There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Transparent ceramics have various potential applications such as infrared (IR) windows/domes, lamp envelopes, opto-electric components/devices, composite armors, and screens for smartphones and they can be used as host materials for solid-state lasers. Transparent ceramics were initially developed to replace single crystals because of their simple processing route, variability in composition, high yield productivity, and shape control, among other factors. Optical transparency is one of the most important properties of transparent ceramics. In order to achieve transparency, ceramics must have highly symmetric crystal structures; therefore, the majority of the transparent ceramics have cubic structures, while tetragonal and hexagonal structures have also been reported in the open literature. Moreover, the optical transparency of ceramics is determined by their purity and density; the production of high-purity ceramics requires high-purity starting materials, and the production of high-density ceramics requires sophisticated sintering techniques and optimized sintering aids. Furthermore, specific mechanical properties are required for some applications, such as window materials and composite armor. This review aims to summarize recent progress in the fabrication and application of various transparent ceramics.

Materials development and potential applications of transparent ceramics: A review

Low-threshold wide-band lasing was achieved for a YAG crystal with optically and thermally stable color centers. The absorption and luminescence spectra were determined, and the gain was measured in the range of wavelengths corresponding to the color-center luminescence. The cross section of the lasing transition was estimated (8 × 10−19 cm2) and the efficiency of conversion of the pump radiation from a neodymium laser into the output radiation was determined (10%).

Lasing due to impurity color centers in yttrium aluminum garnet crystals at wavelengths in the range 1.35-1.45 μm

A compact pulsed Nd:LuAG laser at 1064 nm based on the self-Q-switching technique is reported, having the output power as high as 6.61 W at the incident pump power of 21.32 W, corresponding to the optical conversion efficiency of ∼31%. The temporal width of the pulse was in the range from 532.2 to 652.6 ns, and the repetition rate varied between 488.6 and 551.9 kHz. To the best of our knowledge, this is the first report on the self-Q-switching Nd:LuAG laser. With the nonlinear refractive index calculated to be 1.8 × 10–19 m2/W, and the numerical simulation made with the modified rate equations, the Kerr lens effect was believed to be the reason for the self-Q-switching of Nd:LuAG. The compact cavity generating pulses with high output power and high repetition rate not only reveal that the self-Q-switching technique could be an efficient method for the generation of pulses with high output power and high repetition rate, but enrich the characteristics of Nd:LuAG crystal.

/pdf/high-power-self-q-switching-in-nd-luag-laser-2iqypllym9.pdf

High Power Self-Q-Switching in Nd:LuAG Laser

We experimentally demonstrated dual-wavelength synchronous operation of a high-power passively mode-locked 2-μm Tm:CaYAlO4 (Tm:CYA) disordered crystal laser with semiconductor saturable absorber mirror (SESAM) as mode locker. The mode-locked laser emitted an average output power as high as 830 mW with pulse duration of 35.3 ps and repetition rate of 145.4 MHz. The mode-locking dual wavelengths were centered at 1958.9 nm and 1960.6 nm, respectively. Autocorrelation trace clearly shows beating pulses with pulse width of 3.5 ps and repetition rate of 0.13 THz.

Dual-wavelength synchronous operation of a mode-locked 2-μm Tm:CaYAlO4 laser.

A diode-end-pumped dual-wavelength mode-locked laser based on Nd:LuYSiO5 crystal is demonstrated. With a SESAM, simultaneous mode locking at the 1075.8 nm and 1078.1 nm is achieved and the dual-wavelength mode locked pulses have a pulse width of 8.9 ps. Due to frequency beating, ultrahigh repetition rate ultrafast pulses with 997 fs pulse width and 0.59 THz repetition rate are further formed. Under 12.7 W absorbed pump power 1.7 W mode-locked output power was obtained, the slope efficiency of the mode locked laser was 24.3%.

Dual-wavelength passively mode-locked Nd:LuYSiO5 laser with SESAM.

Fabrication and laser properties of transparent Yb:YAG ceramics

The femtosecond and cw laser performances of a Yb3+: Sc 2 SiO 5 (Yb: SSO) are investigated. The laser produced a maximum cw output of 2.73 W at 1063 nm. The corresponding slope efficiency and optical to optical efficiency were 70 % and 59 % respectively. The laser mode-locked at 1041 nm, 1060 nm and 1077 nm with near Fourier transformed limited pulse width of 145 fs, 144 fs and 125 fs with average output power of 40 mW, 52 mW and 102 mW, respectively.

Passive femtosecond mode-locking and cw laser performances of Yb 3+ : Sc 2 SiO 5

Yb:LuAG laser ceramics with different Yb3+ doping concentrations were successfully fabricated by using a solid-state reactive sintering method. SEM graphs demonstrate that the samples have a dense and pore-free microstructure. Based on the spectroscopic studies the ceramics have a large emission cross-section of 2.7 × 10−20 cm2 at 1030 nm emission peak. CW laser operation of the samples has given 7.2 W output power with 65% slope efficiency.

/pdf/yb-luag-laser-ceramics-a-promising-high-power-laser-gain-7n6bghydne.pdf

Changwen Xu

Papers

Dual-wavelength passively mode-locked Nd:LuYSiO5 laser with SESAM.

Fabrication and laser properties of transparent Yb:YAG ceramics

Passive femtosecond mode-locking and cw laser performances of Yb 3+ : Sc 2 SiO 5

Yb:LuAG laser ceramics: a promising high power laser gain medium

Diode-end-pumped Nd:CaYAlO4 mode locked laser