Femtosecond

About: Femtosecond is a research topic. Over the lifetime, 35106 publications have been published within this topic receiving 691405 citations. The topic is also known as: 1 E-15 s & fs.

Sub-500-fs soliton-like pulse in a passively mode-locked broadband surface-emitting laser with 100 mW average power

Abstract: We report on femtosecond operation of a broadband diode-pumped external-cavity surface-emitting semiconductor laser, passively mode locked with a fast quantum–well Semiconductor Saturable Absorber Mirror grown at 735 °C. We obtained 477 fs pulses at 1.21 GHz. The average output power is 100 mW at 1040 nm, the pulse peak power 152 W, with ∼1 W of 830 nm pump. The rf spectrum shows a linewidth <50 kHz at the noise level (−65 dB). We believe that the group-delay dispersion is compensated by the negative self-phase modulation in the absorber structure, leading to soliton-like mode locking. This system requires no additional technological step after the growth of the structures.

275 W average output power from a femtosecond thin disk oscillator operated in a vacuum environment.

Abstract: We present an ultrafast thin disk laser that generates an average output power of 275 W, which is higher than any other modelocked laser oscillator. It is based on the gain material Yb:YAG and operates at a pulse duration of 583 fs and a repetition rate of 16.3 MHz resulting in a pulse energy of 16.9 μJ and a peak power of 25.6 MW. A SESAM designed for high damage threshold initiated and stabilized soliton modelocking. We reduced the nonlinearity of the atmosphere inside the cavity by several orders of magnitude by operating the oscillator in a vacuum environment. Thus soliton modelocking was achieved at moderate amounts of self-phase modulation and negative group delay dispersion. Our approach opens a new avenue for power scaling femtosecond oscillators to the kW level.

10-GHz Self-Referenced Optical Frequency Comb

Abstract: The femtosecond laser–based frequency comb has played a key role in high-precision optical frequency metrology for a decade. Although often referred to as a precise optical frequency ruler, its tick marks are in fact too densely spaced for direct observation and individual use, limiting important applications in spectroscopy, astronomy, and ultrafast electromagnetic waveform control. We report on a femtosecond laser frequency comb with a 10-gigahertz repetition rate that creates a stabilized output spectrum with coverage from 470 to 1130 nanometers. The individual modes can be directly resolved with a grating spectrometer and are visible by eye.

Femtosecond optical ranging in biological systems.

Abstract: Optical ranging using femtosecond laser pulses and nonlinear-optical cross correlation is demonstrated for the investigation of the microstructure of biological systems. By using pulses of 65-fsec duration generated by a colliding-pulse mode-locked ring dye laser, a spatial resolution of less than 15 μm is achieved with a detection sensitivity to remitted signals as small as 10−7 of the incident pulse energy. This technique is applied to measure the cornea in rabbit eyes in vivo as well as to investigate the epidermal structure of human skin in vitro.

Theory of dynamic absorption spectroscopy of nonstationary states. 4. Application to 12-fs resonant impulsive Raman spectroscopy of bacteriorhodopsin

Abstract: A time-dependent theory for femtosecond dynamic absorption spectroscopy is used to describe the creation and observation of molecular ground-state vibrational coherence through the resonance impulsive stimulated Raman mechanism. Model calculations show that the oscillatory absorption signal that arises from this ground-state coherence is maximized for a limited range of pulse lengths and that there is a complex relationship between the probe wavelength and the strength of the spectral oscillations. The generalized time-dependent linear susceptibility of the nonstationary system created by the impulsive pump pulse is defined and used to discuss the strong dependence of the measured signals on the properties of the probe pulse. Finally, calculations are presented to analyze the high-frequency oscillations ({approximately}20-fs period) recently observed in the transient absorption spectra of light-adapted bacteriorhodopsin (BR{sub 568}) following excitation with a 12-fs optical pulse. At the probe wavelengths used in this experiment, the contribution of stimulated emission is negligible at long times because of the extremely rapid excited-state isomerization; as a result, the spectral oscillations observed after this time are due to the impulsive excitation of coherent vibrations in the ground state. The transient response observed for BR{sub 568} is calculated using a 29-mode harmonic potential surface derived from amore » prior resonance Raman intensity analysis. Both the oscillatory signals and their dependence on the probe wavelength are satisfactorily reproduced. 68 refs., 11 figs.« less