Appl Phys B (2012) 107:41–45 DOI 10.1007/s00340-011-4831-6 Continuous-wave and actively Q-switched Nd:LSO crystal lasers S. Zhuang · D. Li · X. Xu · Z. Wang · H. Yu · J. Xu · L. Chen · Y. Zhao · L. Guo · X. Xu Received: 14 July 2011 / Revised version: 11 October 2011 / Published online: 22 November 2011 © Springer-Verlag 2011 Abstract With a fiber coupled laser diode array as the pump source, Nd-doped Lu 2 SiO 5 (Nd:LSO) crystal lasers at 4 F 3/2 → 4 I 11/2 and 4 F 3/2 → 4 I 13/2 transitions were demon- strated. The active Q-switched dual-wavelength lasers at about 1.08 μm, as well as continuous-wave (CW) and ac- tive Q-switched lasers at 1357 nm are reported for the first time, to the best of our knowledge. Considering the small emission cross-sections and long fluorescence life- time, this material possesses large energy storage ability and excellent Q-switched properties. The special emission wavelength at 1357 nm will have promising applications to be used in many fields, such as THz generation, pumping of Cr 3+ :LiSAF, repumping of strontium optical clock, laser Doppler velocimeter and distributed fiber sensor. S. Zhuang · Z. Wang ( ) · H. Yu · L. Chen · Y. Zhao · L. Guo · X. Xu State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China e-mail: zpwang@sdu.edu.cn X. Xu ( ) e-mail: xgxu@sdu.edu.cn D. Li · X. Xu Key Laboratory of Materials for High Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China J. Xu Key Laboratory of Transparent and Opto-functional Inorganic Materials, Shanghai Institute of Ceramics, Shanghai 201800, China S. Zhuang School of Science, Shandong Jianzhu University, Jinan 250101, China 1 Introduction Lutetium oxyorthosilicate, Lu 2 SiO 5 (LSO) is well-known to be used for scintillator applications. In recent years, many studies have been conducted on rare earth doped LSO as laser material. e.g., Yb:LSO [1–5], Tm:LSO [6], Ho:LSO [7, 8], and Dy:LSO [9]. One of the main ad- vantages is that this monoclinic biaxial crystal has strong natural birefringence which overwhelms the thermally in- duced stress birefringence [8]. Tkachuk et al. [10] reported a spectral-luminescence investigation of Nd:LSO more than two decades ago, but until very recently the CW laser per- formance of Nd:LSO was not demonstrated [11]. Soon after, Cong et al. [12] performed passively mode-locking laser op- erations of Nd:LSO crystal with a semiconductor saturable absorption mirror, and achieved 12.3 ps mode-locked pulse with 148.3 MHz repetition rate. A certain structural disor- der due to the two different occupation sites with low sym- metry for Nd 3+ ion in LSO crystal broadens the absorption and emission bands [10, 11], which are favorable for diode pumping and ultrashort pulse laser generation. For the 4 F 3/2 → 4 I 11/2 transition of Nd:LSO, the emis- sion cross-sections at about 1.08 μm are only 1/5 of the value for Nd:YAG crystal (2.8 × 10 −19 cm 2 ), and 1/18 of the value for Nd:YVO 4 crystal (10.7 × 10 −19 cm 2 ). The flu- orescence lifetime of Nd:LSO crystal is measured to be 220– 230 μs, which is similar to that of Nd:YAG crystal, but much longer than for Nd:YVO 4 crystal (110 μs). Its small emis- sion cross-section led to high CW and mode-locking thresh- olds [11, 12], but is favorable for Q-switching operation be- cause the emission cross-section and fluorescence lifetime determine the energy storage ability. For the 4 F 3/2 → 4 I 13/2 transition, Nd:LSO has an emission peak at 1357 nm, which has promising applications in laser-based metrology, laser Doppler velocimeter [13], and distributed fiber sensor [14],