High Repetition Rate Ultrashort Pulse Research Articles

Picosecond pulse generation from continuous-wave light in an integrated nonlinear Bragg grating

Abstract The generation of optical pulse trains from continuous-wave light has attracted growing attention in recent years because it provides a simple way to obtain high repetition rate ultrashort pulses. While pulse generation has been extensively demonstrated in optical fibers, pulse train generation from weak, continuous wave light in photonic chips has posed significant challenges because of the short interaction length and therefore difficulty in acquiring sufficient new frequency content, and/or absence of the appropriate dispersion environment. In this manuscript, we report the pulse train generation of a low continuous-wave signal to 18 ps, by leveraging cross-phase modulation induced by co-propagating pump pulses with a peak power of 3.7 W in an ultra-silicon-rich nitride grating. The pulse train generation dynamics are documented both experimentally and theoretically to arise from cross-phase modulation-induced generation of new spectral content, and dispersive re-phasing. This is a new approach in which picosecond pulse generation may be achieved from low power, continuous-wave light.

Accurate modeling of high-repetition rate ultrashort pulse amplification in optical fibers

A numerical model for amplification of ultrashort pulses with high repetition rates in fiber amplifiers is presented. The pulse propagation is modeled by jointly solving the steady-state rate equations and the generalized nonlinear Schrödinger equation, which allows accurate treatment of nonlinear and dispersive effects whilst considering arbitrary spatial and spectral gain dependencies. Comparison of data acquired by using the developed model and experimental results prove to be in good agreement.

Fracture toughness of ultrashort pulse-bonded fused silica

We determined the bond interface strength of ultrashort pulse laser-welded fused silica for different processing parameters. To this end, we used a high repetition rate ultrashort pulse laser system to inscribe parallel welding lines with a specific V-shaped design into optically contacted fused silica samples. Afterward, we applied a micro-chevron test to measure the fracture toughness and surface energy of the laser-inscribed welding seams. We analyzed the influence of different processing parameters such as laser repetition rate and line separation on the fracture toughness and fracture surface energy. Welding the entire surface a fracture toughness of \(0.71\,\hbox {MPa}\,\hbox {m}^{1/2}\), about 90 % of the pristine bulk material \(({\approx } 0.8\,\hbox {MPa}\,\hbox {m}^{1/2})\), is obtained.

High harmonic generation by novel fiber amplifier based sources

Significant progress in high repetition rate ultrashort pulse sources based on fiber technology is presented. These systems enable operation at a high repetition rate of up to 500 kHz and high average power in the extreme ultraviolet wavelength range via high harmonic generation in a gas jet. High average power few-cycle pulses of a fiber amplifier pumped optical parametric chirped pulse amplifier are used to produce µW level average power for the strongest harmonic at 42.9 nm at a repetition rate of 96 kHz.

Materials for Photonic Switching and Information Processing

In electronic processors, heat dissipation and interconnection delay are serious design and performance limiting factors. Why then consider photonic components where both the energy and size of the photon are large (˜1 eV and ˜1 μm, respectively) and the required nonlinear interactions between electric or magnetic fields and photons for switching or modulation are small? There are several answers to this question. First, the wide bandwidth of optical communications systems is taxing the current capabilities of electronic switching technologies. Even a slow optical switch can switch a very wide bandwidth optical signal from one fiber to another. External optical modulators will likely be required in ultrawide bandwidth communications because of basic limitations on direct modulation of lasers. Because of the weak electromagnetic interaction and low dispersion, optical interconnection of electronic circuits offers considerable advantages in high speed computer architectures. Some of these applications would appear to be relatively near term since they build on current capabilities of optical communication.Longer term and more speculative are applications of photonics to computation and image processing — areas where electronics technology is already mature. Current research can be divided into two groups — ultrafast processing and parallel processing. The first group concentrates on processing with ultra-fast optical pulses. Optical pulses as short as 6 fs — orders of magnitude shorter than any electronic pulses — have been generated in the research laboratory. High processing rates are achievable by serial processing of high repetition rate ultrashort pulses. This approach requires ultrafast switches, which in turn requires materials with ultrafast nonlinear optical response time. Indeed, the shortest electrical signals are now measured by optical sampling techniques.