Description
Introduction
Ytterbium Doped Calcium Gadolinium Aluminate (Yb:CaGdAlO4 or Yb:CALGO) is a promising new laser gain material which possess several important advantages. The crystal structure of CALGO is tetragonal. When it is pumped at 979 nm under π configuration, we can get broad emission spectra from 994 nm to 1050 nm in σ configuration. This implies a very low quantum defect (down to 1.5%) and gives a good expectation of obtaining ultra-fast pulse. In addition, Yb:CALGO also has a thermal conductivity of up to k=6.7 W/m/K, making it suitable for high-power laser applications.
CASTECH’s Yb:CaGdAlO4 is featured by
• High absorption coefficient @979 nm
• High stimulated emission cross section
• Low laser threshold
• Extremely low quantum defect
• Broad output @994-1050 nm
• High slope efficiency with diode pumping (up to 55%)
• Various Yb-doping concentration
Applications
• Over 5.5 W output power is obtained by 23 W incident pumping diode laser with 10% output coupler;
• Output power as high as 12.5 W and 94 fs pulses for 28 W pumping power was reported.
Table 1. Basic Properties
| Crystal Structure | Tetragonal |
| Point group | I4/mm |
| Lattice Parameter | a = 3.6585 Å, c = 11.978 Å |
| Melting Point | 1850 ℃ |
| Mohs Hardness | 6 Mohs |
| Density | 4.8 g/cm3 |
| Thermal Conductivity | K[001] = 6.3 W/m/K, K[100] = 6.9 W/m/K |
| Thermal Expansion Coefficients | 10.1×10-6 /K (∥a), 16.2 ×10-6 /K (∥c) |
| Laser Wavelength | 994-1050 nm |
| Absorption Wavelength | 979 nm |
| Absorption Cross Section
(π configuration at 979 nm) |
2.7×10-20 cm2 |
Table 2. Specifications of Yb: CaGdAlO4
| Orientation | a or c |
| Standard Dopant Concentration | Yb: 1, 2, 3, 5 at.% |
| Maximum Length | 50 mm |
| Surface Quality (Scratch/Dig) | 10/5 to MIL-PRF-13830B |
| Dimensional Tolerances | Diameter: ±0.1mm
Length: ±0.5 mm |
| Parallelism | 20 arc sec |
| Perpendicularity | ≦15 arc min |
| Coating | AR-1030/980 nm,
R<0.2% @1030 nm, R<0.5% @980 nm. Other coatings are available upon request. |
