50-mJ,Q-switched, 2.09-microm holmium laser resonantly pumped by a diode-pumped 1.9-microm thulium laser

We report >50-mJ Q-switched energy output from a 2.09-microm Ho:YAG oscillator, resonantly pumped at 1.9-microm by a diode-pumped Tm:YLF laser. We demonstrate a Q-switched-to-normal-mode extraction efficiency of 100% at an output energy of 30 mJ and over 64% at the 50-mJ output level. Operating at 50 mJ (60 Hz) of output, a pulse width of 14 ns is achieved from the holmium oscillator, which corresponds to approximately 3.6 MW of peak power. At the 50-mJ output level, a beam-propagation factor M2 approximately 1.2 is achieved.     

Efficient and compact diode-end-pumped conductively cooled Q-switched Nd:YLF laser operating at 527 nm

A novel, compact diode-end-pumped conductively cooled Q-switched Nd:YLF laser is developed. A diode-end-pumped pair of Nd:YLF slabs and an intracavity-frequency-doubled configuration are adopted to increase conversion efficiency. Using 49.8-mJ incident pump pulse energy at 500-Hz repetition rate, the laser obtains 11-mJ pulse energy and 5.5-W average output power at 527-nm wavelength, achieving an optical-optical conversion efficiency of 22%. The pulsewidth is less than 15 ns, and the beam quality factors are Mx2=1.28 and M y2=1.12.     

High-peak power,passively Q-switched,composite, all-poly-crystalline ceramics Nd:YAG/Cr<Superscript>4+</Superscript>:YAG laser and generation of 532-nm green light

Output performances of passively Q-switched, composite Nd:YAG/Cr⁴⁺:YAG lasers that consisted of bonded, all-poly-crystalline ceramics Nd:YAG and Cr⁴⁺:YAG are reported. Laser pulses at 1.06 μm with 2.5-mJ energy and 1.9-MW peak power are obtained from a 1.1-at % Nd:YAG/Cr⁴⁺:YAG ceramics that was quasi-continuous-wave (quasi-CW) pumped with a diode laser. Single-pass frequency doubling with LiB₃O₅ (LBO) nonlinear crystal at room temperature yielded green laser pulses at 532 nm of 0.36-mJ energy and 0.3-MW peak power, with a conversion efficiency of 0.27.     

30-mJ, diode-pumped, chirped-pulse Yb:YLF regenerative amplifier

A diode-pumped chirped-pulse regenerative amplifier with a cooled Yb:YLF crystal has been developed. The output pulse energy is 30 mJ at 20-Hz repetition rate. A high effective extraction efficiency of 68% is obtained, which is attributed to reduced saturation fluence at low temperature and to a high effective pulse energy fluence during regenerative amplification. After pulse compression by use of a parallel grating pair, 18-mJ pulse energy and 795-fs pulse duration are obtained.     

Diode-side-pumped AO Q-switched Tm,Ho:LuLF laser

A diode-side-pumped Tm,Ho:LuLiF laser at 2-m wavelength obtained in a ring resonator and its amplification experiment are reported. At the maximum pump energy of 4.7 J available for the oscillator,the output energy per pulse for the oscillator decreases from 904 to 483 mJ in free running mode,and decreases from 106 to 68 mJ in Q-switched mode,with an increase of pump pulse repetition rate from 1 to 5 Hz. When considering the amplifier,99-mJ Q-switched output energy is achieved at 5-Hz repetition rate.     

1-mJ, sub-5-fs carrier–envelope phase-locked pulses

We report the routine generation of sub-5-fs laser pulses with 1-mJ energy and stable carrier–envelope phase at 1-kHz repetition rate, obtained by compressing the multi-mJ output from a phase-locked Ti:sapphire amplifier in a rare-gas-filled hollow fiber. The dual-stage amplifier features a hybrid transmission grating/chirped mirror compressor providing 2.2-mJ, 26-fs pulses at 1 kHz with standard phase deviation of 190 mrad rms. We demonstrate hour-long phase stability without feedback control of grating position or rigorous control of the laser environment, simply by using small pulse stretching factors in the amplifier, which minimize the beam pathway in the compressor. The amplifier also integrates a versatile AOPDF (acousto-optic programmable dispersive filter) for closed-loop spectral phase optimization. The various factors influencing the overall phase stability of the system are discussed in detail. Using the optimized output, 1-mJ, 4.5-fs pulses are generated by seeding the neon gas filled hollow fiber with a circularly polarized input beam. A standard phase deviation of 230 mrad after the HCF is obtained by direct f-to-2f detection and slow-loop feedback to the oscillator locking electronics without any additional spectral broadening.     

High-conversion-efficiency optical parametric chirped-pulse amplification system using spatiotemporally shaped pump pulses

High-conversion-efficiency, high-stability optical parametric chirped-pulse amplification is demonstrated with a spatiotemporally shaped pump laser system. Broadband 5-mJ pulses are produced at a 5-Hz repetition rate with a pump-to-signal conversion efficiency of 29% and energy stability better than 2% rms. To our knowledge this is the highest conversion efficiency and stability achieved in an optical parametric chirped-pulse amplification system.     

High-energy in-fiber pulse amplification for coherent lidar applications

An Er:Yb codoped fiber amplifier chain for the generation of pulses for coherent lidar applications at a wavelength near 1.5 microm is reported. The final 1.8-m-long power amplification stage had a 50-microm core diameter and yielded a 23-dB energy gain, resulting in 0.29-mJ, 100-ns pulses at a repetition rate of 4 kHz with no Brillouin scattering and an M2 of 2.1.     

Generation of 0.1-TW 5-fs optical pulses at a 1-kHz repetition rate

A compact all-solid-state femtosecond Ti:sapphire oscillator?amplifier system using no grating-based pulse stretcher produces 20-fs, 1.5-mJ pulses at a 1-kHz repetition rate. The pulses are subsequently compressed in a hollow-fiber chirped-mirror compressor. The system delivers bandwidth-limited 5-fs, 0.5-mJ pulses at 780 nm in a diffraction-limited beam.     

Backward Raman amplification in a plasma waveguide

Backward Raman amplification of a short laser pulse in a plasma waveguide is demonstrated. With a guided seed pulse of 0.8-microJ energy and a pump pulse of 345-mJ energy in a 9-mm-long optically preformed plasma waveguide, 910-fold energy amplification is achieved. Heating of the plasma by the long pump pulse is identified to be a key issue for plasma-waveguide-based backward Raman amplifiers.     

Efficient high-power diode-end-pumped TEM(00) Nd:YVO(4) laser with a planar cavity

We demonstrate a compact and efficient diode-end-pumped TEM>(00) laser with output power of 30 W for 48 W of incident pump power by use of two coated Nd:YVO> (4) crystals to form a thermally stabilized flat-flat cavity. In Q -switched operation 25 W of average power at a pulse-repetition rate of 100 kHz and ~0.9-mJ pulse energy at a pulse-repetition rate of 10 kHz were produced.     

High-energy picosecond Nd:YVO4 slab amplifier for OPCPA pumping

We demonstrate 12-ps pulses with up to 0.6-mJ pulse energy at repetition rates of 50 kHz and 100 kHz from a Nd:YVO₄ slab amplifier built in a simple four-pass configuration. Excellent noise performance with pulse energy fluctuations below 0.8% rms has been achieved by using 10-μJ seed pulses from a highly stable industrial laser system and moderate gain (30–46) in the slab amplifier.     

High-power diode-bar end-pumped Nd:YLF laser at 1.053 microm

We describe efficient cw operation of a Nd:YLF laser end pumped by two beam-shaped 20-W diode bars on the 1.053-microm transition. Fundamental transverse-mode operation with output power of 11.1 W for ~29.5 W of incident pump power was demonstrated. In Q-switched operation 8.4 W of average power at a pulse repetition frequency of 40 kHz and ~2.6-mJ pulse energy at a pulse repetition frequency of 1 kHz were achieved.     

Two-color chirped-pulse amplification in an ultrabroadband Ti:sapphire ring regenerative amplifier

We have developed a high-energy, ultrabroadband Ti:sapphire ring regenerative amplifier capable of producing in excess of 20-mJ output at a 10-Hz repetition rate. The technique of chirped-pulse amplification is used to generate two-color, time-synchronized pulses with central wavelength separations of up to approximately 120 nm and with a total energy of 10 mJ by use of a regenerative pulse-shaping technique. Mid-infrared pulses tunable from 6 to 11 microm are generated by difference frequency mixing the two-color outputs.     

0.09-terawatt pulses with a 31% efficient, kilohertz repetition-rate Ti:sapphire regenerative amplifier

We present an efficient, ultrafast regenerate amplifier that increases the energy of a laser pulse from 300 pJ to 6 mJ and produces average powers of as much as 9 W in a TEM(00) spatial mode. As an ultrafast amplifier, the system produces 4-mJ pulses with 0.09 TW of peak power.     

High-efficiency parametric oscillation and spectral control in the red spectral region with periodically poled KTiOPO(4)

Narrow-linewidth optical pulses at wavelengths near 630 nm with 2.2-mJ energy were generated with 61% efficiency in a periodically poled KTiOPO(4) parametric oscillator pumped by a frequency-doubled Q -switched Nd:YAG laser. The tuning range was extended to 30 nm by a noncollinear elliptical pumping geometry. We demonstrate that by angular dispersion a noncollinear optical parametric oscillator can be used to control the spectral and spatial characteristics of the output signal beam.     

Generation of 0.2-TW 5.5-fs optical pulses at 1 kHz using a differentially pumped hollow-fiber chirped-mirror compressor

Optical pulses with 1.1-mJ energy and 5.5-fs duration have been generated at 1-kHz repetition rate from a chirped pulse amplification Ti:Sapphire laser incorporating a differentially pumped hollow-fiber chirped-mirror compressor. The effects of self-focusing and multi-photon ionization during the beam propagation were minimized by differentially pumping the hollow fiber filled with neon. The spectral broadening at the hollow-fiber compressor was optimized by adjusting gas pressure, laser intensity, and laser chirp, covering from 540 nm to 950 nm. PACS 42.65.Jx; 42.65.Re     

High-energy, high-power ytterbium-doped Q-switched fiber laser

We report on a Q -switched, cladding-pumped, ytterbium-doped large-mode-area fiber laser operating at 1090 nm that is capable of generating 2.3 mJ of output pulse energy at a 500-Hz repetition rate and more than 5 W of average output power at higher repetition rates in a high-brightness beam (M(2) = 3) . Using a similar fiber with a smaller core, we generated >0.5-mJ pulses in a diffraction-limited beam. Our results represent a threefold increase in pulse energy over previously published values for Q-switched fiber lasers and firmly establish fiber lasers as compact, multiwatt, multimillijoule pulse sources with large scope for both industrial and scientific applications.     

A compact Ti:sapphire femtosecond pulse amplifier without stretcher at high repetition rate

We report a simple approach to amplify Ti:sapphire femtosecond pulses to moderate energy levels by achirped regenerative amplifier. The seed pulses are broaden naturally because of the material dispersionof system components in regenerative cavity. The off-focusing Ti:sapphire crystal avoids effectively theoptical damage. It sustains amplification over a wavelength range from 775 nm to more than 810 nmwith a birefringent filter and an oscillation bandwidth of 7.7 nm, and produces 2.1 ps chirped outputpulse energy of 100μJ at 1.1-mJ pumping energy. This system shows good performances in stability andefficiency with the benefits of two thin-film polarizers and TEM00 mode pumping laser.     

Efficient rotational Raman conversion of XeCl laser radiation in H2

2 is investigated with a XeCl laser. It is shown that energy conversion to rotational Stokes radiation can be efficiently obtained by properly choosing the focusing geometry of pump radiation and the pressure of the Raman medium even at moderate pulse energies. Energy conversion to the first rotational Stokes at 313.8 nm with efficiencies as high as 38% is obtained with a circularly polarised XeCl pump beam of 10-mJ energy focused in 30 bar of H₂. The spectral and optical characteristics of the pump and the rotational Stokes radiation are analysed. Received: 29 May 1996/Revised version: 7 March 1997