Study of a low power dissipation,miniature laser-pumped rubidium frequency standard

This paper studies a miniature low power consumption laser-pumped atom vapour cell clock scheme. Pumping ^87Rb with a vertical cavity surface emitting laser diode pump and locking the laser frequency on a Doppler-broadened spectral line, it records a 5 × 10^-11τ-1/2 （τ〈500 s） frequency stability with a table-top system in a primary experiment. The study reveals that the evaluated scheme is at the level of 2.7 watts power consumption, 90 cm^3 volume and 10^-12τ-1/2 short-term frequency stability.

Efficient Nd:YVO4 laser in-band pumped by wavelength-locked 913.9-nm laser diode and Q-switch operation

An efficient 1064-nm Nd：YVO_4laser in-band pumped by a wavelength-locked laser diode（LD） at 913.9 nm was demonstrated. The maximum continuous wave（CW） output power of 23.4 W at 1064 nm was realized with the incident pump power of 40 W, corresponding to a total optical-to-optical efficiency of 58.5%. This is to the best of our knowledge the highest total optical-to-optical efficiency and output power of Nd：YVO_4laser in-band pumped by a 913.9-nm laser diode.The Q-switched operation of this laser was also investigated. Through a contrast experiment of pumping at 808 nm, the experimental results showed that an Nd：YVO_4laser in-band pumped by a wavelength-locked LD at 913.9 nm had excellent pulse stability and beam quality for high repetition rate Q-switching operation.

Analytical model for thermal lensing and spherical aberration in diode side-pumped Nd:YAG laser rod having Gaussian pump profile

In this paper, according to the temperature and strain distribution obtained by considering the Gaussian pump profile and dependence of physical properties on temperature, we derive an analytical model for refractive index variations of the diode side-pumped Nd：YAG laser rod. Then we evaluate this model by numerical solution and our maximum relative errors are 5% and 10% for variations caused by thermo–optical and thermo–mechanical effects; respectively. Finally, we present an analytical model for calculating the focal length of the thermal lens and spherical aberration. This model is evaluated by experimental results.

An Actively Mode-Locked Ho:YAG Solid-Laser Pumped by a Tm-Doped Fiber Laser

An actively mode-locked Ho： YAG laser pumped by a diode-pumped Tin-doped fiber laser is reported. For the cw operation, we obtain the maximum output power of 3.43 W with a central wavelength 2022.2nm at the maximum incident pump power of 11.4 W, corresponding to a slope efficiency of 34.5%. The beam quality factor M2 is 1.16, and the output beam is close to fundamental TEMoo. In the case of the CWML operation, a stable pulse train is generated with an average output power up to 3.41 W with a slope efficiency of 34.3% at the incident pump power of 11.4 W and a pulse duration of 294ps at a repetition rate of 81.92MHz. In addition, the maximum single pulse energy is 41.6nJ.

Simultaneous all-solid-state multi-wavelength lasers——a promising pump source for generating highly coherent terahertz waves

A diode-end-pumped Nd：YAG dual-wavelength laser operating at 1319 and 1338 nm is demonstrated. The maximum average output power of the quasi-continuous wave linearly polarized dual-wavelength laser is obtained to be 2.1 W at a repetition rate of 50 kHz with an output power instability of less than 0.38% and beam quality factor M^2 of 1.45. Using the two lines, the highly coherent and narrow linewidth terahertz radiation of 3.23 THz can be generated in an organic 4-N, N-dimethylamino-methyl-stilbazolium tosylate （DAST） crystal. Meanwhile, the multi-wavelength red laser at 659.5, 664 and 669 nm is generated by frequency doubling and sum frequency processes in a lithium triborate （LBO） crystal. The average red laser output power is enhanced up to 1.625 W at a repetition rate of 15 kHz with an output power instability of better than 0.53% and beam quality factor M^2 of 6.05. Using the three lines, it is possible to generate the multi-wavelength THz radiation of 3.3, 3.43 and 6.73 THz in an appropriate difference frequency crystal.

Theoretical and Numerical Study of Stress and Thermo-Optic in Photonic Crystal Fiber Laser in Different Pump Schemes

In this paper, we present a study of thermal, average power scaling, change in index of refraction and stress in photonic crystal fiber lasers with different pump schemes: forward pump scheme, backward pump scheme, forward pump scheme with reflection of 98%, backward pump scheme with reflection of 98% and bi-directional pump scheme. We show that management of thermal effects in fiber lasers will determine the efficiency and success of scaling-up efforts. In addition, we show that the most suitable scheme is the bi-directional.

Influence of pumping laser bandwidth on the quantum fluctuation chracteristic of a non-degenerate optical parametric amplifier

Usually the quantum fluctuation characteristic of a non-degenerate optical parametric amplifier is analysed under the assumption of monochromatic pumping. However, in experiments, a driving beam with finite bandwidth is used to obtain the non-degenerate signal and idler beam amplifications. On account of that, we derive an analytical solution for the non-degenerate optical parametric amplification system with finite bandwidth laser pumping, and evaluate the associated quantum fluctuation. Finally, the application of the V1 criterion to bipartite entanglement is discussed.

Cs 5D_(5/2)-6F 728 nm Laser Spectroscopy with Single Pumping Laser

The sub-Doppler absorption laser spectroscopy at 728nm transition from the 5D5/2 state to the 6F state of cesium with linewidth near 10 MHz is first experimentally performed with indirect pumping from the ground state 6S1/2 to the state 7P3/2 by a 455.5nm diode laser. Using a 455.5nm diode laser as an indirect pump laser, several excited states will be populated due to spontaneous decay from the 7P state. We first implement the sub-Doppler absorption laser spectroscopy at 728nm from the 5D5/2 state to the 6F state when Cs atoms within thermal glass cell decay to the 5D5/2 state. Due to velocity transfer effect, the hyperfine structure of 5D5/2 shows a mixed and complicated pattern but very e/ear structure when the 455.5nm pumping laser is counter-propagating （or co-propagating） with the 728nm probing laser.

Transmittance investigation on capacitive mesh on thick dielectric substrates as output windows for optically pumped terahertz lasers

This paper reports that an output window for optically pumped terahertz （THz） laser has been fabricated by depositing a capacitive nickel-mesh on a thick high-resistivity silicon substrate （approximating to 5 mm thick）. Unlike the conventional process of depositing a gold film approximating to 100 nm on negative photoresist using electron-beam evaporation, a nickel film approximating to 1.5 μm thick is directly deposited on the clean surface of dielectric substrate using magnetron sputtering and then a positive photoresist is spun onto the nickel metal surface at 6000 r for 60 s. A transmittance spectrum of the output window in a certain frequency range （say, from zero to 1 THz） has been obtained by using THz time domain spectroscopy. Moreover a transmittance spectrum simulated numerically has also been estimated with respect to the output window using the transmission-line model （TLM） containing attenuation component from dielectric substrate. The simulation results show that the TLM can explain well the experimental curve in a certain frequency range from zero to 1 THz. Thus it is demonstrated that the improved optical component can be efficiently used as both output coupler and output window for optically pumped THz lasers.

Dual-Wavelength Holmium-Doped Fiber Laser Pumped by Thulium-Ytterbium Co-Doped Fiber Laser

We present an all-fiber dual-wavelength holmium-doped veloped holmium-doped fiber （HDF） as a gain medium fiber laser operating in 2 #m region using a newly de- The proposed fiber laser is constructed by using a hybrid gain medium, i.e., a thulium ytterbium co-doped fiber （TYDF） and an HDF in conjunction with a simple half-opened linear cavity, which is formed by a broadband mirror and an output coupler reflector. Without the HDF, the TYDF laser operates at wavelengths of 1991 and 1999nm with a signal-to-noise ratio of more than 34dB and the slope efficiency of 26.16 %. With the HDF, dual-wavelength output lines are obtained at 2075 and 2083nm with signal-to-noise ratios of more than difference between the two peaks of less than 1 dB at 17dB, 3dB bandwidth of less than 0.2nm and the power the TYDF laser pump power of 320roW.

Improvement of Laser Frequency Stabilization for the Optical Pumping Cesium Beam Standard

A method is presented to improve the laser frequency stabilization for the optical pumping cesium clock. By comparing the laser frequency stabilization of different schemes, we verify that the light angle is an important factor that limits the long-term frequency stability. We minimize the drift of the light angle by using a fiber- coupled output, and lock the frequency of a distributed-feedback diode laser to the fluorescence spectrum of the atomic beam. The measured frequency stability is about 3.5 ×10^-11 at i s and reaches 1.5 × 10^-12 at 2000s. The Allan variance keeps going down for up to thousands of seconds, indicating that the medium- and long-term stability of the laser frequency is significantly improved and perfectly fulfills the requirement for the optical pumping cesium clock.

Diode-pumped laser performance of Tm:Sc2SiO5 crystal at 1971 nm

The 4-at.% Tm：Sc_2SiO_5 （Tm：SSO） crystal is successfully obtained by the Czochralski method. The optical properties and thermal conductivity of the crystal are investigated. The broad continuous wave（CW） laser output of（100）-cut Tm：SSO with the dimensions of 3 mm×3 mm×3 mm under laser diode（LD）-pumping is realized. The full width at half maximum（FWHM） of the laser emitting reaches up to 21 nm. The laser threshold of Tm：SSO is measured to be 0.43 W. Efficient diode-pumped CW laser performance of Tm：SSO is demonstrated with a slope efficiency of 25.9% and maximum output power of 934 mW.

Design of LD in-band direct-pumping side surface polished micro-rod Nd:YVO_4 laser

To diminish the thermal load, two ways, that is, in-band direct pumping and micro-rod crystal, could be adopted at the same time. The efficiency of LD in-band direct-pumping side surface polished micro-rod Nd：YVO_4 laser is numerically analyzed. By optimizing parameters such as crystal length, laser mode radius, pump beam radius, doping concentration and crystal cross-section size, the overall efficiency can reach over 50%. It is found that with micro-rod crystal implemented in the laser oscillator, high overall efficiency LD in-band direct-pumping Nd：YVO_4 laser could be realized. High efficiency combined with low thermal load makes this laser an outstanding scheme for building high-power Nd：YVO_4 lasers.

NUMERICAL SIMULATION OF DIODE-PUMPED DOUBLE-CLAD Tm-Ho DOPED FLUORIDE LASERS

报导芯泵浦和包层泵浦两种情况下，工作于２．０４μｍ的Ｔｍ－Ｈｏ双掺氟基光纤激光器的数值模拟．数值模型考虑了交叉弛豫和能量转移过程对激光运转的影响，并考虑了沿光纤传输过程的信号和泵光损耗．模型用一个子程序来模拟包层泵浦的吸收过程并给出了与实验符合的结果，与芯泵浦Ｔｍ－Ｈｏ双掺光纤激光器的实验结果比较说明理论计算和实验结果符合得相当好，并在此基础上为建造新的包层泵浦高效Ｔｍ－Ｈｏ氟基光纤激光器提供了优化参数．

Widely Tunable Middle Infrared Optical Parametric Oscillator Pumped by the Q-Switched Ho：GdVO_4 Laser

We demonstrate a middle infrared ZnGeP_2 optical parametric oscillator pumped by the Q-switched Ho：GdVO_4 laser. When the incident Ho pump power is 4.12 W, the maximum average output power of the ZGP-OPO laser is 2.05 W, corresponding to a slope efficiency of 74.6%. The ZGP-OPO laser produces 4.2 ns mid-infrared pulses at a pulse repetition rate of 5 kHz. In addition, we obtain 0.8 um of tunable range for the signal wave and 2.1 um of tunable range for the idler wave.

A 515-nm laser-pumped idler-resonant femtosecond BiB_(3)O_(6) optical parametric oscillator

We report on an idler-resonant femtosecond optical parametrical oscillator(OPO)based on BiB_(3)O_(6)(BiBO)crystal,synchronously pumped by a frequency-doubled,mode-locked Yb:KGW laser at 515 nm.The idler wavelengths of OPO can be tuned from 1100 nm to 1540 nm.At a repetition rate of 75.5 MHz,the OPO generates as much as 400 mW of idler power with 3.1 W of pump power,the corresponding pulse duration is 80 fs,which is 1.04 times of Fourier transform-limited(FTL)pulse duration at 1305 nm.In addition,the OPO exhibits excellent beam quality with M^(2)<1.8 at 1150 nm.To the best of our knowledge,this is the first idler-resonant femtosecond OPO pumped by 515 nm.

FLASHLAMP- PUMPED PULSED DYE LASER IN TREATMENT OF PORT- WINE STAINS

To assess the effectiveness of the flashlamp- pumped pulsed dye laser (Photogeneca V, Synosure Corp, Boston, United States) in the treatment of port- wine stains. Methods. One hundred and ninety- four consecutive patients with port- wine stains were treated with a flashlamp- pumped pulsed dye laser in Peking Union Medical College Hospital from January 1998 to August 1999. Results. Of 194 patients who completed treatment, 56.2％ had more than 60％ fading of the lesion and only 6.7％ had less than 20％ fading. An average of 3.6 treatments were needed to achieve more than 60％ fading. The response was better in children than in adults, although the difference was not significant. Pigmentary change (usually transient) occurred in 3.1％ of patients. Conclusions. This study confirms the efficacy of the flashlamp- pumped pulsed dye laser in the treatment of port- wine stains in children and adults.

Self-Mixing Interference Effects in LD Pumped Multi-Mode Solid-State Laser

Based on the effective structure of the self-mixing interference effects,a general model for the self-mixing interference effects in the LD pumped solid-state laser has been established for the first time.The numerical simulation of the self-mixing interference signal has been done,the results show that when the external cavity length is integral times of 1/2,1/3,2/3,1/4,3/4 of the effective cavity length,the intensity of the self-mixing interference signals reach maximum in value.While that of single mode laser is integral times of half of the effective cavity length,the measuring precision of displacement of single mode laser is λ/2.A conclusion can be drawn from the above results that the measuring precision of displacement of multi-mode laser is higher than that of single mode laser.

Efficient and high-power laser-diode single-end-pumped Nd：YVO4 continuous wave laser at 1342nm

A compact, efficient and high-power laser diode （LD） single-end-pumped Nd：YVO4 laser with continuous-wave emission at 1342 nm is reported. With a single crystal single-end-pumped by fibre-coupled LD array, an output power of 7.36W is obtained from the laser cavity of concave-convex shape, corresponding to an optical-to-optical efficiency of 32.8%. The laser is operated in TEM00 mode with small rms amplitude noise of 0.3%. The influences of the Nd concentration, transmissivity of the output mirror and the cavity length on the output power have been studied experimentally.