Baigang Zhang

Continuous-wave operation at 1386 nm in a diode-end-pumped Nd:YVO4 laser.

We report a diode-end-pumped continuous wave (cw) Nd:YVO4 laser operation at 1386 nm. A maximum output power of 305 mW is achieved at an incident pump power of 4.24 W, achieving a slope efficiency of 13.9%. To the best of our knowledge, this is the first time that cw operation at this transition of Nd:YVO4 crystal is reported. By using the experimentally measured threshold data, the stimulated-emission cross-section of this gain medium at 1386 nm transition is determined to be 3x10- 19cm2. In addition, simultaneous cw operation at 1342 nm and 1386 nm is also observed.

8.3 W diode-end-pumped continuous-wave Nd:YAG laser operating at 946-nm

This paper reports a diode-end-pumped continuous-wave (CW) Nd:YAG laser operating at 946-nm by utilizing the 4F3/2-4I9/2 transition. We demonstrated that at an incident pump power of 27.7 W, an output power of 8.3-W could be achieved with a slope efficiency of 33.5%. To the best of our knowledge, this is the highest CW output power at 946 nm generated by LD end-pumped Nd:YAG lasers. By using intracavity frequency doubling with an LBO crystal, we further obtained a 473-nm blue laser with an output power of 1.2 W, achieving an optical-to-optical conversion efficiency of 7.1% at a pump power of 16.9 W. The short-term power instability of the blue laser was less than 1 %.

Experimental study on a high conversion efficiency, low threshold, high-repetition-rate periodically poled lithium niobate optical parametric generator

A high-conversion-efficiency, low-threshold, quasi-continuous-wave optical parametric generator (OPG) based on a periodically poled lithium niobate (PPLN) crystal is presented. Pumped by an acousto-optically Q-switched 1064 nm Nd:YAG laser with a power output of 848 mW, the OPG generated an output power of 452 mW for the signal and the idle waves, achieving an internal conversion efficiency of 62.7% and a slope efficiency of 75.6%. To the best of our knowledge, this is the highest efficiency ever reported for single-pass, quasi-continuous-wave OPGs by using periodically poled crystals.

Tunable dual-signal PPLN optical parametric generator by using an acousto-optic beam splitter

A tunable dual-signal optical parametric generator (OPG) based on multi-grating periodically poled lithium niobate (PPLN) is presented. An acousto-optic device (AOD) was used as a beam splitter outside the cavity of a high-repetition-rate, Q-switched 1064 nm Nd:YAG laser. A synchronous and widely tunable dual-signal OPG was obtained by coupling the split beams into two parts with different poled periods in the same PPLN crystal and by tuning the temperature of the crystal. A total conversion efficiency of 27.9% was achieved when the system operated at 1687 and 1864 nm.

High-repetition-rate dual-signal intracavity optical parametric generator based on periodically-phase-reversal PPMgLN

A high-repetition-rate dual-signal intracavity optical parametric generator (IOPG) inside a diode-end-pumped acousto-optically (AO) Q-switched Nd:YVO4 laser is presented. The nonlinear material is a periodically-phase-reversal periodically poled MgO-doped lithium niobate (ppr-PPMgLN). At an incident diode pump power of 6.1?W and a Q-switch repetition rate of 20?kHz, an average dual-signal output power of 0.44?W is achieved. The dual-signal wavelengths of 1477 and 1491?nm are obtained at a crystal temperature of 40??C. The measurements of the beam quality factor of 1.4 and the pulse duration of 77?ns show good spatial and temporal overlaps for the dual-signal radiation.

Design of a broadband source by using the retracing behavior of a collinear quasi-phase-matching optical parametric generator

In this paper, we introduce a concept of phase matching bandwidth of broadband sources by using the retracing behavior of collinear quasi-phase-matching (CQPM) optical parametric generation (OPG) in periodically poled lithium niobate (PPLN). By comparing various pump wavelengths we derive the pumping condition and parameters of PPLN to realize a broadband source near 1550 nm in the CQPM-OPG. We predict the optimum pump wavelength and the maximum ideal bandwidth range to be 940.75 nm and 1475-1681 nm respectively. Experimentally we have demonstrated a 946 nm Nd:YAG laser which serves as the pumping source of CQPM-OPG.

The study of stability on a laser-diode-pumped high-power high-repetition-rate intracavity frequency-doubled 532-nm laser

High power laser-diode-pumped 532nm laser sources (including continuous wave and high repetition rate operation) are directly used for precise processing of metals and plastics. Furthermore, high power green laser will be used in some fields such as ocean exploration, laser probe and underwater communication. Recently, we reported a 110W diode-side-pumped Nd:YAG intracavity frequency doubled high stability 532nm laser. In the experiment, we found that the average output power of second harmonic fluctuated acutely with the variety of pumping current. Moreover, the length of arms between the mirrors were very sensitive to this cavity. We consider that one of the reason is the focus length of thermal lens of Nd:YAG rod alter with the variational pumping current, which makes the cavity be unstable. We consider the KTP crystal as a thin lens for its short length. As thermal lensing effect of the Nd:YAG rod is quite severe, so we consider it as thermal lensing medium. By ray matrix methods, we have obtained the stable regions and beam waist radii distribution in the flat-concave cavity. In our experiment, we used a pump head consisting of 80 diode bars with pentagon pump model and employed flat-concave cavity structure in order to achieve high stability output and increase output power. The total cavity length is 505mm. By using an acousto-optic Q-switching with high diffraction loss and the KTP crystal which is type II phase matching, 110 W high stability 532nm laser is achieved. The experimental result is in good agreement with the calculation.

High-average-power, high-repetition-rate dual signal optical parametric oscillator based on PPMgLN

A high-average-power, high-repetition-rate dual signal optical parametric oscillator based on periodically poled MgO-doped lithium niobate (PPMgLN) with a phase-reversed grating is reported. The pump laser is an acousto-optically Q-switched Nd:YVO4 laser with a maximum average power of 7.6 W. When the repetition rate is 50 kHz and the pulse width of the pump source is 23 ns, the maximum average dual signal output power is about 1.9 W, leading to a conversion efficiency of 25%. Over a 30-min interval, the instability of the signal power measured is less than 0.5%.

High conversion efficiency continuous wave quasi-phase-matched second harmonic generation in MgO doped stoichiometric lithium tantalate

In this paper, for the first time we have demonstrated a continuous wave single-pass extracavity frequency doubling by use of MgO doped stoichiometric lithium tantalite (PP-MgO: SLT). The maximum output of the second harmonic green light is 905mW with the pumping power of 7.69W. The second harmonic conversion efficiency is 11.77%. We have theoretically calculated the tolerance of the temperature of SLT SHG which is about 1.5°C. The experimental tolerance of the temperature is consistent with the calculated value.

Parameters option of a pressure fiber sensor

A pressure sensor based on fiber-optical sensor (FOS) is discussed about the design parameters option in this paper. An elastic spherical diaphragm is used as a reflective target of displacement fiber sensor in this paper. The spherical diaphragm coils when force is performed upon, light intensity of receiving fiber changes depending on the deformation of it. The relationship between sensitivities of the sensor and diameters of the elastic diaphragm, diameters of fibers and the distance from the terminal of fiber to the initial diaphragm before force performed are calculated based on light distributing theory. From the consequence of calculations, we give out the optimum condition for this kind fiber sensor design. The receiving intensity of light have a goood linear relationship to the fore is presented meanwhile.