Maximum value of the pulse energy of a passively Q-switched laser as a function of the pump power

The finite recovery time T-s of the bleached absorber is presented as one of the possible mechanisms accounting for the increase-maximum-decrease in pulse energy E with the pumping rate W-p in cw-pumped passively Q-switched solid-state lasers. by analytically evaluating the sign of the derivative partial derivative E/partial derivative W-p. The results show that. in the low punipinie (T > T-s, T is the interpulse period). the initial repopulation density n, remains constant. the final population density n(i) decreases with W-p. and this results in a monotonic increase of E with W-p. In the high pump regime (T < T-s). n, decreases but n(i) remains the same with W-P; this results in a monotonic decrease of E with W-p. At the critical region (T approximate to T), E reaches its maximum value. A cw-pumped Yb:YAG laser passively Q switched by a Cr4-:YAG absorber is demonstrated to confirm this model. The theoretical model is also applied to the analysis of three previously reported passive Q switching solid-state [Nd:GdVO4, Nd-:LaSc3(BO3)(4) (Nd-:LSB), and Nd:YAG] lasers experiments. (c) 2006 Optical Society of America

Transient temperature profile in the gain medium of CW- and end-pumped passively Q-switched microchip laser

The transient temperature profile in CW- and end-pumped passively Q-switched (PQS) microchip laser is investigated qualitatively by treating the population inversion (thereby the thermal load) as the sawtooth function of the time. The numerical results reveal not only the dynamics of thermal buildup, but also the dependence of the quasi-steady-state temperature rise and the repetitively oscillatory amplitude on the incident pump power and the pulse repetition rate of PQS laser. The abruptly ascending branch of the repetitive temperature oscillation is synchronized with the pulsing stage of PQS laser. As the result, the abrupt temperature transition during the pulsing stage would introduce the fluctuation into the PQS pulse parameters (pulse energy, pulse width, and peak power) via temperature-dependent stimulated emission and thermal lensing effect. (c) 2006 Elsevier B.V. All rights reserved

Efficient emission of Laguerre-Gaussian beam from Nd-doped Yttrium Vanadate laser

An laser-diode (LD) end-pumped Nd-doped Yttrium Vanadate (Nd: YVO4) laser was demonstrated to emit the first order Laguerre-Gaussian (LG(01)) mode. This LG(01)-mode laser is compact and efficient

3D free-assembly modular microfluidics inspired by movable type printing

Abstract Reconfigurable modular microfluidics presents an opportunity for flexibly constructing prototypes of advanced microfluidic systems. Nevertheless, the strategy of directly integrating modules cannot easily fulfill the requirements of common applications, e.g., the incorporation of materials with biochemical compatibility and optical transparency and the execution of small batch production of disposable chips for laboratory trials and initial tests. Here, we propose a manufacturing scheme inspired by the movable type printing technique to realize 3D free-assembly modular microfluidics. Double-layer 3D microfluidic structures can be produced by replicating the assembled molds. A library of modularized molds is presented for flow control, droplet generation and manipulation and cell trapping and coculture. In addition, a variety of modularized attachments, including valves, light sources and microscopic cameras, have been developed with the capability to be mounted onto chips on demand. Microfluidic systems, including those for concentration gradient generation, droplet-based microfluidics, cell trapping and drug screening, are demonstrated. This scheme enables rapid prototyping of microfluidic systems and construction of on-chip research platforms, with the intent of achieving high efficiency of proof-of-concept tests and small batch manufacturing