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Tunable coherent radiation is generated in the vacuum ultraviolet down to 121 nm using random quasi-phase matching in strontium tetraborate, the shortest wavelength ever produced with a second-order nonlinear optical process in a solid-state material. Relevant properties of this radiation, the nonlinear process, and the nonlinear crystal are investigated.

One of the limiting noise sources in the current generation of gravitational wave detectors, such as the advanced laser interferometer gravitational wave observatory (aLIGO), is the thermal noise in the interferometer's test mass coatings. One proposed method to reduce the coupling of this noise source to the gravitational wave readout is using a laser beam in the higher-order spatial LGsub33/submode within the interferometer. Here we show that the current four-mirror cavities of aLIGO are not compatible with Laguerre-Gauss modes due to astigmatism. A non-degeneracy of modes of the same order could be observed in experiment and simulation. We demonstrate that a non-planar cavity could be used instead as it compensates for the astigmatism and transmits the LGsub33/submode undisturbed.

Generation of sub-45 fs vacuum UV (VUV) pulses tunable across the spectral range of 146-151 nm at 1 kHz repetition rate is reported. The pulses are produced using noncollinear difference-frequency four-wave mixing between the third-harmonic of an amplified Ti:sapphire laser and the signal wavelength of an infrared optical parametric amplifier (ω(VUV)=2ω(TH)-ω(IR)) in krypton and argon. The generated VUV pulses have energies as high as 90 nJ. Pulse duration measurements are realized by cross correlation between the VUV pulses and the laser fundamental wavelength using pump-probe ionization in xenon.

Third-harmonic generation of high-intensity, sub-100-fs idler pulses from a Ti:sapphire-laser-pumped optical parametric amplifier is demonstrated by using a single nonlinear crystal of BiB₃O₆ (BIBO). Maximum internal energy conversion as high as 11% from the fundamental to the third harmonic is achieved by phase- and group-velocity matching for the direct cubic nonlinear process together with the velocity-mismatched cascading quadratic processes.

We report on the generation of femtosecond pulses at 160 nm with energies up to 240 nJ at 1 kHz repetition rate and sub-50-fs pulse duration. This pulse energy is a 1-order-of-magnitude improvement compared with previous sub-100-fs sources in this wavelength range. The pulses are generated by four-wave difference-frequency mixing process between the fundamental of a Ti:sapphire laser and its third harmonic in argon. Pulse duration measurements are achieved by pump–probe ionization of Xe gas providing the cross correlation between the fifth harmonic and the fundamental.

Nearly transform-limited femtosecond pulses have been generated between 585 and 620 nm by simultaneous narrow-band seeding at 1.053 μm of an optical parametric amplifier pumped by a tunable high-power Ti:sapphire laser system at 1 kHz and sum-frequency mixing between the resulting idler and the pump pulses in the same nonlinear crystal.

170-fs, 0.8-microJ optical pulses at 193 nm generated by frequency quadrupling of high-power Ti:sapphire laser pulses are amplified in an ArF gain module. Double-pass amplification at a 400-Hz repetition rate resulted in 290-mW average power with pulse durations of ~ 300 fs.

A tunable 1-kHz repetition-rate regenerative Ti:sapphire amplifier system is used to produce 200-fs vacuum-ultraviolet pulses in the range of 172.7-187 nm by phase-matched sum-frequency mixing in lithium triborate of the Ti:sapphire's fourth harmonic and a parametrically generated infrared pulse.

Infrared light pulses as short as 70 fs that are nearly bandwidth limited are obtained in a simple double-pass optical parametric generator with a single beta-barium borate nonlinear crystal. Tunability in the 1.2-1.3microm range is demonstrated with sub-100-fs pulse duration, microjoule pulse energy, and 1-kHz repetition rate.

Phase-matched sequential frequency mixing in three ,beta-barium borate crystals was used for efficient generation of subpicosecond UV pulses tunable at approximately 193 nm. Double-pass amplification of these seed pulses in a conventional ArF excimer gain module resulted in 800-fs, 1.5-mJ optical pulses.

We report the compression by a factor of 7 of 2-microJ pulses of 5-psec duration from a mode-locked Nd:phosphate glass laser. The pulses were chirped and their spectrum broadened while traveling through a graded-index core fiber. After amplification to 500 microJ, they were finally compressed by traveling through a dispersive delay line, and 0.7-psec pulse widths were achieved.

We report efficient generation of tunable femtosecond pulses in the near IR using a two stage, white-light seeded, collinear, femtosecond optical parametric amplifier (OPA). The OPA, based on BiB(3)O(6) crystal in both stages and pumped at 807 nm by a 1 kHz Ti:sapphire laser amplifier, provides sub-30 fs signal pulses after compression with energies exceeding 200 microJ, which corresponds to fivefold pulse shortening and approximately 30% internal conversion efficiency in the second stage considering 150 fs pump pulses with 1.5 mJ energy. The corresponding idler pulses with more than 100 microJ have sub-60 fs duration without compression. The first stage alone is capable of producing sub-20 fs pulses near 1400 nm at the microjoule level without using any compression.

We investigate the potential of four-wave mixing in dielectric hollow waveguides for vacuum ultraviolet pulse generation with unprecedented short durations. Taking into account higher-order transverse modes and plasma effects we predict the generation of a 2.5 fs pulse at 160 nm using an intense 10 fs, 800 nm pulse and its weaker third harmonic at 267 nm, both coupled to the fundamental transverse mode. Excitation of higher transverse modes allows an increase of the signal energy (up to by a factor of 20) but with a pulse duration of 13 fs (compressible to 7.7 fs).

We report a 30% internal conversion efficiency for the first Stokes pulse in stimulated Raman scattering of femtosecond pulses that are dispersively stretched to 250 ps, obtained by use of an all-solid-state laser system. A transfer of the linear chirp is observed, leading to a Raman pulse duration of 190 fs after recompression. Compressed pulse energies of 80 μJ at a repetition rate of 1 kHz are obtained, with a potential for an easy increase to more than 150 μJ. The temporal and spectral characteristics of the Raman and pump pulses are calculated, and the results explain the observed transient features in the presence of chirp.

Optical parametric oscillation using the new lithium selenoindate nonlinear crystal is reported for what is to our knowledge the first time. A 17 mm long, type II phase-matched sample is pumped by a 10 ns Nd:YAG laser. The minimum pump energy threshold is 3 mJ for a signal-resonant configuration. The signal and idler waves are tunable between 1.47 and 1.57 microm, and 3.3 and 3.78 microm, with a total output energy of 170 microJ corresponding to a 2.4% energy conversion at 8 mJ pump, only limited by the AR coatings damage. With optimized crystal quality and coatings, lithium selenoindate should show superior performance as compared with AgGaS(e)2 crystals, owing to its 4x larger thermal conductivity.

We present our latest results on the generation of ultrashort vacuum UV (VUV) pulses by nonresonant four-wave mixing of chirped broadband pulses generated by filamentation of the fundamental of a Ti:sapphire laser with relatively narrowband pulses at the third harmonic. Positive chirp at the broadband idler yields negatively chirped VUV pulses necessary to compensate for material dispersion of a MgF(2) window in the VUV beam path. Pulse energies exceeding 400 nJ are available for time-resolved experiments. Pulse duration is measured by pump-probe ionization of Xe gas, providing the cross correlation between the fifth harmonic and the fundamental.

Third-harmonic generation of high-intensity, sub-100-fs idler pulses from a Ti:sapphire-laser-pumped optical parametric amplifier is demonstrated by using a single nonlinear crystal of BiB3O6 (BIBO). Maximum internal energy conversion as high as 11% from the fundamental to the third harmonic is achieved by phase- and group-velocity matching for the direct cubic nonlinear process together with the velocity-mismatched cascading quadratic processes.

Generation of sub-50fs vacuum UV pulses with more than 2.5μJ energy at a 1kHz repetition rate is reported. The pulses at 160nm are produced using noncollinear difference-frequency four-wave mixing between the fundamental and third harmonics of an amplified Ti:sapphire laser in argon. While the pulse duration is maintained by increasing the phase-matching pressure, noncollinear interaction improves the conversion efficiency by 1 order of magnitude in comparison with the previous results in collinear geometry.

We report the generation of tunable femtosecond pulses in the near-IR using a two-stage, white-light seeded, collinear, femtosecond optical parametric amplifier (OPA). The OPA, based on BiB(3)O(6) crystal in both stages and pumped at 800 nm by a 1 kHz Ti:sapphire laser amplifier, provides sub-30 fs signal pulses across the whole tuning range of 1.15-1.6 microm with minimum duration of 22 fs and maximum signal energy of 80 microJ.

We report on the generation of powerful sub-20 fs deep UV pulses with 10 microJ level energy and broadly tunable in the 250-310 nm range. These pulses are produced by frequency doubling a high-power noncollinear optical parametric amplifier and compressed by a pair of MgF2 prisms to an almost transform-limited duration. Our results provide a power scaling by an order of magnitude with respect to previous works.

Ultrabroadband parametric amplification of a white-light continuum in the near IR (approximately 100 THz, 1.2-2.4 microm) is demonstrated in BiB3O6 pumped by 45 fs long pulses at 800 nm at a repetition rate of 1 kHz. The energy obtained with a 5 mm thick crystal reached 50 microJ, corresponding to external conversion efficiency of 20%.

We used non-phase-matched second-harmonic generation (SHG) in the highly nonlinear but low-birefringence crystal SrB4O7 for temporal characterization (autocorrelation) of femtosecond UV pulses to convert these pulses to wavelengths as low as 125 nm, close to the transparency limit of SrB4O7. The sensitivity of this method was approximately 1 microJ at the fundamental for a repetition rate of 1 kHz. We also used SHG at longer wavelengths to estimate the three nonlinear coefficients of SrB4O7.

We report traveling-wave optical parametric generation in short (2-mm) ZnGeP(2) samples with reduced anomalous absorption, using femtosecond pump pulses near 2 mum . The signal and the idler waves generated could be tuned from 2.5 to 10 mum , and they extend the tunability of the beta-barium borate optical parametric generator used as a pump source to the mid-infrared. At a single-pass internal conversion efficiency of 2.5% we estimate pulse durations of 75 fs (signal near 3 mum) and 200 fs (idler near 6 mum).

We generated synchronized sub-200-fs pulses between 3 and 4.4 mm at a 1-kHz repetition rate by pumping a KNbO(3) optical parametric amplifier with a femtosecond Ti:sapphire regenerative amplifier and seeding it by narrow-band quasi-cw radiation. Output idler energies as high as 7 microJ at 4 microm are reported from this extremely simple single-stage device, which correspond to amplification factors as high as 3 x 10(5) and a conversion efficiency of 15.