Laser Performance Parameters Research Articles

Visible light generation and lasing from a fluoroindate glass fiber

We report on a Dy3+-doped fluoroindate glass fiber laser operating in the yellow (∼576 nm) wavelength region that is pumped by a blue GaN diode laser (∼450 nm). Using single-clad Dy3+-doped fluoroindate glass fiber with 0.5 mol% concentration and a ∼0.48 m length, a slope efficiency of ∼26.6% and maximum output power of ∼467 mW was produced. This result demonstrates that fluoroindate glass fiber has a sufficiently low background loss at visible wavelengths to support efficient visible light generation. We compared all our measurements with a Dy3+-doped fluorozirconate glass fiber and found that most of the laser performance and spectroscopic parameters are similar to ZBLAN. We therefore conclude that fluoroindate glass fiber can be further developed for visible light emission.

Gain-switching of 1.55 µm InP-based Qdash lasers grown on Si

Reliable lasers on Si with large bandwidth are desirable for high-performance data communication systems on Si-photonics platforms. Here, we report short optical pulses generated by gain-switched InP-based 1.55 µm quantum dash (Qdash) lasers directly grown on (001) Si. The laser performance and related physical parameters were investigated by carrying out a gain-switching test for lasers on both Si and native InP substrates. The shortest pulses obtained were 217 and 252 ps for the lasers on InP and Si, respectively. By varying the electrical bias and pulse duration systematically, the evolution of the generated optical pulse duration and peak power was studied. The impact of cavity size on the optical pulse was also examined. Parameters were extracted using established equations fitted with our measurement results to gain insight into the underlying physics and correlation with the observed behavior. The obtained results indicate that the pulse width is limited by the low differential gain and strong gain compression of the active material. Our results indicate that Qdash lasers on Si can demonstrate comparable performance to those on a native InP substrate and manifest its potential application in an Si-based photonics chip for optical on-chip communications.

0.25–30 kGy γ Irradiation-induced modifications on the density, optical absorption, thermo-, and photo-luminescence of the 10BaO–20ZnO–20LiF-49.3B2O3-0.7Er2O3 glass

The influence of 0.25–30 kGy γ doses on the 10BaO–20ZnO–20LiF-49.3B2O3-0.7Er2O3 glass was analyzed through the density, optical absorption, thermo-, and photo-luminescence. With a successive increase in the dose, the density of the glass increased, confirming radiation-induced compaction. The color of the glass deepened progressively with the increase in the γ dose, leading to the enhancement in the optical absorption. A continuous fall in the bandgap and an increase in the Urbach energy was also observed. The rise in the electron density with dose, caused a gradual upsurge in the covalency around the Er3+ ions, as inferred from the bonding parameter (δ), and the Judd-Ofelt parameters (Ω2,Ω4,Ω6). The defects produced in the glass because of irradiation were evaluated using the trap parameters deduced from the Computerized Glow Curve Deconvolution and Chen's peak shape methods. The 30 kGy irradiated glass contained deeper traps when compared to the 0.25 kGy irradiated glass. The excitation spectrum recorded by monitoring the emission at 550 nm revealed the spectral transitions originating from the ground state 4I15/2 of the Er3+ ion to 4G9/2, 4G11/2, (2G,4F)9/2, 4F5/2, and 4F7/2 excited states, among which the 4I15/2 → 4G11/2 transition at 379 nm was very intense. In the emission spectra, one violet (2H9/2→4I15/2) and two green emissions (2H11/2→4I15/2 and 4S3/2→4I15/2) were detected out of which the 4S3/2→4I15/2 transition was the most prominent. The decrement in the intensity of this emission with dose was attributed to the radiation-induced quenching. The laser performance parameters computed by the Fuchtbauer-Ladenburg theory validated the emission quality of the irradiated glasses. The quantum efficiency did not fall below 60% for all the doses. The color coordinates were clustered in the green region and showed not much variation with dose. The present study manifests the remarkable radiation hardness of the titled glass as a green emission device and laser.

A potential ultrafast pulse laser crystal with disordered melilite structure: Yb3+: CaLaGa3O7

The Yb3+: CaLaGa3O7 crystal with high-quality was grown successfully by the Czochralski method. The structure parameters of Yb3+: CaLaGa3O7 crystal are determined by the X-ray Rietveld refinement method. The absorption and fluorescence spectra, fluorescence lifetime and laser performance parameters were investigated in detail. The large absorption cross-section (1.14 × 10−20 cm2 for π-polarization and 1.06 × 10−20 cm2 for σ-polarization) of the crystal at around 980 nm indicates that the crystal can be pumped efficiently by the commercialized InGaAs laser diode. The stimulated emission-cross section at 1004 nm was calculated to be 1.11 × 10−20 cm2 for π-polarization and 1.04 × 10−20 cm2 for σ-polarization. The above results reveal that Yb3+: CaLaGa3O7 crystal can be regarded as a potential candidate for realizing tunable solid-state and ultrashort pulsed lasers with LD pumping.

Yb:Ca9Gd(VO4)7, a potential ultrafast pulse laser crystal with promising spectral properties

The Yb3+:Ca9Gd(VO4)7 crystal with dimensions of Φ19 × 25 mm3 was grown by the Czochralski method for the first time. The polycrystalline materials, crystal growth, absorption and fluorescence spectra, energy level schema, fluorescence lifetime and laser performance parameters were investigated in detail. For π-polarization, the absorption coefficients, cross-sections, maximal full width at half maximum (FWHM) at around 976 nm are 1.05 cm−1, 1.27 × 10−20 cm2 and 33 nm, respectively. For σ-polarization, the relevant absorption spectral parameters at around 981 nm are 1.58 cm−1, 1.90 × 10−20 cm2 and 28 nm, respectively. At the laser wavelength around 1023 nm, the FWHM and emission cross-sections are 57 nm and 0.94 × 10−20 cm2 for π-polarization, 54 nm and 2.18 × 10−20 cm2 for σ-polarization, respectively. The results reveal that Yb3+:Ca9Gd(VO4)7 crystal can be regarded as a potential candidate for efficient LD-pumping and ultrashort pulse laser crystal.

Two-dimensional material as a saturable absorber for mid-infrared ultrafast fiber laser

The two-dimensional (2D) nanomaterial saturable absorber represented by graphene is widely used in ultrafast fiber lasers due to its unique nonlinear optical properties. In this paper, we summarize the research and development of 2D nanomaterials as saturable absorbers in mid-infrared ultrafast mode-locked fiber lasers in recent years, and introduce the atomic structure and nonlinear optical characteristics of 2D nanomaterials, and saturable absorber device integration methods. The laser performance parameters such as center wavelength, repetition frequency and average output power of the laser are discussed, and the femtosecond fiber laser based on black phosphorus saturable absorber in the middle infrared band is highlighted. Finally, the developments and challenges of 2D materials in mid-infrared pulsed fiber laser are also addressed.

A novel solid-solution garnet Yb:YAG-MnASG with enhanced spectral properties

A novel solid-solution garnet Yb3+ doped Y3Al5O12Mn3Al2(SiO4)3 (Yb:YAG-MnASG) has been designed and grown for the first time. The polycrystalline materials, crystal growth, crystal structures, absorption and emission spectra, energy level schema, fluorescence lifetime and laser performance parameters were investigated in detail. Owing to the inhomogeneity in the local environment of Yb3+ caused by the cationic substitutions of Mn2+ for Y3+, Si4+ for Al3+ and high crystal-field strengths caused by distorted host sites, both of the absorption and emission spectral bandwidth of Yb:YAG-MnASG crystal are broadened compared with Yb:YAG. The maximal full width at half maximum (FWHM) of absorption spectra around 940 nm and emission spectra around 1030 nm for Yb:YAG-MnASG crystal are almost 1.2 and 2.5 times larger than those of Yb:YAG crystal, respectively. The results reveal that the novel solid-solution garnet Yb:YAG-MnASG is an excellent candidate for ultrafast pulse laser crystal.

双端键合复合结构被动调Ｑ微型测距用激光器

A passively Q-switched human-eye safety micro-ranging laser with a double-end bonded composite structure was reported. The double-end bonded structure was formed by the heterogeneous material composite technology, including the gain medium Er3+/Yb3+:glass, F2 glass and passively Q-switched crystal Co2+:MgAl2O4. The output characteristics of the double-bonded composite structure and the non-composite structure were compared in the experiment. The former laser performance parameters are significantly better than the latter. The double-bonded composite structure achieved a human eye-safe laser output of pulse energy 330 J, beam quality 1.4, pulse width 5.5 ns with 10 Hz repetition frequency; the non-composite structure laser had a single pulse energy 245 J, pulse width 6.5 ns, and the beam quality 1.9. The thermal simulation of double-bonded composite structure gain media and monolithic Er3+/Yb3+:glass shows that the former has a 51.2% increase in thermal focal length relative to the latter, and the thermal effect of the double-bonded composite structure is significantly improved. The above shows that the double-bonded composite technology can reduce the temperature gradient inside the gain medium, make the thermal focal length longer, increase the volume of the mold, and improve the mode matching of the oscillating light and the pump light, so that the single pulse energy is increased.

Fabrication and Laser Parameters of Yb:YAG Transparent Ceramics with High Optical Quality

Yb:YAG transparent ceramics with high optical quality were fabricated by solid-state reaction and vacuum sintering method (1750 ℃×30 h) using high-purity Y2O3, α -Al2O3 and Yb2O3 powders as raw materials. The measured concentration of Yb 3+in 5.0at% Yb:YAG ceramics is 6.41×10 20 cm -3, and the cell density is 4.65 g/cm 3. The microstructures, spectral characteristics and laser performance parameters of Yb:YAG ceramics were studied in this work. FESEM results show that Yb:YAG ceramics have uniform and compact structure, clean and straight grain boundaries, and the average grain size is about (19±3) μm. The in-line transmittance of Yb:YAG ceramics with thickness of 4.0 mm reaches 82.5% at 400 nm and 85.2% at 1100 nm. The minimum pump saturation light intensity occurs at 940 nm, and the pump threshold power at 1030 nm is the lowest. The quality factor of 1030 nm laser pumped at 940 nm is 1.02×10 -22 cm·s. By calculating the gain cross section, it is indicated that Yb:YAG ceramics can be tuned broadband, and are ideal laser gain media.

Structural and spectroscopic properties of Yb3+ doped borophosphate glasses for IR laser application

Ytterbium (Yb3+) doped borophosphate (BPYb) glasses have been prepared and studied by means of their physical, optical, structural and spectroscopic properties aiming laser performance parameters. The main structural groups, PO32−, P2O74− and BO4 of the borophosphates were analyzed through their FTIR-ATR and Raman spectra. A linear increment of the absorption coefficient and of the integrated emission intensity were observed with increase of Yb3+ ions. The absorption and emission cross-sections have been evaluated and reported. Decay lifetimes were found to decrease with the increase of Yb3+ ions. The evaluated laser performance parameters (Isat and Imin), figure of merit and cross-sections (absorption and emission) suggest that 0.5 mol% of Yb3+ doped borophosphate glass is the most appropriate candidate for solid state infrared (IR) laser applications.

Analysis on the optical properties for the ytterbium doped silica glasses prepared by laser sintering technology

The paper demonstrates the optical properties of the ytterbium doped silica glasses that were fabricated by laser sintering technology combined with liquid phase doping method, and analyzed the influence of the fabricated process on the formation of Yb2+. The spectral parameters and laser performance parameters were also calculated and analyzed. The results indicate that the formation of Yb2+ can be effectively restrained through the optimized preparation process. The prepared ytterbium doped silica glass presents typical absorption and emission cross sections of Yb3+, and possesses attractive laser performance parameters. The material would have potential applications for the gain medium of large mode area photonic crystal fiber lasers.

Spectroscopy and radiation trapping of Yb3+ ions in lead phosphate glasses

This paper reports ytterbium-doped lead phosphate (PbPhYb) glasses made by melt-quenching technique and their linear and nonlinear refractive indices. Raman and FTIR spectral analysis has been carried out to investigate the functional groups that constitute the host matrix. The oscillator strength of the absorption transition, (2F7/2→2F5/2) has been evaluated by using the Smakula model for various concentrations. The near infra-red emission and excitation spectra have been investigated and observed that the profile of the emission spectra changes as a function of Yb2O3 concentration, temperature, optical path length and thickness of the sample. From the optical absorption spectra, the spectroscopic and laser performance parameters have been evaluated and in turn used to estimate the gain cross-section of the Yb3+ ions. On the other hand, the lifetime for the 2F5/2 level of Yb3+ ion decreases with increase in Yb2O3 concentration up to 6mol% after an initial increase due to energy migration among the Yb3+ ions. The increase in lifetime could be due to radiation trapping but when the concentration is enlarged the energy migration processes are more predominant. The emission profile and lifetime change when the temperature is reduced to cryogenic temperature (11K). The results reveal that the prepared glasses could be considered for high energy and high power laser as well as solid state cryocooler applications.

Polarized spectral properties of a notable Yb3+: LaCa4O(BO3)3 crystal

Yb3+: LaCa4O(BO3)3 single crystal, as a laser material with disordered structure, was successful grown by the Czochralski method. The important polarized spectra and laser performance parameters were analyzed in detail. The crystal has broad emission cross-section (FWHM=57.1nm for E‖Y) at 1029nm, wide gain cross-section (FWHM=42.0nm for E‖Y) at 1029nm, and long fluorescence lifetime of 2.88ms, which are beneficial to the tunable laser emission and Q-switching ultra-short laser pulse. The results also report a lower pump threshold value which was calculated to be 0.4kW/cm2 at 1029nm compared with other well-known crystals.

Optical properties of Yb3+ ions in fluorophosphate glasses for 1.0 μm solid-state infrared lasers

Yb3+-doped fluorophosphate glasses were prepared by melt-quenching technique and characterized their spectroscopic properties to assess the laser performance parameters. The magnitude of absorption (emission) cross-sections at 975 nm for all the studied Yb3+-doped glasses is found to be in the range of 0.29–1.50 × 10−20 (0.59–1.99 × 10−20 cm2) which is much higher than those of commercial Kigre QX/Yb: 1.06 × 10−20 (0.5 × 10−20 cm2) laser glass. The luminescence lifetimes of 2F5/2 level decrease (1.15–0.45 ms) with increase in Yb2O3 concentration (0.1–4.0 mol%). Effect of OH− content on luminescence properties of Yb3+ ions has also been investigated. The effect of radiative trapping has been discussed by using McCumber (McC) and Fuchtbauer–Ladenburge (F–L) methods. The product of experimental lifetimes and emission cross-sections for 0.1 mol% Yb2O3-doped glass is found to be 2.28 × 10−20 cm2 ms which indicates that the higher energy storage and extraction capability could be possible. The detailed spectroscopic results suggest that the studied glasses can be considered for high-power and ultrashort pulse laser applications.

Optical properties of Yb3+-doped Sr3Y2(BO3)4 crystal

Abstract

Yb^3+ ion concentration effects on ∼1 μm emission in tellurite glass

The effects of Yb3+ ion concentration on physical, optical, and spectroscopic properties have been studied in a low phonon (∼590 cm−1) barium-lanthanum-tellurite glass. Due to the unfeasibility of Judd-Ofelt theory Yb3+-doped systems, the oscillator strength of absorption transition, F27/2→F5/22 has been evaluated by using the Smakula equation. The nature of emission from F25/2→F7/22 transition of Yb3+ ions is described theoretically by using a rate equation in comparison with experimental results. By applying reciprocity (RM) and Fuchtbauer-Ladenburg methods on emission spectra as well as the excitation random walk model on measured fluorescence lifetimes, the radiation trapping and concentration quenching effects have been discussed. Considering all the spectroscopic and laser performance parameters, an optimum Yb-ion doping concentration (YT1) has been determined, and the gain measurements performed on the sample revealed a flat gain over a broad wavelength range could be achieved even with a low (∼20%) excitation population density. A comparative study with other hosts revealed the potentiality of the present glass for ∼1 micron emission.

Spectroscopic characteristics of Yb3+-doped Li3Ba2Y3(WO4)8 crystal

This paper reports the spectroscopic properties of Yb3+:Li3Ba2Y3(WO4)8 crystal. The polarized spectral properties of Yb3+:Li3Ba2Y3(WO4)8 crystal were investigated. The laser performance parameters βmin, Isat and Imin of Yb3+:Li3Ba2Y3(WO4)8 crystals have been also established. Yb3+:Li3Ba2Y3(WO4)8 crystal has a broad FWHM of the gain cross-section and larger absorption and emission cross-sections. These results may regard the Yb3+:Li3Ba2Y3(WO4)8 crystal as a tunable laser material.

Fluorescence and Spectroscopic Properties of Yb3+-Doped Phosphate Glasses

Abstract The concentration dependent Yb 3+ : phosphate (P2O5 + K2O + MgO + Al2O3 + Yb2O3) glasses have been prepared and characterized their fluorescence and laser properties. The stimulated emission cross-section and laser performance parameters were determined from the measured absorption spectra using the method of reciprocity. The refractive index, absorption and emission cross-sections and fluorescence lifetimes varied with Yb3+ ion concentration. The higher emission cross-section was found to be 1.01 × 10-20 cm2 at the extraction wavelength of 1005 nm. The fluorescence lifetime of 2F5/2 level decreases from 1.04 ms to 0.28 ms with increase of Yb2O3 concentration from 0.05 to 6.0 mol %. The gain cross-section spectra can be obtained from the measured absorption and emission cross-sections with different population levels. The values of emission cross-section, fluorescence lifetime, minimum pulse duration, pump power, extraction efficiency and gain coefficients suggest that these glasses can be used as a laser gain media for the generation of ultrashort pulse and high power laser applications.

Investigation on the Spectroscopic Properties of Yb3+-doped Phosphate Glass

A series of the Yb3+ -doped phosphate laser glass have been prepared under high temperature and different doping content and the fluorescence and absorption spectrum is observed, respectively. The influences of the Yb3+ -doped content on the spectral properties of the glass are analyzed and the optimal mole fraction is 4 %. The emission cross-section and fluorescent lifetime is calculated with McCumber theory. Furthermore, the integrated absorption cross-section, the full width at half maximum of the emission spectra and the laser performance parameters such as least particle count, saturation pump intensity and lowest pump intensity of Yb3+ -doped laser glass is calculated.

Growth and characterization of Nd:Lu 3Sc xGa 5 − x O 12 series laser crystals

A new series Nd:Lu 3Sc xGa 5 − x O 12 (x = 0.5, 0.8, 1, 1.2 and 1.5) laser crystals have been successfully grown by the optical floating zone method. Their absorption and luminescence spectra were measured at room temperature and spectral parameters were systemically calculated using Judd–Ofelt (JO) theory. The fluorescence τ f lifetimes were experimentally measured and compared with the theoretical results. Diode-pumped continuous-wave (CW) laser performance at 1.06 μm with mixed crystals was demonstrated. The influence of different x values on laser performance and spectral parameters was also discussed. All the results show that Nd:Lu 3Sc xGa 5 − x O 12 series crystals should be suitable for laser application.