Arbitrary Temporal Profiles Research Articles

Quantum vacuum amplification in time-varying media with arbitrary temporal profiles

In this work we address quantum vacuum amplification effects in time-varying media with an arbitrary time-modulation profile. To this end, we propose a theoretical formalism based on the concept of conjugated harmonic oscillators, evaluating the impact on the transition time in temporal boundaries, shedding light into the practical requirements to observe quantum effects at them. In addition, we find nontrivial effects in pulsed modulations, where the swiftest and strongest modulation does not lead to the highest photon production. Thus, our results provide key insights for the design of temporal modulation sequences to enhance quantum phenomena. Published by the American Physical Society 2024

Dual color, frequency, pulse duration and shape agile laser system for particle spectroscopy and manipulation.

A dual color, frequency and pulse duration agile laser system, capable of delivering laser pulses in arbitrary temporal profiles with ∼1 ns to ∼1 µs pulse duration, chirping rates of ∼27 MHz/ns with an achievable chirping range of several GHz across the pulse duration, and with energies ranging from a few nJ to hundreds of mJ per pulse has been developed. The flexibility and capability of this laser system provide a wide range of laser parameters that can be exploited to optimize operational conditions in various experiments ranging from laser diagnostics to spectroscopy and optical manipulation of matter. The developed system is successfully demonstrated to obtain coherent Rayleigh-Brillouin scattering (CRBS) in both single and dual color configuration, in an effort to expand the non-intrusive accessibility towards lower pressure regime for neutral gas and plasma diagnostics.

Lower bounds for the time-bandwidth product of a single-photon pulse

Two complementary properties, such as frequency and duration of a pulse, cannot be precisely measured simultaneously. The lower bound on the time-bandwidth product, known also as uncertainty relation, plays a very important role in quantum theory. In this work, we consider single-photon pulses with arbitrary temporal and spectral profiles, and derive a lower bound for the single-photon time-bandwidth product. We investigate how this bound depends on the modal purity, the single-mode fidelity, and the effective number of modes. Our results can be used to solve the inverse problem, namely, to estimate characteristics of the single-photon pulse based on the time-bandwidth product obtained from temporal and spectral measurements of the pulse.

Demonstration of arbitrary temporal shaping of picosecond pulses in a radially polarized Yb-fiber MOPA with > 10 W average power.

High precision surface processing has an unmet demand for picosecond pulses with arbitrary temporal profiles in radial polarization states and at high average powers. Here, simultaneous spatial and arbitrary temporal shaping of chirped 10 - 100 picoseconds pulses is demonstrated with an Yb-doped fiber laser system generating an output power of more than 10 W at 40 MHz repetition frequency. The closed-loop control algorithm carves the pulses using a commercial, rugged, and fiberized optical pulse shaper placed at the front end of the system and uses feedback from the output pulse shapes for optimization. Arbitrary complex temporal profiles were demonstrated using a dispersive Fourier transform based technique and limits set by the system were investigated. Pulse shaping in the spatial domain was accomplished using an S-waveplate, fabricated in-house, to change the linearly polarized fundamental mode into a doughnut mode with radial polarization. This was amplified in a final-stage few-mode large-mode area fiber amplifier. Placing both temporal and spatial shaping elements before the power-amplifier avoids complex and potentially lossy conversion of the spatial mode profile at the output and provides an efficient route for power-scaling. The use of properly oriented quarter- and half-wave plates, which have both low loss and high power handling capability, enabled the output to be set to pure radial or azimuthal polarization states. Using commercial off-the-shelf components, our technique is able to immediately enhance the versatility of ultrashort fiber laser systems for high precision material processing and other industrial applications.

Interconversion between single-rail and dual-rail photonic qubits

We investigate schemes for conversion between qubits encoded into superpositions of vacuum and single-photon states and qubits encoded into states of single photons. The analyzed schemes combine linear optics, homodyne or heterodyne detection, single-photon detection, and electro-optical feedforward, and are designed to be suitable for signals with arbitrary temporal profiles. To achieve perfect conversion, quantum filtering is utilized based on conditioning on no-clicks of single-photon detectors, which makes the conversion probabilistic. High-quality conditional conversion is nevertheless possible even without single-photon detectors, by conditioning on outcomes of a homodyne or heterodyne detector. Deterministic high-quality conversion of dual-rail qubits to single-rail qubits is possible with an array of homodyne detectors where the phases of the measured quadratures are controlled by a feedforward scheme, which represents an alternative to conversion via homodyne detection with a real-time continuous feedback [T. C. Ralph, A. P. Lund, and H. M. Wiseman, J. Opt. B 7, S245 (2005)].

In-fiber reconfigurable generation of arbitrary (asymmetric) picosecond temporal intensity waveforms by time-domain optical pulse shaping

A fiber-optic programmable optical pulse shaper is experimentally demonstrated using multi-level phase-only linear filtering, capable of synthesizing arbitrary (including asymmetric) temporal intensity waveforms. The reconfigurable filtering operation is implemented in the time domain with a single electro-optic phase modulator (EO-PM) driven by a high-speed electronic arbitrary waveform generator (AWG). The required multi-level modulation signal is calculated from a combination of optimization algorithms, namely the Gerchberg-Saxton algorithm (GSA) and a genetic algorithm (GA). We report the synthesis of high-quality, arbitrary temporal intensity profiles, including asymmetric triangular waveforms and ∼150 Gbaud random on-off keying (OOK) pulse and pulse amplitude-modulation (PAM) code sequences, with a temporal resolution of ∼2 ps over a maximum time window of ∼60 ps.

Effects of line-narrowing of amplified spontaneous emission analyzed by a Monte Carlo model

This work focuses on the effects caused by line-narrowing of the amplified spontaneous emission (ASE) encountered in two-photon laser-induced fluorescence (TPLIF) processes. The line-narrowing effects complicate the TPLIF problem significantly, but are important for the quantitative interpretation of the TPLIF measurements. Past models are predominately developed for one-dimensional (1D) problem under ideal conditions. Therefore, this work develops a Monte Carlo (MC) method to robustly and flexibly incorporate non-ideal conditions including arbitrary temporal, spatial, and spectral beam profiles in multi-dimension practical problems. The MC model was the applied to analyze the TPLIF processes, both in 1D and 2D. The results show that the ASE radiation is more effectively amplified when the line-narrowing effects are considered than not. Because the ASE serves as a depopulation mechanism in TPLIF, such enhanced amplification has direct implications to the quantification of signals typically measured in practice. For example, our results show that neglecting the line-narrowing effects can cause significant error in the interpretation of the LIF and ASE signals. These results are hence expected to be useful for the design and analysis of experiments.

Diffraction properties of multi-layer volume holographic gratings under an ultrashort pulsed beam with arbitrary temporal profiles

The diffraction properties of a system of multi-layer volume holographic gratings under an ultrashort pulsed beam with arbitrary temporal profiles are investigated using the multi-layer coupled wave theory. The dependence of the pulse profiles of the diffracted beams, diffraction bandwidth and the total diffraction efficiency of the multi-layer system on the temporal profiles of the input ultrashort pulse are investigated. The calculated results indicate that the temporal shape of the input pulsed beams is an important factor in the analysis of the propagation characteristics. The analysis of this paper will be valuable for the applications of pulse shaping, processing and filter.

Diffraction properties of ultrashort pulsed beams with arbitrary temporal profiles by a reflection volume holographic grating

The diffraction properties of reflection volume holographic gratings are studied when the gratings are illuminated by an ultrashort beam with arbitrary temporal profiles. The modified Kogelnik's theory of coupled waves is used. Simple analytical expressions for spectral and temporal distribution of the transmitted and diffracted are obtained. The dependences of the diffraction bandwidth, the Bragg selectivity bandwidth and the total diffraction efficiency of the reflection volume grating on the temporal profiles of the input ultrashort pulse are investigated. Study shows that the bandwidth of the reflection volume holographic gratings varies with the grating parameters more slowly than the transmitting volume holographic gratings. For three different temporal profiles, numerical results about diffraction properties of the reflection volume holographic gratings are given and compared with the transmitting volume holographic gratings.

Electro-optic shocks from blowout laser wakefields

Laser wakefield accelerators operating in the blowout regime exhibit unique forward scattering characteristics. When a cavitation region is formed, the drive pulse excites currents in the electron sheath that lead to conical emission of harmonic radiation in the near-forward direction. Theoretical expressions for the spectral-angular distribution in the far field are derived. These expressions allow for arbitrary temporal profiles of both the laser pulse and the sheath density. The characteristics of the emission can be related to key characteristics of the accelerating structure. The theoretical results are compared with the results of the experiment.

Diffraction properties of ultrashort pulsed beams with arbitrary temporal profiles by a volume holographic grating

In this paper, the diffraction properties of an ultrashort optical pulse with arbitrary profiles in time diffracted by a volume holographic grating are investigated using the modified Kogelnik coupled-wave theory. Simple analytical expressions for the spectrum and spatial profiles of the transmitted and diffracted beams are obtained. The dependences of the diffraction bandwidth, the Bragg selectivity bandwidth and the total diffraction efficiency of the volume grating on the temporal profiles of the input ultrashort pulse are investigated. For three different temporal profiles, numerical results of diffraction properties are given. It is shown that the temporal shapes of the input pulsed beams have been found to be an important factor in the analyses of the propagation characteristics.

Diffraction properties of ultrashort pulsed beams with arbitrary temporal profiles studied with a volume holographic grating

Using modified two-dimensional coupled-wave theory, the diffraction properties of ultrashort pulsed beams with arbitrary temporal profiles are studied with a volume holographic grating. Analytical expressions for the profiles of the transmitted and diffracted beams are obtained. It is shown that the Bragg selectivity bandwidth of the volume grating can be influenced by the geometry parameter. Numerical results are illustrated for three different temporal profiles. For different temporal profiles, the ratios of the diffraction bandwidths to input bandwidths are discussed.

Interaction of free charged particles with a chirped electromagnetic pulse

We study the effect of chirp on electromagnetic (EM) pulse interaction with a charged particle. Both the one-dimensional (1D) and 3D cases are considered. It is found that, in contrast to the case of a nonchirped pulse, the charged particle energy can be changed after the interaction with a 1D EM chirped pulse. Different types of chirp and pulse envelopes are considered. In the case of small chirp, an analytical expression is found for arbitrary temporal profiles of the chirp and the pulse envelope. In the 3D case, the interaction with a chirped pulse results in a polarization-dependent scattering of charged particles.

Computationally efficient spectral analysis of an FEL oscillator using a Green function analysis

Previous work on a Green function approach to the evolution of the small gain linear FEL oscillator assumed a long electron pulse. Here this restriction is eliminated and a new expression for the complex amplitude of the optical field at the nth pass is obtained. The fully causal formalism includes arbitrary temporal profiles of the electron and optical beams and cavity detuning and losses. In our formalism, the solution for the field at the nth pass requires exponentiating a single matrix rather than sequentially evaluating the field at each pass. Various numerical studies are presented.

Optical Double-resonance Spectra with Time-dependent Pulses

Abstract The optical double-resonance spectrum for a three-level atom interacting with two monochromatic laser pulses with arbitrary temporal profiles is calculated by use of Light's perturbation theory. Unlike some earlier work, the theory is not restricted to exact resonance of the pump laser, or to pulse areas which are exact multiples of 2π. A variety of pulse profiles are investigated, and the spectra are found to depend strongly on the detuning of the pump laser.