The results from experiments relating to the CW operation of a Tm-Ho-doped silica fiber laser which is pumped with the fundamental output from a Nd:YAG laser are presented. The measured maximum output power from the fiber laser of 11 mW was generated at a slope efficiency of approximately 1.8% for a fiber length of 0.574 m and an output coupling of 10%. An output wavelength of 2170 nm (one of the longest lasing wavelengths to be achieved with the use of a silica host material) was also generated from the Tm-Ho-doped fiber User when the fiber length was extended to 1.240 m and a 5% output coupling incorporated. The reduced efficiency and increased threshold for the Nd:YAG·pumped Tm-Ho-doped silica fiber laser when compared to previous reports of Ti:sapphire pumping is discussed in detail with the aid of a comprehensive numerical model. The numerical model solves the rate equations for the Tm-Ho-doped silica fiber laser syslem by taking into account the cross relaxation, energy transfer, and upconversion mechanisms, and it utilizes all published speclroscopic parameters relevant to Tm-Ho-doped silica and Tm-Ho:ZBLAN glass materials. It is established that the excited state absorption relevant to Nd:YAG pumping severely depletes the 3H4 energy level of Tm3+ and consequently hinders the energy transfer process to the 5I7 energy level of Ho3+. Optimum dopant concentrations are also established for both Nd:YAG and Ti:sapphire pump schemes.
|Number of pages||10|
|Journal||IEEE Journal of Quantum Electronics|
|Publication status||Published - Sep 1998|
- CW lasers
- Laser excitation
- Neodymium: YAG lasers
- Optical fibers