Mode-locked laser pulse sources for wavelength division multiplexing

Recent theoretical investigations have demonstrated that the stability of mode-locked solution of multiple frequency channels depends on the degree of inhomogeneity in gain saturation. In this paper, these results are generalized to determine conditions on each of the system parameters necessary for both the stability and existence of mode-locked pulse solutions for an arbitrary number of frequency channels. In particular, we find that the parameters governing saturable intensity discrimination and gain inhomogeneity in the laser cavity also determine the position of bifurcations of solution types. These bifurcations are completely characterized in terms of these parameters. In addition to influencing the stability of mode-locked solutions, we determine a balance between cubic gain and quintic loss, which is necessary for existence of solutions as well. Furthermore, we determine the critical degree of inhomogeneous gain broadening required to support pulses in multiple frequency channels

The Design and Construction of Novel Near -Infrared Time -Correlated Single Photon Counting Devices for the Identification of Analytes in Multiplexed Applications.

This manuscript details the design, construction, and application of novel near infrared time correlated single photon counting devices to the identification of analytes in analytical separations. The thrust of this research is to provide a simple, low cost technique for the high-speed identification of DNA sequencing bases that are labeled with a series of unique near infrared fluorophores. These fluorophores are unique because they possess the same emission and absorption maxima, but different fluorescence lifetimes. Consequently, they allow analytes to be discriminated by fluorescence lifetime as opposed to color. The first goal of this dissertation research was to implement a time correlated single photon counting system with the use of single mode fiber optics. Utilizing a passively mode locked Ti: Sapphire Laser, a single photon avalanche diode, single mode fiber optics and a mechanical switch a fiber optic based time correlated single photon counting device with subnanosecond resolution was constructed. The experimental results showed that group velocity dispersion was low and that it was possible to perform multiple time correlated single photon counting experiments with a limited number of excitation sources and detectors. It was determined that the average instrumental response of each channel was 181 picoseconds. The fluorescence lifetime of a near infrared dye, aluminum tetrasulfonated naphthalocyanine was determined to be 3.08 nanoseconds. The second phase of this doctoral research involved the construction and characterization of a near infrared time correlated single photon counting scanning device. This integrated device consisted of a pulsed diode laser, single photon avalanche diode, and a time correlated single photon counting board. The instrument response function of this system was determined to be less than 300 ps. The sensitivity and ability to discriminate between various fluorophores was determined. In addition to its application for scanning solid surfaces such as DNA microarrays, the device was utilized to detect analytes in a micro-capillary electrophoresis separation. The fluorescence lifetimes of these analytes were determined on-line

Application of waveguide arrays and spectral filtering for a multi-frequency picosecond mode-locked pulse source

Current optical fiber-communication networks increasingly rely on wavelength-division multiplexing (WDM) technologies in conjunction with optical time-division multiplexing (OTDM) of individual WDM channels. The combination of high-repetition-rate data streams with a large number of WDM channels has pushed transmission rates to nearly 1 TB/s, creating a demand for all-optical transmission sources that can generate pico-second modelocked pulses at various wavelengths. Through nonlinear mode-coupling in a wave-guide array and a periodically applied multi-notch frequency filter, robust multi-frequency mode-locking can be achieved in a laser cavity in both the normal and anomalous dispersion regimes. We develop a theoretical description of this multiplewavelength mode-locking, and characterize the mode-locked solutions and their stability for an arbitrary number of frequency channels. The theoretical investigations demonstrate that the stability of the mode-locked pulse solutions of multiple frequency channels depends on the degree of inhomogenity in gain saturation. Specifically, only a small amount of inhomogeneous gain-broadening is needed for multi-frequency operation in the laser. In this presentation, the conditions on the system parameters necessary for generating stable mode-locking is explored for arbitrary number of frequency channels. The model suggests a promising source for multi-frequency photonic applications

Waveguide arrays and spectral filtering for multi-frequency mode-locked pulse sources

Current optical fiber-communication networks increasingly rely on wavelength-division multiplexing (WDM) technologies in conjunction with optical time-division multiplexing (OTDM) of individual WDM channels. The combination of high-repetition-rate data streams with a large number of WDM channels has pushed transmission rates to nearly 1 TB/s, creating a demand for all-optical transmission sources that can generate pico-second modelocked pulses at various wavelengths. Through nonlinear mode-coupling in a wave-guide array and a periodically applied multi-notch frequency filter, robust multi-frequency mode-locking can be achieved in a laser cavity in both the normal and anomalous dispersion regimes. We develop a theoretical description of this multiplewavelength mode-locking, and characterize the mode-locked solutions and their stability for an arbitrary number of frequency channels. The theoretical investigations demonstrate that the stability of the mode-locked pulse solutions of multiple frequency channels depends on the degree of inhomogenity in gain saturation. Specifically, only a small amount of inhomogeneous gain-broadening is needed for multi-frequency operation in the laser. In this presentation, the conditions on the system parameters necessary for generating stable mode-locking is explored for arbitrary number of frequency channels. The model suggests a promising source for multi-frequency photonic applications

Waveguide arrays and spectral filtering for multi-frequency mode-locked pulse sources

Current optical fiber-communication networks increasingly rely on wavelength-division multiplexing (WDM) technologies in conjunction with optical time-division multiplexing (OTDM) of individual WDM channels. The combination of high-repetition-rate data streams with a large number of WDM channels has pushed transmission rates to nearly 1 TB/s, creating a demand for all-optical transmission sources that can generate pico-second modelocked pulses at various wavelengths. Through nonlinear mode-coupling in a wave-guide array and a periodically applied multi-notch frequency filter, robust multi-frequency mode-locking can be achieved in a laser cavity in both the normal and anomalous dispersion regimes. We develop a theoretical description of this multiplewavelength mode-locking, and characterize the mode-locked solutions and their stability for an arbitrary number of frequency channels. The theoretical investigations demonstrate that the stability of the mode-locked pulse solutions of multiple frequency channels depends on the degree of inhomogenity in gain saturation. Specifically, only a small amount of inhomogeneous gain-broadening is needed for multi-frequency operation in the laser. In this presentation, the conditions on the system parameters necessary for generating stable mode-locking is explored for arbitrary number of frequency channels. The model suggests a promising source for multi-frequency photonic applications

Mid-infrared quantum optics in silicon

Applied quantum optics stands to revolutionise many aspects of information technology, provided performance can be maintained when scaled up. Silicon quantum photonics satisfies the scaling requirements of miniaturisation and manufacturability, but at 1.55 $\mu$m it suffers from unacceptable linear and nonlinear loss. Here we show that, by translating silicon quantum photonics to the mid-infrared, a new quantum optics platform is created which can simultaneously maximise manufacturability and miniaturisation, while minimising loss. We demonstrate the necessary platform components: photon-pair generation, single-photon detection, and high-visibility quantum interference, all at wavelengths beyond 2 $\mu$m. Across various regimes, we observe a maximum net coincidence rate of 448 $\pm$ 12 Hz, a coincidence-to-accidental ratio of 25.7 $\pm$ 1.1, and, a net two photon quantum interference visibility of 0.993 $\pm$ 0.017. Mid-infrared silicon quantum photonics will bring new quantum applications within reach.Comment: 8 pages, 4 figures; revised figures, updated discussion in section 3, typos corrected, added referenc

Broad Bandwidth, All-fiber, Thulium-doped Photonic Crystal Fiber Amplifier for Potential Use in Scaling Ultrashort Pulse Peak Powers

Fiber based ultrashort pulse laser sources are desirable for many applications; however generating high peak powers in fiber lasers is primarily limited by the onset of nonlinear effects such as self-phase modulation, stimulated Raman scattering, and self-focusing. Increasing the fiber core diameter mitigates the onset of these nonlinear effects, but also allows unwanted higher-order transverse spatial modes to propagate. Both large core diameters and single-mode propagation can be simultaneously attained using photonic crystal fibers. Thulium-doped fiber lasers are attractive for high peak power ultrashort pulse systems. They offer a broad gain bandwidth, capable of amplifying sub-100 femtosecond pulses. The longer center wavelength at 2 ?m theoretically enables higher peak powers relative to 1 [micro]m systems since nonlinear effects inversely scale with wavelength. Also, the 2 [micro]m emission is desirable to support applications reaching further into the mid-IR. This work evaluates the performance of a novel all-fiber pump combiner that incorporates a thulium-doped photonic crystal fiber. This fully integrated amplifier is characterized and possesses a large gain bandwidth, essentially single-mode propagation, and high degree of polarization. This innovative all-fiber, thulium-doped photonic crystal fiber amplifier has great potential for enabling high peak powers in 2 [micro]m fiber systems; however the current optical-to-optical efficiency is low relative to similar free-space amplifiers. Further development and device optimization will lead to higher efficiencies and improved performance

Analysis of near-infrared dye-labeled Sanger sequencing fragments with gel electrophoresis using the time-resolved flourescence lifetime indentification methods

The research presented in this dissertation involves the identification of sequencing fragments with time-resolved methods. For this application, near-infrared heavy-atom tricarbocyanine dyes were developed in our laboratory, which can be excited with a single laser and emission collected using a single detection channel. The dyes have four spectroscopically unique, but relatively short lifetimes that can be altered by the intramolecular heavy-atom they contain. The work described here involves the optimization of dye-primer chemistry for preparing Sanger sequencing reactions for longer reads and the optimization of the separation matrix for capillary gel electrophoresis that produces favorable statistical analysis of the aforementioned dyes’ lifetimes. The performance of a two-lifetime experiment in which we modified an automated DNA sequencer to allow implementation of lifetime identification of DNA fragments labeled with near-IR fluorochromes and fractionation via slab-gel electrophoresis was investigated. A two-dye/two-lane sequencing experiment was carried out, in which two terminal bases, labeled with near-infrared dyes, were run in one lane and the other two bases in an adjacent lane. A lifetime evaluation of the resulting electropherogram on a pixel-by-pixel basis allowed the identification of the terminal nucleotide comprising a DNA band. The read accuracy was found to be better than a one-dye/four-lane approach using the software of the commercial instrument in spite of the fact that a spectroscopic call was implemented. An automated peak recognition and base calling algorithm was also implemented and evaluated on two-tract dye-primer and dye-terminator capillary electrophoresis runs. The base calling accuracy was greater than 97% for both

Wavelength tunable transmitters for future reconfigurable agile optical networks

Wavelength tuneable transmission is a requirement for future reconfigurable agile optical networks as it enables cost efficient bandwidth distribution and a greater degree of transparency. This thesis focuses on the development and characterisation of wavelength tuneable transmitters for the core, metro and access based WDM networks. The wavelength tuneable RZ transmitter is a fundamental component for the core network as the RZ coding scheme is favoured over the conventional NRZ format as the line rate increases. The combination of a widely tuneable SG DBR laser and an EAM is a propitious technique employed to generate wavelength tuneable pulses at high repetition rates (40 GHz). As the EAM is inherently wavelength dependant an accurate characterisation of the generated pulses is carried out using the linear spectrogram measurement technique. Performance issues associated with the transmitter are investigated by employing the generated pulses in a 1500 km 42.7 Gb/s circulating loop system. It is demonstrated that non-optimisation of the EAM drive conditions at each operating wavelength can lead to a 33 % degradation in system performance. To achieve consistent operation over a wide waveband the drive conditions of the EAM must be altered at each operating wavelength. The metro network spans relatively small distances in comparison to the core and therefore must utilise more cost efficient solutions to transmit data, while also maintaining high reconfigurable functionality. Due to the shorter transmission distances, directly modulated sources can be utilised, as less precise wavelength and chirp control can be tolerated. Therefore a gain-switched FP laser provides an ideal source for wavelength tuneable pulse generation at high data rates (10 Gb/s). A self-seeding scheme that generates single mode pulses with high SMSR (> 30 dB) and small pulse duration is demonstrated. A FBG with a very large group delay disperses the generated pulses and subsequently uses this CW like signal to re-inject the laser diode negating the need to tune the repetition rate for optimum gain-switching operation. The access network provides the last communication link between the customer’s premises and the first switching node in the network. FTTH systems should take advantage of directly modulated sources; therefore the direct modulation of a SG DBR tuneable laser is investigated. Although a directly modulated TL is ideal for reconfigurable access based networks, the modulation itself leads to a drift in operating frequency which may result in cross channel interference in a WDM network. This effect is investigated and also a possible solution to compensate the frequency drift through simultaneous modulation of the lasers phase section is examined