Application of supercontinuum to spectroscopy

The present availability of excitation wavelengths imposes limitations on fluorescence imaging, particularly for confocal microscopy. This diploma thesis concerns the application of novel fibre-based tunable continuum sources to multidimensional fluorescence microscopy. These sources can provide broad spectral coverage and are spatially coherent so they are suitable for confocal microscopy. They are inherently pulsed on ultra-fast timescales and so are also suitable for fluorescence lifetime imaging (FLIM) and related time-resolved imaging modalities. Compared to frequency-doubling and optical parametric amplification using the tunable Ti:sapphire laser, this approach is less complex, less expensive, and more compact

Cascaded Parametric Amplification for Highly Efficient Terahertz Generation

A highly efficient, practical approach to high-energy terahertz (THz) generation based on spectrally cascaded optical parametric amplification (THz-COPA) is introduced. The THz wave initially generated by difference frequency generation between a strong narrowband optical pump and optical seed (0.1-10% of pump energy) kick-starts a repeated or cascaded energy down-conversion of pump photons. This helps to greatly surpass the quantum-defect efficiency and results in exponential growth of THz energy over crystal length. In cryogenically cooled periodically poled lithium niobate, energy conversion efficiencies >8% for 100 ps pulses are predicted. The calculations account for cascading effects, absorption, dispersion and laser-induced damage. Due to the coupled nonlinear interaction of multiple triplets of waves, THz-COPA exhibits physics distinct from conventional three-wave mixing parametric amplifiers. This in turn governs optimal phase-matching conditions, evolution of optical spectra as well as limitations of the nonlinear process.Comment: 5 pages, double colum

Demonstration of generalized higher-order Bessel-Gauss beam solutions in optical resonators

We propose azimuthally symmetric higher-order Bessel-Gauss beams, and experimentally demonstrate them as higher-order eigenmodes in optical resonators comprising aspheric mirror

Pre-chirp managed, core-pumped nonlinear PM fiber amplifier delivering sub-100-fs and high energy (10 nJ) pulses with low noise

We demonstrate a pre-chirp managed amplification (PCMA) system that is based on two stages of core-pumped, polarization maintaining (PM) fiber amplifiers. It produces output pulses with 10 nJ pulse energy from single-mode fibers. Tailoring of the spectra in the amplification chain enables pulse compression to near-perfect transform limited pulses (Strehl-ratio >0.9) and low intensity noise levels (0.008%) despite B-integrals >40 rad in the PCMA amplifier. Design strategies are presented. We expect this PCMA system to become an easy to implement add-on to a variety of existing sources while maintaining the advantages of the robustness of the PM standard fiber format

Observation and analysis of generalized higher-order Bessel-Gauss beams in optical resonators

We propose and experimentally demonstrate new beam solutions in form of azimuthally symmetric higher-order Bessel-Gauss beams. We experimentally observe these beams as higher-order eigenmodes in optical resonators consisting of aspheric mirrors

Decrease of pulse-contrast in nonlinear chirped-pulse amplification systems due to high-frequency spectral phase ripples

It is analytically shown that weak initial spectral phase modulations cause a pulse-contrast degradation at the output of nonlinear chirped-pulse amplification systems. The Kerr-nonlinearity causes an energy-transfer from the main pulse to side-pulses during nonlinear amplification. The relative intensities of these side-pulses can be described in terms of Bessel-functions. It is shown that the intensities of the pulses are dependent on the magnitude of the accumulated nonlinear phase-shift (i.e., the B-integral), the depth and period of the initial spectral phase-modulation and the slope of the linear stretching chirp. The results are applicable to any type of laser amplifier that is based on the technique of chirped-pulse amplification. The analytical results presented in this paper are of particular importance for high peak-power laser applications requiring high pulse-contrasts, e. g. high field physics

Radially Polarized Bessel-Gauss Beams in ABCD Optical Systems and Fiber-Based Generation

We derive solutions for radially polarized Bessel-Gauss beams in ABCD optical systems by superimposing decentered Gaussian beams with linear polarization states. We experimentally confirm the expression by employing a fiber-based mode-converter