J. Teipel

Group velocity dispersion of tapered fibers immersed in different liquids

We investigate the group velocity dispersion of tapered fibers that are immersed in different liquids. Using the Sellmeier equations fitted from measured refractive indices of these liquids, we are able to analyze the dispersion characteristics of the tapered fibers in a tailored liquid environment. Theoretical results show a large span of slowly varying anomalous group velocity dispersion characteristics. This leads to potentially significant improvements and a large bandwidth in supercontinuum generation in a tapered fiber. This holds true as well for a range of new fiber materials.

Compact multi-Watt picosecond coherent white light sources using multiple-taper fibers

The combination of a diode-pumped Nd:YVO4 picosecond laser source with tapered fibers allows the realization of a compact white light source with an average output power of up to 5.65 W. We generated supercontinua with a throughput of ~50% over a spectral range of up to 1140 nm by using a series of tapered fibers that were spliced together.

Coherence of subsequent supercontinuum pulses generated in tapered fibers in the femtosecond regime

We measure the degree of coherence of supercontinua generated in tapered fibers by subsequent fs pulses. By means of interference experiments we study its dependence on the input pulse duration and power. We also present numerical simulations that allow us to explain the experimental observations which show a decreasing degree of coherence with increasing input power. We attribute this loss of coherence to phase noise due to the cross-phase modulation by several solitons with randomly varying parameters due to quantum noise.

Excitation beyond the monochromatic laser limit: simultaneous 3-D confocal and multiphoton microscopy with a tapered fiber as white-light laser source

Confocal and multiphoton microscopy are essential tools in modern life sciences. They allow fast and highly resolved imaging of a steadily growing number of fluorescent markers, ranging from fluorescent proteins to quantum dots and other fluorophores, used for the localization of molecules and the quantitative detection of molecular properties within living cells and organisms. Up to now, only one physical limitation seemed to be unavoidable. Both confocal and multiphoton microscopy rely on lasers as excitation sources, and their monochromatic radiation allows only a limited number of simultaneously usable dyes, which depends on the specific number of laser lines available in the used microscope. We have overcome this limitation by successfully replacing all excitation lasers in a standard confocal microscope with pulsed white light ranging from 430 to 1300 nm generated in a tapered silica fiber. With this easily reproducible method, simultaneous confocal and multiphoton microscopy was demonstrated. By developing a coherent and intense laser source with spectral width comparable to a mercury lamp, we provide the flexibility to excite any desired fluorophore combination.

Diode-pumped, ultrafast, multi-octave supercontinuum source at repetition rates between 500 kHz and 20 MHz using Yb:glass lasers and tapered fibers

We present a compact, all diode-pumped supercontinuum source based on a SESAM mode-locked Yb:glass oscillator at 1040 nm and a tapered fiber. The oscillator has a repetition rate of 20 MHz, a pulse duration of 200 fs, and a maximum pulse energy of about 15 nJ. This system delivers an 1100 nm broad spectrum with an output power of more than 100 mW. Decreasing the repetition rate to 500 kHz by cavity-dumping results in a supercontinuum with a high pulse energy of about 50 nJ. Furthermore, using the frequency-doubled output of this laser at 520 nm with 300 fs pulse duration resulted in supercontinua in the near-UV and visible spectral region. We compare the experimental spectra with theoretical simulations.

Generation of white light laser radiation in tapered fibers

Tapered fibers have shown high efficiency to generate white light continua, which have many important applications such as pulse compression, spectroscopy, pump-probe measurements, and optical frequency metrology. In this paper, we discuss the principle of white light continuum generation in tapered fibers with incident pulse durations in the femtosecond and picosecond range. We are going to demonstrate some new technologies to design and improve the spectral characteristics of supercontinuum generation, which make tapered fibers very convenient for the construction of white light sources.

Spectrally and temporally resolved measurements of white light continuum generated in tapered fibers

Spectrally and temporally resolved crosscorrelation measurements of a white light continuum in tapered fibers created by 75 fs pulses at 800 nm show a transition from self-phase modulation to a break-up into several pulses.