Diode Pumping Research Articles

High-power 2.3 µm Tm:YLF laser with intracavity upconversion pumping by a Nd:ASL laser at 1051 nm.

A Tm:LiYF4 laser operating on the 3H4 → 3H5 transition is embedded in a high-power diode-pumped Nd:ASL laser for intracavity upconversion pumping at 1.05 µm. This leads to a record-high output power at 2.3 µm for any bulk thulium laser pumped by an upconversion process. The continuous-wave Tm:LiYF4 laser delivers 1.81 W at 2.3 µm for 32 W of laser-diode pump power, making this kind of pumping competitive with direct diode pumping. The intracavity pumping process allows for counteracting the low absorption inherent to upconversion pumping and to dispatch the thermal loads on two separate laser crystals. The proposed laser architecture also features a relatively weak heating of the Tm:LiYF4 crystal and an increased tolerance to Tm3+ absorption. This laser design opens a new paradigm that holds great promise for high-power 2.3-µm solid-state lasers based on thulium ions.

Structural Properties, Energy Interaction, and Applications of CdS Nanomaterial Doped with Rare‐Earth Ions

AbstractSpectroscopic analysis of trivalent praseodymium (Pr+3) and neodymium (Nd+3) ions have received very much interest and reveals good fluorescence efficiency in visible and near IR (NIR) region. Cadmium sulfide (CdS) nanomaterial sample doped with Pr+3 and Nd+3 ions are synthesized at room temperature by simple chemical precipitation method. The synthesized sample has been characterized by powder X‐ray diffraction studies, scanning electron microscopy, transmission electron microscopy, and energy dispersive X‐ray spectra. Absorption spectra of CdS:Nd3+ and CdS:Pr3+ nanoparticles have been recorded at room temperature. Various parameters such as interplanar spacing, micro strain, dislocation density, distortion parameter, and particle size of nanomaterial are computed. TEM and XRD analysis reveal the spherical structure of the CdS:Nd3+ and CdS:Pr3+ nanoparticles in the prepared samples. Energy interaction parameters of the CdS:Nd3+ and CdS:Pr3+ nanoparticles are computed using UV‐visible absorption spectrum. Actually, CdS nanoparticle amplifies the luminescence intensity of Pr+3, Nd+3 ions by up conversion processes. So energy transfer can be observed from CdS nanoparticles doped with Pr+3, Nd+3 ions. Therefore, the use of pump sources and diode lasers in the UV range can be used to excite these samples to work as lasers. CdS:Nd3+ and CdS:Pr3+ nanoparticles find potential application as a window material for hetero‐junction solar cell, light emitting diodes (LED), biological sensors, address decoders, gas detectors, opto‐electronic devices, etc. CdS nanomaterials are also used as pigment in paints and in engineered plastic due to their good thermal stability.

All-solid-state ultrafast 2µm laser with 1.83  W output power.

In this paper, a high-power all-solid-state ultrafast 2µm mode-locked laser is investigated. The particularity of this laser is the simultaneous utilization of two Tm:YAP crystals in the same resonant cavity, independently pumped by two laser diodes. Using a 20% output coupler, pulses with output power as high as 1.83W are achieved at a wavelength of 1938nm with a pulse duration of 1.97ps and a pulse repetition frequency of 100MHz. To our knowledge, this mode-locked laser achieves the highest output power of any mode-locked Tm:YAP ultrafast laser reported to date. In addition, this paper provides a new approach to solve the problem of low output power due to multi-mode low-brightness laser diode pumping.

Wavelength-switchable watt-level continuous wave near-infrared Pr3+:LiYF4 lasers pumped by an InGaN laser diode.

We report a high-performance wavelength-switchable near-infrared Pr3+:LiYF4 (Pr:YLF) laser by InGaN laser diode (LD) pumping. The 895, 922, and 924 nm lasers with low emission cross sections in the Pr:YLF crystal have been successfully realized using a birefringent filter Lyot as well as designing and optimizing optical thin films and the laser resonant cavity. The maximum output powers of the 895, 922, and 924 nm lasers are 2.01, 1.92, and 1.95 W, respectively. As far as we know, these are the highest power for Pr:YLF lasers at 895, 922, and 924 nm so far. The beam quality M x2 and M y2 factors are measured to be 1.85 and 1.71 at 895 nm, 1.94 and 1.67 at 922 nm, and 1.76 and 1.60 at 924 nm, respectively. The laser output power fluctuates within ±3%. In addition, the transmittance of the Lyot is theoretically calculated to achieve laser wavelength switching. The successful realization of the wavelength-switchable watt-level continuous wave near-infrared Pr:YLF laser can provide many practical applications in biomedicine and other fields.

Numerical analysis of cascade lasing in Ho:ZBLAN fiber lasers with efficient output at ∼750 nm

Recent advances in blue-emitting laser diodes (LDs) have enabled visible laser operation in rare-earth-doped fluoride fibers. Therefore, investigation of the power scaling of visible fiber lasers enabled by direct blue diode pumping is significant. In this study, we numerically investigated the performance of a continuous-wave (CW) Ho:ZBLAN fiber laser operating at approximately 750 nm for the 5F4,5S2→5I7 transition using a cascade lasing process. Direct diode pumping at 450 nm is used in conjunction with double-clad fiber geometry. Simultaneous lasing for the mid-IR 5I7→5I8 transition effectively depopulated the 5I7 level and significantly enhanced efficiency and power scalability. A slope efficiency of 49% was associated with the calculated CW output power of 14.2 W at a launched pump power of 30 W. This study demonstrates the significance of depopulating the lower laser level in the development of an efficient Ho:ZBLAN 750 nm fiber laser and offers an alternative approach for developing high-power visible laser sources.

Continuous-wave second-harmonic generation in the far-UVC pumped by a blue laser diode

Far-UVC light in the wavelength range of 200–230 nm has attracted renewed interest because of its safety for human exposure and effectiveness in inactivating pathogens. Here we present a compact solid-state far-UVC laser source based on second-harmonic generation (SHG) using a low-cost commercially-available blue laser diode pump. Leveraging the high intensity of light in a nanophotonic waveguide and heterogeneous integration, our approach achieves Cherenkov phase-matching across a bonded interface consisting of a silicon nitride (SiN) waveguide and a beta barium borate (BBO) nonlinear crystal. Through systematic investigations of waveguide dimensions and pump power, we analyze the dependencies of Cherenkov emission angle, conversion efficiency, and output power. Experimental results confirm the feasibility of generating far-UVC, paving the way for mass production in a compact form factor. This solid-state far-UVC laser source shows significant potential for applications in human-safe disinfection, non-line-of-sight free-space communication, and deep-UV Raman spectroscopy.

Direct white light luminescence from Ho3+/Pr3+ co-doped fluoride fiber with blue diode pumping

White light luminescence induced by a blue diode laser was investigated in a double-clad Ho3+/Pr3+ co-doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber. The pump laser at 442 nm can simultaneously excite Ho3+ and Pr3+ ions, resulting in synergistic luminescence. The emission spectra include multiple visible bands in the blue, green, orange, red, and deep-red spectral regions, which correspond to the 4f-4f electronic transitions of Ho3+ and Pr3+ ions. The relative intensity of emission bands is dependent on the pump power, and the CIE 1931 chromaticity diagram illustrates the dependence of color tunability on the pump power. Under laser excitation at 442 nm, the CIE coordinates are within the white light range, and the CCT values are between 6900 and 8700 K. The results indicate that double-clad Ho3+/Pr3+ co-doped ZBLAN fibers that are directly blue diode-pumped have the potential to be used in high-power white light fiber lasers.

14.1 W continuous-wave dual-end diode-pumped Er:Lu2O3 laser at 2.85 µm

14.1 W continuous-wave dual-end diode-pumped Er:Lu2O3 laser at 2.85 µm

Yellow-orange wavelength-switchable laser emission generated from c-cut Nd:YVO4 self-Raman with 890 and 259 cm−1 shifts

Wavelength-switchable output at yellow-orange waveband was achieved based on second harmonic generation (SHG) and sum frequency generation (SFG) of c-cut Nd:YVO4 crystal self-Raman laser operation with 890 and 259 cm−1 shifts. Cascade-shifted the fundamental wave (1066 nm) to the first-Stokes wave (1178 nm) with 890 cm−1 shift and then to the second-Stokes wave (1216 nm) with 259 cm−1 shift was realized. Visible laser with 589, 598 and 608 nm wavelength-switchable output was achieved in temperature tuning LBO crystal, which were converted from the 1178 and 1216 nm by second order optical nonlinear processes. Under a diode pump power of 17.7 W, output powers of 2.56, 1.07, and 1.76 W were obtained for visible laser at 589, 598 and 608 nm wavelengths, respectively. These results highlight a promising approach of generating new visible wavelengths based SHG and SFG of Nd:YVO4 self-Raman laser with the 259 cm−1 shift participated, which could fill the visible gap of the wavelengths generated in those of Nd:YVO4 self-Raman laser with only primary shift of 890 cm−1.

Efficient continuous-wave Nd:YVO4/KGW intracavity Raman laser

We demonstrate an efficient Nd:YVO4/KGW intracavity Raman laser in continuous-wave (CW) scheme. With a V-shaped fundamental laser cavity and a short Stokes cavity in it, the oscillating beam sizes are designed to alleviate the thermal effect and to enhance the Raman gain for efficient CW operation. The output power of CW Stokes wave at 1177 nm reached 9.33 W under an incident laser diode pump power of 36.65 W, with corresponding optical efficiency being 25.5%. To the best of our knowledge, these are the highest Stokes output power and conversion efficiency of CW intracavity Raman lasers.

Laser Generation without Population Inversion in the Red Wing of the $${D}_{1}$$-Line of Alkali Metal Atoms under Resonant Diode Pumping

Laser Generation without Population Inversion in the Red Wing of the $${D}_{1}$$-Line of Alkali Metal Atoms under Resonant Diode Pumping

Color tunable upconversion luminescence from ex-situ sol-gel derived Titania-Silicate dense glass-ceramic co-doped with Pr3+-Yb3+ ion pair

Praseodymium–Ytterbium (Pr3+-Yb3+) ion pair co-doped with Silica-Titania dense glass ceramic material was synthesized by novel ex-situ sol-gel method after annealing at ca. 900 °C and investigated for their morphological, structural and luminescence characteristics. Color-tunable upconversion luminescence (UCL) are observed from varying Yb3+ (X mol%; X = 0.0, 0.7, 1.5, 3.0) and fixed Pr3+ (0.7 mol%) ions co-doped ex-situ sol-gel silicate-titania (STPYX) dense glass-ceramic (DGC) materials under 980 nm laser diode pumping source due to the transfer of energy from the Yb3+→ Pr3+ ion. An original ultra-broadband UCL spectra is achieved from the STPYX-DGC materials for excitation photon of wavelength (λex = 980 nm) for varying Yb3+ ion concentration, where the optimized UCL has been observed for material with 1.5 mol% Yb3+ ion concentration. Further, two dimensional spatially resolved photoluminescence intensity distribution study has also been performed using 2D-PL confocal mapping throughout the STPY15-DGC material for a similar excitation source. The color tunability from white to red is evident from the CIE co-ordinate of corresponding UCL spectra of the as-synthesized materials at different activator (Yb3+) ion concentrations. An intense absorption spectrum with peaks assigned to both Pr3+ and Yb3+ ions is also observed for the STPY07-DGC material.

CURRENT TRENDS IN THE DEVELOPMENT OF HIGH-ENERGY LASERS

Current trends in developing high-energy lasers with pulse energies in the tens and hundreds of joules are considered. Active media are analyzed for their use in such lasers. Yb:YAG active crystalline and ceramic elements (AE) of Russian production are experimentally investigated at temperatures from 100 K to 295 K. The data of the AE cryogenic cooling system are presented. A diode pumping system for AE and a homogenizer of its radiation are described. The physical and technical characteristics of the pumping system are given. Fresnel losses, absorption losses, and losses due to amplified spontaneous emission (ASE), which reduce the energy stored in an inverted population, are experimentally measured. The results of measuring the gain in multipass circuits with different sets of AEs are presented.

The influence of Pr3+ ions on the emission characteristics of Er3+-doped YSGG single crystal fibers in the 1–3 μm wavelength range

A series of 20 mol% Er3+, x mol% Pr3+: Y2.4-3xSc2Ga3O12 (Er3+, Pr3+: YSGG) single-crystal fibers (SCFs) were successfully grown by micro-pulling-down (μ-PD) method. Er3+, Pr3+: YSGG SCFs with varying concentrations of Pr3+ dopant exhibit consistent retention of the identical cubic structural space group. Under 980 nm laser diode (LD) pumping, Er3+, Pr3+: YSGG exhibits two emission bands centered at 1.6 and 2.7 μm, respectively. The incorporation of Pr3+ ions in Er3+, Pr3+: YSGG SCF materials has a negative impact on the emission peak intensity at 1.6 μm within a specific range of doping concentration, while it can relatively enhance the emission peak intensity at 2.7 μm. The lifetime of Er3+ ions at 4I13/2 is showing a significant decrease trend with increasing Pr3+ ions doping concentration. The results presented above indicate that the incorporation of Pr3+ ions increase the likelihood of particle number inversion, improving laser operation and demonstrating the desensitizing influence of Pr3+ ions. Quantitative analysis of the gain cross-section reveals a particle number inversion rate of 52.73% at approximately 2.7 μm. These findings provide valuable insights for developing applications aiming to achieve efficient and precise emission at 2.7 μm using Erbium–Praseodymium co-doped yttrium scandium gallium garnet single crystal fibers.

Growth and spectral properties of a novel praseodymium-doped alpha-barium borate laser crystal

A novel Praseodymium-doped borate (Pr:α-BBO) laser crystal was grown successfully by using the Czochralski method. The phase structure, absorption and fluorescence lifetime, as well as blue laser diode (LD) pump performances of Pr:α-BBO were totally studied. The segregation coefficient and valence state of Pr ions in the crystals were investigated using inductively coupled plasma atomic emission spectroscopy and X-ray photoelectron spectroscopy. A 450 nm blue LD was employed to carry out a pump experiment on the Pr:α-BBO slab crystal with a doping concentration of 0.22 at.%. The main emission peaks of Pr3+ ions in the orange-red light band were found to be at 611.5 nm, 634.7 nm, and 638.3 nm. The experimental results show that the Pr:α-BBO crystal exhibits higher orange light fluorescence emission performance, with an emission peak intensity at 611 nm that is 2.1 times stronger than that at 635 nm due to the splitting of the 3P0→3F2 transition (635 nm). By optimizing the Pr:α-BBO laser crystal growth process and further solid-state laser experiments, it can be expected to have broad applications in laser medicine, spectral detection, and nonlinear optical frequency conversion fields.

Broadband Amplification in the 2.6–2.9 μm Wavelength Range in High-Purity Er3+-Doped Zinc-Tellurite Fibers Pumped by Diode Lasers

In recent years, great progress has been made in the technology of high-purity and ultra-dry tellurite glasses, which has enabled the creation of high-purity single-mode tellurite fibers doped with rare-earth ions. This technology has made it possible to demonstrate laser generation in the range of about 2.7 μm in erbium-doped tungsten tellurite fibers. In this paper, we present an experimental study of broadband amplification in erbium-doped zinc-tellurite fibers. Zinc-tellurite glasses containing modifying components, such as Na2O, La2O3, Bi2O3, or rare-earth metal oxides, are known to have noticeably lower phonon energy than heavy metal-tellurite systems, namely, tungsten tellurite glasses, which leads to better lasing output. The on-off gain of 30- and 60-cm long zinc-tellurite fibers has been measured in a wide range of diode pump powers. It has been shown for the first time that the amplification band is essentially extended, with pump power reaching over 250 nm (2600–2850 nm) at a peak power of about 40 W for a 30-cm long fiber.

New SOS Diode Pumping Circuit Based on an All-Solid-State Spiral Generator for High-Voltage Nanosecond Applications

New SOS Diode Pumping Circuit Based on an All-Solid-State Spiral Generator for High-Voltage Nanosecond Applications

Pumping scheme for Holmium‐doped fiber amplifiers using traditional 1480 nm pumps exploiting cascaded lasers implemented using fiber Bragg gratings

AbstractDiversity in design is an important factor that enables developers to explore techniques aiming to reduce cost, complexity, and manufacturability. The optical window around 2000 nm is attracting rapid research considerations for the next generation optical networks as a continuation of C‐, L‐, and U‐bands. Optical amplifier is considered to be one of the major research directions in this optical window. Holmium‐doped fiber amplifier is an appropriate component to amplify signals in this optical window. But, the major issue is the pump laser for pumping the Holmium‐doped fiber (HDF) is that it is costly and not readily procurable. In a pioneering design, the authors introduced a method to pump the HDF using traditional 1480 nm pump diode by taking the advantage of cascaded lasers which were made of Erbium‐doped fiber (EDF) and Thulium‐doped fiber (TDF). In this paper, we propose an alternate method for pumping the HDF using commercially available 1480 nm pump diode by exploiting cascaded lasers implemented using two pairs of reflective fiber Bragg gratings (FBGs) and pieces of EDF and TDF. The EDF in the first laser is excited with a standard 1480 nm pump diode to create 1610 nm continuous wave (CW) laser which is used to excite the TDF in the second laser to generate 1950 nm CW laser that is used to pump the HDF. Peak gain of 40.5, 36, and 23 dB can be attained corresponding to –30, –15, and 0 dBm signal powers, respectively at 2055.6 nm signal wavelength. Output powers of 10.5, 21, and 23 dBm are obtained for –30, –15, and 0 dBm signal powers, respectively at 2055.6 nm signal wavelength. Noise figures (NFs) of 5, 4.2, and 4 dB are observed at signal wavelength of 2066.7 nm for signal powers of −30, −15, and 0 dBm, respectively. Penalty of 4.5 dB has been observed both in peak gain and power at 2055.6 nm signal wavelength for signal power of −15 dBm considering the pair induced quenching. Finally, the proposed alternate pumping scheme is compared with the previous pumping scheme in terms of 3 dB gain bandwidth and NF. It has been observed that 88% increase in 3 dB gain bandwidth and 19% decrease in NF at a signal wavelength of 2044.4 nm for signal power of –30 dBm is noticed in the proposed pumping scheme.

Experimental study of the effect of pump pulse duration on liquid crystal laser performance.

Much work has been done to understand the factors that impact photonic band-edge liquid crystal (LC) laser threshold and slope efficiency, two parameters often stated to quantify performance. Conventionally, LC lasers are optically pumped using Q-switched lasers with a fixed pulse duration, and thus the effect of pump pulse duration on LC laser performance has received little attention. While some studies have been published at different pump pulse durations, these use different laser sources and experimental conditions, making the data incomparable. By exploiting a recent breakthrough in laser diode pumping, our experimental results prove and quantify the detrimental effect of an increase in pump pulse duration on LC laser performance. We also show that the dependency of threshold on pump pulse duration depends on how threshold is defined, owing to an ambiguity in the definition of pulse energy in systems where peak power and pulse duration can be independently controlled. For improved comparison within the literature on LC laser device performance, we thus propose an alternative convention, whereby threshold is stated in units of peak power density.

35 W highly effective Ytterbium-Erbium-Thulium tandem all-fiber 1.947 µm laser system at 975 nm diode pumping

We report on progress towards effective mid-IR lasing using a tandem Ytterbium-Erbium/Thulium all-fiber laser system at near-IR diode pumping. ∼35 W 1.947 µm continuous-wave output power at ∼120 W 975 nm pump power (29% overall efficiency) is reached.