 1.574 µm.

In this work, comparative long-wave infrared (LWIR) laser-induced breakdown spectroscopy (LIBS) emission studies of two excitation sources: conventional 1.064 μm and eye-safe laser wavelength at 1.574 μm were performed to analyze several widely-used inorganic energetic materials such as ammonium and potassium compounds as well as the organic liquid chemical warfare agent simulant, dimethyl methylphosphate (DMMP). LWIR LIBS emissions generated by both excitation sources were examined using three different detection systems: a single element liquid nitrogen cooled Mercury Cadmium Telluride (MCT) detector, an MCT linear array detection system with multi-channel preamplifiers + integrators, and an MCT linear array detection system with readout integrated circuit. It was observed that LWIR LIBS studies using an eye-safe pump laser generally reproduced atomic and molecular IR LIBS spectra as previously observed under 1.064 µm laser excitation.

Comparative Signal-to-Noise Ratio Assessment for the Atmospheric Sounder Lidars with Eye-Safe Laser Wavelengths

Проведен сравнительный анализ эффективности использования (с точки зрения величины отношения сигнал-шум) безопасных для зрения лазерных длин волн зондирования 0,355 мкм и 1,54 мкм в ближней ультрафиолетовой и ближней инфракрасной спектральных областях для задачи дистанционного зондирования земной атмосферы. Показано, что величина отношения сигнал-шум заметно больше на лазерной длине волны зондирования 0,355 мкм. Причем, преимущество длины волны зондирования 0,355 мкм растет с увеличения расстояния z от лазерного локатора и при z=4 км величина отношения сигнал-шум на длине волны зондирования 0,355 мкм в два раза больше величины отношения сигнал-шум на длине волны зондирования 1,54 мкм

Multi-spectral antireflection coating on zinc sulphide simultaneously effective in visible, eye safe laser wave length and MWIR region

In recent years multi-spectral device is steadily growing popularity. Multi-spectral antireflection coating effective in visible region for sighting system, laser wavelength for ranging and MWIR region for thermal system can use common objective/receiver optics highly useful for state of art thermal instrumentation. In this paper, design and fabrication of antireflection coating simultaneously effective in visible region (450–650nm), Eye safe laser wave length (1540nm) and MWIR region (3.6–4.9μm) has been reported. Comprehensive search method of design was used and the number of layers in the design was optimised with lowest evaluated merit function studied with respect to various layers. Finally eight-layer design stack was established using hafnium oxide as high index layer and silicon-di-oxide as low index coating material combination. The multilayer stack had been fabricated by using electron beam gun evaporation system in Symphony 9 vacuum coating unit. During layer deposition the substrate was irradiated with End-Hall ion gun. The evaporation was carried out in presence of oxygen and layer thicknesses were measured with crystal monitor. The result achieved for the antireflection coating was 85% average transmission from 450 to 650nm in visible region, 95% transmission at 1540nm and 96% average transmission from 3.6 to 4.9μm in MWIR region.

Yb 3+ effect on the spectroscopic properties of Er–Yb codoped SnO 2 thin films

We have investigated the optical properties of sol–gel thin films of tin dioxide (SnO 2) codoped with Er 3+–Yb 3+ as a function of Yb 3+ concentration. The Judd–Ofelt model has been applied to absorption intensities of Er 3+ (4f 11) transitions to establish the so-called Judd–Ofelt intensity parameters: Ω 2, Ω 4, Ω 6. Various spectroscopic parameters were obtained to evaluate their dependence and the potential of the samples as a laser material in the eye-safe laser wavelength (1.53 μm) as a function of Yb 3+ concentration. An amelioration of the quality factor Ω 4/ Ω 6 was found with Yb content. Both the IR photoluminescence (PL) intensity and the up-conversion emission, from Er 3+ ion in SnO 2, were found to increase with Yb concentration. We show that the Yb 3+ ion acts as sensitizer for Er 3+ ion and contributes largely to the improvement of the spectroscopic properties of SnO 2:Er. The mechanism of up-conversion emission is discussed and a model is proposed. The results showed that sol–gel SnO 2 is promising gain media for developing the solid-state 1.5 μm optical amplifiers and tunable up-conversion lasers.

Study of photoluminescence quenching in Er 3+-doped tellurite glasses

Erbium-doped tellurite glasses (TeO 2–ZnO–Na 2O 3: Er 3+ (TZNE)) were elaborated from the melt-quenching method. Various spectroscopic parameters were obtained to evaluate their dependence and the potential of the samples as a laser material in the eye-safe laser wavelength (1.53 μm) as a function of the Er 3+ concentration. The dependence of infrared photoluminescence (PL) spectra on doping concentration shows a quenching of the PL intensity for Er 3+ concentration above 2 mol%. Such dependence is discussed in terms of interactions between Er 3+ ions and OH − content. FTIR spectra were measured in order to calculate the exact content of OH − groups in samples. It was found that PL quenching with Er concentration in the tellurite glass is independent of OH − content. Stimulated cross-section at 1.53 μm was determined and was discussed using the McCumber theory.

Multispectral antireflection coating simultaneously effective in visible, diode laser, Nd-YAG and eye safe laser wavelength

Multi-spectral antireflection coating effective in visible region for sighting system, Nd-YAG laser wavelength for designator/seeker system, both diode laser and eye safe laser wavelength for ranging purpose can use common objective/receiver optics highly useful for state of art laser instrumentation. In this paper, design and fabrication of antireflection coating simultaneously effective in visible region (500 to 650nm), diode laser at 904±25nm and Nd-YAG laser at 1064±25nm, and erbium-glass laser wavelength at 1540±25nm has been reported. Inhomogeneous refractive index profile as suggested by Southwell was used to design this coating. The inhomogeneous profile was then approximated with eleven steps from substrate to air medium in order to obtain desirable antireflection property in the visible and laser wavelengths. These steps were then converted into the available coating materials (titanium-di-oxide and magnesium fluoride) of twenty-two layer stack. The multilayer stack was fabricated by using electron beam gun evaporation system in Balzers BAK-600 vacuum coating unit. The result achieved were less than 2% average reflection (98% average transmission) from 500 to 650nm, 1.5% reflection (98.5% average transmission) at 904nm, 1064nm and 1540nm. The coated samples successfully passed the specifications of MIL-C-14806 tests.

Comparative studies of spectroscopic properties in Er3+–Yb3+ codoped phosphate glasses

Abstract A spectroscopic investigation of an extensive series of commercially available Er 3+ –Yb 3+ codoped phosphate glasses (IOG-1) with different Er–Yb concentrations have been presented based upon spectroscopic measurements and Judd–Ofelt theory. The composition and the atomic concentration of the respective elements of the glass samples were analyzed. Various spectroscopic parameters were obtained to evaluate the performances of these glasses as a laser material in the eye-safe laser wavelength of 1.53 μm. Using the measured fluorescence lifetimes the radiative quantum efficiency of the 4 I 13/2 → 4 I 15/2 transition is estimated to be ∼100% for the glass substrates with an Er 3+ concentration of lower than 2.0 × 10 20 ions/cm 3 . The stimulated emission and absorption cross-sections were also determined and compared. The infrared and upconversion fluorescence were studied, and under 975 nm excitation the dominant upconversion mechanisms are excited state absorption (ESA) and energy transfer (ET) for the green emission, and ET for the red emission. The data obtained here provide useful guidelines on the choice of IOG-1 glasses with the fixed Er–Yb concentrations.

Cryogenic Temperature Measurement Using Silicon Carbide-Based Wireless Optical Sensor

Demonstrated is a novel silicon carbide (SiC)-based wireless optical sensor for cryogenic temperatures. The proposed design uses two wavelength processing and free-space optical beam interrogation of a remoted single crystal SiC chip placed in the cryogenic vacuum chamber to enable wireless temperature measurement. Experimental temperature sensing using the proposed sensor is reported from near room temperature to 100 K with an estimated 0.2 K resolution. The sensor uses eye safe laser wavelengths at 1550 and 1540 nm to implement the signal processing to determine the temperature value

Concentration effect of Er3+ ion on the spectroscopic properties of Er3+ and Yb3+/Er3+ co-doped phosphate glasses

Abstract Spectroscopic properties of Er 3+ and Er 3+ –Yb 3+ co-doped phosphate glass matrix have been analyzed by fitting the experimental data with the standard Judd–Ofelt theory. Various spectroscopic parameters were obtained to evaluate their dependence and the potential of the samples as a laser material in the eye-safe laser wavelength (1.53 μm) as a function of the Er 3+ and Yb 3+ concentration. Results indicate that the increment in the active ion concentration and the small variation in the Ba content in phosphate matrix reduce the Ω t parameters and modify the fluorescence spectral properties of Er 3+ ion. The fluorescence decay time range from 3 to 8.5 ms depending on the ionic concentration and the maximum quantum efficiency for the 1.53 μm was 86% for 0.25 mol% of Er 3+ with 2.5 mol% of Yb 3+ . The effect of Er 3+ concentration on the quantum efficiency was discussed in terms of the cluster formation of the active ion and by the dynamics change induced by the presence of Yb 3+ . Calculated and measured parameters are in agreement with others results reported recently.

Room-temperature diode-pumped continuous-wave SrY4(SiO4)3O: Yb3+, Er3+ crystal laser at 1554 nm

Continuous-wave (cw) laser operation at room temperature of an Yb3+, Er3+ doped oxyapatite single crystal SrY4(SiO4)3O pumped at 980 nm by an InGaAs diode laser has been achieved around the eye-safe laser wavelength of 1554 nm.