Acousto-Optically Q-Switched Operation of Yb:CNGG Disordered Crystal Laser

We report the repetitively Q-switched laser operation of the Yb-doped calcium niobium gallium garnet disordered garnet crystal, achieved with an acousto-optic modulator in a compact plano-concave resonator that is endpumped by a 935-nm diode laser. An average output power of 1.96 W is produced at pulse repetition rate of50 k Hz at emission wavelengths around 1035 nm, with a slope efficiency of 16%. The highest pulse energy of 269 μJ is generated at pulse repetition rate of 1 k Hz, with pulse width 12.1 ns and peak power 20.53 kW.

High-power xenon lamp-pumped Er:YAP pulse laser operated in free-running and acousto-optical Q-switching modes

We demonstrate a high-energy and high-power pulse laser on a xenon lamp-pumped Er:YAP crystal. The laser performance and thermal focal lengths under different working frequencies are discussed. The results show that the thermal lens effect is gradually aggravated with the increase of working frequencies, and even working at 100 Hz, a single pulse energy of 234 m J can be achieved. A maximum average power of 41.5 W is achieved with a working frequency of 20 Hz and slope efficiency of 2.82%. This output power is much higher than other xenon lamp-pumped erbium laser devices.A Q-switched laser is demonstrated by using the TeO2crystal, the maximum output energies of 11.5 m J and 3.5 m J are obtained at 50 and 100 Hz, the corresponding peak powers are 93.4 k W and 17.2 kW, respectively.The laser wavelengths and beam quality factors are also characterized in the free-running and Q-switched modes. A higher pulse energy and peak power laser could be achieved further by improving the damage threshold of TeO2acousto-optical Q-switching. All the experimental results illustrate that the xenon lamp-pumped Er:YAP laser is a promising candidate for high-power and high-frequency mid-infrared laser devices.

Double-AOTF-based aberration-free spectral imaging endoscopic system for biomedical applications

The problem of in vrivo photoluminescence diagnostics of the tissues acessible by endoscopes is discussed.The spectral imaging module attachable to conventional rigid and flexible medical endoscopes is developed and described.It is based on a double acousto-optical tunable filter(AOTF)and a specialized optical coupling system.The module provides wide field of view(FOV),absence of image distortions,random spectral access,fast spectral image acquisition at any wavelength in the visible range and accurate measurement of reflectance spectrum in each pixel of the image.Images of typical biomedical samples are presented and discussed.Their spectra are compared to the reference data.

An acousto-optic Q-switched fiber laser using China-made double-cladding fiber

A simple laser-diode pumped acoustic-optic Q-switched fiber laser is reported by using China-made largemode-area ytterbium-doped fiber. Q-switched pulses with a beam quality factor of M^2 ≈ 2 and several hundred nanoseconds pulse duration are achieved at the repetition rate of 1 - 50 kHz. When the repetition rate is 1 kHz, the pulse energy is 0.93 mJ with the pulse duration of 132 ns. Meanwhile, the profile of laser pulses shows some mode-locking phenomena, the mechanism of the phenomena is discussed.

LD-pumped acousto-optic 2-switched Pr:YLF pulsed laser at 604 nm

We demonstrated an actively acousto-optic Q-switched pulsed laser based on Pr:YLF at 604 nm.A 604 nm continuous-wave(CW)laser with a maximum output power of 3.84 W was achieved for the first time,to the best of our knowledge.The Q-switched laser with a maximum average output power of 0.384 W,a narrowest pulse duration of 44.5 ns,a maximum single pulse energy of~64.1μJ,and a maximum peak power of~1.44 kW was obtained at a repetition rate of 6 kHz.As far as we know,this was the first report of such a narrow pulse duration,high-power,and high-energy Q-switched pulsed laser at604 nm.The beam quality factors M_(x)^(2)and M_(y)^(2)were measured to be 2.87 and 2.40,respectively.The results show that acousto-optic Q-switching is a promising method for obtaining pulsed lasers.

Double Q-switched 946 nm laser with MgO：LN electro-optic crystal and MoSe2 saturable absorber

We report a double Q-switched 946 nm laser with a magnesium-oxide-doped LiNbO3 （MgO：LN） electro-optic （EO） crystal and a monolayer molybdenum diselenide （MoSe2） saturable absorber （SA）. A pulsed laser diode side-pumped long neodymium-doped yttrium aluminum garnet rod （φ3×65 mm） is used as the gain medium. Large pulse energy up to 3.15 mJ and peak power up to 346 kW are generated at the repetition rate of 550 Hz, corresponding to the beam quality factors of Mx^2=3.849, My^2=3.868. Monolayer MoSe2 nanosheets applied in the experiment would be a promising SA for a passive Q-switching operation.

Highly efficient dual-wavelength acousto-optically Q-switched Tm,La:CaF_(2)laser

A highly efficient milli-joule-level Q-switched Tm,La:CaF_(2)laser is experimentally demonstrated.By employing an acousto-optic modulator,the diode-pumped pulsed lasers are stably operated at repetition rates ranging from 500 Hz to 10 kHz.Dual-wavelength operation of 1881.7 nm and 1888.5 nm is achieved with slope efficiency of 64.7%.Up to 1.89 mJ of pulse energy is obtained at a pulse width of 100 ns,corresponding to a peak power of 18.88 kW.These results verified that the Tm,La:CaF_(2)crystal could be a promising candidate for achieving highly efficient and high-energy pulsed lasers.

Efficient corner-pumped Nd:YAG/YAG composite slab laser

A corner-pumped type is a new pumping type in the diode-pumped all-solid-state lasers, which has the advantages of high pump efficiency and favourable pump uniformity. A highly efficient corner-pumped Nd：YAG/YAG composite slab laser is demonstrated in this paper. The maximal continuous-wave output power of the 1064 nm laser is up to 18.57 W with a slope efficiency and an optical-to-optical conversion efficiency of 44.9% and 39.8%, respectively. Inserting an acousto-optic Q-switch in the cavity, the highest average output power of the quasi-continuous wave 1064 nm laser of 6.73W is obtained at a repetition rate of 9.26 kHz. The experimental results show that a corner-pumped type is a kind of feasible schedules in the design of diode-pumped all-solid-state lasers with low or medium output powers.

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.

Highly efficient electro-optically Q-switched 473 nm blue laser

An external frequency doubling electro-optically Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) 473 nm blue laser was demonstrated. With absorbed pump energy of 48 mJ at 100 Hz repetition rate, about 2 mJ of 473 nm blue laser pulse energy was achieved by cascade frequency doubling. The second harmonic conversion efficiency was 64.5%, and overall optical-optical efficiency was 4.2%, respectively. The blue laser pulse width was less than 10 ns, and beam quality factor was less than 2.4.

Laser at 532 nm by intracavity frequency-doubling in BBO

A simple and compact linear resonator green laser at 532 nm is generated by intracavity frequencydoubling of a diode-side-pumped acousto-optically（AO）Q-switched Nd：YAG laser at 1064 nm.Two acoustooptic Q-switches were placed orthogonally with each other to improve the hold-off capacity.As high as 214 W of continuous-wave（CW）and 154 W of quasi-continuous-wave（QCW）output power at 1064 nm were obtained when the pumping power was 1598 W.The type I phase-matched BBO crystal was used as the nonlinear medium in the second harmonic generation.A green laser with an average output power of 37 W was obtained at a repetition rate of 20 kHz and a pulse width of 54 ns,which corresponds to pulse energy of 1.85 mJ per pulse and a peak power34.26 kW,respectively.