Generation Of Tunable Femtosecond Pulses Research Articles

Broadly tunable, sub-30 fs near-infrared pulses from an optical parametric amplifier based on BiB_3O_6

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.

High-energy, sub-30 fs near-IR pulses from a broadband optical parametric amplifier based on collinear interaction in BiB_3O_6

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.

Effects of thickness of β-barium borate and angle of non-collinearity on the fs pulse generation by optical parametric amplification

Non-collinear optical parametric amplifiers (NOPAs) are used for the generation of tunable femtosecond pulses. The spectra of the uncompressed output from a lab-built NOPA in the 470–650 nm range have been recorded. Theoretical simulations for the effect of the length of the β-barium borate (BBO) crystal as well as the non-collinear angles between the pump and seed wavelengths have been carried out. For these we have obtained the initial experimental data from a 2 mm-thick BBO crystal when pumped with the second harmonic of the Ti:sapphire laser pulses of 100 fs duration. The pulse splitting length (PSL) and the group velocity mismatch (GVM) have been considered in simulations of the output. It was found that the crystal length of 1.3 mm and the crystal tilt of approximately 3.7° are optimal for the generation of pulses of ∼11 fs at 600 nm.

Efficient, high-repetition-rate, femtosecond optical parametric oscillator tunable in the red

We report efficient generation of tunable femtosecond pulses in the red by internal frequency doubling of an optical parametric oscillator (OPO) based on periodically poled LiNbO3 (PPLN). The OPO, based on a 1-mm-thick PPLN crystal, is synchronously pumped by a femtosecond Ti:sapphire laser at 810 nm, providing signal pulses across 1.33-1.57 microm at a 76 MHz repetition rate. Using a 1-mm-thick crystal of BiB3O6 (BIBO) internal to the OPO cavity, we achieve frequency doubling of signal pulses across 665-785 nm with up to 260 mW of average power for 1.51 W of pump. The high nonlinear gain and phase-matching acceptance in PPLN and BIBO permit convenient tuning across the full range by simple detuning of OPO cavity delay. Intracavity dispersion compensation results in near-transform-limited red pulses with durations down to 140 fs for 185 fs input pump pulses.

Tunable, high-repetition-rate, femtosecond pulse generation in the ultraviolet

We report efficient generation of tunable femtosecond pulses in the ultraviolet (UV) by intracavity doubling of a visible femtosecond optical parametric oscillator (OPO). The OPO, based on a 400 microm BiB3O6 crystal and pumped at 415 nm in the blue, can provide visible femtosecond signal pulses across 500-710 nm. Using a 500 microm crystal of beta-BaB2O4 internal to the OPO cavity, efficient frequency doubling of the signal pulses into the UV is achieved, providing tunable femtosecond pulses across 250-355 nm with up to 225 mW of average power at 76 MHz. Cross-correlation measurements result in UV pulses with durations down to 132 fs for 180 fs blue pump pulses.

Low-loss GaInNAs saturable Bragg reflector for mode-locking of a femtosecond Cr/sup 4+/ : forsterite-laser

A GaInNAs saturable Bragg reflector is used to mode-lock a Cr/sup 4+/ : forsterite solid-state laser. This low-loss saturable absorber mediates the generation of tunable femtosecond pulses having durations as short as 62 fs in the 1300-nm spectral region.

Efficient second-harmonic generation of tunable femtosecond pulses into the blue in periodically poled KTP

We report efficient single-pass second-harmonic generation of tunable femtosecond pulses into the blue in periodically poled KTP (PPKTP). Using a 2 mm crystal with 4 μm grating period and femtosecond fundamental pulses at 76 MHz, we show that average powers of up to 320 mW in the blue at conversation efficiencies as high as 20% are attainable despite the limitations of group velocity mismatch and spectral acceptance in PPKTP. Accurate measurements of phase-matching acceptance in PPKTP have been performed and excellent agreement between experimental data and calculations is confirmed. Using temperature phase matching, a significant tuning range of 422–427 nm in the blues is also demonstrated. Cross-correlation measurements of the fundamental and second-harmonic pulses in a 500 μm thick β-BaB2O4 result in blue pulse durations of 700–800 fs for 130 fs fundamental pulses.

High-average-power femtosecond pulse generation in the blue using BiB_3O_6

Efficient generation of tunable femtosecond pulses in the blue is reported in the nonlinear crystal BiB3O6. By use of fundamental pulses from a mode-locked Ti:sapphire laser at 76 MHz, single-pass second-harmonic average powers of as much as 830 mW have been generated at 50% conversion efficiency, and a tunable range of 375-435 nm in the blue is demonstrated. Temporal measurements using cross correlation of the fundamental and second-harmonic pulses in a 100-microm-thick beta-BaB2O4 crystal result in blue pulse durations of 220 fs for 130-fs fundamental pulses. Direct experimental comparison with beta-BaB2O4 confirms the superior performance BiB3O6 for second-harmonic generation of femtosecond pulses.

Mid-IR optical parametric amplification with femtosecond pumping near 800 nm using Cd xHg 1− xGa 2S 4

Tunable femtosecond pulse generation in the mid-IR between 6.6 and 11 μm is demonstrated by optical parametric amplification in Cd 0.35Hg 0.65Ga 2S 4 pumped at 820 nm by a 1 kHz repetition rate Ti:sapphire regenerative amplifier. Femtosecond pulses at the idler wave with energies as high as 2 μJ at 6.6 μm are produced for the first time by such a single conversion step from the Ti:sapphire spectral range.

Generation of femtosecond laser pulses tunable from 380 nm to 465 nm via cascaded nonlinear optical mixing in a noncollinear optical parametric amplifier with a type-I phase matched BBO crystal

We report the generation of tunable femtosecond pulses from 380nm to 465nm near the degenerate point of a 405-nm pumped type-I BBO noncollinearly phase-matched optical parametric amplifier (NOPA). The tunable UV/blue radiation is obtained from sum frequency generation (SFG) between the OPA output and the residual fundamental beam at 810-nm and cascaded second harmonic generation (SHG) of OPA. With a fixed seeding angle, the generated SFG and SHG covers from 385 nm to 465-nm. With a pumping energy of 75 J at 405 nm, the optical conversion efficiency from the pump to the tunable SFG is more than 5% and the efficiency of SHG of the OPA is about 2%.

Broadly tunable femtosecond pulse generation in the near and mid-infrared

High-repetition-rate (80-MHz) femtosecond infrared pulses are generated by difference frequency mixing (DFM) a femtosecond Ti:sapphire laser with a phase-locked synchronized cw mode-locked Nd:YAG picosecond laser. This DFM scheme is of particular interest for generating ultrashort near-IR pulses (~10 fs) because group velocity mismatch with a pump pulse can be ignored. The simplicity and the broad wavelength tunability (from the near IR to the mid-IR) of this scheme is demonstrated. Short (125-fs FWHM) optical pulses in the near IR around 1.5 mum are obtained with noncritical type-I phase-matched LiB(3) O(5). We also used a similar scheme to generate mid-infrared pulses at 3.0 mum with type-II phase-matched KTiOPO(4).

Tunable femtosecond-pulse generation by an optical parametric oscillator in the saturation regime

We demonstrate the generation of powerful, bandwidth-limited pulses in a KTP optical parametric oscillator synchronously excited by the pulse train of a f lash-lamp-pumped, mode-locked Nd:YLF laser. Operating the optical parametric oscillator a factor of 4 above threshold and optimizing the cavity length yields pulses of 260 +/- 30 fs. The shortening by a factor of 15 relative to the pump is accompanied by extended pulse wings. Tunability of the device is shown in the wavelength range 1.2 -1.6 microm.

Group-velocity self-matching of femtosecond pulses in noncollinear parametric generation.

We show that the parametric superfluorescence generated by a 200-fs pulse at 0.6 \ensuremath{\mu}m in a \ensuremath{\beta}-barium borate crystal occurs in directions, and at wavelengths, that minimize the group-velocity mismatch between pump and generated pulses. Favorable conditions for generation of tunable femtosecond pulses are found in noncollinear phase matching, a geometry of interaction which is worth exploiting in parametric devices.

Generation of tunable femtosecond pulses to as low as 1727 nm by sum-frequency mixing in lithium triborate

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.

Generation of tunable femtosecond pulses in the 1.21-1.27 μm and 605-635 nm wavelength region by using a regeneratively initiated self-mode-locked Cr:forsterite laser

A detailed description of the design and operational characteristics of a regeneratively initiated, self-mode-locked Cr:forsterite laser pumped by a continuous-wave Nd:YAG laser is given. Without compensating for the intracavity positive group velocity dispersion, regenerative acoustooptic modulation produced pulses of between 41 and 6.5 ps (FWHM) at 1.23 /spl mu/m with average output powers of between 280 and 380 mW, respectively. Using intracavity negative group-velocity-dispersion compensation, nearly transform-limited femtosecond pulses of 48 fs (FWHM) duration were generated with average TEM/sub 00/ output powers of 380 mW at 1.23 /spl mu/m. By tuning the output of the mode-locked laser from 1.211 to 1.264 /spl mu/m, the dispersion (second and third order) of the Cr:forsterite gain medium has been measured. The operational wavelength range of the laser was extended to the visible region from 605 to 635 nm by external frequency doubling in a LiIO/sub 3/ nonlinear crystal. With approximately 250 mW of fundamental pump power at 1.23 /spl mu/m, red pulses of 116 fs (FWHM) duration at 615 nm were obtained with conversion efficiencies approaching 10 percent. >

Generation of tunable femtosecond pulses in the 690–750 nm wavelength region

We report the generation of intense wavelength tunable pulses between 690 and 750 nm, of 65–85 fs duration and energies per pulse 1–2 μJ, via continuum amplification at 8.5 kHz. These pulses are compressed to durations of 12–13 fs.

Generation of tunable femtosecond pulses by traveling wave amplication

A simple system consisting of an amplified spontaneous emission source (ASE), a grating and a traveling wave (TW) amplifier which were pumped by the amplified output of a colliding-pulse mode-locked dye laser permits generation of continuously tunable femtosecond pulses. With three different dyes pulses shorter than 150 fs have been obtained between 660 nm and 785 nm. We have shown that the pulse duration of the amplifier output can be even shorter than the pump pulse. 23 fs pulses were generated at 700 nm by subsequent pulse compression in a fiber grating compressor.

Generation of tunable 9 femtosecond optical pulses in the near infrared

We report the generation of tunable femtosecond pulses in the 800–850 nm range. These pulses were obtained by generating a femtosecond continuum and selectively amplifying a portion of that continuum. The amplified femtosecond infrared pulses thus obtained were then compressed to a duration of 9 fs by a fiber followed by a grating and prism sequence.