Intracavity coherent addition of 16 laser distributions

The efficient intracavity coherent addition of 16 separate laser Gaussian mode distributions is presented. The coherent addition is achieved in a multichannel pulsed Nd:YAG laser resonator by use of four intracavity interferometric beam combiners. The results reveal 88% combining efficiency with a combined output beam of nearly pure Gaussian distribution.     

Conversion of a high-order mode beam into a nearly Gaussian beam by use of a single interferometric element

We present a new, compact, and practical optical mode converter that efficiently transforms a high-order Hermite-Gaussian (HG) laser beam into a nearly Gaussian beam. The mode converter is based on coherently adding different transverse parts of the high-order mode beam by use of a single planar interferometric element. The method, configuration, and experimental results obtained with a pulsed Nd:YAG HG TEM10 laser beam are presented. The results reveal that the efficiency of conversion of a HG beam to a nearly Gaussian beam can be as high as 90%.     

Phase-coherent frequency combs in the vacuum ultraviolet via high-harmonic generation inside a femtosecond enhancement cavity

We demonstrate the generation of phase-coherent frequency combs in the vacuum utraviolet spectral region. The output from a mode-locked laser is stabilized to a femtosecond enhancement cavity with a gas jet at the intracavity focus. The resulting high-peak power of the intracavity pulse enables efficient high-harmonic generation by utilizing the full repetition rate of the laser. Optical-heterodyne-based measurements reveal that the coherent frequency comb structure of the original laser is fully preserved in the high-harmonic generation process. These results open the door for precision frequency metrology at extreme ultraviolet wavelengths and permit the efficient generation of phase-coherent high-order harmonics using only a standard laser oscillator without active amplification of single pulses.     

Diode-pumped regenerative amplifier delivering 100-mJ single-mode laser pulses

We report on a side-pumped Nd:phosphate laser regenerative amplifier that delivers laser pulses of as much as 100 mJ in a single TEM mode. The laser beam is mode matched to the amplification medium by an intracavity fused-silica phase plate for mode shaping and a telescope for adjustment of the beam mode to the amplification rod section such that most of the energy stored in the rod is transferred to the laser pulses. As a result of the good overlap and the low loss, an optical-to-optical conversion efficiency of as much as 10% was measured for a pumping current of 80 A and greater than 100-mJ output pulses.     

Efficient improvement of laser beam quality by coherent combining in an improved Michelson cavity

The efficient improvement of laser beam quality is demonstrated by coherent combining of two Nd:YVO4 lasers in an improved Michelson cavity. When the two lasers are separately operated with beam qualities of M(x)2 = 1.74 and M(y)2 = 1.34 for laser 1 and M(x)2 = 1.53 and M(y)2 = 1.39 for laser 2, by coherent combining of the two lasers, a single beam output exceeding 2 W with a nearly perfect TEM00 mode (M(x)2 = 1.08, M(y)2 = 1.04) is obtained. Moreover, it can withstand environmental perturbations with no change in beam quality or output power and has the potential for scaling to much higher output power with high beam quality by coherent addition of multiple lasers in this configuration.     

Field properties and vacuum electron acceleration in a laser beam of high-order Laguerre–Gaussian mode

The electric field intensity distribution and the phase velocity distribution of high-order Laguerre–Gaussian (LGρ?) mode laser beams are analyzed. Using three-dimensional test particle simulation, the numerical results of electrons accelerated by LG00, LG40 and LG41 mode laser beams are presented. Compared with the LG00 mode (the fundamental mode) laser beam, low-energy injection electrons can be more favorably accelerated in a high-order LG mode laser beam. Contrary to anticipation, a high-order LG mode laser beam with intense axial electric field distribution is inferior to the LG00 mode in capture acceleration for electrons with high injection energy.     

Diode-Pumped Nd:YAP sum-frequency mixing orange-red laser at 616 nm

We report for the first time a coherent orange-red radiation at 616 nm by intracavity sum-frequency generation of the 1080 and 1433 nm laser-lines of two Nd:YAP lasers. Orange-red laser is obtained by using a doubly linear resonator, type-II critical phase matching KTiOPO₄ (KTP) crystal sum-frequency mixing. With a total diode pump power of 26.5 W (8.7 W pump power for 1080 nm Nd:YAP laser and 17.8 W pump power for 1433 nm Nd:YAP laser), TEM00 mode orange-red laser at 616 nm of 127 mW is obtained. The power stability in 30 min is better than 3.3%.     

腔内倾斜扰动对正支共焦腔本征模式的影响

针对激光器出光过程中腔内像差扰动带来的光束质量下降问题,分析了正支共焦腔腔内不同位置倾斜扰动对本征模式的影响,采用数值迭代法计算了理想状态及腔内不同位置倾斜扰动状态下的本征模式、相位Zernike像差拟合系数.结果表明：对大小给定的扰动,相位相对敏感性从凸面镜到凹面镜逐渐增加,且腔模倾斜像差增大的同时还将导致离焦、像散等高阶像差的增大,因此作腔内补偿时,应使补偿平面尽可能靠近凹面镜.     

Generation of super-high-order petal-like laser beam using Theon-sieve resonator

The Laguerre-Gaussian(LG) mode beam has very important applications in many research fields.Here,the Theon sieve is first introduced into the laser resonator to generate petal-like laser beams by coherently superimposing two high-order LG modes.The effectiveness was verified by GLAD software.The petal-like laser beam is derived from the light field redistribution and coherent superposition caused by the diffraction effect of the Theon sieve.The relationship between the order of the petal-like laser and the cavity structures has also been investigated in detail.Light field operation in the laser cavity greatly simplifies the optical structure and is more beneficial to optical diagnostics and imaging.     

High Efficient LD-pumped Nd:YVO4/ LBO Red Laser

A design of high efficient LD-pumped Nd:YVO4/LBO red laser was reported in this paper. For the first time, type-I critical phase-matched LBO was used for 1.342 μm intracavity frequency-doubling to obtain 671 nm red laser. With 760 mW incident pump power, 78 mW TEM00 mode red laser output was obtained, the optical-to-optical conversion up to 10%. Measurements showed the beam divergent angle less than 0.5 mrad, polarization degree more than 100:1 and power instability in 48 hours less than ±2%.     

Femtosecond diode-pumped Nd:glass laser with more than 1 W of average output power

We have demonstrated 175-fs pulses with 1 W and 300-fs pulses with 1.2 W of average output power at a pulse repetition rate of 117 MHz from a Nd:phosphate (Schott LG 760) glass laser pumped by a 1-cm-wide, 20-W diode laser bar. Stable soliton mode locking was achieved by use of an intracavity semiconductor saturable absorber mirror. We obtained more than 2 W of average power without mode locking. Using cylindrical cavity mirrors, we adapted the laser mode inside the Nd:glass to the highly elliptical pump beam in both dimensions (tangential and sagittal axes) while maintaining a nearly ideal circular TEM(00) output beam with M(2) approximately 1.2 . Overpumping the laser mode in the tangential plane and efficient unidirectional heat removal in the sagittal plane using a 0.8-mm thin Nd:glass also contributed to the good output-beam quality.     

High Efficient LD-pumped Nd∶YVO4/ LBO Red Laser

A design of high efficient LD-pumped Nd∶YVO4/LBO red laser was reported in this paper. For the first time, type-I critical phase-matched LBO was used for 1.342 μm intracavity frequency-doubling to obtain 671 nm red laser. With 760 mW incident pump power, 78 mW TEM00 mode red laser output was obtained, the optical-to-optical conversion up to 10%. Measurements showed the beam divergent angle less than 0.5 mrad, polarization degree more than 100∶1 and power instability in 48 hours less than ±2%.     

Intracavity frequency doubling of a diode-pumped 946-nm Nd:YAG laser with bulk periodically poled MgO LiNbO(3)

We report what we believe is the first cw quasi-phase-matched intracavity frequency doubling of a diode-pumped 946-nm Nd:YAG laser by use of bulk periodically poled MgO-LiNbO(3). A maximum second-harmonic power of 5.9 mW was obtained at a laser diode power of 500 mW. The blue beam profile showed a TEM(00) single spatial mode of low ellipticity (1:1) because there was no walk-off problem. Bulk periodic domain inversion was accomplished by a corona discharge method with a first-order modulation period of 4.75 microm for a wavelength of 946 nm over a 2-mm interaction length in Z-cut 0.4-mm-thick MgO-LiNbO(3).     

新型部分相干光束的产生及其相干特性

利用相干理论,研究了新型部分相干光束的相干特性.用激光光束透过旋转的特殊毛玻璃,产生一种相干性分布特殊的新型部分相干光束.实验上经双孔干涉,记录了该光束经不同小孔间距双孔产生的干涉条纹,计算得出所对应的相干度,并获得了该光束在不同传输距离下的相干度分布情况,发现该光束的相干度分布与高斯-谢尔模型光束的相干度分布不相同,其相干度随着传输距离的增大而变强.     

激活介质热效应对振荡模式的影响研究

理论分析了激活介质热效应对端面泵浦固体激光器激光振荡模式分布的影响,并以光纤耦合半导体激光器端面泵浦Nd∶YAG激光器实验研究了激活介质热效应对激光振荡模式的影响。实验结果表明：由于热效应,基模的模体积随泵浦功率的增加而变大,基模在模式竞争中占优;在泵浦光轴线偏离几何腔轴时,基模光斑中心位置朝泵浦光轴线所在位置移动,偏离量与泵浦光轴线的偏离量近似成线性关系。利用实验结果指导腔调节,可使泵浦光轴线与几何腔轴精确重合,获得了椭圆率为0.98、M2因子为1.01的基模输出。     

High-order mode Laguerre–Gaussian beam transformation using a 127-actuator deformable mirror: numerical simulations

Transforming high-order mode Laguerre–Gaussian beams in the far-field using a 127-actuator deformable mirror controlled by a stochastic parallel gradient descent algorithm is presented. As a phase shift of half wave exists between every neighboring lobes of high-order mode Laguerre–Gaussian beams, there are multiple lobes in the far-field. The suitable beam radius related to the aperture size of the deformable mirror is discussed. Three system performance metrics are evaluated, and encircled energy is preferred. Simulation results show that it is possible to compensate for the phase shifts and other phase aberrations of a high-order mode Laguerre–Gaussian beam and achieve a single bright lobe with this approach. Transforming the far-field intensity distribution of high-order mode Laguerre–Gaussian beams into Gaussian and super Gaussian distributions are also investigated.     

All-solid-state doubly resonant sum-frequency continuous-wave laser at 555 nm

A new kind of resonator for doubly resonant continuous-wave (CW) intracavity sum-frequency mixing(SFM) is presented. A coherent radiation of 327 mW at 555 nm is generated by mixing 1342-nm Nd:YVO4 laser and 946-nm Nd:YAG laser. The M2 beam quality factor of the sum-frequency mixed yellow-green laser is less than 1.7. The low-noise characteristic of the yellow laser is demonitrated.     

A 4.8-W M^2 = 4.6 Continuous-Wave Intracavity Sum-Frequency Diode-Pumped Solid-State Yellow Laser

A yellow continuous wave with beam quality M^2= 4.6 and output power of 4.8 W at 589nm is generated by intracavity sum-frequency mixing of 1064 nm and 1319 nm radiations of a Nd：YAG laser. To achieve high beam quality at high power, thermally near-unstable flat-flat resonators with two-rod birefringence compensation are designed to obtain the large fundamental mode size inside the Nd：YAG rods and the same beam width inside the KTP crystal. The optimal intracavity power ratio of both 1064nm and 1319nm beams is also considered. The output power fluctuation of the yellow laser remains less than 5% in four hours.     

Superradiance-Driven Phonon Laser

We propose to enhance the generation of a phonon laser by exploiting optical superradiance. In our scheme, the optomechanical cavity contains a movable membrane, which supports a mechanical mode, and the superradiance cavity can generate the coherent collective light emissions by applying a transverse pump to an ultracold intracavity atomic gas. The superradiant emission turns out to be capable of enhancing the phonon laser performance.This indicates a new way to operate a phonon laser with the assistance of coherent atomic gases trapped in a cavity or lattice potentials.     

激光二极管抽运Nd∶YVO4/LBO腔内倍频5.3 W连续波激光器

报道了激光二极管双向抽运Nd∶YVO4 晶体、LBO腔内倍频、最大输出功率为 5 .3W的连续波绿光激光器。采用LBO晶体Ⅰ类非临界相位匹配 (NCPM) ,温度调谐 ,当抽运光功率为 2 0W时 ,获得了 5 .3WTEM0 0 模 5 32nm绿光输出 ,光光转换效率达 2 6 .5 %。并对绿光模式及输出功率随LBO晶体温度的变化关系进行了测量 ,与理论结果符合较好。