Tm doped crystals embrace several attractive features that nominate them as the material of choice for solid-state laser sources with emission wavelength tunable around 2um. It was demonstrated that Tm:YAG laser can be tuned from 1.91 up to 2.15um. Similarly,Tm:YAP laser can tuning range from 1.85 to 2.03 um.The quasi-three level system of Tm:doped crystals requires appropriate pumping geometry and good heat extraction from the active media.
Ho:YAG Ho3+ ions doped into insulating laser crystals have exhibited 14 inter-manifold laser channels, operating in temporal modes from CW to mode-locked . Ho:YAG is commonly used as an efficient means to generate 2.1-μm laser emission from the 5I7- 5I8 transition, for applications such as laser remote sensing, medical surgery, and pumping Mid-IR OPO’s to achieve 3-5micron emission. Direct diode pumped systems,and Tm: Fiber Laser pumped system have demonstrated hi slope efficiencies, some approaching the theoretical limit.
Active elements from Erbium doped Yttrium Scandium Gallium Garnet crystals (Er:Y3Sc2Ga3012 or Er:YSGG), single crystals, are desinged for diode pumped solid-state lasers radiating in the 3 µm range. Er:YSGG crystals show the perspectiveness of their application alongside with the widely used Er:YAG, Er:GGG and Er:YLF crystals.
Erbium and ytterbium co-doped phosphate glass has a broad application because of the excellent properties. Mostly, it is the best glass material for 1.54μm laser due to its eye safe wavelength of 1540 nm and high transmission through atmosphere. It’s also suitable for medical applications where the need for eye protection may be difficult to manage or diminish or hinder essential visual observation. Recently it is used in optical fiber communication instead of EDFA for its more super plus. There is a great progress in this field.
Er: YAG is a kind of excellent 2.94 um laser crystal, widely used in laser medical system and other fields. Er: YAG crystal laser is the most important material of 3nm laser, and the slope with high efficiency, can work at room temperature laser, laser wavelength is within the scope of the human eye safety band, etc. 2.94 mm Er: YAG laser has been widely used in medical field surgery, skin beauty, dental treatment.
Nd:YVO4 is the most efficient laser host crystal for diode pumping among the current commercial laser crystals, especially, for low to middle power density. This is mainly for its absorption and emission features surpassing Nd:YAG. Pumped by laser diodes, Nd:YVO4 crystal has been incorporated with high NLO coefficient crystals ( LBO, BBO, or KTP) to frequency-shift the output from the near infrared to green, blue, or even UV.