Yuzo Ishida

Generation of 50-fsec pulses from a pulse-compressed, cw, passively mode-locked Ti:sapphire laser

Stable pulses of less than 150 fsec are generated directly from a tunable cw passively mode-locked Ti:sapphire laser, through a balance of self-phase modulation in the Ti:sapphire rod and negative group-velocity dispersion produced by a prism pair. After external fiber compression, 50-fsec pulses are obtained at approximately 750 nm.

All solid-state cw passively mode-locked Ti:sapphire laser using a colored glass filter

All solid‐state cw passive mode locking of a Ti:sapphire laser is accomplished using a colored glass filter, instead of an organic dye, as a saturable absorber. The tuning range is remarkably wide (785–855 nm), and 2.7 ps pulses are obtained directly from the cavity.

cw passive mode locking of a Ti:sapphire laser

cw passive mode locking of a Ti:sapphire laser is achieved with 1,1’‐dietyl‐2,2’‐dicarbocyanine iodide as the saturable absorber dye, using a 5 μm thin dye jet flow. The pulse width is 4.0 ps, which is almost the transform‐limited pulse for the observed spectrum width. The output power is ∼50 mW, when it is pumped by a 5 W cw Ar laser, while the tuning range is 745–755 nm.

Self-phase modulation in hybridly mode-locked CW dye lasers

Largely asymmetric spectra are observed for ultrashort light pulses from a synchronously and passively mode-locked CW rhodamine 6G dye laser, with relatively high intra-cavity intensity. The spectral shape shows a broad wing on the long-wavelength side alone. When the asymmetric spectrum occurs, the conventional SHG intensity auto-correlation trace shows exponential-like long tails. Further, the temporal characteristics of the mode-locked pulses, including both the shape and phase, are also examined by a new method of SHG autocorrelation, where the SH output is spectrally resolved. These experimental results are explained with self-phase modulation (SPM) process due to the optical Kerr effect in a mixed dye jet stream inside the laser cavity. The main observed characteristics are in reasonable agreement with the theoretical expectation from the slow SPM mechanism, where the pulse width is much shorter than the relaxation time τ r of refractive index. The measured nonlinear refractive index n 2 and τ r also support the above interpretation.

Compact diode-pumped all-solid-state femtosecond Cr(4+):YAG laser.

We have developed a compact, all-solid-state self-mode-locked Cr(4+):YAG laser. The laser is pumped by a cw laser-diode-pumped Nd:YVO(4) laser and produces highly stable femtosecond pulses near 1.50 microm. Measurements of noise power spectra for frequencies below 10 kHz show that the diode-pumped laser system greatly improves the output energy fluctuation and pulse timing jitter compared with a laser system that uses a conventional arc-lamp-pumped cw Nd:YAG laser.

Characteristics of femtosecond pulses near 1.5 μm in a self-mode-locked Cr 4+ :YAG laser

The operating characteristics of a self-mode-locked Cr(4+) :YAG laser that produces sub-100-fs pulses are described. Stable, nearly transform-limited pulses are obtained at a central wavelength longer than 1.50 microm, and the spectrum of the wavelength is extended past 1.60 microm, over the net gain bandwidth of the laser material. The group-velocity dispersion and the third-order dispersion of the Cr-doped YAG rod are measured by a Fourierindicating that the group-velocity dispersion vanishes at a transform interferometric cross-correlation technique, wavelength of 1.59 microm.

Pulse evolution dynamics of a femtosecond passively mode-locked Ti:sapphire laser

The pulse-formation process in a femtosecond passively mode-locked Ti:sapphire laser with a saturable absorber is investigated. The time to reach the steady state is 200 micros. The formation time dependence on the dye concentration and the coincidence of the steady-state pulse width with the self-mode-locked state without a saturable absorber indicate that the function of the saturable absorber is mainly to induce the initial modulation and to shorten the pulse-formation time.

Characteristics of a new-type SHG crystala β-BaB2O4 in the femtosecond region

Abstract The optical characteristics of a new nonlinear crystal β-BaB 2 O 4 , including the group-velocity dispersion and the nonlinear coefficient in the femtosecond region, are investigated through the second-harmonic generation (SGH). The performances of β-BaB 2 O 4 relative to KDP are evaluated from both calculations and measurements. From the measurements using the crystals with different thicknesses, the influence of the group-velocity mismatch of β-BaB 2 O 4 on the broadening of the correlation width is revealed, and is found to be smaller than that of KDP. Overall performance of the SHG conversion efficiency of β-BaB 2 O 4 including all affecting factors is evaluated to show higher values by a factor of 10 to 10 2 than that of KDP depending on operating conditions.

Ultrashort pulse generation from a passively mode-locked Ti:sapphire laser based system

The detailed characteristics of a passively mode-locked Ti:sapphire laser using saturable absorbers are described. This laser can stably generate nearly transform-limited sub-100-fs pulses around 780 nm. Combining this oscillator and a double-pass Ti:sapphire amplifier pumped by a CW Q-switched YAG laser (3 kHz) allows fiber-grating pulse compression down to 14 fs. >

Generation of Broadly Tunable Subpicosecond Light Pulses from a Synchronously and Passively Mode-Locked CW Dye Laser

Transform-limited pulses with a minimum width as short as 0.30 ps have been obtained from a synchronously pumped rhodamine 6G dye laser with a dye solution of mixed gain and saturable absorber (DODCI) media. Stable subpicosecond pulses (0.30–0.85 ps) were generated in a wide tuning range of 574–611 nm using a broad-band wedged-etalon tuning element. With the frequency tuning element inside the cavity, the cavity-length detuning range to maintain perfect mode-locking was ±10 µm which is less critical than for synchronous mode-locking alone, and the range extended to ±1.5 mm without the frequency tuning element.