Ceramic Gain Media Research Articles

Highly transparent Ce:Nd:YAG ceramic with good light conversion capacity for solar-pumped solid-state lasers

Developing a high quality ceramic laser gain medium for solar directly pumped solid state lasers is essential, and yet the light conversion efficiency of the gain media for solar pumping remains a challenge. In this study, Ce and Nd ions, co-doped YAG transparent ceramics with theoretical transmittance and stable Ce3+ valent state were developed, and revealed that the absorbed visible light and light conversion efficiency in Ce,Nd:YAG ceramics were 3.98 times and 1.34 times higher than those in widely reported Cr,Nd:YAG ceramics, respectively. A concentration matching principle between Ce3+ and Nd3+ ions in YAG was established, and a higher Nd3+ ion doping concentration with a relatively low Ce3+ concentration was favorable to improve both the light conversion efficiency and emission intensity at 1064 nm of Ce,Nd:YAG ceramics. Energy transfer efficiency from Ce3+ to Nd3+ of the 0.3 at.%Ce,1.5at.%Nd:YAG ceramic reached as high as 61.71% at room temperature. Surprisingly, it was further promoted to 64.31% at a higher temperature of 473 K. More excited electrons at the upper energy level of Ce3+ ion under the high temperature accounted for this novel phenomenon. This study proposes a new design strategy of gain materials for solar directly pumped solid state lasers.

Nickel-vanadium layered double hydroxide for a mid-infrared 2 µm Tm:YAG ceramic ultrafast laser.

In this study, a nickel-vanadium layered double hydroxide (NiV-LDH) nanosheet was prepared as a saturable absorber (SA) by liquid phase exfoliation and a drop-coating method. The microstructure and optical transmission properties of the obtained NiV-LDH nanosheet were then systematically studied. An "X"-type fold cavity was designed to evaluate the ultrafast laser modulation performance of the NiV-LDH nanosheet with a Tm:YAG ceramic gain medium. A stable passively Q-switched mode-locked (QML) pulse centered at 2011.6 nm has successfully been realized, with a repetition frequency of 145 MHz and a pulse duration of 320 ps. To the best of our knowledge, this is the first time that the LDH has been used as an SA in a mid-infrared range ultrafast laser.

Fabrication of heavily doped Nd:YAG transparent ceramics and their thin disc solid state laser performance

Compared to the single crystal counterparts, the laser ceramic materials can achieve higher ion doping concentrations and thus have a considerable application potential in thin disc lasers as laser gain media. In this study, heavily doped Nd:YAG transparent ceramics with excellent optical quality were fabricated, and a watt level thin disc laser output with high efficiency without saturation was realised in 3.0 at.% Nd:YAG ceramic (500 μm thickness). However, the trends in transmission and laser performance of Nd:YAG transparent ceramics were inconsistent with the Nd3+ doping concentration owing to the sintering additive effect of the introduced Nd2O3, and the laser performance of a 2.5 at.% Nd:YAG transparent ceramics with 1.0 mm thickness was almost identical to that of 1.0 at.% samples. This study demonstrates that the ceramic laser gain medium is of great significance for miniaturising and integrating solid state lasers.

Sub-100 fs pulse generation from a Kerr-lens mode-locked Yb:Lu2O3 ceramic thin-disk laser.

In this Letter, we demonstrate, to the best of our knowledge, the first Kerr-lens mode-locked (KLM) ceramic thin-disk laser. Ceramic laser gain media have many advantages for a high-power laser such as high fracture toughness, size scalability, low cost, and short time fabrication. By using the Yb:Lu2O3 ceramic thin disk, the pulse duration of 98fs with the output power of 3.7W was demonstrated. The shortest pulse duration was 86fs with the decreased output power of 0.36W. From our results, it was proven that a KLM thin-disk laser with ceramic gain media can become a new option for high-power, sub-100fs pulse laser sources.

Dual-Wavelength Temporal Dynamics of a Gain-Switched 2-μm Tm3+:Lu2O3 Ceramic Laser

We provide a detailed experimental investigation of the energy efficiency and rich temporal dynamics of a gain-switched 2-μm Tm3+:Lu2O3 ceramic laser pumped near 800 nm. A tunable Ti3+:sapphire laser was used to determine the full excitation spectrum and the optimum pumping bands for the 1.5% Tm3+:Lu2O3 ceramic gain medium. These bands were centered at 774, 796, and 811 nm. The highest output pulse energy was obtained when the pump wavelength was set to 796 nm. In the experiments, a free-running x-cavity was used to investigate the energy efficiency of the Tm 3+:Lu2O3 ceramic laser. Extracavity grating-dispersed output and prism-tuned resonator were used to further assess the role of cross-relaxation for the 1.5% Tm3+:Lu2 O3 ceramic. Finally, we demonstrate that as the pump energy was increased, a transition occurred from single-wavelength output (2068 nm) to dual-wavelength multipulse output (2068 and 1968 nm). We performed systematic temporal and spectral characterization measurements by using the free-running resonator, extracavity-grating-dispersed laser output, and prism-tuned resonator to investigate how the laser pulses at 1968 and 2068 nm evolved in time. A plane-wave rate equation model was further used to investigate the temporal dynamics of the Tm3+:Lu2O3 ceramic laser and provided predictions in qualitative agreement with experimental data.

1.9 µm waveguide laser fabricated by ultrafast laser inscription in Tm:Lu2O3 ceramic.

The ultrafast laser inscription technique has been used to fabricate channel waveguides in Tm3+-doped Lu2O3 ceramic gain medium for the first time to our knowledge. Laser operation has been demonstrated using a monolithic microchip cavity with a continuous-wave Ti:sapphire pump source at 796 nm. The maximum output power achieved from the Tm:Lu2O3 waveguide laser was 81 mW at 1942 nm. A maximum slope efficiency of 9.5% was measured with the laser thresholds observed to be in the range of 50-200 mW of absorbed pump power. Propagation losses for this waveguide structure are calculated to be 0.7 dB⋅cm-1 ± 0.3 dB⋅cm-1 at the lasing wavelength.

Yb3+-doped CaF2-LaF3 ceramics laser.

Highly transparent ceramic is an attractive gain medium for high-power lasers due to its high fracture toughness, homogeneity, and size scalability. Here we report the first Yb3+-doped CaF2-LaF3 ceramics laser. Codoping of La3+ ion can reduce the formation of Yb2+ ions and enhance the laser efficiency. In the laser experiment, the maximum output power of 4.36 W and the maximum slope efficiency of 69.5% were obtained with a 3% La, 2% Yb sample and a 2% La, 1% Yb sample, respectively. Due to the combined properties of Yb:CaF2 and a ceramic laser gain medium, Yb:CaF2-LaF3 ceramic is a promising gain medium for a high-power ultrashort pulse laser and amplifier.

266 nm陶瓷激光器反射照相在指纹显现中的应用

本文研究潜在指纹显现的新技术，用自主研发的266 nm短波紫外陶瓷激光器作为光源照射检材，通过反射照相方法显现各种非渗透性客体表面的潜在指纹。紫外陶瓷激光器能有效显现出光滑客体表面的潜在指纹，并且油脂指纹检出率高于汗液指纹检出率。陶瓷材料由于其良好的化学稳定性、耐高温性、尺寸稳定性、光漫反射特性等优点，利用该266 nm短波紫外陶瓷激光器可以显现非渗透性客体表面的潜在指纹，在刑侦领域上有较好的应用前景。 This paper describes visualization of latent fingerprints by 266 nm ultraviolet ceramic laser. Self-made 266 nm ultraviolet laser with a ceramic gain medium was used to illuminate the latent fingerprints on the non-porous substrates. The images were recorded by ultraviolet camera through reflection photography. The results showed that the marriage of ultraviolet ceramic laser and reflection photography was an effective method on visualization of latent fingerprint on non-porous substrates. The visualization rate of oil fingerprints is higher than the sweat fingerprints. Ceramic materials have the advantages of good chemical stability, high-tem- perature resistance, size stability and light diffuse reflection. The 266 nm ultraviolet ceramic laser could be adopted to the visualized latent fingerprints on the non-porous substrates. The ultraviolet ceramic laser operating at 266 nm has potential application in the field of criminal investigation.

Challenges of high power diode-pumped lasers for fusion energy

Abstract This paper reviews the different challenges that are encountered in the delivery of high power lasers as drivers for fusion energy. We will focus on diode-pumped solid-state lasers and we will highlight some of the main recent achievements when using ytterbium, cryogenic cooling and ceramic gain media. Apart from some existing fusion facilities and some military applications of diode-pumped solid-state lasers, we will show that diode-pumped solid-state lasers are scalable to inertial fusion energy (IFE)’s facility level and that the all-fiber laser scheme is very promising.

Efficient diode-end-pumped actively Q-switched Nd:YAG/SrWO_4/KTP yellow laser

An efficient intracavity frequency-doubled Raman laser was obtained by using an SrWO(4) Raman medium, an Nd:YAG ceramic gain medium, and a KTP frequency-doubling medium. Three laser cavities, including a two-mirror cavity, a three-mirror coupled cavity, and a folded cavity, were investigated. With the coupled cavity, a 2.93 W, 590 nm laser was obtained at an incident pump power of 16.2 W and a pulse repetition frequency of 20 kHz; the corresponding conversion efficiency was 18.1%. The highest conversion efficiency of 19.2% was obtained at an incident pump power of 14.1 W and a pulse repetition frequency of 15 kHz. The obtained maximum output power and conversion efficiency were much higher than the results previously obtained with intracavity frequency-doubled solid-state Raman lasers.

Comparison of Potential Ceramic Gain Media

The real advantage of the laser driver as compared to other drivers is its ability to provide a high quality focal spot on target. Heat generation in solid-state media has always been recognized as a limiting feature because at high repetition rate, the quality of this focal spot depends on the beam wave-front distortions. It is not easy to design the driver baseline because there are too many different parameters to deal with. In this paper, we introduce two figures of merit that show that Yb doped ceramics (either garnets or sesquioxides) are promising laser materials opening new fields during the research phase to demonstrate ignition and fusion gain (including the fast ignitor concept). When driven at low temperature (cryogenic cooling), all of the operational features of the laser amplifier can be demonstrated at an aperture scale of only 10-15 cm.

Characteristics of Nd 3+-doped Y 3ScAl 4O 12 ceramic laser

Highly transparent Nd 3+-doped Y 3ScAl 4O 12 (YSAG) ceramics with up to 5.0 at.% Nd 3+-concentration ( C Nd) were synthesized from commercial oxide powders with purity of >99.99% by a solid-state reaction method. Absorption, fluorescence, and decay properties of these materials were evaluated. Considering the influence of increasing C Nd on these spectroscopic characteristics, it became clear that Nd:YSAG ceramics is suitable for the microchip laser or the mode-locked laser. We demonstrated microchip laser operation using highly concentrated Nd:YSAG. One-micron laser output power of 165 mW (37.0% optical-to-optical overall efficiency) and 49.5% slope efficiency were obtained under direct pumping into the emitting levels by a Ti:Sapphire laser from uncoated ceramic gain medium. Short-pulse generation from a passively mode-locked Nd 3+-doped YSAG ceramic laser was also demonstrated, and this laser generated pulses of ∼10 ps with 560 mW average power (35% optical-to-optical efficiency) under cw mode-locking operation.

Femtosecond Yb 3+-doped Y 3(Sc 0.5Al 0.5) 2O 12 ceramic laser

A passively mode-locked femtosecond Yb 3+-doped Y 3(Sc 0.5Al 0.5) 2O 12 (Yb:YSAG) ceramic laser has been studied. The new material, fabricated by sintering method, exhibited relatively low minimum pump intensity ( I min) and broad emission bandwidth even in the yttrium aluminum garnet systems. The value of I min in the Yb:YSAG ceramics was found to be 2/3 compared with the Yb:YAG single crystal under 970-nm direct pumping. Efficient continuous-wave laser oscillation of 72% slope efficiency for incident pump power and wide tuning range of 53 nm ( λ = 1012.9 nm ∼1065.5 nm) were obtained. By using a semiconductor saturable-absorber mirror (SESAM) for mode-locking operation, pulses as short as 280 fs having an average output power of 62 mW at 1035.8 nm were achieved. This is the shortest femtosecond pulse oscillation based on rare-earth-doped ceramic gain medium. The possibility of sub 100 fs pulse generation in a Yb:YSAG is discussed.