Mid-Infrared nonlinear silicon photonics

Recently there has been a growing interest in mid-infrared (mid-IR) photonic technology with a wavelength of operation approximately from 2-14 mu m. Among several established mid-IR photonic platforms, silicon nanophotonic platform could potentially offer ultra-compact, and monolithically integrated mid-IR photonic devices and device arrays, which could have board impact in the mid-IR technology, such as molecular spectroscopy, and imaging. At room temperature, silicon has a bandgap similar to 1.12 eV resulting in vanishing two-photon absorption (TPA) for mid-IR wavelengths beyond 2.2 mu m, which, coupled with silicon's large nonlinear index of refraction and its strong waveguide optical confinement, enables efficient nonlinear processes in the mid-IR. By taking advantage of these nonlinear processes and judicious dispersion engineering in silicon waveguides, we have recently demonstrated a handful of silicon mid-IR nonlinear components, including optical parametric amplifiers (OPA), broadband sources, and a wavelength translator. Silicon nanophotonic waveguide's anomalous dispersion design, providing four-wave-mixing (FWM) phase-matching, has enabled the first demonstration of silicon mid-IR optical parametric amplifier (OPA) with a net off-chip gain exceeding 13 dB. In addition, reduction of propagation losses and balanced second and fourth order waveguide dispersion design led to an OPA with an extremely broadband gain spectrum from 1.9-2.5 mu m and > 50 dB parametric gain, upon which several novel silicon mid-IR light sources were built, including a mid-IR optical parametric oscillator, and a supercontinuum source. Finally, a mid-IR wavelength translation device, capable of translating signals near 2.4 mu m to the telecom-band near 1.6 mu m with simultaneous 19 dB gain, was demonstrated

Performance limits in optical communications due to fiber nonlinearity

In this paper, we review the historical evolution of predictions of the performance of optical communication systems. We will describe how such predictions were made from the outset of research in laser based optical communications and how they have evolved to their present form, accurately predicting the performance of coherently detected communication systems

Analysis of the nonlinear Kerr effects in optical transmission systems that deploy optical phase conjugation

In this work, we will derive, validate, and analyze the theoretical description of nonlinear Kerr effects resulted in various transmission system that deploy single or multiple optical phase conjugators (OPC). We will show that the nonlinear Kerr compensation can be achieved, with various efficiencies, in both lumped and distributed Raman transmission systems. The results show that first order distributed Raman systems are superior to the discretely amplified systems in terms of the nonlinear Kerr compensation efficiency that a mid-link OPC can achieve. Also, we will show that the multi-OPC approach will diminish the nonlinearity compensation efficiency in any system as it will act as periodic dispersion compensators

Investigation of single-frequency high-power Raman fiber amplifier for guide star application

This work presents theoretical, numerical, and experimental investigations of power scaling of core-pumped single-frequency Raman fiber amplifiers operating at 1178 nm. A numerical model was developed that accounts for stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) in relation to the fiber mode field diameter, length, seed power, and available pump power in both co-pumped and counter-pumped configurations. The backward travelling Stokes light is initiated from both spontaneous Brillouin and spontaneous Raman processes. In order to mitigate the SBS process for further power scaling, a multi-step longitudinal temperature distribution along the gain fiber was employed and optimized. Although higher amplifier efficiency is obtained with higher seed power, the output power diminishes at SBS threshold if the same length of fiber is considered. However, if the fiber length is optimized for a given seed power, more power can be extracted; thus indicating further power scaling is expected by constructing a two-stage amplifier system. As an initial experimental step, a commercial off-the-shelf (COTS) fiber is used to obtain 10 W of single-frequency output power through the application of a multi-step thermal gradient in a counter-pumped configuration. A cutback experiment performed on the COTS fiber indicated a linear relation between signal output and pump power at SBS threshold; a result that showed agreement with the theoretical predictions. In addition, 18 W of output was achieved in the single-stage amplifier by designing and utilizing an acoustically tailored fiber for SBS suppression. Further power scaling was demonstrated by constructing a counter-pumped two-stage amplifier system as predicted by the numerical model. In comparing co- and counter-pumped systems, it was shown that while the latter preserves the single-frequency characteristic of the seed laser, the former leads to spectral broadening of the amplified signal output

A new concept short pulse fiber laser source

Ultrashort-pulse fiber laser systems, which offer, due to their high peak pulse intensity in combination with high pulse frequencies (repetition rate), an innovative technology of nonlinear interaction with materials, help to fabricate components with unprecedented quality, precision and speed. Also due to the short pulse duration, laser energy can be introduced into the material in a shorter time than heat transfer occurs, which thus prevents thermal damage to the part. It is not surprising that industrial laser systems with a sub-nanosecond pulse length are widely used in the markets of precision processing, medical devices and in many other applications. The most critical component of such systems is the seed laser source. To date, the existing devices in the commercial market do not fully satisfy the industrial requirements. In this thesis I describe a new concept for the generation of ultrashort laser pulses using an all-passive, fiber-ring, mode-locked laser with at least two passive spectral filters incorporated. Also presented is a full theoretical model of the operation of the laser. I report on the development and the comprehensive characterization of a fully optimized laser configuration, finding excellent agreement of the theoretical model and the experimental results. Various practical configurations and their application were demonstrated. During the period of the project, a fully commercially developed laser scheme was implemented in a variety of IPG Photonics picosecond and femtosecond laser systems.Open Acces