Franz X. Kaertner

Direct frequency comb generation from an octave-spanning, prismless Ti:sapphire laser

An octave spanning prismless Ti:sapphire laser is demonstrated. The octave is reached at 20 dB below the average power level. A highly stable carrier-envelope beat note with 30 dB signal to noise in a 100 kHz detection bandwidth is observed.

Toward single-cycle laser systems

Few-cycle pulse generation based on Ti:sapphire, Cr:forsterite, and Cr:YAG gain media is reviewed. The dynamics of these laser systems is well understood in terms of soliton and dispersion managed soliton formation stabilized by artificial saturable absorber action provided by Kerr-lens modelocking. These systems generate 5-, 14-, and 20-fs pulses with spectral coverages of 600-1150, 1100-1600, and 1200-1500 nm, respectively. The design of dispersion compensating laser optics providing high reflectivity and prismless operation over this bandwidth is discussed. A novel active synchronization scheme based on balanced optical cross correlation, the equivalent to balanced microwave detection, for synchronization of independently mode-locked lasers is introduced. Its use in synchronizing an octave-spanning Ti:sapphire laser and a 30-fs Cr:forsterite laser yields 300 attoseconds timing jitter measured from 10 mHz to 2.3 MHz. The spectral overlap between the two lasers is large enough to enable direct detection of the difference in the carrier-envelope offset frequency between the two lasers. These are the most important steps in the synthesis of single-cycle optical pulses with spectra spanning 600-1600 nm.

All silicon infrared photodiodes: photo response and effects of processing temperature

CMOS compatible infrared waveguide Si photodiodes are made responsive from 1100 to 1750 nm by Si(+) implantation and annealing. This article compares diodes fabricated using two annealing temperatures, 300 and 475 degrees C. 0.25-mm-long diodes annealed to 300 degrees C have a response to 1539 nm radiation of 0.1 A W-(-1) at a reverse bias of 5 V and 1.2 A W(-1) at 20 V. 3-mm-long diodes processed to 475 degrees C exhibited two states, L1 and L2, with photo responses of 0.3 +/-0.1 A W(-1) at 5 V and 0.7 +/-0.2 A W(-1) at 20 V for the L1 state and 0.5 +/-0.2 A W(-1) at 5 V and 4 to 20 A W(-1)-1 at 20 V for the L2 state. The diodes can be switched between L1 and L2. The bandwidths vary from 10 to 20 GHz. These diodes will generate electrical power from the incident radiation with efficiencies from 4 to 10 %.

Low-cost, single-mode diode-pumped Cr:Colquiriite lasers

We present three Cr3+:Colquiriite lasers as low-cost alternatives to Ti:Sapphire laser technology. Single-mode laser diodes, which cost only

Effect of carrier lifetime on forward-biased silicon Mach-Zehnder modulators

150 each, were used as pump sources. In cw operation, with approximately 520 mW of absorbed pump power, up to 257, 269 and 266 mW of output power and slope efficiencies of 53%, 62% and 54% were demonstrated for Cr:LiSAF, Cr:LiSGaF and Cr:LiCAF, respectively. Record cw tuning ranges from 782 to 1042 nm for Cr:LiSAF, 777 to 977 nm for Cr:LiSGaF, and 754 to 871 nm for Cr:LiCAF were demonstrated. In cw mode-locking experiments using semiconductor saturable absorber mirrors at 800 and 850 nm, Cr:Colquiriite lasers produced approximately 50-100 fs pulses with approximately 1-2.5 nJ pulse energies at approximately 100 MHz repetition rate. Electrical-to-optical conversion efficiencies of 8% in mode-locked operation and 12% in cw operation were achieved.

Multi-photon microscopy with a low-cost and highly efficient Cr:LiCAF laser.

We present a systematic study of Mach-Zehnder silicon optical modulators based on carrier-injection. Detailed comparisons between modeling and measurement results are made with good agreement obtained for both DC and AC characteristics. A figure of merit, static VpiL, as low as 0.24Vmm is achieved. The effect of carrier lifetime variation with doping concentration is explored and found to be important for the modulator characteristics.

Possibility of self-similar pulse evolution in a Ti:sapphire laser

Multi-photon microscopy (MPM) is a powerful tool for biomedical imaging, enabling molecular contrast and integrated structural and functional imaging on the cellular and subcellular level. However, the cost and complexity of femtosecond laser sources that are required in MPM are significant hurdles to widespread adoption of this important imaging modality. In this work, we describe femtosecond diode pumped Cr:LiCAF laser technology as a low cost alternative to femtosecond Ti:Sapphire lasers for MPM. Using single mode pump diodes which cost only

Experimental implementation of optical clockwork without carrier-envelope phase control

150 each, a diode pumped Cr:LiCAF laser generates approximately 70-fs duration, 1.8-nJ pulses at approximately 800 nm wavelengths, with a repetition rate of 100 MHz and average output power of 180 mW. Representative examples of MPM imaging in neuroscience, immunology, endocrinology and cancer research using Cr:LiCAF laser technology are presented. These studies demonstrate the potential of this laser source for use in a broad range of MPM applications.

An extended cavity femtosecond Cr:LiSAF laser pumped by low cost diode lasers.

A theoretical investigation of the possibility of achieving self-similar pulse propagation in a solid-state laser is presented. Limited group-velocity dispersion hinders true self-similar pulse evolution, but an intermediate regime that exhibits some of the characteristic features (and offers some of the benefits) of self-similar propagation can be reached. This regime of operation offers the potential to increase the pulse energy by at least an order of magnitude compared to energies obtained in the usual operation of Kerr-lens mode-locked lasers with anomalous dispersion. Ti:sapphire lasers that generate pulse energies as high as one microjoule and peak powers of ~100 MW should be possible based on this mode of operation.

300 attosecond active synchronization of passively mode-locked lasers using balanced cross-correlation

We demonstrate an optical clockwork without camer-envelope phase control using sum-frequency generation between a CW optical parametric oscillator at 3.39 μm and a modelocked Tisapphire laser with dominant spectral peaks at 834 and 670 nm.