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Lasers and Their Emission Characteristics
Published in F.J. Duarte, Tunable Laser Optics, 2017
All-solid-state Ti:sapphire lasers are available commercially with TEM00 beam profiles, and emission in the SLM domain, delivering average powers in the watt regime at ~10 kHz. Using CVL pumping, narrow-linewidth emission has been demonstrated at average powers of 5 W at 6.2 kHz, at a conversion efficiency of ~26% (Coutts et al. 1998). Liquid nitrogen cooling of Ti:sapphire gain media has resulted in CW output powers of up to 43 W at an efficiency of ~42% for broadband lasing (Erbert et al. 1991). In the ultrashort pulse regime, Ti:sapphire lasers have been shown to deliver pulses as short as 5 fs (Ell et al. 2001).
Laser Sources Based on Gaseous, Liquid, or Solid-State Active Media
Published in Helmut H. Telle, Ángel González Ureña, Laser Spectroscopy and Laser Imaging, 2018
Helmut H. Telle, Ángel González Ureña
Typical applications of Ti:sapphire lasers in laser spectroscopy and imaging are found, for example, in multiphoton microscopy and imaging techniques for which the wavelengths and pulse durations can be ideally tailored.
Ultrashort Pulses
Published in Chunlei Guo, Subhash Chandra Singh, Handbook of Laser Technology and Applications, 2021
The first passively mode-locked Ti:sapphire lasers were based on APM in which mode-locking is achieved using interference between the intra-cavity pulse and a self-phase-modulated replica propagating in an auxiliary cavity. An important breakthrough was made when in 1990 it was reported that an APM Ti:sapphire laser continued to operate even when the auxiliary cavity was blocked [34]. This discovery was attributed to an entirely new mode-locking effect known as KLM or self-mode-locking in which the presence of a Kerr-lens within the gain medium during mode-locked-operation changes the mode focusing within the cavity so that, compared to cw operation, mode-locked pulses experience higher gain. Two configurations of KLM exist and are known as soft aperture mode-locking [35], where the presence of the Kerr-lens increases the gain by improving the overlap between the pump and laser modes, and hard-aperture mode-locking [36], in which a physical aperture such as a slit or the edge of a prism is adjusted to introduce greater loss for cw operation. Because KLM is based on a non-resonant non-linearity, Ti:sapphire lasers can be mode-locked at any wavelength in their gain bandwidth using this technique. Using specially designed broad-bandwidth mirror sets, femtosecond Ti:sapphire lasers have been demonstrated with continuous tunability across ~300 nm [37]. Independently tunable dual wavelength operation from a single mode-locked laser has also been reported [38] and enables two exactly synchronized pulse sequences to be produced which are suitable for spectroscopic pump-probe experiments [39]. Recent advances in controlling the intra-cavity group-velocity dispersion characteristics have led to the generation of sub-5 fs pulses directly from a Ti:sapphire oscillator [40] which utilize the entire gain bandwidth of the material. The principal drawback of the KLM method is that it is not self-starting because mode-locked operation must be seeded by an intense noise spike or other short fluctuation. Different starting methods have been applied successfully including mirror tapping, acousto-optic modulation [41] and mode-dragging [42]; once mode-locking has been initiated, it is generally stable until some external perturbation disturbs the intra-cavity beam.
Optically tuneable broadband terahertz metamaterials using photosensitive semiconductor material
Published in Journal of Modern Optics, 2018
Qinglong Meng, Yan Zhang, Zheqiang Zhong, Bin Zhang
Figure 2 shows schematically the experimental set-up for coherent generation and detection of THz radiation. The femtosecond laser pulse used in the experiments was generated from an amplified Ti:sapphire laser system, whose standard output is 40 fs, 800 nm at a 1-kHz repetition rate. The emitted THz radiation was collimated and focused onto the sample by a pair of off-axis parabolic mirrors. The transmitted THz radiation was then collected and focused using another pair of off-axis parabolic mirrors onto the THz detector for detection. The absorption and dispersion of the THz radiation in the sample were minimized as described in the previous literature (28). The thickness of (110) GaAs, (110) ZnTe and (110) CdTe samples (without anti-reflection coating) all were 1 mm and the spot size of the THz beam was smaller than the sample size in all three cases of samples. In the experiments, the experimental conditions were remained unchanged in order to obtain reliable experimental results.
Effects of heterodyne signals on femtosecond optical Kerr measurements
Published in Journal of Modern Optics, 2019
In our experiments, a Ti: sapphire laser, emitting 100 fs and 800 nm laser pulses at a repetition rate of 1 kHz, was employed. The laser output was split into two beams, and one part was used as the pump light and the other as the probe beam. Two beams were focused into the sample at an angle of 15°. A delay tine was introduced into the pump light path to control the delay time between the two pumps and probe light. The probe light was finally detected by a positioned behind the sample and an analyser. A half-wave plate was introduced into the optical path of the pump beam, which was used change the angle between the polarization planes of the pump and probe beams.