We reported an actively mode-locked Ho:LuVO4 laser pumped with a Tm-doped fiber laser as the pump source for the first time. In the continuous wave (CW) mode, the maximum output power of 3.07 W at the absorbed pump power of 16.3 W was achieved with a central wavelength of 2073.8 nm, corresponding to an optical–optical conversion efficiency of 18.8%. The beam quality factor M2 was calculated to be 1.4. In CW mode-locked operation, the maximum laser output of 3.04 W at the same pump power was obtained with the same central wavelength of 2073.8 nm, corresponding to an optical–optical conversion efficiency of 18.7%. The repetition rate of the mode-locked pulse was 82.7 MHz with a single pulse energy of 36.8 nJ and pulse duration of 363.3 ps.
A compact continuous-wave and actively Q-switched Ho:LuVO4 laser pumped by a 1.94 μm Tm:YAP laser is demonstrated. The maximum output power of 6.7 W at 2058.13 nm in continuous-wave regime is obtained at an absorbed pump power of 17.8 W, corresponding to a slope efficiency of 48.4%. For Q-switched operation, average output power of 6.65 W and pulse width of 22.3 ns are obtained with a repetition frequency of 20 kHz, corresponding to a central wavelength of 2058.13 nm. In addition, different Q-switched pulses at repetition frequencies of 20, 30, 40, 50, and 60 kHz are investigated comparatively.
We report a continuous wave (CW) Tm:YLF laser-resonantly pumped Ho:LuAG laser in CW mode and passive Q-switched (PQS) mode with multilayer graphene as a saturable absorber. The lasing performance with different output couplers is analyzed. The best result was obtained with −150-mm radius curvature and 10% transmission output coupler. Under the CW mode, Ho:LuAG laser generated a maximum 1.3-W output power at the center wavelength of 2100.65 nm, corresponding to a slope efficiency of 34.6%. In PQS mode, the minimum pulse width observed is 784.7 ns with a center wavelength of 2100.65 nm at the pump power of 5.4 W. Meanwhile, the maximum output power is 0.37 W with a pulse repetition frequency of 47.3 kHz. The results show that the multilayer graphene can be used as a saturable absorber in a Ho3+-doped laser around a 2-μm wavelength.
The influence of energy-transfer up-conversion (ETU) on diode-end-pumped actively Q-switched Tm,Ho:YLF lasers is
investigated by the rate equation analysis. The theoretical results show that the energy-transfer up-conversion reduces not
only pulse energy but also effective upper level life. The practical example of the diode-end-pumped Q-switched
Tm,Ho:YLF laser has been used to verify the present model.
In this paper, we report a diode pumped Tm,Ho:GdVO<sub>4</sub> laser operating at cryogenic temperature, which has 3.5W of 2-μm output. Tm,Ho:GdVO<sub>4</sub> crystal has very stronger and broader absorption spectrum than Tm-Ho co-doped YLF and YAG, and very favorable for diode pumping. The fiber-coupled laser diode of 808nm (core diameter 0.4mm,N.A 0.22) is a pumping source to end-pumping Tm,Ho:GdVO<sub>4</sub> crystal. The optical-optical conversion efficiency of 34% and threshold pump power of 0.79W has been achieved. The laser design and laser performance is described.
A gain-switched Tm-doped double-clad silica fiber laser operating at a wavelength of approximately 2μm with moderate output energy is realized. A gain-switched Nd:YAG laser is used to pump the 3 5 H energy level of the doped Tm<sup>3+</sup> ions at 1.064μm, and a maximum total output energy of 14.7mJ per pulse is produced at a slope efficiency of 39.5% (with respect to launched pump energy). As we know, this is the first time to realize the gain-switched Tm<sup>3+</sup>-doped double-clad silica fiber laser pumped at 1.064μm, and both the single pulse energy and the slope efficiency exceed the reported results that produced from single-clad Tm<sup>3+</sup>-doped silica fiber laser in the past. The results of three different length fibers in experiments are present and contrasted. Because the absorption section at 1.064μm is only 2.5% at 0.79 μm in Tm<sup>3+</sup>-doped silica fiber, we use three relative long fibers (the fiber.1 length 35 m, fiber.2 length 8m, the fiber.3 length 1m.) to increase the absorption ratios. The laser threshold in fiber.1, fiber.2 and fiber.3 is 37.5mJ, 39.4mJ and 48 mJ, and the slope efficiency is 39.5%, 11.6% and 1% respectively. The output peak wavelength from fiber.1 fiber.2 and fiber.3 is 2.04μm, 2.01μm and 1.92μm measured by a monochromator respectively.
In this paper, we report a high power of cryogenic cooling Tm(8 at %), Ho(1.4 at %):YLF dual end pumped by two fiber coupled laser diodes at 792nm. Each pumping laser head delivers 15W power in an inner fiber core area of 0.4mm and numerical number of 0.3. The highest continuous-wave (cw) power of 10.2W at 2.051μm is attained under pumping power of 30W, corresponding to optical-optical conversion efficiency of 33%, and the slope efficiency is greater than 36%. The maximum acousto-optical Q-switched quasi-continuous wave output power is 9.2 W at pulse repetition frequency of 10kHz, corresponding to greater than 90% extraction efficiency in the full-width half-maximum pulse width of 34ns.
A room-temperature Tm,Ho:YLF laser is constructed with a 2.5-mm-long Tm(6%) and Ho(0.4%) co-doped yttrium lithium fluoride crystal pumped by a laser diode operating at 792nm. The output power as a function incident pump power at different output coupler transmission values is given. At room temperature, the laser operates on a single transverse mode (TEM<sub>00</sub>) at 2.066μm, the laser threshold pump power is 55mW, and its maximum output power and optical-to-optical conversion efficiency are 388mW and 14.1% respectively. At the same time, the output power and optical-to-optical conversion efficiency as a function of incident pump power at different temperatures are obtained. Furthermore, the experimental results are explained reasonably.
In this paper, we report a high efficient and high power continuous wave diode-pumped cryogenic Tm(5% at.), Ho(0.5% at.):GdVO<sub>4</sub> laser. One pumping source of Tm,Ho:GdVO<sub>4</sub> laser is a fiber-coupled laser diode with fiber core diameter of 0.4 mm and numerical aperture (N. A.) of 0.3, supplying 14.8 W power at 793.6 nm. Another fiber-coupled LD radiation wavelength is centered at 805 nm with 0.22 N.A. and the same core diameter delivering power of greater than 30 W. For input pump power of 13.6 W at 794.2nm, the maximum output power of 4.2W, optical-to-optical conversion efficiency of 31% and slope efficiency 38% have been attained at 2.048 μm. The maximum cw power of 7.9-W is achieved by 805 nm LD under power of 26 W, corresponding to 40% optical-optical conversion efficiency relative to absorbed pumping power, which is close to quantum limited efficiency of 2 μm laser.
This paper report the A-O Q-switched LD end pumped 8% Tm, 1.4%Ho:YLF laser. The fiber-coupled pump laser deliver maximum 15W around 792nm At 10 KHz pulse repetition frequencies (PRF), The average output power of 4.1 W, the pulse width of 32ns and peak power of 0.012MW at 2.05um were achieved. The pulse fluctuation is less than ± 2%. The pulse amplitude instability at last higher rate equation was analyzed.
The wavefront aberration of laser beam produced in the process of laser propagation in the atmosphere can be compensated with the stimulated Brillouin-scattering (SBS) effect. However, in case of an uncooperative extensive target, the beacon is remained as a problem. Based on the method of active beacon, and making use of threshold effect of SBS, we present a method to obtain a beacon of small area on an uncooperative target, and with it, the laser beam can be focused on the small area.
We have developed a high efficient, all-solid-state approach by using potassium titanyl phosphate (KTP)-based optical parametric oscillator to frequency shift Nd:YAG 1.064 micrometer to eye-safe wavelength at 1.57 micrometer. To reduce the threshold of KTP OPO, we reflected back the deleted pump wave according to original light path. The maximum energy conversion efficiency 64% and quantum conversion efficiency 94% was achieved when the OPO was pumped by Nd:YAG laser at 1064 nm.
In laser propagation in the atmosphere, the wavefront of laser beam will be distorted by the atmospheric turbulence. The wavefront aberration can be compensated with the stimulated Brillouin-scattering (SBS) effect. In this paper, an outdoor experiment is presented. In the experiment, a ruby oscillator and an amplifier are used as source; a laser beam travels from the source to a reflector; which simulates a target; the reflected laser beam travels through the atmosphere and is focused into a SBS cell by a lens; finally the phase conjugate light produced by the stimulated Brillouin scattering (SBS) effect return to the target. The distance between the target and the SBS cell is 70 m. The Output energy of the ruby laser is 2 J. The laser beam spot and the phase conjugate light spot are recorded by a camera at the target. The result of the experiment shows that: the wavefront aberration is compensated in the process of laser beam and the phase conjugate light travels between the target and the SBS cell.
The laser can be focused on a distant target with stimulated Brillouin-scattering (SBS) effect in the atmosphere. To a moving target, the target can be tracked with an isoplanatic angel between the phase conjugate light and the beacon light. We present a method to produce an angle between the light in SBS.
In some applications of laser propagation in the atmosphere by means of athptive optical technique or nonlinear optical
effect, the method of active beacon light is used, in which a probe light is transmitted to the target and the reflective light
acts as beacon light. However, the large reflective light spot on the target can't meet the application of focusing laser beam.
In this paper, the threshold effect of phase conjugated light on the target is demonstrated by the presence of atmospheric
turbulence. We present that through one or several times of conjugation, a large beacon light spot on the target can be
reduced to a beacon light point. In our laboratory, the threshold effect is verified in the cases of two sparkles and a large
area light spot on the target. In the experiment, the distance between the target and the conjugation system is lOm, and area
of conjugated light spot is one-fifteenth ofthat oflarge area light spot on the target.
Potassium Titanium Oxide Phosphate (KTP) is a new nonlinear frequency-conversion crystal. It has high nonlinear coefficient, high damage threshold, easily-polished surface, and a broad transparency range. In this paper, the calculation method of angle phase-matching for parametric generation in KTP was presented. The angle phase-matching curve and their characteristics in KTP pumped by 532 nm, 694.3 nm radiation were calculated and analyzed. The propagating principal plane (x-y plane) and 56 degree(s) cut angle to z-axis were selected in our experiment, and the measured results agreed well with the calculated ones. The quality of laser beam is an important factor of affecting OPO threshold fluence and conversion efficiency, so the phase-conjugate technology of Stimulated Brillouin Scattering (SBS) for improving the pump laser beam quality was discussed and applied to the pump laser system. The tuning curves and output energy of KTP OPO pumped by Ruby laser (0.6943 micrometers ), the second harmonic of Nd:YAG (0.532 micrometers ) were measured and compared with the theoretical cases. An important result was obtained that the amplified back SBS light which was employed to pump KTP OPO could greatly reduce the OPO threshold.
In some applications of optical phase conjugation in laser beam propagation in the atmosphere, the method of active beam light is used, in which a probe light is transmitted to the target and the reflective light acts as the beacon light. Generally, it is believed that the reflective area on the target must be small enough to be regarded as an unresolved glint, and this limits the application. In this paper, the effect of the reflective area on the optical phase conjugation is discussed, and an experiment by means of nonlinear optical phase conjugation using a ruby laser, Stimulated Brillouin Scattering is an acetone device and a hole to change the reflective area is made. We demonstrate that, the wavefront of light can be restored correctly on the target. In the case of motionless target, the limitation of the reflective area must be satisfied, otherwise the amplified phase conjugated light on the target will return to the probe light source and damage it, whereas, in the case of the remote and high speed moving target, because the reflective place on the target is changed during the period of phase conjugation, the light is only reflected on the target, and so the area may be larger than the limitation.
Coupling amplification of Stokes seed beam in a light guide filled with high pressure H<SUB>2</SUB>, excited by an unfocused laser beam during multi-reflection is reported. The amplification coefficient is about 5.5 and the quality of the amplified beam is the same as or better than that of seed beam.