Observation of Antiphase State in a Self-Q-switched Nd,Cr:YAG Laser

We experimentally investigate the antiphase dynamics phenomenon in a self-Q-switched Nd, Cr：YAG laser operating at 946 nm. Due to the effect of spatial hole burning, the Q-switched pulses sequences of one, two and three modes at different pump power are observed. The experimental results show that the pulse sequences display classic antiphase dynamics.     

High power CW diode-side-pumped Nd:YAG rod laser

We report on the characterization of a diode-side-pumped Nd:YAG rod laser operating at high CW output power. A four-fold pump configuration is designed and the pump light is directly coupled into the Nd:YAG rod without the help of any cylindrical lenses. The distribution of pump light in the Nd:YAG rod has been calculated by using ray tracing program. The thermal lens effect of the Nd:YAG rod has been experimentally measured. A maximum output power of 800 W at 1064 nm in multimode operation is obtained for a pump power of 2400 W with 33% optical-optical efficiency. At the same time, the maximum beam parameter product of 25 mm·mrad is achieved.     

Self-Mixing Interference in Dual-Polarization Microchip Nd：YAG Lasers

The self-mixing interference in dual-polarization microchip Nd: YA G lasers is demonstrated. Under optical feedback, the orthogonal polarization components of the laser would undergo antiphase intensity modulations; at high feedback level, the polarization switching appears. We also observe that the laser self-mixing sensitivity changes periodically with the frequency difference of orthogonal polarizations. An initial theoretical model is put out and agrees well with the experiments. The results are useful for self-mixing sensitivity enhancement and offer a new way of absolute distance measurement.     

Pre-pumped passively Q-switched Nd:YAG/Cr:YAG microchip laser

A pre-pumped passively Q-switched Nd:YAG/Cr: YAG microchip laser is demonstrated with a peak power of 7.5 kW at pulse repetition rate of serveral kilohertzs. The full-width at half-maximum (FWHM) is 734 ps, and the pulse energy is 5.5 μJ with a fundamental spatial mode. In this system, the pre-pumped microchip laser of Nd: YAG/Cr: YAG wafer which is bonded through the thermal-bonding technique has achieved a time jitter value of 12 μs and a Q-switched amplitude instability of 1.26% (1δ) through the pre-pumped modulation technique.     

Performance of the Self—Q—Switched Cr,Yb：YAG Laser

We report on the spectral properties of Cr,Yb:YAG crystal co-doped with 0.025 at.% Cr and 10 at.% Yb are reported.Using a continuous wave Ti:sapphire laser as a pumping source,we have demonstrated the self-Q-switched Cr,Yb:YAG laser at room temperature.We obtained an average output power as much as 75mW at 1.03μm with a pulse width (FWHM)as short as 0.4μs.The laser experiment demonstrated that the Cr,Yb:YAG crystal exactly combines the Cr^4 saturable absorber and Yb^3 gain medium.The Cr,Yb:YAG crystal can be a most promising self-Q-switched laser crystal for compact and efficient solid-state lasers.     

A high-power high-stability Q-switched green laser with intracavity frequency doubling using a diode-pumped composite ceramic Nd：YAG laser

We successfully obtain a high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd:YAG in a straight plano-concave cavity. The temperature distribution in composite ceramic Nd:YAG crystal is numerically analyzed and compared with that of conventional Nd:YAG crystal. By using a composite ceramic Nd:YAG rod and a type-II high gray track resistance KTP (HGTR-KTP) crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd:YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.     

High Power Diode-End-Pumped Nd：YAG 946-nm Laser and Its Efficient Frequency Doubling

We report a high power operation of the ^4Fa/2 → ^4I9/2 transition in diode-end-pumped laser at 946nm. The maximum output of 5.1 W is obtained with a short linear plano-concave cavity, and the slope efficiency is 24.5% at incident pump power of 23.3 W. To our knowledge, this is the highest value of the LD-pumped Nd:YAG 946 nm lasers that employ the conversional Nd:YAG rod as the gain medium. By intracavity frequency doubling with an LBO crystal, up to 982mW cw output power in the blue spectral range at 473nm is achieved at an incident pump power of 10.9 W with a compact three-element cavity, leading to optical-to-optical conversion efficiency of 9%. The conversion efficiency should be increased to 15.1%, if the rather low absorption coefficient of this Nd:YAG is considered.     

High Efficiency Multi-kW Diode-Side-Pumped Nd：YAG Laser with Reduced Thermal Effect

We demonstrate a high efficiency multi-kW diode-side-pumped Nd：YAG laser. High cooling efficiency of the diode-side-pumped module in the laser is achieved. The middle portion of the Nd：YAG rod in the module is cooled by a coolant jet with screwed side surface, and the end-caps of the rod without screwed side surface are cooled by Au coated on the surface. The thermal effect of the laser rod is reduced, which leads to high output power with high optical-optical conversion efficiency. By using three identical Nd：YAG laser modules, an output power of 4.2 kW and beam quality of 58 mm＆#12539;mrad with an optical-optical efficiency of 35% at 1064 nm is obtained in a laser oscillator. By using four identical Nd：YAG laser modules, an output power of 3.1 kW and beam quality of 17 mm＆#12539;mrad with an optical-optical efficiency of 25.8% is demonstrated in a master oscillator power-amplifier system.     

Comment on Q-Switched Tm：YAG Laser Intracavity-Pumped by a 1064 nm Laser

The paper published in Chin. Phys. Lett. 26 （2009） 124211 reported a Q-switched 2-tim Tm：YAG laser that is intracavity pumped by a Nd： YAG laser with emission at 1.06μm. However, analysis of the experimental setup concludes that only the Nd：YAG laser is Q-switched, and the Tm：YAG laser operates in the free-generation regime. Therefore, Q-switch operation for the 2μm emission wavelength is not realized.     

Q-Switched Tm：YAG Laser Intracavity-Pumped by a 1064nm Laser

We report a Q-switched 2-μm Tm：YAG laser based on intracavity-pumped by a 1064-nm Nd：YAG laser operating at room temperature for the first time. An average output power of 5.1W is obtained with the repetition rate of 30kHz and a pulse width of 300ns. In addition, we demonstrate a 12.5-W continuous-wave 2-μm Tm：YAG laser, which is, to our best knowledge, the highest power for intracavity-pumping configuration.     

Large-aperture end-pumped Nd：YAG thin-disk laser directly cooled by liquid

A large-aperture Nd:YAG thin-disk laser directly cooled by liquid is end-pumped by two spatial selforganized laser diode arrays. The pump coupling efficiency reaches as high as 93%. Without any complex pump coupling components, the structure becomes simplified and compact. By optimizing the incident angle of the pump beam, a pump power density of 578 W/cm2 is achieved with a pump uniformity of 5.52%. Up to 1 346-W peak output power with a slope efficiency of 54.9% is obtained when pumping with a long pulse. The near-field pattern of the laser output is uniform.     

Experimental 511 W Composite Nd：YAG Ceramic Laser

We demonstrate a 511 W laser diode pumped composite Nd：YAG ceramic laser. The optical pumping system is consisted of five laser diode stacked arrays arranged in a pentagonal shape around the ceramic rod whose size is φ6.35×144mm. When the pumping power is 1600 W, the cw laser output up to 511 W at 1064nm can be obtained with a linear piano-piano cavity, and the optical-to-optical efficiency is 31.9%. To our knowledge, this is the highest value of laser output by using a newly invented composite Nd：YAG ceramic rod as the gain medium.     

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 946nm 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 80kHz repetition rate and 40.8 ns pulse width. The slope efficiency and optical conversion efficiency are 17.6% and 14.7%, respectively.     

Flash-lamp-pumped picosecond Nd:YAG regenerative amplifier

A flasli-lamp-pumped Nd:YAG regenerative amplifier has been developed at 1.06 μm, seeded with 10-ps pulses from a diode-end-pumped and mode-locked Nd:YAG oscillator with homemade semiconductor saturable absorber mirror (SESAM). The pulse energy was amplified to 2 mJ by the regenerative amplifier at 10-Hz repetition rate. In two-stages amplifier the regenerative amplified pulse energy was amplified to 100 mJ, and 35-mJ double frequency at 532 nm was obtained by extra-cavity double frequency with a KTP crystal.     

Kilohertz Electro-Optic Q-Switched Nd：YAG Ceramic Laser

We investigate the lasing characteristics of a laser-diode-array side-pumped electro-optic Q-switched Nd： Y3Al5O12 ceramic laser operating at 1000 Hz pulse repetition rate. Using a YAG polycrystalline rod with Nd^3＋ concentration of 1 at. % as the gain medium, pumping with 808 nm laser-diode-arrays, the Q-switched laser output at 1064 nm wavelength with 23mJ pulse energy and less than 12ns FWHM pulse width are obtained at a pumping power of about 400 W, the slope efficiency is around 15%, the output beam divergence angle is about 1.2mrad.     

Ti: sapphire Laser Pumped Yb: YAG Laser with Cr~(4 ): YAG as a Passive Q-switch

The Ti: sapphire laser pumped Yb: YAG passively- Q-switched laser with Cr~(4 ): YAG as asaturable absorber experiment was performed. The Mira 900 tunable Ti: sapphire laser with anoutput power up to 1 W was used as a pump source. The optical pump system was composed of aspherical lens (f = 75 mm) for focusing the pump beam to a circular spot with a diameter of about50 up, the pumping power was measured to be up to 920 mW. The laser cavity was configured tobe semispherical, and was formed…     

Three-Rod Resonator for Krypton Lamp Pumped 1.8 kW Continuous-Wave Nd：YAG Laser

A three-rod series resonator cw Nd:YAG laser suitable for the industrial applications is presented. The symmetrical resonator laser has been developed and is rated at 1820-W output power with beam parameter product 24 mm.mrad. By utilizing the symmetrical resonator design, the characteristic of beam with multi-rod is not obviously decreased compared with that of a single one. The system total electro-optics efficiency of lamp pumped YAG crystal is as high as 4.0%. The main factors, which affect output power and beam quality of high power solid-state laser module, are theoretically analysed.     

Investigation on Performance of High Repetition Diode-Pumped Heat-Capacity Nd：YAG Laser

We demonstrate the improvements of both beam quality and thermal depolarization loss of an all-solid-state heat-capacity Nd:YAG laser with repetition rate of 50Hz, for the first time to our best knowledge, compared with the conventional steady-state laser. The beam quality of the heat-capacity laser has been improved three times higher than the conventional steady-state laser within the lasing periods of 60s. The depolarization loss caused by thermo-optical effects which is definitely considerable in steady-state Nd:YAG laser has almost not been observed under heat-capacity operation. Design and operations of the all-solid-state heat-capacity Nd: YAG laser with average output power of 25 W with repetition 50 Hz are also studied with the optical-to-optical efficiency of 33.3%.     

Diode-Pumped Passively Q-Switched Yb：YAG Microchip Laser with a GaAs as Saturable Absorber

A passively Q-switched Yb: YAG microchip laser has been constructed by using a doped GaAs as the saturable absorber as well as the output coupler. At 13.5 W of pump power the device produces high-quality 3.4μJ 52ns pulses at 1030nm with a pulse repetition rate of 7.8 kHz in a TEM00-mode.     

Deep learning for position fixing in the micron scale by using convolutional neural networks

We propose here a novel method for position fixing in the micron scale by combining the convolutional neural network(CNN) architecture and speckle patterns generated in a multimode fiber. By varying the splice offset between a single mode fiber and a multimode fiber, speckles with different patterns can be generated at the output of the multimode fiber. The CNN is utilized to learn these specklegrams and then predict the offset coordinate. Simulation results show that predicted positions with the precision of 2 μm account for 98.55%.This work provides a potential high-precision two-dimensional positioning method.