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.

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.

A Mid-IR Optical Parametric Oscillator Pumped by an Actively Q-Switched Ho:YAG Ceramic Laser

We demonstrate a mid-IR ZnGeP2 （ZGP） optical parametric oscillator （OPO） pumped by a dual-end-pumped actively aeoasto-optie Q-switched Ho：YAG ceramic laser. The maximum average output power of 35 W is obtained at a pulse repetition frequency of 20 kHz from the Ho：YAG ceramic laser. Under the maximum incident pump power of Ho：YAG ceramic laser, the maximum output power of 14 W is obtained from the ZGP OPO, corresponding to the slope efficiency of 49.6% with respect to the incident pump power. The wavelength can be tuned from 3.5 μm to 4.2μm （signal）, corresponding to 5.24.1 μm （idler）. The beam quality M2 is less than 2.3 from the ZGP OPO.

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.

Optically pumped terahertz lasers with high pulse repetition frequency:theory and design

Optically pumped terahertz （THz） lasers with high pulse repetition frequency are designed. Such a laser includes two parts： the optically pumping laser and the THz laser. The structures of the laser are described and analyzed. The rate equations for the pulsed THz laser are given. The kinetic process and laser pulse waveform for this kind of laser are numerically calculated based on the theory of rate equations. The theoretical results give a helpful guide to the research of such lasers.

Optically pumped semiconductor nanowire lasers

This paper reviews our recent work on fabrication, optical characterization and lasing application of semiconductor nanowires, with brief introduction of related work from many other groups.

Diode-pumped single frequency Tm,Ho:YLF laser at room temperature

A diode-pumped single frequcncy Tm,Ho：YLF laser operating at an eye-safe wavelength of 2 μm has been developed. Temperature of the laser crystal was controlled at room temperature with a thermoelectric cooler. The line-width narrowing elements were two solid uncoated fused silica etalons whose thicknesses were 1 and 0.1 mm, respectively. Continuous wave single frequency power of 113 mW was obtained.

Compact and high-energy diode-side-pumped Q-switched Nd:YAG slab laser system for space application

We develop a compact and high-energy Nd：YAG slab laser system consisting of an oscillator and an amplifier for space applications. The oscillator is a diode-side-pumped electro-optically Q-switched slab laser with a cross-Porro resonator. The KD＊P Pockels cell with a low driving voltage of 950 V is used to polarization output coupling. The amplifier is a Nd：YAG zigzag slab pumped at bounces. The maximum output pulse energy of 341 m3 with 13 ns pulse duration is obtained from the system at the repetition rate of 20 Hz and the beam quality factors are M2=3.1 and M2=3.5. The beam pointing stabilities of the laser system are 3.05μrad in the X-direction and 3.99 grad in the Y-direction, respectively.

Diode-pumped 1123-nm Nd:YAG laser

We demonstrated a diode-pumped Nd:YAG laser with a plano-concave resonator. When the pump power is 1.57 W, the output power of 1123-nm laser is 132 mW at the temperature of 20 ℃, and the power change is less than 2% in an hour. A periodically poled LiNbO3 (PPLN) was used as outer cavity frequency-doubling crystal and 561-nm laser was observed.

10-W cladding-pumped fiber laser with single transverse mode output

A Yb-doped double-clad fiber laser is demonstrated with a measured power output of 10.6 W and a fundamental spatial mode. The optical-to-optical conversion efficiency is 44% and the slope efficiency is 86% closed to quantum efficiency of optical conversion. In our laser system, a D-shape (340 μm/400 μm) inner cladding Yb-doped fiber is used as the gain material within the Fabry-Perot cavity. Multimode diode pump radiation is injected into the cladding through an end facet of the composite fiber.

Compact and efficient diode-pumped passively Q-switched Nd:GdVO_4 laser at 1.06μm

Diode-pumped passively Q-switched Nd:GdVO4/Cr4+:YAG lasers with a simple flat-flat cavity were demonstrated. The maximum average output power at 1.06 μm was 1.25 W. The highest peak power and pulse energy were 7.56 kW and 75μJ, respectively, with the pulse repetition rate of 11.1 kHz and pulse width of 10 ns at the incident pump power of 8 W.

Diode-pumped passively Q-switched Nd:YVO_4 laser with GaAs saturable absorber

The intracavity photon density is assumed to be of Gaussian spatial distributions and its longitudinal variation is also considered in the rate equations for a laser diode (LD) end-pumped passively Q-switched Nd:YVO4 laser with GaAs saturable absorber. These space-dependent rate equations are solved numerically. The dependences of pulse width, pulse repetition rate, single-pulse energy, and peak power on incident pump power are obtained. In the experiment, the LD end-pumped passively Q-switched Nd:YVO4 laser with GaAs saturable absorber is realized and the experimental results are consistent with the numerical solutions.

1.88μm,Ba(NO3)2-based Raman laser pumped by a potassium-titanyl-phosphate-based optical parametric oscillator laser

A 1.88μm Ba（N3）2-based stimulated Raman scattering（SRS） laser pumped by a potassium-titanylphosphate-based optical parametric oscillator（OPO） laser is presented.Under the pumping energy of a130 mJ 1064 nm Q-switched Nd：YAG laser,a 40 mJ 1.57μm laser is achieved;the maximum output energy of the 1.88μm Raman laser reaches 7.5 mJ with a pulse duration of 5.3 ns at repetition rates of 10 Hz,and the corresponding total optical conversion efficiency is about 5.8%.The combination of the SRS and OPO techniques significantly extends the wavelength from 1.064 to 1.57μm（OPO） and then demonstrates Stokes-shifting to 1.88μm（SRS）.

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.

Transverse modes of a diode-laser pumped monolithic unidirectional non-planar ring laser

Diode-laser pumped monolithic single-frequency non-planar ring laser has the advantages of compactness, reliability and high efficiency. But when the pump power is high enough, the thermal effect will be serious and the high-order transverse modes will appear. Therefore the single-mode output power is limited. In this paper, the mechanism of generating the high-order transverse modes in the monolithic unidirectional non-planar ring cavity is analyzed using ray tracing method. The calculated results are in agreement with the experiments.

4-W single transverse mode Yb^(3+)-doped fiber laser pumped by 915-nm laser diode array

A cladding-pumped ytterbium-doped fiber laser is described in this letter. Using unusual pumping source with 915-nm wavelength, slope efficiency up to 75% with respect to absorbed input power and output power is obtained, a maximum output power of 4.006 W with fundamental mode is measured.

Pulse width reduction in diode-pumped,doubly Q-switched Nd:GdVO_4/KTP green laser

Using both acoustic-optic (AO) Q-switeh and GaAs saturable absorber, a diode-pumped doubly Q-switehed Nd:GdVO4/KTP green laser is realized. This laser can generate a shorter and more symmetric pulse in comparison with purely AO and passively Q-switched lasers. In the meantime, the rate equations describing the operation of a diode-pumped, AO and GaAs doubly Q-switched Nd:GdVO4/KTP green laser are introduced. These equations are solved numerically and the dependence of pulse width on incident pump power is obtained. The numerical solutions are in agreement with the experimental results.

Highly efficient H-β Fraunhofer line optical parametric oscillator pumped by a single-frequency 355 nm laser

A highly efficient laser system output at the H-13 Fraunhofer line of 486.1 nm has been demonstrated. A high pulse energy single-frequency hybrid 1064 nm master oscillator power amplifier was frequency-tripled to achieve 355 nm laser pulses, which acted as the pmnp source of the beta barium borate nanosecond pulse optical para- metric oscillator. With pump energy of 190 mJ, the laser system generated a maximum output of 62 mJ blue laser pulses at 486.1 nm, corresponding to conversion efficiency of 32.6%. The laser spectrum width was measured to be around 0.1 ran, being in conformity with the spectrum width of the solar Fraunhofer line.

Efficient femtosecond optical parametric oscillator pumped by all solid-state mode-locking Yb:YCOB laser

We experimentally demonstrate a femtosecond optical parametric oscillator （OPO） synchronously pmnped by a home-made solid-state mode-locking Yb：YCOB laser, which is capable of laser pulse as short as 102 fs and average power of 620 mW at the central wavelength of 1052 nm. By using a periodically poled lithium niobate with tuning of the grating periods from 28.5 to 31.5μm as the nonlinear gain crystal, tunable femtosecond pulses from 1444 to 1683 nm are realized by conveniently adjusting the OPO cavity length with 76.8 MHz repetition rate. The maximum average output power is 152 mW at 1568 nm, corresponding to an idler power of 75 mW at 3197 nm as well as 36.6% total extraction efficiency.