Li De-Hua

Surface oxidation of vanadium dioxide films prepared by radio frequency magnetron sputtering

This paper reports that the thermochromic vanadium dioxide films were deposited on various transparent substrates by radio frequency magnetron sputtering, and then aged under circumstance for years. Samples were characterized with several different techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, and Raman, when they were fresh from sputter chamber and aged after years, respectively, in order to determine their structure and composition. It finds that a small amount of sodium occurred on the surface of vanadium dioxide films, which was probably due to sodium ion diffusion from soda-lime glass when sputtering was performed at high substrate temperature. It also finds that aging for years significantly affected the nonstoichiometry of vanadium dioxide films, thus inducing much change in Raman modes.

Diode-pumped passive Q-switched 946-nm Nd : YAG laser with 2.1-W average output power

We demonstrate a diode-pumped passive Q-switched 946 nm Nd:YAG laser with a diffusion-bonded composite laser rod and a co-doped Nd,Cr:YAG as saturable absorber. The average output power of 2.1 W is generated at an incident pump power of 14.3 W. The peak power of the Q-switched pulse is 643 W with 80 kHz repetition rate and 40.8 ns pulse width. The slope efficiency and optical conversion efficiency are 17.6% and 14.7%, respectively.

Generation of 170-fs Laser Pulses at 1053 nm by a Passively Mode-Locked Yb:YAG Laser

A novel method is developed to obtain 1.05 μm laser operation with a Yb:YAG laser. By using a Yb:YAG crystal with proper length and doping concentration, a femtosecond Yb:YAG laser is realized at the central wavelength of 1053 nm. The measured pulse duration and spectral bandwidth (FWHM) are 170 fs and 7 nm; the repetition rate is 80 MHz. Under a power pump of 2 W, an average mode-locking power of 180 mW is achieved.

Diode-pumped self Q-switched and mode-locking Nd3+Cr4+: YAG laser

Using Nd3+,Cr4+:YAG as a laser crystal and saturable absorber simultaneously, we obtain a self-Q-switched and mode-locking laser at 1.06 μm with straight cavity structure. Self mode-locking phenomenon was observed at an intracavity intensity of only about 2000 W/cm2. More than 90% modulation depth is achieved at an intracavity intensity of less than 3.0×104 W/cm2 for the first time. The Q-switched pulse width and repetition rate are found to be connected with the cavity length and the output power.

Compact High-Power Blue Light from a Diode-Pumped Intracavity-Doubled Nd:YAG Laser

We report an efficient continuous wave (cw) operation of 946 nm and 473 nm laser beams generated from a diode-pumped composite Nd:YAG rod. A very simple compact linear cavity was employed with cavity length of 35 mm. A composite Nd:YAG laser rod was used to release thermal effects. The maximum cw output of 3.3 W at 946 nm was obtained with slope efficiency of 22% at incident pump power of 17.5 W. By intracavity doubling with an LBO crystal, as much as 590 mW of single-ended blue output at 473 nm was achieved with an optical-optical conversion efficiency of 3.4%. The total blue output would be 1.06 W with overall conversion efficiency of 6.1% if the lasers emitted in both the directions were taken into account.

Diode-Pumped Compact cw Frequency-Doubled Nd:YAG Laser in the Watt Range at 473 nm

We report a diode-pumped cw Nd:YAG laser operating on the 4F3/2-4I9/2 transition at 946 nm, for which a maximum output power of 4.5 W with a slope efficiency of 21% is achieved at an incident pump power of 26 W. Two LiB3O5 (LBO) crystals of different lengths (3×3×10 mm and 3×3×15 mm), cut for critical type I phase matching at room temperature, have been used for intracavity frequency doubling, and through optimization of the structure and elements of the cavity, a maximum single-ended blue output power of 1.1 W has been obtained with an optical conversion efficiency of 4.2%. A stability better than 4.8% with no mode hopping over a period of 2 h has been achieved.

Intracavity-doubled self-Q-switched Nd,Cr : YAG 946/473 nm microchip laser

We carried out the operation of an intracavity frequency-doubled self-Q-switched Nd, Cr: YAG/KNbO3 946/473 nm microchip laser pumped by a Ti:sapphire laser. The overall cavity length was about 4 mm. The maximum average blue power of 12 mW was achieved with a repetition rate of 13 kHz at an absorbed pump power of 545 m W. The pulses of the 4 73 nm laser had a duration of 7 ns and a peak power of 132 W at this pump level. The conversion efficiency was 2.2% with respect to the absorbed pump power of a 808 nm laser.

Passively Mode-Locked Quasi-Three-Level Nd:LuVO4 Laser with Semiconductor Saturable Absorber Mirror

We demonstrate a passively cw mode-locked Nd:LuVO4 laser operating on the quasi-three-level at 916 nm with a Z-folded resonator. Using a semiconductor saturable absorber mirror (SESAM) as the passive mode-locking device, we achieve stable cw mode locking with 6.7 ps pulse duration at repetition rate of 133MHz and 88mW average output power under the pump power of 17.1 W.

Green Output of 1.5 W from a Diode-Pumped Intracavity Frequency-Doubled Self-Q-Switched and Mode-Locked Cr,Nd:YAG Laser

The spontaneous emmission (SE) progress of polarized atoms in a stratified structure of air-dielectric (D0-metal(M)-dielectric(D1)-air can be controlled effectively by changing the thickness of the D1 layer and rotating the polarized direction of atoms. It is found that the normalized SE rate of atoms located inside the D0 layer crucially depends on the atomic position and the thickness of the D1 layer. When the atom is located near the D0-M interface, the normalized atomic SE rate as a function of the atomic position is abruptly onset for the thin D1 layer. However, with the increasing thickness of the D1 layer, the corresponding curve profile exhibits plateau and stays nearly unchanged. The substantial change of the SE rate stems from the excitation of the surface plasmon polaritons in metal-dielectric, and the feature crucially depends on the thickness of D1 layer. If atoms are positioned near the D0-air interface, the substatial variation of the normalized SE rate appears when rotating the polarized direction of atoms. These findings manifest that the atomic SE processes can be flexibly controlled by altering the thickness of the dielectric layer D1 or rotating the orientation of the polarization of atoms.

Characteristics of Nd:YGG Laser Operating at 4F3/2–4I9/2

The laser properties of the Nd:YGG crystal are investigated. The absorption spectrum from 500 to 900 nm and emission spectrum from 850 to 1400nm of Nd:YGG are measured. As much as 1.35 W output power of fundamental laser operating at 935 and 938 nm with a slope efficiency of 15.7% and 105 mW output power of frequency doubled blue laser are successfully obtained.