A passively Q-switched mode locking operation was first realized in a Tm, Ho:LLF laser by using a reflection-type MoS<sub>2</sub> saturable absorber. When the absorption pump power is greater than 1.1W, a stable Q-switched mode locking operation was achieved, corresponding to a 100MHz of the mode-locked frequency. The modulation depth in Q-switching envelopes is close to 100%. The results show that the reflection-type MoS<sub>2</sub> can be used as the absorber material for 2μm all solid state lasers.
The structure of organic light-emitting diodes (OLEDs) is one of most important issues that influence the light output intensity (LOI) of OLEDs. In this paper, based on a simple but accurate optical model, the influences of hole and electron transport layer thickness on the LOI of bilayer OLEDs, which with N,N0- bis(naphthalen-1-yl)-N,N0- bis(phenyl)- benzidine (NPB) or N,N′- diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4-diamine (TPD) as hole transport layer, with tris(8-hydroxyquinoline) aluminum (Alq3) as electron transport and light emitting layers, were investigated. The laws of LOI for OLEDs under different organic layer thickness values were obtained. The results show that the LOI of devices varies in accordance with damped cosine or sine function as the increasing of organic layer thickness, and the results show that the bilayer OLEDs with the structure of Glass/ITO/NPB (55 nm)/Alq3 (75 nm)/Al and Glass/ITO/TPB (60 nm)/Alq3 (75 nm)/Al have most largest LOI. When the thickness of Alq3 is less than 105 nm, the OLEDs with TPD as hole transport layer have larger LOI than that with NPB as hole transport layer. The results obtained in this paper can present an in-depth understanding of the working mechanism of OLEDs and help ones fabricate high efficiency OLEDs.