Dongzhen Li

First laser oscillation of diode-pumped Tm 3+ -doped LuScO 3 mixed sesquioxide ceramic

Tm3+-doped LuScO3 mixed sesquioxide ceramics were successfully fabricated by using a solid-state reactive sintering method. The absorption and emission spectra were measured at room temperature. Continuous-wave (CW) and passively Q-switched laser operation of Tm3+:LuScO3 ceramic were investigated for the first time to our knowledge. A CW output power of 211 mW with slope efficiency of about 8.2% was obtained. With single-walled carbon nanotube (SWCNT) as saturable absorber, a maximum average output power of 32 mW was achieved. The shortest pulse width was 0.59 μs at pulse repetition rate of 34.72 kHz.

Passively Q-Switched Tm:CaGdAlO_4 laser using a Cr^2+:ZnSe saturable absorber

Diode-pumped Tm:CGA lasers at 1938 and 1854 nm are reported in continuous-wave and Q-switched regimes. For continuous-wave laser operation, the maximum output powers for the two lasers are 3.05 and 2.41 W with slope efficiencies of 33.7% and 28.5%, respectively. For Q-switching, using a Cr:ZnSe saturable absorber, the maximum average output powers reach 0.64 and 0.37 W with corresponding shortest pulse widths, maximum pulse repetition rates, maximum pulse energies and maximum pulse peak powers of (44ns, 13.9 kHz, 46 μJ, 1.04 kW) and (47 ns, 9.9 kHz, 37.4 μJ, 0.79 kW), respectively.

Crystal growth, polarized spectroscopy and Judd-Ofelt analysis of Tb:YAlO 3

Tb3+-doped YAlO3 (YAP) single crystal was grown by Czochralski (Cz) method. Based on the polarized absorption spectra, the spectroscopic parameters were calculated to be Ω2=3.49×10-20cm2, Ω4=5.87×10-20cm2 and Ω6=2.55×10-20cm2, and then the spontaneous transition rate, fluorescent branching ratio and radiative lifetime of 5D4 multiplet were obtained. The yellow emission cross sections of 5D4→7F4 transition were calculated to be 1.72×10-22cm2, 2.73×10-22cm2 and 2.65×10-22cm2 for a, b and c polarization, respectively. The fluorescence lifetime of the 5D4 multiplet was fitted to be 1.72ms. All the data indicate that Tb:YAP crystal is a promising candidate for yellow laser operation.

Comparative study of eye-safe Nd:LuAG crystal and ceramic lasers at 1.83 μm operating on 4F3/2 → 4I15/2 transition

Metamaterials, artificially structured electromagnetic (EM) materials, have enabled the realization of many unconventional electromagnetic properties not found in nature, such as negative refractive index, magnetic response, invisibility cloaking and so on. Based on these man-made materials with novel EM properties, various devices have been designed and realized. However, quantum analog devices based on metamaterials have not been achieved so far. Here we designed and printed metamaterials to perform quantum search algorithm. The structures, comprising of an array of two-dimensional (2D) sub-wavelength air holes with different radii perforated on the dielectric layer, have been fabricated by using 3D printing technique. When an incident wave enters in the designed metamaterials, the profile of beam wavefront is processed iteratively as it propagates through the metamaterial periodically. After roundtrips, precisely the same as the efficiency of quantum search algorithm, searched items will be found with the incident wave all focusing on the marked positions. Such a metamaterial-based quantum searching simulator may lead to remarkable achievements in wave-based signal processors.

Crystal growth, spectroscopic characteristics, and Judd-Ofelt analysis of Dy:Lu2O3 for yellow laser

Dy:Lu2O3 was grown by the float-zone (Fz) method. According to the absorption spectrum, the Judd–Ofelt (JO) parameters Ω 2, Ω 4, and Ω 6 were calculated to be 4.86 × 10−20 cm2, 2.02 × 10−20 cm2, and 1.76 × 10−20 cm2, respectively. The emission cross-section at 574 nm corresponding to the 4F9/2→6H13/2 transition was calculated to be 0.53 × 10−20 cm2. The yellow (4F9/2→6H13/2 transition) to blue (4F9/2→6H15/2 transition) intensity ratio ranges up to 12.9. The fluorescence lifetime of the 4F9/2 energy level was measured to be 112.1 μs. These results reveal that Dy:Lu2O3 is a promising material for use in yellow lasers.

Fabrication and Sintering Behavior of Er:SrF2 Transparent Ceramics using Chemically Derived Powder

In this paper, we report the fabrication of high-quality 5 at. % Er3+ ions doped SrF2 transparent ceramics, the potential candidate materials for a mid-infrared laser-gain medium by hot-pressing at 700 °C for 40 h using a chemically-derived powder. The phase structure, densification, and microstructure evolution of the Er:SrF2 ceramics were systematically investigated. In addition, the grain growth kinetic mechanism of Er:SrF2 was clarified. The results showed lattice diffusion to be the grain growth mechanism in the Er:SrF2 transparent ceramic of which highest in-line transmittance reached 92% at 2000 nm, i.e., very close to the theoretical transmittance value of SrF2 single crystal. Furthermore, the emission spectra showed that the strongest emission band was located at 2735 nm. This means that it is possible to achieve a laser output of approximately 2.7 μm in the 5 at. % Er3+ ions doped SrF2 transparent ceramics.