G. Steinmeyer

Brewster-angled chirped mirrors for broadband pulse compression without dispersion oscillations

We use Brewster-angled chirped mirrors for dispersion compensation of a noncollinear optical parametric amplifier. This novel mirror design virtually eliminates spurious surface reflections and resultant dispersion ripple. The absence of compression artifacts is demonstrated by the generation of clean 5.6 fs pulses, with what is believed to be an unprecedented low ripple-induced satellite content for a nonadaptive scheme. In addition, the 270 THz spectral coverage allows generation of widely tunable visible pulses of 8 to 15 fs duration.

Bandwidth-independent linear method for detection of the carrier-envelope offset phase.

We propose and demonstrate a novel linear procedure for measurement of the carrier-envelope offset (CEO) phase of femtosecond oscillators. The technique is based on a Mach-Zehnder interferometer, a ring resonator, and a spectrograph. In this scheme, interference between subsequent pulses from a pulse train may frustrate the interference between identical pulses in the Mach-Zehnder, resulting in a modification of interference contrast depending on the CEO phase. We suggest spectrally and spatially resolved interferometry for robust detection of the fringe visibility. It is shown by numerical simulations and experimentally demonstrated that the visibility of such fringes uniquely depends on the CEO phase of the pulse train. Since the method relies only on linear interactions and does not require any nonlinear conversion, it allows characterizing the CEO frequency of mode-locked oscillators with virtually arbitrarily low bandwidth and power levels.

Spatially resolved amplitude and phase characterization of ultrashort optical pulses using SPIDER

Summary form only given.So far, ultrashort pulse characterization techniques have measured the spatially averaged amplitude and phase of the input beam. For beams exhibiting a significant spatial structure, however, it is desirable to completely spatially resolve the pulses to be characterized. Complex spatial structure can be found, for example, in broadband Kerr-lens modelocked lasers as a consequence of the frequency-dependent mode-size. In this contribution we demonstrate a technique based on spectral phase interferometry for direct electric-field reconstruction (SPIDER) that allows for measurement of the amplitude and phase of an ultrashort pulse at an arbitrary lateral position of the input beam. Only a single measurement is required for the acquisition of the spatially resolved data along one beam axis.

Smooth dispersion compensation: novel chirped mirrors with suppressed dispersion oscillations

We present a novel design approach for chirped mirror dispersion compensation, suitable for octave-filling spectra with strongly reduced dispersion oscillations. This method is experimentally demonstrated on a mode-locked Ti:sapphire laser. From the full amplitude and phase characterization of the resulting ultrabroadband pulses, we obtained a full width at half maximum duration of 5.8 fs.

Ultrabroadband pulses in the two-cycle regime by SESAM-assisted Kerr-lens modelocking of an all-solid-state Ti:sapphire laser

We demonstrate Ti:sapphire laser pulses of unprecedented spectral width, covering an optical octave without external continuum generation. The pulse spectrum spans more than 170 THz and supports bandwidth-limited two-cycle pulses. Assuming a sech2 pulse, the autocorrelation corresponds to a 4.8-fs pulse duration. The average power is 300 mW at a repetition rate of 100 MHz. The key features of the cavity are: dispersion compensation with broadband double-chirped mirrors combined with a prism pair, a broadband semiconductor saturable absorber mirror (SESAM) to assist Kerr-lens modelocking, and an output coupling mirror specifically designed to broaden the pulse spectrum.

Carrier-envelope offset frequency dynamics of a modelocked Ti:sapphire laser

Summary form only given. With pulse durations in the two-optical-cycle range, the typical assumption of a slowly-varying envelope in optics is expected to fail. Experimentally, the breakdown of this assumption manifests itself in a dependence of the conversion efficiency of nonlinear optical processes on the relative phase between carrier and envelope of a short pulse. Recently, the discussion on a sub-cycle-sensitivity in nonlinear optics has been stimulated by a proposal of several methods to measure and control the carrier-envelope offset (CEO). Meanwhile measurement of the CEO frequency has been successfully used for precision metrology, providing a direct phase-coherent link between microwave and optical frequency standards. Still, a CEO phase dependence in nonlinear optics has not yet been directly demonstrated. We measured and stabilized the CEO-frequency of a Ti:sapphire laser oscillator, Our set-up employs continuum generation in a microstructure fiber, frequency-doubling of the long-wavelength part of the spectrum and subsequent heterodyning with the short-wavelength part. This relatively simple set-up allows isolating the CEO-frequency with a signal-to-noise ratio of more than 40 dB in a 300-kHz bandwidth.

Back-side coated chirped mirrors for dispersion compensation over one octave

Summary form only given. We introduce a novel chirped mirror design technique to further extend the dispersion compensation range and to reduce detrimental dispersion oscillations. The fundamental idea behind this new approach is to suppress unwanted reflections at the top of the mirror stack by coating the mirror structure in reverse on the back side of a substrate with an index identical to either of the coating materials. Our technique works ideally if the double-chirp design technique is employed for the layers of the mirror stack.

Kerr-lens mode-locked lasers as ultra-low noise microwave sources

Summary form only given. Kerr-lens mode-locked (KLM) femtosecond lasers provide a dense comb of phase coherent reference frequencies and thus are versatile tools for optical frequency measurements. We demonstrate that the quantum-limited pulse timing noise level of such a laser is substantially smaller than the noise generated by state-of-the-art microwave oscillators.