Ultrafast thin-disk multipass amplifier with 720 mJ operating at kilohertz repetition rate for applications in atmospheric research.

We present an ultrafast thin-disk based multipass amplifier operating at a wavelength of 1030 nm, designed for atmospheric research in the framework of the Laser Lightning Rod project. The CPA system delivers a pulse energy of 720 mJ and a pulse duration of 920 fs at a repetition rate of 1 kHz. The 240 mJ seed pulses generated by a regenerative amplifier are amplified to the final energy in a multipass amplifier via four industrial thin-disk laser heads. The beam quality factor remains ∼ 2.1 at the output. First results on horizontal long-range filament generation are presented.

Reduction of thermocoagulative injury via use of a picosecond infrared laser (PIRL) in laryngeal tissues.

The carbon dioxide (CO2) laser is routinely used in glottic microsurgery for the treatment of benign and malignant disease, despite significant collateral thermal damage secondary to photothermal vaporization without thermal confinement. Subsequent tissue response to thermal injury involves excess collagen deposition resulting in scarring and functional impairment. To minimize collateral thermal injury, short-pulse laser systems such as the microsecond pulsed erbium:yttrium-aluminium-garnet (Er:YAG) laser and picosecond infrared laser (PIRL) have been developed. This study compares incisions made in ex vivo human laryngeal tissues by CO2 and Er:YAG lasers versus PIRL using light microscopy, environmental scanning electron microscopy (ESEM), and infrared thermography (IRT). In comparison to the CO2 and Er:YAG lasers, PIRL incisions showed significantly decreased mean epithelial (59.70 µm) and subepithelial (22.15 µm) damage zones (p < 0.05). Cutting gaps were significantly narrower for PIRL (133.70 µm) compared to Er:YAG and CO2 lasers (p < 0.05), which were more than 5 times larger. ESEM revealed intact collagen fibers along PIRL cutting edges without obvious carbonization, in comparison to diffuse carbonization and tissue melting seen for CO2 and Er:YAG laser incisions. IRT demonstrated median temperature rise of 4.1 K in PIRL vocal fold incisions, significantly less than for Er:YAG laser cuts (171.85 K; p < 0.001). This study has shown increased cutting precision and reduced lateral thermal damage zones for PIRL ablation in comparison to conventional CO2 and Er:YAG lasers in human glottis and supraglottic tissues.

Heat generation during ablation of porcine skin with erbium:YAG laser vs a novel picosecond infrared laser.

IMPORTANCE: Despite significant advances in surgery, most surgical tools remain basic. Lasers provide a means of precise surgical ablation, but their clinical use has remained limited because of undesired thermal, ionizing, or acoustic stress effects leading to tissue injury. A novel ultrafast, nonionizing, picosecond infrared laser (PIRL) system has recently been developed and is capable, in theory, of ablation with negligible thermal or acoustic stress effects. OBJECTIVE: To measure and compare heat generation by means of thermography during ablation of ex vivo porcine skin by conventional microsecond-pulsed erbium:YAG (Er:YAG) laser and picosecond infrared laser (PIRL). DESIGN AND SETTING: This study was conducted in an optics laboratory and used a pretest-posttest experimental design comparing 2 methods of laser ablation of tissue with each sample acting as its own control. INTERVENTION: Ex vivo porcine skin was ablated in a 5-mm line pattern with both Er:YAG laser and PIRL at fluence levels marginally above ablation threshold (2 J/cm² and 0.6 J/cm², respectively). MAIN OUTCOMES AND MEASURES: Peaks and maxima of skin temperature rises were determined using a thermography camera. Means of peak temperature rises were compared using the paired sample t test. Ablation craters were assessed by means of digital microscopy. RESULTS Mean peak rise in skin surface temperature for the Er:YAG laser and PIRL was 15.0°C and 1.68°C, respectively (P < .001). Maximum peak rise in skin surface temperature was 18.85°C for the Er:YAG laser and 2.05°C for the PIRL. Ablation craters were confirmed on digital microscopy. CONCLUSIONS AND RELEVANCE: Picosecond infrared laser ablation results in negligible heat generation, considerably less than Er:YAG laser ablation, which confirms the potential of this novel technology in minimizing undesirable thermal injury associated with lasers currently in clinical use.

A novel tool in laryngeal surgery: preliminary results of the picosecond infrared laser.

OBJECTIVES/HYPOTHESIS: Conventional lasers ablate tissue through photothermal, photomechanical, and/or photoionizing effects, which may result in collateral tissue damage. The novel nonionizing picosecond infrared laser (PIRL) selectively energizes tissue water molecules using ultrafast pulses to drive ablation on timescales faster than energy transport to minimize collateral damage to adjacent cells. STUDY DESIGN: Animal cadaver study. METHODS: Cuts in porcine laryngeal epithelium, lamina propria, and cartilage were made using PIRL and carbon dioxide (CO2) laser. Lateral damage zones and cutting gaps were histologically compared. RESULTS: The mean widths of epithelial (8.5 µm), subepithelial (10.9 µm), and cartilage damage zones (8.1 µm) were significantly lower for cuts made by PIRL compared with CO2 laser (p < 0.001). Mean cutting gaps in vocal fold (174.7 µm) and epiglottic cartilage (56.3 µm) were significantly narrower for cuts made by PIRL compared with CO2 laser (P < 0.01, P < 0.05). CONCLUSION: PIRL ablation demonstrates superiority over CO2 laser in cutting precision with less collateral tissue damage.

Fully reflective external-cavity setup for quantum-cascade lasers as a local oscillator in mid-infrared wavelength heterodyne spectroscopy.

To our knowledge we present the first experiments with a fully reflective external-cavity quantum-cascade laser system at mid-infrared wavelengths for use as a local oscillator in a heterodyne receiver. The performance of the presented setup was investigated using absorption spectroscopy as well as heterodyne techniques. Tunability over approximately 30 cm(-1) at 1130 cm(-1) was demonstrated using a grating spectrometer. A continuous tuning range of 0.28 cm(-1) was verified by observing the spectra of an internally coupled confocal Fabry-Pérot interferometer and the absorption lines of gas phase SO(2). In a second step the output from the system was used as a local oscillator signal for a heterodyne setup. We show that spectral stability and side mode suppression are excellent and that a compact external-cavity quantum-cascade laser system is well suited to be used as a local oscillator in infrared heterodyne spectrometers.