This PDF file contains the front matter associated with SPIE Proceedings Volume 11671, including the Title Page, Copyright information, and Table of Contents.

Welcome and Introduction to SPIE Photonics West LASE conference 11671: Real-time Measurements, Rogue Phenomena, and Single-Shot Applications VI

Shannon's information theory teaches us that the amount of information gained in a measurement is inversely proportional to its predictability. Difficult to capture, flash-like signals contain far more information than repetitive waveforms. The Photonic Time Stretch data acquisition invented two decades ago, has emerged as the most successful solution to single-shot measurements of transient events. This talk will review the fundamentals of photonic time stretch and its numerous applications in science, biomedicine and as mathematical inspiration for a new class of numerical algorithms.

Due to three-dimensional (3D), stochastic and non-repeatable transitions of dissipative solitons (DSs), it is challenging to monitor the 3D dynamics. Here we report multi-dimensional (space xy + discrete time t + wavelength λ) DS dynamics imaged by spatial-temporal-spectral compressed ultrafast photography, enabling imaging at up to trillions of frames per second. Various transient and random phenomena of multimode DSs are revealed, highlighting the importance of real-time multi-dimensional observation without the need for event repetition in decomposing the complexities of DSs.

Graded-index multimode optical fibers have recently attracted a renewed attention, thanks to the discovery of new nonlinear effects, such as Kerr beam self-cleaning. In essence, Kerr self-cleaning involves a flow of the propagating beam energy into the fundamental mode of the fiber, accompanied by a redistribution of the remaining energy among high-order modes. Increasing the fundamental mode energy leads to a significant improvement of the output beam quality. A standard method to determine beam quality is to measure the M² parameter. However, since self-cleaning involves the nonlinear redistribution of energy among a large number of fiber modes, measuring a single beam quality parameter is not sufficient to characterize the effect. A properly informative approach requires performing the mode decomposition of the output beam. Mode decomposition permits to evaluate the energy distribution among all of the excited fiber modes, which enables investigations of nonlinear mode coupling processes at a qualitatively new level. In this work, we demonstrate an efficiency mode decomposition method based on holography, which is suitable for analyzing the self-cleaning effect. In a theoretical study, we describe the solution of the mode decomposition problem for the modes of the gradedindex multimode fiber. In an experimental investigation, we demonstrate the decomposition of both low-power (speckled) and self-cleaned beams, involving more than 80 modes.

We review our recent work on the generation of novel optical solitons arising from different, high orders of dispersion and combinations thereof. By incorporating a spectral pulse-shaper in a mode-locked laser cavity, we can tailor the net-cavity dispersion, allowing us to access a wide range of new operating regimes corresponding to previously unobserved soliton pulses. We demonstrate the generation of solitons arising between self-phase modulation and any pure, negative even order of dispersion, as well as soliton molecules consisting of multiple solitons with different frequencies but that are temporally coincident.

We report the use of an optoacoustically mode-locked fiber laser to create hundreds of temporal trapping potentials in parallel, within each of which multiple optical solitons can be isolated and manipulated to interact using a variety of control methods. Using these parallel “reactors”, we achieved on-demand synthesis and dissociation of soliton molecules both globally and individually and unfolded a novel panorama of stochastic soliton dynamics. Moreover, statistical analysis based on the massive dynamic events has revealed matter-light analogy on a collective level, suggesting that the soliton molecule dynamics follow classical theory of chemical kinetics.

Bound-states of temporal solitons − termed “Soliton molecules” or “Soliton crystals” – are observed in microcavities and ultrafast resonators. Recently, we introduced high-speed spectroscopy to resolve the formation and control of such states in mode-locked Ti:sapphire oscillators by employing real-time spectral interferometry [1,2]. In this contribution, we resolve a novel mechanism mediating short-range soliton bound-states based on real-time measurements and by introducing a refined analysis of relative soliton phases. We corroborate our findings with a numerical interaction model for the coherent soliton coupling and discuss prospects for future schemes of high-speed intra-cavity spectroscopy.

The spontaneous breaking of symmetry and homogeneity through dissipative pattern formation is a long-standing fundamental examination in mathematics and nonlinear physics. Self-organized patterns arise in nature, and are postulated to occur from stochastically driven nonlinear processes. These threshold-dependent patterns can be remarkably robust in the presence of noise. In this talk we describe the dispersive dynamics in nonlinear resonator frequency microcombs and their statistical distributions. We describe the frame-by-frame fluctuations in the different microcomb states including fast breathers and their thresholds. These observed self-organized patterns support applications in communications and the understanding of nonlinear physics at the fundamental limits.

Nowadays, real-time measurements of complex dynamics of ultrashort structures in dissipative nonlinear systems have attracted a lot of interest. In this work, we present experimentally obtained real-time dynamics of two closely-separated solitons in a mode-locked erbium fibre laser. Both solitons experienced strong temporal vibrations due to mutual attractive and repulsive forces, alongside with oscillation in their energies. We experimentally demonstrate the influence of the dispersive waves (DWs) on the dynamics of the soliton complex. Eventually, the pulses experienced a collision dynamics that resulted in the formation of a single soliton at a shifted central wavelength with highly energetic Kelly sidebands and increased background radiation. Our experimentally obtained results prove the theoretical works on soliton interaction and enrich the knowledge on the complexities of ultrashort coherent features and their behaviour in nonlinear systems.

In this paper, we experimentally and theoretically analyse the formation and interaction of dark solitons in a long laser. The laser includes a semiconductor optical amplifier (SOA), centred around 1300nm, an intracavity filter and a fibre cavity whose length can vary from 20m to 20km. Near the lasing threshold the laser exhibits slowly evolving power dropouts the circulate the cavity. These dropouts are associated with the formation of Nozaki-Bekki Holes (NBH), also referred to as dark solitons. We observe both experimentally and numerically that the core of these holes exhibit chaotic dynamics and emit short light pulses. These pulses are found to be blue shifted with respect to the frequency of the dark solitons and therefore travel with a faster group velocity. These pulses are strongly damped, as they are detuned with respect to the filter transmission, but they may lead to the creation of new dark solitons. These pulses also play a major role in the development of optical turbulence when the filter is set at a frequency above 1310nm. In this case, the laser displays numerous dark solitons per round trip and the fast travelling pulses act as an interaction between the solitons, which can lead to the development of defect mediated turbulence.

Breathing-like dynamics, which is a ubiquitous phenomenon found in numerous physical systems, has recently been observed in mode-locked Erbium-doped fiber lasers. In this paper, we further generalize these fascinating phenomenon by reporting the real-time experimental observations of a breathing-like structure in an all-normal dispersion all-polarization maintaining Ytterbium-doped fiber laser. Contrary to previous studies, we show that the pulsation period increases with the pump power until a stationary dissipative soliton is formed. Our results can help better understand laser physics, and further optimize and improve a fiber cavity design.

Broadband time resolved absorption and dispersion spectroscopy using a conventional Fourier transform spectroscopy is often a challenging task due to very long measurement times. Here, we present time resolved mid-infrared dual-comb absorption and dispersion spectroscopy of methane and ethane under electrical discharge, covering a spectral bandwidth of 2850-3150 cm-1, with spectral resolution of 5 GHz and temporal resolution of 20 µs. This new approach enabled the direct measure of broadband complex refractive index of materials involved in plasma, which is an indication of plasma density.

Spectroscopic polarimetry (SP) is a powerful tool for characterization of thin film, polarization optics, semiconductor, and so on. However, mechanical polarization modulation of broadband light hampers its application for dynamic monitoring of a sample. In this article, we demonstrate the dynamic SP with features of polarization-modulation-free polarimetry and spectrometer-free spectroscopy benefiting from dual-comb spectroscopy (DCS) using a pair of optical frequency combs (OFCs). Effectiveness of the proposed system is highlighted by visualizing the hysteresis property of dynamic response in a liquid-crystal-on-silicon spatial light modulator at a sampling rate of 105 Hz.

Recordings of rare events require detection strategy in single-shot. It is also of crucial interest for recordings of terahertz waveforms in terahertz spectroscopy of irreversible processes. The time-domain spectroscopy usually requires scanning techniques that prevent the applications of very low repetition rate sources such as strong THz pulse sources based on table-top high power lasers or accelerators. We present a strategy allowing complex electric fields to be recorded in single-shot using the chirped pulse electro-optic sampling technique at 1550 nm with signal processing techniques based on DEOS (Diversity Electro-Optic Sampling).

In this work, we demonstrated real-time spectroscopy using a discreetly and fast wavelength tunable injection-seeded THz wave parametric generator (is-TPG). In our is-TPG, pump and seed beams shine the MgO:LiNbO3 crystal to generate the THz wave. At that time, the wavelength was tuned by changing the wavelength of the seed beam. Therefore, in order to achieve real-time measurement, we introduced fast wavelength switchable ECDL that we developed recently using a digital micromirror device (DMD) as a wavelength selector. As a result of this improvement, we achieved to identify the reagents hidden in cardboard box in real-time.

We propose the use of a new precision monitoring technique based on speckle analysis (SuPreMe). This technique only requires three parts: a laser, a weak optical diffuser (e.g. unpolished metallic surface) and a camera, all elements widely available at a low cost, while allowing absolute position estimation. The technique relies on the emergence of rings in the power spectrum density of the collected speckle intensity, related to Talbot distance. Using simulation and prior experimental data, we are demonstrating the viability of the technique, showing for example that it is possible to extract absolute displacement measurement of 100 μm with a precision range of 7 nm-rms.