Cw Mode-locked Ti Research Articles

Optical detection system using time structure of UVSOR for combined laser–SR experiments

A new TAC-MCA detection system has been developed for combined laser–SR spectroscopy such as two-photon excitation or pump-probe experiments in the VUV region. In order to improve the signal to noise ratio, the time structure under partial-filling operation of UVSOR is utilized together with this detection system. In our experiment, where the two-photon excitation efficiency of laser and SR is more important than the time resolution, a pulse stretching technique using optical fiber is applied to the output pulse of a CW mode-locked Ti : sapphire laser. The usefulness of the present system is successfully demonstrated by observing luminescence signals from the two-photon-excited core state in BaF 2 crystals.

Optical second-harmonic generation from CuGaS 2 (1 1 2) bulk single crystals

Optical second-harmonic generation from CuGaS 2 bulk single crystals with a (1 1 2) plane was observed as a function of sample azimuthal angle using a cw mode-locked Ti:sapphire laser as a fundamental light source. From fitting experimental results to theoretical formula, the second-order nonlinear susceptibilities of χ 14 (2) and χ 36 (2) in CuGaS 2 at 852–918 nm were obtained to be (0.10±0.02) χ 14(GaAs) (2) and (0.11±0.02) χ 36(GaAs) (2), respectively, with reference to GaAs.

Ultraviolet Femtosecond Pulse Amplification with High Gain Using Solid-State, Broad-Band Gain Medium Ce3+:LiCaAlF6

Femtosecond pulse amplification with high gain in the ultraviolet region has been demonstrated using the solid-state, broad-band crystal Ce3+:LiCaAlF6. With the seed pulses coming from the third harmonic generation of a cw mode-locked Ti:sapphire laser, the confocal, four-pass amplifier pumped by 15-mJ, 266-nm, 10-ns pulses from a Q-switched Nd:YAG laser demonstrates 60-dB gain and delivers 54-µJ, 289-nm, 200-fs, 10-Hz pulses. There is almost no satellite pulse even without any special single-pulse selection.

Dipole traps with mode-locked lasers

We investigate the properties of two separate dipole traps, realised using a cw mode-locked Ti:sapphire laser and a cw mode-locked Nd:YVO4 laser, red-detuned by 25 nm and 284 nm, respectively. Approximately 103 laser-cooled 85Rb atoms were confined in the traps at ≈50 μK, with no observable heating after initial loading. The lifetimes of the traps were consistent with limitations imposed by wavelength-dependent photoassociation losses and collisions with background vapour. Determination of the ac Stark shift of the 780 nm cooling transition using a weak probe beam showed no observable difference between using narrow-bandwidth or mode-locked trapping light. Techniques for trapping and focusing of atoms based on the dipole force of blue and uv light become much more accessible through efficient doubling, tripling and quadrupling of mode-locked sources. This opens up the possibility of manipulating more technologically interesting species.

Picosecond Ti:sapphire-pumped optical parametric oscillator based on periodically poled LiNbO_3

Periodically poled lithium niobate has been used in a singly resonant optical parametric oscillator pumped by a cw mode-locked Ti:sapphire laser. A tuning range of 1.15 to 2.4 microm was achieved when the pump was tuned, and this range was limited only by the mirror reflection bandwidth. Thresholds as low as 18 mW and an overall slope efficiency of 44% were observed, with average output powers of 130 mW (70 mW) for the signal (idler).

Synchronously pumped optical parametric oscillators with LiB_3O_5

We have constructed a synchronously pumped parametric oscillator that uses temperature-tuned, noncritically phase-matched LiB3O5 as the nonlinear medium. We have synchronously pumped this LiB3O5 parametric oscillator with two different pump sources. The first is a cw mode-locked Ti:sapphire laser that produces 2 W of 100-fs pulses near 800 nm. Using this pump source, we have generated pulses as short as 40 fs, or as much as 550 mW of average power. We demonstrate the synchronization between the pump and the signal pulses by generating a 100-fs cross correlation. Our second pump source is a novel frequency-doubled diode-pumped Nd:YVO4 laser that produces 2 W of 6-ps pulses at 532 nm. We have generated pulses as short as 270 fs with extracavity dispersion compensation from this all-solid-state system.

Synchronously pumped optical parametric oscillators

Recent work on the development of high-repetition-rate, synchronously pumped picosecond and femtosecond Optical Parametric Oscillators (OPOs) is reviewed. With KTP, BBO or LBO crystals and solid-state pumps such as cw mode-locked Ti:Sapphire, Nd:YAG or Nd:YLF lasers, the singly resonant OPOs or their nonlinear optical accessories yield pulses as short as 40 fs, average powers up to hundreds of milliwatts, and tunability from 200 nm to > 10 µm.

Mid-infrared pulse generation using a sub-picosecond OPO

We describe a synchronously pumped LBO parametric oscillator pumped by a cw mode-locked Ti:Sapphire laser. We demonstrate the synchronization between the pump pulses and the signal pulses by measuring a 100 fs cross correlation. We then generate pulses tunable from 2.6 to 5.3 µm by mixing the signal and idler pulses in an AgGaS2 crystal and obtain as much as 400 µW of average power.

High-power second-harmonic generation with picosecond and hundreds-of-picosecond pulses of a cw mode-locked Ti:sapphire laser

A cw mode-locked Ti:sapphire laser was efficiently frequency doubled with a lithium triborate crystal in an external enhancement cavity. Second-harmonic output powers of 1.28 W and 860 mW have been generated at 399 nm with fundamental pulse widths of 1.5 and 320 ps, respectively. At the 1.5-ps pulse width the conversion efficiency was 75%. The spectral width of the 320-ps pulses, produced by modification of a laser cavity, is as narrow as the bandwidth of a normal cw, multimode, narrow-bandwidth Ti:sapphire laser. The frequency-doubled output can be thus used as a high-power, narrow-bandwidth light source in the UV region.

Tunable picosecond pulses below 200 nm by external frequency conversion of cw modelocked Ti:Al 2O 3 laser radiation

Sum frequency mixing of the fundamental and third harmonic radiation of a cw modelocked Ti: sapphire laser leads to tunable picosecond pulses down to a wavelength of 192 nm with average powers in the mW range.

External frequency conversion of cw mode-locked Ti:Al_2O_3 laser radiation

Efficient frequency conversion of cw mode-locked Ti:A1(2)O(3) laser radiation using lithium triborate, beta-barium borate, and lithium iodate crystals as the nonlinear material is demonstrated. Second-, third-, and fourth harmonic generation results in tunable blue and ultraviolet radiation down to 205 nm with transform-limited pulses and pulse lengths below 1 ps. Maximum average powers (repetition rate 82 MHz) of 700 mW at 400 nm, 120 mW at 272 nm, and 10 mW at 210 nm were obtained. The effects of group-velocity dispersion have to be taken into account to optimize the different frequency-conversion processes.